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Chuck Mozina Clemson University

VIEWS: 16 PAGES: 23

									 CLEMSON UNIVERSITY DG CONFERENCE


  UPDATE ON THE CURRENT
       STATUS OF DG
     INTERCONNECTION
        PROTECTION

WHAT IEEE 1547 DOESN’T TELL YOU ABOUT
   INTERCONNECTION PROTECTION

             Chuck Mozina
               Consultant
        Beckwith Electric Co., Inc.
CLEMSON UNIVERSITY DG CONFERENCE

               OUTLINE

  Update the Current Status of DG
   Interconnection Protection


  Tell You What IEEE 1547 Doesn’t


  Discuss New DG Method and Practices
         + Calf. Rule 21
CLEMSON UNIVERSITY DG CONFERENCE


  Types of DG Generators

       • Induction

       • Synchronous

       • Asynchronous
    CLEMSON UNIVERSITY DG CONFERENCE

                                     To Utility System




Typical
                         Interconnection
                           Transformer

Interconnection
Protection
                                                            Interconnection
                                                                 Relay
                                                                              Utility System

                                                                              IPP System

                                                                               Point of common coupling



                                                     Local Loads
•   Disconnects the generator when it is no longer operating in parallel
    with the utility.
•   Protects the utility system from damage caused by connection of the
    generator (fault current and overvoltage).
•   Protects the DG generator from damage from the utility system,
    especially through automatic reclosing.
   CLEMSON UNIVERSITY DG CONFERENCE

    Typical Generator Protection
• Generator internal short
  circuits.
• Abnormal operating
  conditions (loss of field,
  reverse power,
  overexcitation and
  unbalance currents).




                                      Local Loads
CLEMSON UNIVERSITY DG CONFERENCE



             IEEE 1547
   Addresses Generators 10 MVA or
    Less
   Started Work in 1997
   Has Over 300 Participants
   Met Every Other Month
   Referred Most Issues of Substance to
    3 New Standards Groups
CLEMSON UNIVERSITY DG CONFERENCE

                  What 1547 SAYS
                     A DG SHALL:
 Not Cause Overvoltages or Loss of Utility Relay
   Coordination
 Disconnect When No Longer Operating in Parallel With
   the Utility.
         + Only Discusses 81O/U and 27, 59
 Not Energize the Utility when it is De-energized
 Not Create an Unintentional Islands
 Use “Utility Grade” Relays
 Not Cause Objectionable Harmonics
 Not Cause Loss of Synchronism That Results in
   Objectionable Flicker
CLEMSON UNIVERSITY DG CONFERENCE

                  What 1547 SAYS
                    A DG SHALL:
 Not Cause Overvoltages or Loss of Utility Relay
   Coordination
 Disconnect When No Longer Operating in Parallel With
   the Utility.
         + Only Discusses 81O/U and 27, 59
 Not Energize the Utility when it is De-energized
 Not Create an Unintentional Islands
 Use “Utility Grade” Relays
 Not Cause Objectionable Harmonics
 Not Cause Loss of Synchronism That Results in
   Objectionable Flicker
CLEMSON UNIVERSITY DG CONFERENCE

OVERVOLTAGE AND LOSS OF
     COORDINATION
Two Sources of Overvoltage
     +Choice of Delta Interconnection Transformer
      Primary Winding

      + Ferroresonance

Loss of Coordination
       +Choice of Grounded Interconnection
        Transformer Primary Winding.
   CLEMSON UNIVERSITY DG CONFERENCE

Typical 4-Wire Distribution Feeder Circuit
                                             DG




        Pole-top transformer rated for line-to-neutral voltages
                       example: 13.2 KV 3  7.6 KV
  CLEMSON UNIVERSITY DG CONFERENCE

Ungrounded Interconnection Transformers

                                      Advantages
                                   Provide no ground fault
                                   backfeed for fault at F1 &
                                   F2. No ground current from
                                   breaker A for a fault at F3.

                                        Problems
                                    Can supply the feeder
                                    circuit from an
                                    underground source
               Low       High
                                    after substation breaker A
               Voltage
               (SEC.)
                         Voltage
                         (PRI.)     trips causing overvoltage
     DG
CLEMSON UNIVERSITY DG CONFERENCE
 Grounded Primary Interconnection
          Transformers
                                        Advantages
                                   No ground current from
                                   breaker A for faults at
                                   F3(    ). No overvoltage
                                   for ground fault at F1.

                                   No overvoltage for
                                   ground fault at F1.
          2
                                        Problems
                                  Provides an unwanted
                                  ground current for supply
                                  circuit faults
                                  at F1 and F2.
              Low       High
                                  Allows source feeder
                                  relaying at A to respond to
              Voltage   Voltage
              (SEC.)    (PRI.)
                                  a secondary
    DG    3                       ground fault at F3(    ).
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       FERRORESONANCE
         NEW YORK FIELD TESTS –1989
             FIELD TEST CIRCUIT
CLEMSON UNIVERSITY DG CONFERENCE


         FERRORESONANCE
           NEW YORK FIELD TESTS -1989
50KW Synchronous DG, 9KW load, 100KVAR Capacitance
                        and
       Wye-Delta Interconnection Transformer
           A=2.74 pu B=2.34 pu C=2.92 pu
CLEMSON UNIVERSITY DG CONFERENCE

         FERRORESONANCE
           NEW YORK FIELD TESTS -1989
50KW Synchronous DG, 9KW load, 100KVAR Capacitance
                        and
       Wye-Delta Interconnection Transformer
           A=2.74 pu B=2.34 pu C=2.92 pu

PROTECTION SOLUTION: MEASURE PEAK OVERVOLTAGE
                     NOT RMS (59I)
CLEMSON UNIVERSITY DG CONFERENCE


          CONDITIONS FOR
         FERRORESONANCE
1. DG Must be Separated From the Utility System
   (islanded condition)
2. KW Load in the Island Must be Less than 3 Times
   DG Rating
3. Capacitance Must be Greater Than 25 and Less
   Than 500 Percent of DG Rating
4. There Must be a Transformer in the Circuit to
   Provide Nonlinearity
  CLEMSON UNIVERSITY DG CONFERENCE

PROTECTION FUNCTION BEYOND
      81O/U,27 AND 59

      Total Interconnect Package
           Loss of Parallel
           Fault backfeed removal
           Damaging conditions
           Abnormal power flow
           Restoration
    CLEMSON UNIVERSITY DG CONFERENCE

TYPICAL INTERCONNECTION PROTECTION FOR WYE-
      GROUNDED (PRI.) INTERCONNECTION
               TRANSFORMER
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TYPICAL INTERCONNECTION PROTECTION FOR
  UNGROUNDED (PRI.) INTERCONNECTION
             TRANSFORMER
CLEMSON UNIVERSITY DG CONFERENCE

RECIPROCATING ENGINE OUT OF
  SYNCHRONISM CONDITION
  CLEMSON UNIVERSITY DG CONFERENCE

           Power Angle Analysis of
         Out-of-Synchronism Condition
Power
                                 P = |Eg| |ES|          If A1>A2 DG goes
                                  Max
                                         X
                                   STABLE
                                                        unstable and slips a
                                     120
                                                        pole, results in high
                            A2                          levels of transient shaft
                                            UNSTABLE
 Pm= e
    P
                                                        torque


               A1
                                      Line
                                  Recloser
                                     Trips
PFAULT

                    Angle                        180
                    Q -Q
                     g s
 CLEMSON UNIVERSITY DG CONFERENCE


         CONCLUSIONS
1. DGs Interconnected on Distributions Systems
  Present Significant Technical Problems

2. There are No “Standard” Solutions Only Choices
  with Undersirable Drawbacks

3. IEEE 1547 Provides Limited Real Guidance –
  Simply Cites Obvious Requirements

4. Hopefully, the Three Newly Formed IEEE
  Standards Groups Will Address the Technical
  Issues Raised in this Paper
CLEMSON UNIVERSITY DG CONFERENCE




       THE END
UPDATE ON THE CURRENT STATUS OF DG
   INTERCONNECTION PROTECTION


        QUESTIONS

								
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