WINDING TEMPERATURE MEASUREMENT by liaoqinmei

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									WINDING TEMPERATURE MEASUREMENT
              Techniques, Devices and Operation

   Andreas Garnitschnig, Phil McClure, Lenny Shaver, Mark Teetsel
                       and Robert Thompson
 Winding Temperature Measurement

                              Introduction
                Reasons for the Presentation
• Concern over Slow Response of Legacy Winding
  Temperature Indicators to:
  • Large step-load increases, including loading beyond nameplate.
  • Loss of cooling events.

• Limited Understanding of Present WT Methods & Options
  • Dispel mystique surrounding winding temperature measurement.
  • Introduce new equipment, communications and alarm options.

• Differing Attitudes About Winding Temperature
  Measurement.
  • Express Users, Transformer and WTI Manufacturer’s Perspectives.
 Winding Temperature Measurement

                     INTRODUCTION

• Two Types of Early Winding
  Temperature Indicators
   • Direct Measurement
      • Thermistor
      • RTD

   • Simulated
      • Thermometer in Heated Thermowell
      • RTD in Heated Thermowell
 Winding Temperature Indicators

                     INTRODUCTION

• Present Winding Temperature Indicators
  • Direct Measurement
     • Fiber-Optic

  • Simulated
     • Thermal Sensor in Heated Thermowell

  • Calculating
    • Physical
    • Virtual
Winding Temperature Measurement




    Direct Winding Temperature Measurement




               Lenny Shaver
   Direct Winding Measurements
      using Fiber Optics (F.O.)
Modern transmission
 technology of
 information by means
 of a light signal
 guided by a small
 diameter fiber
 Fiber Optics (F.O.) Pros and Cons
Pros                         Cons
• Direct “Hot Spot”          • Cost
  Measurement
                             • Difficult to retrofit
• Passive (all dielectric)
                             • Fragility during
• Immune to EMI
                               installation
• Inert (long life)
• Light Weight
• Small Size
• Vibration and Shock
  resistance
     Two Types of F.O. Sensors
Extrinsic
Fiber carries signal to
  external sensor



Intrinsic (a.k.a. all fiber)
Fiber itself is the sensor
            Extrinsic vs. Intrinsic
                   Extrinsic                     Intrinsic
 Sensor
                    Point Sensor           Distributed or Point Sensor
  Type
              Commercially Available for
Application       over 15 years
                                                      R&D


               Instrument cost ranges      Instrument cost ranges from
   Cost           from $3k to $20k               $100k to $150k

               Requires knowledge or        Distributed sensor version
  Sensor
               assumption of hot spot      can map temperatures along
 Location             location                         path
        Extrinsic vs. Intrinsic
• Intrinsic F.O Sensors
  – Fiber Bragg Grating
  – Raman Scattering
• Extrinsic F.O. Sensor
  – Fluoroptic (Luxtron)
  – Absorption Edge (Nortech)
  – Fabry-Perot Interferometry
      Extrinsic Sensor – Fluoroptic
                (Luxtron) Luxtron FOT Instrument
                  Sensor
                                                    Optics/Electronics


                            Probe (Optical Fiber)


Fluorescent Signal Decay
is Temperature Dependent:
• At Hotter temperatures
decay is faster.
• At Colder temperatures
decay is slower.
  Extrinsic Point Sensor –
 Absorption Edge (Nortech)
• Semiconductor crystal (such as GaAs)
  attached to the end of fiberoptics
• The “Absorption Edge” moves to longer
  wavelengths as the temperature rises
     Reflectivity




                    λ = ΑΕ
                             Wavelength
F.O. Sensor Signal Path
               Accuracy
• Systems capable of accuracies better than
  1°C
• Most systems optimized for Transformers
  are specified at accuracy +/- 2°C over
  entire operating range of -30 to 200°C
• Of course, this is dependant on probe
  position
   Response to Load Variation
• Response time is effectively instant
• F.O. probe is directly measuring winding
  temperature
• Response is dependant on probe tip
  location
Winding Temperature Measurement




           Current Technologies:
         Analog Simulating Devices


                  Mark Teetsel
             Winding Simulation Systems
                                    BUSHING CT

• Thermowell
  – Heater Coil
                                   BALANCE
  – Plate Style                  TRANSFORMER

                                  CALIBRATION
                                   RESISTOR




                                                 HEATER
              Winding Simulation Systems
                   Response Times
• Time Constant (t )
   – Derived mathematically from y = 1-e -t/ t
   – Time for system to rise 63.2% of total step
   – Reaches 99.8% of final value in six time constants


• Liquid System is typically less than 1 minute
• Winding System up to 33 minutes
Oil Well Response Times
Winding Response Times
               Measurement Device Types
• Bimetal Element Sensors
   – Direct drive mechanism.
   – Typically lowest cost, lowest accuracy
   – Used for indication and simple control
                Measurement Device Types
• Capillary (Bulb type or remote)
   – Liquid or gas filled probe at top oil level, gauge at eye level
   – Indication, Control, and remote output functions.
Winding Temperature Measurement


          Current Technologies:
        Physical Electronic Devices




                  Phil McClure
 Winding Temperature Measurement

                            Analog Electronic Thermowell-Simulating WTI


                                                             WINDG                               82.0
Name Derivation                                                                             DIGITAL DC
                                                                                            VOLTMETER
• Winding temperature is




                                                RETRANSMIT
                                                  ANALOG
  simulated by the
  thermowell
                                                             +v                                                                                                   BUSHING CT
• Displays and alarms
  are driven electrically      A


                                   ALARM(s)
                                                                                                                                                                 BALANCE
                                                                                                                                                               TRANSFORMER
                                       A

                                                                                                                                                                CALIBRATION




                                                                                                                     EMI / RFI / SURGE ISOLATION
                                                                                                                                                                 RESISTOR




                                                                     RELAY DRIVE CIRCUITS
                                                                                                                                                   SENSE +




                                                                                                                                                                               HEATER
                                                                                                         C URRENT                                  SOUR CE +
                             PUMP(s)                                                                     SOU RCE
                                                                                                           (mad c)                                 SOU RCE -
                                                                                                                                                                    RTD1

                                                                                                                                                   SENSE -

                                       FAN(s)
Winding Temperature Measurement

                      Analog Electronic Thermowell-Simulating WTI: Sensor Section


                                         WINDG                               82.0
                                                                        DIGITAL DC
                                                                        VOLTMETER




                            RETRANSMIT
                              ANALOG

                                         +v                                                                                                  BUSHING CT



     A

         ALARM(s)
                                                                                                                                            BALANCE
                                                                                                                                          TRANSFORMER
             A

                                                                                                                                           CALIBRATION




                                                                                                 EMI / RFI / SURGE ISOLATION
                                                                                                                                            RESISTOR
                                                 RELAY DRIVE CIRCUITS




                                                                                                                               SENSE +




                                                                                                                                                          HEATER
                                                                                     CURRENT                                   SOURCE +
   PUMP(s)                                                                            SOURCE
                                                                                       (m adc)                                 SOURCE -
                                                                                                                                               RTD1

                                                                                                                               SENSE -

             FAN(s)
     Winding Temperature Measurement

                            Analog Electronic Thermowell-Simulating WTI: Sensor Section


                                                                                                 BUSHING CT

                                                                                                                       Heated Thermowell
                                                                                                                        • Oil temperature
                                                                                                                          biases thermowell to
                                                                                                BALANCE
                                                                                              TRANSFORMER
                                                                                                                          platform temperature

                                                                                               CALIBRATION              • Heater raises the
 FOR A RANGE OF -40 TO 200 DEGREES                   EMI / RFI / SURGE ISOLATION                RESISTOR                  platform temperature
    CELSIUS AND A PLATINUM RTD:
                                                                                   SENSE +                                to the same
RTD RESISTANCE = 84.27 TO 175.84 OHMS
                                                                                                                          temperature as the




                                                                                                              HEATER
                                           CURRENT                                 SOURCE +
  AT A SOURCE CURRENT OF 2 MA THE          SOURCE
                                            (madc)                                 SOURCE -
                                                                                                   RTD1                   winding hottest spot
SENSE VOLTAGE FROM THE RTD WILL BE:

0.002 X 84.27 = 0.169 V @ -40 DEGREES C                                            SENSE -
                                                                                                                        • WTI simply measures
0.002 X 175.84 = 0.352 V @ 200 DEGREES C                                                                                  the temperature of the
                                                                                                                          thermowell through
                                                                                                                          measurement of RTD
                                                                                                                          resistance.
Winding Temperature Measurement

                        Analog Electronic Thermowell-Simulating WTI: Alarm Section


                                             WINDG                               82.0
                                                                            DIGITAL DC
                                                                            VOLTMETER




                                RETRANSMIT
                                  ANALOG     +v                                                                                                  BUSHING CT



       A


           ALARM(s)
                                                                                                                                                BALANCE
                                                                                                                                              TRANSFORMER
               A

                                                                                                                                               CALIBRATION




                                                                                                    EMI / RFI / SURGE ISOLATION
                                                                                                                                                RESISTOR
                                                     RELAY DRIVE CIRCUITS




                                                                                                                                  SENSE +




                                                                                                                                                              HEATER
                                                                                         CURRENT                                  SOURCE +
     PUMP(s)                                                                              SOURCE
                                                                                           (madc)                                 S OURCE -
                                                                                                                                                   RTD1

                                                                                                                                  S ENSE -

               FAN(s)
 Winding Temperature Measurement

                   Analog Electronic Thermowell-Simulating WTI: Alarm Section

                                       +v




  A

      ALARM(s)

                                                                   Alarm Characteristics
          A

                                                                     • Set point values set through



                                            RELAY DRIVE CIRCUITS
                                                                       adjustment of pots.
                                                                     • Unalarmed state of relay coil
                                                                       (energized / de-energized) may
PUMP(s)
                                                                       be selected using jumpers.

          FAN(s)
  Winding Temperature Measurement

          Analog Electronic Thermowell-Simulating WTI: Communication Section


                                                        WINDG                               82.0
                                                                                       DIGITAL DC
Communications                                                                         VOLTMETER




                                           RETRANSMIT
                                             ANALOG
  • Typically Limited
    to current loops
                                                        +v                                                                                                  BUSHING CT
    and voltage
    levels.
                          A

                              ALARM(s)
  • Choice of levels                                                                                                                                       BALANCE
                                                                                                                                                         TRANSFORMER
    typically 0-1 and             A
                                                                                                                                                          CALIBRATION




                                                                                                               EMI / RFI / SURGE ISOLATION
                                                                                                                                                           RESISTOR




                                                                RELAY DRIVE CIRCUITS
    /or 4-20 madc.
    Some offer 0-10                                                                                                                          SENSE +




                                                                                                                                                                         HEATER
                                                                                                    CU RRENT                                 SOUR CE +
    and / or 1-5 vdc.   PUMP(s)                                                                     SOU RCE
                                                                                                     (madc)                                  SOU RCE -
                                                                                                                                                              RTD1

                                                                                                                                             SENSE -

                                  FAN(s)
  • Level selection
    typically made
    by moving
    jumpers.
  Winding Temperature Measurement

            Analog Electronic Thermowell-Simulating WTI: Display Section


                                                       WINDG                               82.0
                                                                                      DIGITAL DC
                                                                                      VOLTMETER




                                          RETRANSMIT
                                            ANALOG
Display Options
                                                       +v                                                                                                  BUSHING CT
 • Analog meter
   movement
                         A
   typically
                             ALARM(s)
                                                                                                                                                          BALANCE
   standard.                                                                                                                                            TRANSFORMER
                                 A

                                                                                                                                                         CALIBRATION




                                                                                                              EMI / RFI / SURGE ISOLATION
 • Digital meter                                                                                                                                          RESISTOR




                                                               RELAY DRIVE CIRCUITS
   optional.                                                                                                                                SENSE +




                                                                                                                                                                        HEATER
                                                                                                   CUR RENT                                 SOUR CE +
                       PUMP(s)                                                                     SOUR CE
                                                                                                    (madc)                                  SOU RCE -
                                                                                                                                                             RTD1

                                                                                                                                            SENSE -

                                 FAN(s)
Winding Temperature Measurement


        Analog Electronic Thermowell-Simulating WTI:
                  Response and Accuracy

Response to Step Loads

• Thermowell-simulating WTI should be thought of as a winding temperature
  system, comprising the measurement instrument, sensor (RTD) and
  thermowell & heater assembly.
• Measurement Instrument’s electronics are virtually instantaneous due to
  low-gain amplifiers and slowly varying signal.

• The sensor RTD’s response time is in the order of unit seconds.

• The thermowell & heater assembly’s response time is measured in terms
  of decades of minutes to the first 60% of load increase and unit hours for
  the final 40%. Basis test studies were done 50 years ago and data is no
  longer available. Data from later tests using state of the art fiber optics is
  closely guarded.
Winding Temperature Measurement


        Analog Electronic Thermowell-Simulating WTI:
                  Response and Accuracy
Accuracy
• The measurement instrument is calibrated as a high accuracy ohmmeter,
  for measuring the resistance of the RTD. Uncertainty of the resistance
  measurement can be within a small fraction of a percent.

• The RTD probe’s uncertainty is related to the theoretical temperature
  versus resistance curve of international specifications such as DIN-43760-
  1980. A high quality RTD probe will have uncertainty of less than +/- 0.6
  degrees at 200 degrees Celsius.

• The heated thermowell is calibrated to a specific current value, for a
  specific steady state temperature rise. The calibrating current value was
  determined at some point during the development cycle by applying
  current to the thermowell’s heater while the thermowell is immersed in a
  controlled oil volume, under laboratory conditions.
Winding Temperature Measurement


       Analog Electronic Thermowell-Simulating WTI:
                 Response and Accuracy

 Accuracy: Heated Thermowell (continued)

 • Laboratory conditions are infrequently duplicated in transformers due to
   larger volumes and different oil flow dynamics. As a consequence,
   calibrating current may not be predictably accurate for all conditions.

 • The heated thermowell’s response time lags actual winding temperature,
   and as a consequence large errors exist at instantaneous points in time.



 • The total uncertainty for the thermowell-simulating WTI is the sum of the
   individual components. Although the probe and measurement instrument
   may have an uncertainty of less than a degree, the thermowell error may
   increase the total uncertainty to tens of degrees in transient conditions.
  Winding Temperature Measurement

                       Analog Electronic Internal-Simulating WTI
                                                                                           FLUID        WINDG
Name Derivation
                                                                                             60.0                82.0
 • Displays and alarms
                                                                                         DIGITAL DC   DIGITAL DC
   are driven electrically                                                               VOLTMETER    VOLTMETER




                                                RETRANSMIT
 • Winding temperature




                                                  ANALOG
   is simulated by
   squaring and                                              +v

   summing amplifiers




                                                                                                                                                                                          BUSHING CT
                               A




                                                                                                                                                EMI / RFI / SURGE ISOLATION
Features                           ALARM(s)




                                                                                                                        (SQUARING AMPLIFIERS)
                                                                                                                         SIGNAL CONDITIONING
 • No Heated                           A



   Thermowell

                                                                  RELAY DRIVE CIRCUITS
                                                                                                                                                                              SENSE +

 • Dual Measurement                                                                                   CURRENT




                                                                                                                                                                                          RTD
                                                                                                                                                                              SOURC E +
                                                                                                       SOU RCE
   sources                   PUMP(s)                                                                    (madc)                                                                SOURCE -



 • Dual Displays                                                                                                                                                              SENSE -


                                       FAN(s)
 • Selectable alarm
   source
 • Selectable
   retransmit source
Winding Temperature Measurement

         Analog Electronic Internal-Simulating WTI:
                   Response and Accuracy

Response

 • Measurement instrument’s current and RTD circuit’s response time is
   virtually instantaneous.
 • Measurement instrument’s signal conditioning circuitry contains tunable
   delays intended to duplicate the actual winding response. The response
   can be theoretically tuned from instantaneous to several hours.

 • Measurement instrument’s response is therefore a function of the
   accuracy with which the WTI manufacturer has defined the response
   curve for a particular transformer.
Winding Temperature Measurement

          Analog Electronic Internal-Simulating WTI:
                    Response and Accuracy
Accuracy
• The accuracy basis for the instrument’s measuring circuitry and probe for
  this type of WTI is the same as for the thermowell sensing type above;
  typically less than 1 degree celsius.
• The accuracy basis for the instrument’s squaring and delay circuitry is
  similar to the thermowell’s but it is substantially more predictable and
  repeatable. The accuracy is based on the fidelity with which the circuitry
  can track the calibration curve. Tracking should be quite good, within 2 to
  3 degrees.

• The accuracy basis for the system as a whole still depends on the
  accuracy with which the calibrating curve tracks the actual thermal
  characteristic of the windings. This is difficult to do with simple exponential
  responding amplifiers.
    Winding Temperature Measurement

                                   Digital Electronic Simulating WTI

                                                                                                              DATA
                                                                                                             ENTRY
Name Derivation                                                                                               KEYS

                                                       WINDG                      82.0         DISPLAY
                                                                                               DRIVERS
• Winding temperature                                  LIQUID                     57.0

  source is a heated                                                                                                                                                                             BUSHING CT




                                            COMMUNICTION
  thermowell



                                              HARDWARE
                                                                               COMMUNICATION        MICROCOMPUTER
                                                                                 PROTOCOL

• Input values
                                                                                                                                                                                          BALANCE
  immediately                                                                                                                                                                           TRANSFORMER

                                            RETRANSMIT
                                              ANALOG                                                                                                                                     CALIBRATION
  converted to digital                                                                                                                                                                    RESISTOR

  (binary) numbers                                                                                                                                                                     SENSE +




                                                                                                                                                         EMI / RFI / SURGE ISOLATION




                                                                                                                                                                                                              HEATER
                                                                                                                       SIGNAL CONDITIONING
                                                                                                                                             CURRENT                                   SOURCE +
                           A                                                                        ANALOG / DIGITAL                          SOURCE
                                                                                                                                               (m adc)                                 SOURCE -
                                                                                                                                                                                                  RTD1
• All internal signal          ALARM(s)
                                                                                                         (A/D)
                                                                                                      CONVERTER                                                                        SENSE -

  paths are digital                A
                                                                                                                                                                                       SENSE +


                                                                                                                                             CURRENT                                   SOURCE +
                                                                                                                                                                                                  RTD2
                                                           RELAY DRIVE LOGIC




                                                                                                                                              SOURCE
                                                                                                                                               (m adc)                                 SOURCE -


                                                                                                                                                                                       SENSE -


                         PUMP(s)



                                   FAN(s)
Winding Temperature Measurement

         Digital Electronic Simulating WTI: RTD & Converter Sections

                                                                                           DATA
                                                                                          ENTRY
                                                                                           KEYS

                                    WINDG                      82.0         DISPLAY
                                    LIQUID                     57.0         DRIVERS


                                                                                                                                                                               BUSHING CT

                         COMMUNICTION
                           HARDWARE
                                                            COMMUNICATION
                                                                                 MICROCOMPUTER
                                                              PROTOCOL


                                                                                                                                                                      BALANCE
                                                                                                                                                                    TRANSFORMER
                         RETRANSMIT
                           ANALOG




                                                                                                                                                                      CALIBRATION
                                                                                                                                                                       RESISTOR
                                                                                                                                                                   SENSE +




                                                                                                                                     EMI / RFI / SURGE ISOLATION




                                                                                                                                                                                            HEATER
                                                                                                                          CURRE NT




                                                                                                    SIGNAL CONDITIONING
                                                                                                                                                                   S OURCE +
        A                                                                        ANALOG / DIGITAL                         S OURCE
                                                                                                                           (madc)                                  S OURCE -
                                                                                                                                                                                RTD1
                                                                                      (A/D)
            ALARM(s)                                                               CONVERTER                                                                       S ENS E -


                A                                                                                                                                                  SENSE +


                                                                                                                          CURRE NT                                 S OURCE +
                                                                                                                                                                                RTD2
                                        RELAY DRIVE LOGIC




                                                                                                                          S OURCE
                                                                                                                           (madc)                                  S OURCE -


                                                                                                                                                                   S ENS E -


      PUMP(s)



                FAN(s)
 Winding Temperature Measurement

          Digital Electronic Simulating WTI: RTD & Converter Section


                                                                                                                             BUSHING CT
Signal Path Features
                                  MICROCOMPUTER

• One or two input channels,
  limited by number of A/D                                                                                            BALANCE
                                                                                                                    TRANSFORMER
  channels
                                                                                                                     CALIBRATION
• Analog input values amplified                                                                                       RESISTOR

  & filtered by signal                                                                                             SENSE +




                                                                                     EMI / RFI / SURGE ISOLATION




                                                                                                                                          HEATER
  conditioning circuitry




                                                     SIGNAL CONDITIONING
                                                                           CURRENT                                 SOURCE +
                                  ANALOG / DIGITAL                         SOURCE
                                                                            (madc)                                 SOURCE -
                                                                                                                              RTD1
                                       (A/D)
• Amplified signal immediately      CONVERTER                                                                      SENSE -

  converted to digital values                                                                                      SENSE +


                                                                           CURRENT                                 SOURCE +
• Digital values read from A/D                                             SOURCE
                                                                            (madc)                                 SOURCE -
                                                                                                                              RTD2
  by the microcontroller
                                                                                                                   SENSE -
    Winding Temperature Measurement

                   Digital Electronic Simulating WTI: Alarm Section
                                                                                                              DATA
                                                                                                             ENTRY
                                                                                                             KEYS

Alarm Signal Path                                      WINDG                      82.0         DISPLAY
                                                       LIQUID                     57.0         DRIVERS


• Microcontroller can                                                                                                                                                                             BUSHING CT




                                            COMMUNICTION
                                              HARDWARE
  address each relay                                                           COMMUNICATION
                                                                                                    MICROCOMPUTER
                                                                                 PROTOCOL
  individually
                                                                                                                                                                                        BALANCE
                                                                                                                                                                                      TRANSFORMER
• Microcontroller can

                                            RETRANSMIT
                                              ANALOG
                                                                                                                                                                                         CALIBRATION
  set individual                                                                                                                                                                          RESISTOR

  hysteresis values                                                                                                                                                                   SE NSE +




                                                                                                                                                        EMI / RFI / SURGE ISOLATION




                                                                                                                                                                                                               HEATER
                                                                                                                       SIGNAL CONDITIONING
                                                                                                                                             CURRE NT                                 SOURCE +
                           A                                                                        ANALOG / DIGITAL                         SOURCE
                                                                                                                                              (madc)                                  SOURCE -
                                                                                                                                                                                                   RTD1
                                                                                                         (A/D)
• Unalarmed state of           ALARM(s)                                                               CONVERTER                                                                       SE NS E -



  relay coils                      A                                                                                                                                                  SE NSE +


                                                                                                                                             CURRE NT                                 SOURCE +
  programmable via                                                                                                                                                                                 RTD2
                                                           RELAY DRIVE LOGIC




                                                                                                                                             SOURCE
                                                                                                                                              (madc)                                  SOURCE -



  software prompts                                                                                                                                                                    SE NS E -


                         PUMP(s)

• Delays and
                                   FAN(s)
  supervisory overlap
  precisely controlled
 Winding Temperature Measurement

 Digital Electronic Simulating WTI: Alarm Section, Standard Connections
                                                                 MICROCOMPUTER                                                                    MICROCOMPUTER
           ALARM(s)                                                                        ALARM(s)
    A                                                                               A




                                             RELAY DRIVE LOGIC




                                                                                                                              RELAY DRIVE LOGIC
    A                                                                               A




 PUMP(s)                                                                         PUMP(s)



           FAN(s)                                                                          FAN(s)




   Unalarmed Condition. Note failsafe fan configuration                                        Fans, Pumps and one alarm in alarm state.


           Normally de-energized relay in unalarmed state.                       Normally energized relay in unalarmed state.
           Normally de-energized relay in alarm state.                           Normally energized relay in alarmed state.


Digital Electronic WTI’s typically allow for full configuration of alarm relays.
        • Alarm source, set point value, hysteresis, unalarmed state and sensor fail
          effect.
 Winding Temperature Measurement

Digital Electronic Simulating WTI: Alarm Section, Advanced Connections

                                                                  MICROCOMPUTER                                                                   MICROCOMPUTER
          ALARM(s)                                                                          ALARM(s)
   A                                                                                 A




                                              RELAY DRIVE LOGIC




                                                                                                                              RELAY DRIVE LOGIC
   A                                                                                 A




PUMP(s)                                                                           PUMP(s)



          FAN(s)                                                                            FAN(s)


                                                                    Supervisory
                                                                      Relay


         Unalarmed Condition with failsafe fan and                                       Fans, supervised pumps and one alarm in alarm state,
       relay-supervised failsafe pump configurations.                                            with temperature above 20 degrees C.
         Supervisory relay set point value set to 20
       degrees Celsius to inhibit static electrification.
       Shown at a temperature below 20 degrees C.


                        Normally de-energized relay in unalarmed state                    Normally energized relay in unalarmed state
                        Normally de-energized relay in alarm state                        Normally energized relay in alarm state
Winding Temperature Measurement

     Digital Electronic Simulating WTI: Communications Section
                                                                                         DATA
                                                                                        ENTRY
                                                                                         KEYS

                                  WINDG                      82.0         DISPLAY
                                  LIQUID                     57.0         DRIVERS


                                                                                                                                                                            BUSHING CT
                       COMMUNICTION
                         HARDWARE
                                                          COMMUNICATION        MICROCOMPUTER
                                                            PROTOCOL


                                                                                                                                                                     BALANCE
                                                                                                                                                                   TRANSFORMER
                       RETRANSMIT
                         ANALOG




                                                                                                                                                                    CALIBRATION
                                                                                                                                                                     RESISTOR
                                                                                                                                                                  SENSE +




                                                                                                                                    EMI / RFI / SURGE ISOLATION




                                                                                                                                                                                         HEATER
                                                                                                  SIGNAL CONDITIONING
                                                                                                                        CURRENT                                   SOURCE +
      A                                                                        ANALOG / DIGITAL                          SOURCE
                                                                                                                          (m adc)                                 SOURCE -
                                                                                                                                                                             RTD1
                                                                                    (A/D)
          ALARM(s)                                                               CONVERTER                                                                        SENSE -

                                                                                                                                                                  SENSE +
              A

                                                                                                                        CURRENT                                   SOURCE +
                                                                                                                                                                             RTD2
                                      RELAY DRIVE LOGIC




                                                                                                                         SOURCE
                                                                                                                          (m adc)                                 SOURCE -


                                                                                                                                                                  SENSE -


    PUMP(s)



              FAN(s)
Winding Temperature Measurement

     Digital Electronic Simulating WTI: Communications Section




                         COMMUNICTION
                           HARDWARE
                                        COMMUNICATION
                                                        MICROCOMPUTER
                                          PROTOCOL




                         RETRANSMIT
                           ANALOG




 • Digital Communications
   • Hardware serial or Ethernet
   • Protocols typically ModBus, DNP-3, Simple ASCII (proprietary)


 • Analog Communications
    • Multiple outputs typically offered.
    • Current loop (0-1 madc, 4-20 madc)
    • Voltage source (0-10 vdc, 1-5 vdc)
Winding Temperature Measurement

          Digital Electronic Simulating WTI: Displays and Controls
                                                                                         DATA
                                                                                        ENTRY
                                                                                        KEYS

                                  WINDG                      82.0         DISPLAY
                                  LIQUID                     57.0         DRIVERS


                                                                                                                                                                             BUSHING CT
                       COMMUNICTION
                         HARDWARE
                                                          COMMUNICATION
                                                                               MICROCOMPUTER
                                                            PROTOCOL


                                                                                                                                                                   BALANCE
                                                                                                                                                                 TRANSFORMER
                       RETRANSMIT
                         ANALOG




                                                                                                                                                                    CALIBRATION
                                                                                                                                                                     RESISTOR

                                                                                                                                                                 SE NSE +




                                                                                                                                   EMI / RFI / SURGE ISOLATION




                                                                                                                                                                                          HEATER
                                                                                                  SIGNAL CONDITIONING
                                                                                                                        CURRE NT                                 SOURCE +
      A                                                                        ANALOG / DIGITAL                         SOURCE
                                                                                                                         (madc)                                  SOURCE -
                                                                                                                                                                              RTD1
                                                                                    (A/D)
          ALARM(s)                                                               CONVERTER                                                                       SE NS E -


              A                                                                                                                                                  SE NSE +


                                                                                                                        CURRE NT                                 SOURCE +
                                                                                                                                                                              RTD2
                                      RELAY DRIVE LOGIC




                                                                                                                        SOURCE
                                                                                                                         (madc)                                  SOURCE -


                                                                                                                                                                 SE NS E -


    PUMP(s)



              FAN(s)
 Winding Temperature Measurement

           Digital Electronic Simulating WTI: Displays and Controls


                                                                       DATA
Displays                                                              ENTRY
                                                                       KEYS
• LED and LCD types available
• Multiple or single scrolling    WINDG    82.0       DISPLAY
  type displays offered                               DRIVERS
                                  LIQUID   57.0
• Alarm and sensor failure
  annunciation



Controls                                                   MICROCOMPUTER
• Weather tight and capable of
  operating in all conditions
• Matrix and stacked keypads
  offered
Winding Temperature Measurement

     Digital Electronic Simulating WTI: Response and Accuracy


Response

 • Measurement instrument’s RTD circuit’s response time is virtually
   instantaneous.
 • WTI measurement System is still subject to the heated thermowell’s slow
   response time.

Accuracy

 • Measurement instrument’s uncertainty is typically less than +/- 0.01
   degrees C. Probe accuracy is the same as other WTI types, typically less
   than +/- 0.6 degrees C.
 • WTI System uncertainty suffers from inaccuracy introduced by heated
   thermowell.
     Winding Temperature Measurement
                                     Digital Electronic Calculating WTI
                                                  WINDG                           82.0                     DATA
                                                                                                          ENTRY
                                                  LIQUID                          57.0       DISPLAY       KEYS




                                                                                                                                                                                                                BUSHING CT's
                                                   LOAD                           1200       DRIVERS
                                                 AMBIENT                          38.0




                                                                                                                                                SIGNAL CONDITIONING
                                              COMMUNICTION
                                                HARDWARE
                                                                                 COMMUNICATION
                                                                                                 MICROCOMPUTER
                                                                                   PROTOCOLS
Name Derivation
• Thermal characteristics




                                                                                                                                                                      EMI / RFI / SURGE ISOLATION
                                              RETRANSMIT
  of transformer are


                                                ANALOG
  modeled mathematically                                                                                                                                                                            SE NS E +




                                                                                                                                                                                                                  RTD1
                                                                                                                    SIGNAL CONDITIONING
                                                                                                                                          CURRENT                                                   SOURCE +
                                                                                                                                          SOURCE
• Winding temperature                                                                                                                      (m adc)                                                  SOURCE -



  is calculated from the      A

                                  ALARM(s)
                                                                                                                                                                                                    SENSE -

                                                                                                                                                                                                    SE NS E +

  equations created in                                                                           ANALOG / DIGITAL




                                                                                                                                                                                                                  RTD2
                                                                                                                                          CURRENT                                                   SOURCE +
                                        A                                                             (A/D)                               SOURCE

  the WT model                                                                                     CONVERTER                               (m adc)                                                  SOURCE -
                                                             RELAY DRIVE LOGIC




                                                                                                                                                                                                    SENSE -



• Model equations are




                                                                                                                    SIGNAL CONDITIONING




                                                                                                                                                                                                                    AUXILIARY INPUTS
                           PUMP(s)
  continuously iterated
                                     FAN(s)
Winding Temperature Measurement
                        Digital Electronic Calculating WTI: Auxiliary Inputs
                                    WINDG                           82.0                     DATA
                                                                                            ENTRY
                                    LIQUID                          57.0       DISPLAY       KEYS




                                                                                                                                                                                                 BUSHING CT's
                                     LOAD                           1200       DRIVERS
                                   AMBIENT                          38.0




                                                                                                                                 SIGNAL CONDITIONING
                                COMMUNICTION
                                 HARDWARE
                                                                   COMMUNICATION
                                                                                   MICROCOMPUTER
                                                                     PROTOCOLS




                                                                                                                                                       EMI / RFI / SURGE ISO LATION
                                RETRANSMIT
                                  ANALOG




                                                                                                                                                                                      SENSE +




                                                                                                                                                                                                   RTD1
                                                                                                      SIGNAL CONDITIONING
                                                                                                                            CURRENT                                                   SOURCE +
                                                                                                                            SOURCE
                                                                                                                             (madc)                                                   SOURCE -


        A                                                                                                                                                                             SENSE -


            ALARM(s)                                                                                                                                                                  SENSE +

                                                                                   ANALOG / DIGITAL




                                                                                                                                                                                                   RTD2
                                                                                                                            CURRENT                                                   SOURCE +
                  A                                                                     (A/D)                               SOURCE
                                                                                                                                                                                      SOURCE -
                                                                                     CONVERTER                               (madc)
                                               RELAY DRIVE LOGIC




                                                                                                                                                                                      SENSE -




                                                                                                      SIGNAL CONDITIONING




                                                                                                                                                                                                      AUXILIARY INPUTS
     PUMP(s)



               FAN(s)
Winding Temperature Measurement
         Digital Electronic Calculating WTI; Auxiliary Inputs




                                                                                             BUSHING CT's
                                                               EMI / RFI / SURGE ISOLATION
                                         SIGNAL CONDITIONING
          ANALOG / DIGITAL
               (A/D)
            CONVERTER




     • Power Measurement Can Be Used to Report:
       • Power carried by the transformer
       • Power used by cooling auxiliaries
       • Detect cooling auxiliary failure as well as correct operation
Winding Temperature Measurement
                      Digital Electronic Calculating WTI: Auxiliary Inputs
                                  WINDG                           82.0                     DATA
                                                                                          ENTRY
                                  LIQUID                          57.0       DISPLAY
                                                                                           KEYS




                                                                                                                                                                                                BUSHING CT's
                                   LOAD                           1200       DRIVERS
                                 AMBIENT                          38.0




                                                                                                                                 SIGNAL CONDITIONING
                              COMMUNICTION
                                HARDWARE
                                                                 COMMUNICATION
                                                                                 MICROCOMPUTER
                                                                   PROTOCOLS




                                                                                                                                                       EMI / RFI / SURGE ISOLATION
                              RETRANSMIT
                                ANALOG




                                                                                                                                                                                     SENSE +




                                                                                                                                                                                                  RTD1
                                                                                                                          CURRENT




                                                                                                    SIGNAL CONDITIONING
                                                                                                                                                                                     SOURCE +
                                                                                                                           SOURCE
                                                                                                                            (madc )                                                  SOURCE -


        A                                                                                                                                                                            SENS E -

            ALARM(s)                                                                                                                                                                 SENSE +

                                                                                 ANALOG / DIGITAL




                                                                                                                                                                                                  RTD2
                                                                                                                          CURRENT                                                    SOURCE +
                  A                                                                   (A/D)                                SOURCE
                                                                                                                                                                                     SOURCE -
                                                                                   CONVERTER                                (madc )
                                             RELAY DRIVE LOGIC




                                                                                                                                                                                     SENS E -




                                                                                                    SIGNAL CONDITIONING




                                                                                                                                                                                                     AUXILIARY INPUTS
     PUMP(s)



               FAN(s )
Winding Temperature Measurement

                        Digital Electronic Calculating WTI: Auxiliary Inputs
 PUMP(s)




                                                                      SIGNAL CONDITIONING




                                                                                                                AUXILIARY INPUTS
                                                                                            EMI / RFI / SURGE
                                                                                               ISOLATION
           FAN(s)
                                              ANALOG / DIGITAL
                                                   (A/D)
                                                CONVERTER




           AC Current Switch



                    • Current Sensing Requires:
                           • Current sensing switches, one for each auxiliary bank
                           • Multiple self-powered contact sensing inputs on the WTI
  Winding Temperature Measurement

                        Digital Electronic Calculating WTI: Auxiliary Inputs

     PUMP(s)




                                                                SIGNAL CONDITIONING




                                                                                      EMI / RFI / SURGE
                                                                                         ISOLATION
               FAN(s)
                                       ANALOG / DIGITAL
                                            (A/D)
                                         CONVERTER




                                                                                                          AUXILIARY INPUTS
• Current Sensing Requires:
   • Current transformer (donut or split-core)
   • Analog summing input ports on WTI




                                                    • Voltage Sensing Requires:
                                                       • Multiple analog input ports on WTI
Winding Temperature Measurement

                 Digital Electronic Calculating WTI:
                      Response and Accuracy


 Response
 • Response time is determined by the cumulative response times of the
   sensors, A/D converter and code efficiency of the microcontroller’s
   programming.
   • Response times of RTD’s and CT’s are virtually instantaneous.
   • Response time of a current switch is typically tens of milliseconds.
   • Conversion and polling times for multi-channel A/D converters is in the order of
     units of milliseconds.
   • Microprocessors can typically execute many winding temperature calculation loop
     iterations between A/D converter conversion cycles.
 • Response time can therefore be less than one second, but it is typically
   limited to one second for MMI practicality reasons.
Winding Temperature Measurement

                Digital Electronic Calculating WTI:
                     Response and Accuracy

Accuracy

Accuracy of the Calculating WTI is based on the accuracy of physical and
virtual measurements
 • Physical measurements

   • Uncertainty of the physical measurements such as probe temperature and
     current magnitude is typically less than one percent.
   • Uncertainty of the internal timers which regulate time constants is
     typically in the order of 0.4 parts per million.
Winding Temperature Measurement

                   Digital Electronic Calculating WTI:
                        Response and Accuracy
Accuracy (continued)
• Virtual Measurements
  • The WTI manufacturer creates a winding temperature algorithm (WTA) using
    complex mathematical equations which describe the thermo -dynamic profile of
    transformers. The WTA is sometimes referred to as the WT model.
  • The WTA is frequently based wholly or conceptually on internationally accepted
    documents such as IEEE C57.91-1995, BS 7735: 1994 and / or IEC 354: 1991.
  • The WTA produces data points as it calculates. These data points can be used to
    generate standard curves, which can be compared to a transformer’s thermal
    profile.
  • Because the calculating WTI uses the same equations and constants as are used
    to construct the standard curves, the fidelity of the WTI indication with respect to
    the standard curve is absolute.

  • However; the WTA is only as accurate as the WTI manufacturer’s
    algorithm, the transformer manufacturer’s design data and the
    user’s accurate data entry.
Winding Temperature Measurement
    Digital Electronic Calculating WTI: Winding Temperature Model
Winding Temperature Measurement



              Current Technologies:
                 Virtual Devices

      The Thermo-hydraulic Model (THM)


                 Andreas Garnitschnig
Winding Temperature Measurement


                          THM Basics
 • creates a thermal image of the transformer
 • calculates
    − losses in core, windings (I²R and eddy losses) and tank
    − oil flows
    − temperatures of oil, core and windings, incl. hot spots

 • based on input values
    −   load current, voltage
    −   tap position
    −   ambient temperature
    −   cooling status

 • runs
    − on-line in real-time mode (monitoring)
    − off-line in simulation mode (post-calculation, prognoses)
Winding Temperature Measurement


                       THM Elements
     • Ambient conditions
        – ambient temperature, solar radiation, wind

     • Losses
        – of core, windings (I²R, eddy current losses), tank

     • Heat capacity
        – of core, windings and oil

     • Heat transfer
        – winding - oil, oil - ambient

     • Oil flow
        – natural (by thermal expansion) or forced (by pumps)
Winding Temperature Measurement


 Required Information to Generate a THM


          • Name plate data
                                   Model
          • Basic design data     Generator

          • Type test results
Winding Temperature Measurement


 Required Information to Generate a THM
 • Base data
        Single / three phase, rated voltages and currents, number of windings
 • Cooling definition
        Number of cooling stages, with description of each stage (total losses, top
        and bottom oil temperature rise)
 • Transformer losses
        No-load losses, load losses for each winding, split in I2R and eddy losses,
        stray losses
 • Heat capacity
        Mass of core & clamping, mass of windings separately, oil volume in tank and
        coolers
 • Dimensional data
        Tank dimensions, winding height, cooler height, relative vertical position of
        winding and cooler
 • Temperature gradients
        Average and maximum gradient of core and windings separately, for a given
        cooling stage and reference load
Winding Temperature Measurement


                         THM Operation

   Phase current
   Phase voltage                              Hotspot temperature
   LTC position              THM              Overload capability (p.u. vs. time)
   Cooling status
   Ambient temperature




                          Name plate data
                          Basic design data
                          Type test results
Winding Temperature Measurement

                                THM Example
       Hydraulic network for a 2-winding autotransformer

                                 5                                      20

               4                     5                       16   17     13              16
                   6                               12
           4                    9                       12

               3            8                 10             15              18               21
                   2            3                   4             6                7
                                                                         14              17
           3           7                 8              11
               2            7                 9              14              19               22
          Core         CW                SW             Tank           Cooler 1        Cooler 2
                   5                               11
           2                    6                       10               15              18
                                                                              23
                            1                 25             13                    24
               1                                                         19

                                1
Winding Temperature Measurement


                              THM Accuracy
                           260 MVA GSU Transformer, Heat Run Test
            Calculated and measured temperatures: Hot Oil and Hotspot in LV winding
   °C

  100
                            Calculated by THM     Hotspot
  90

  80

  70

  60
                             Measurement          Hot Oil
  50

  40

  30

  20

  10

   0
        0      60     120     180      240      300         360   420   480   540     600
                                                min
Winding Temperature Measurement




           Transformer Manufacturer,
            Providing Accurate Data



                 Andreas Garnitschnig
Winding Temperature Measurement


         Determination of Hottest Spot
           Magnitude and Location

            • Heat producers - Losses
            • Heat storage - Thermal capacity
            • Heat Removal
               - Transfer mechanisms
               - Heat exchangers
Winding Temperature Measurement


            Heat Producers - Losses

          Losses are generated
             -   in the core
             -   in windings
             -   in additional construction elements

          dependent on
             -   the voltage at a winding close to the core
             -   the current in the individual windings
             -   the tap position, if a tap changer exists
Winding Temperature Measurement


        Heat Producers - Losses (cont´d)

 I²R-losses are determined by
    -   the ohmic winding resistance (temperature dependent)
    -   the currents through the windings

 Eddy current losses are calculated by
    -   using the stray flux distribution (axial, radial) in the winding
        block, which is determined by the current distribution over all
        windings


 Both, I²R- and eddy current losses are dependent on
   temperature.
Winding Temperature Measurement



       Heat Storage - Thermal Capacity

            Heat is stored
            • in the core
            • in the winding copper
               - small time constant (5..10 minutes)
            • in the insulation material
            • in the oil
               - big time constant (several hours)
Winding Temperature Measurement



           Heat Transfer Mechanisms

   • The heat transport through surfaces, e.g. from
     winding to oil or from cooler surface to ambient air,
     follows complex rules
   • Dependencies and factors were gained from
     experiments
   • Many quantities (e.g. viscosity, density, specific
     thermal capacity) are dependent on temperature
   • Impact of the velocity of the flowing oil
Winding Temperature Measurement



            Temperature Calculation
   • Oil exits the cooler at temperature θOb
   • Along the winding, the oil temperature increases to
     θOmax (dependent on number, dimension and
     arrangement of coolers)
   • Between winding and oil, there is a gradient ΘW-O
     (dependent on load and, for ON cooling, type of
     winding)
   • At the top end of the winding, eddy current losses
     increase the winding temperature by the hot spot
     gradient ΘH-W
Winding Temperature Measurement


      Temperature Calculation (cont´d)
Winding Temperature Measurement



    Heat Exchangers - Types of Cooling

     • Radiators / Coolers
     • Natural Oil Cooling (ON)
     • Forced Oil Cooling (OF, OD) by Pumps
     • Natural Air Cooling (AN)
     • Forced Air Cooling (AF) by Fans
Winding Temperature Measurement


            Types of Cooling (cont´d)




                                  Most effective
Winding Temperature Measurement


                   Load Changes



                                  ΘOmax ~
                                  (P/P0)0,9…1


                                  ΘW-O ~
                                  (I/I0)1,6…2
Winding Temperature Measurement



           Selection of a WTI System

      • User input
         - User specifies type of WTI system according to his
           needs

      • Best fit
         - All WTI´s have both advantages and disadvantages
Winding Temperature Measurement


     Selection of a WTI System (cont´d)
      • Accuracy of indirect measurement WTI´s
        depends on the deviation between averaged
        hot oil temperature and the hot oil
        temperature of the individual windings
      • Accuracy of direct measurement WTI´s
        depends on the location of the sensor (i.e. it
        depends on the manufacturer´s ability to
        determine the location of the hottest spot)
      • Direct measurement sensors are difficult to
        install in EHV and UHV transformers
        (dielectric risk !)
WINDING TEMPERATURE
    INDICATORS

 USERS’ PERSPECTIVE

  Robert Thompson
     PARADIGMS – PAST vs. PRESENT

n   Regulated vs. Unregulated business
n   Reliability vs. Profitability
n   Time-based maintenance vs. Condition-
    based maintenance
n   Nameplate loading vs. Thermal loading
              USER OBJECTIVES


n   Acceptable reliability (reasonable risk)
n   Optimized utilization of resources
n   Reduced maintenance cost
      USES OF WINDING TEMPERATURE
              MEASUREMENT


n   Operational Condition Assessment
n   Load Planning
n   Asset Management
n   End-of-life Determination
      BENEFITS OF ACCURATE WINDING
        TEMPERATURE MEASUREMENT

n   Higher safe loading
n   Efficient use of cooling equipment
n   Reduce cooling equipment maintenance
n   More accurate prediction of remaining
    insulation life
n   Reduced physical stress on winding
    CONSEQUENCES OF INACCURATE W.T.
            MEASUREMENT

n   Underutilization of assets
n   Higher running and maintenance costs
n   Physical/thermal stress on winding
    insulation
n   Shortened insulation life due to
    overheating cycles
     APPLYING WINDING TEMPERATURE
    DEVICES – FOR NEW TRANSFORMERS
n   A standard device should include local and remote indication
n   The indicator should accurately represent hottest spot for the
    particular transformer to which it is applied
    -indicator should be programmable for application to different
    transformers
    -indicator should be programmed (or programmable) to respond
    in a timely manner to sudden application of load (should avoid
    overshoot)
n   If practical (economical) the device should include provisions f or
    downloading temperature data for the previous 24 hours
n   Transformer manufacturers should be required to provide critical
    values for creation of a thermal model
    APPLYING W.T. DEVICES – FOR INSERVICE
               TRANSFORMERS

n   The indicator must be designed to provide
    winding and oil temperatures on transformers
    that only have only one thermowell.
n   The indicator must provide accurate indication of
    actual winding (hot spot) temperatures for the
    particular transformer (e.g., programmable to
    follow thermal model)
n   The indicator should include provisions for
    remote indication
ISSUES
                     Consistency

n   Different transformer manufacturers design the
    hot-spot differential into indicators by different
    criteria. One manufacturer sets the differential
    to 15C for all transformers. Others design for as
    little as 4C differential. Also, many existing
    indicators are programmed to reflect average
    winding (vs. hottest spot).
                     Overshoot

n   Fans and pumps are typically controlled by the
    winding temperature indicator. If the
    temperature simulation does not respond quickly
    enough to avoid thermal overshoot following
    sudden application of load, periodic overheating
    of insulation can result in premature failure of
    the transformer
                 Load projections

n   Many users have revised their operation and
    system planning strategy to maximize utilization
    of resources (transformers) and are depending
    on temperature indicators more than ever
   ILLUSTRATION

THERMAL FACTORS RELATING
     TO TRANSFORMER
 PERFORMANCE/RELIABILITY
     ILLUSTRATION

Thermal aging of insulation in a
         transformer
Can you locate the hottest spot in these coils?
              CONCLUSIONS
n   THE ASSUMED VALUE OF HOTTEST SPOT (WINDING)
    TEMPERATURE IS CRITICAL TO USERS’ DECISIONS

n   PRESENT APPLICATION OF INSTRUMENTS DO NOT
    PROVIDE CONSISTENCY NOR ACCURACY IN THEIR
    INDICATIONS OF WINDING TEMPERATURE
Winding Temperature Measurement

                    Future Technologies




                         Phil McClure
Winding Temperature Measurement

                             Future Technologies
• Improving Components of the WTI System
  • Sensors
    • Indestructible fiber optic sensors.
    • Portable fiber optic measurement instruments.
    • Imaging sensors located internal to the tank.
    • Wireless, self-powered thermal devices for winding embedment.
    • Nano-tech based, autonomous, self-navigating thermal sensors.

  • Measurement Instruments
    • More auxiliary features such as dry contact, oil condition and power monitoring.
    • Higher reliability, more environmentally hardened electronics.
    • Flexible digital communications options; more and easier to configure protocols.

  • Winding Temperature Algorithms
    • Standardized WTA configuration parameters.
    • Electronic transfer of transformer design data to winding temperature indicators.
Winding Temperature Measurement

                         Conclusions




                         Phil McClure
 Winding Temperature Measurement

                                    Conclusions
Direct Measurement WTI’s
• Fiber optic still state of the art in many R&D projects and critical installations.
• Intrinsic (distributed) fiber has attractive properties but is not
  popular due to high instrument cost > $100000.
• Cost of intrinsic fiber’s measurement instrument may be spread over many
  transformers, to be used as a calibration tool for indirect WTI’s.
• Extrinsic (point source) fiber practical for many applications but knowledge of
  hottest spot locations critical. Hottest spot is sometimes not in the winding.
Indirect Measurement WTI’s
• Thermowell simulating WTI systems are slow to respond to step load changes.
   • Study-grade data is not commonly available for analysis.
   • New types of simulators have lower thermal mass; may respond faster.

• Electronic measurement instruments are approaching mature technology status.

• Immunity to EMI / RFI and surge needs to be improved.
• WT algorithms need a standard set of curves to be qualified from.
Winding Temperature Measurement

                          Conclusions (continued)

 General
 • Feature sets of mid-range WTI’s are expanding
   • More digital communications protocols are available

 • Utilities are standardizing on WTI’s that they are comfortable with


 Industry
 • Free exchange of knowledge has been inhibited in the past
   • Confidentiality issues govern disclosure of design details.
   • New ways to protect design confidentiality while conveying necessary design data
     must be found.
Winding Temperature Measurement

                Presenter Contact Information


Andreas Garnitschnig   Phone: +43-3172-606-2014
                       Email: andreas.garnitschnig@vatechetg.at

Phil McClure           Phone: 954-755-7111
                       Email: phil.mcclure@weschler.com

Lenny Shaver           Phone: 408-727-1600
                       Email: lenny@luxtron.com

Mark Teetsel           Phone: 623-4341965
                       Email: mark.teetsel@qualitrolcorp.com

Robert Thompson        Phone: 704-382-9331
                       Email: rsthomps@duke-energy.com

								
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