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ADVANCES IN CONTINUOUS PARTIAL DISCHARGE MONITORING

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					      Vienna 21-24 May 2007




            ADVANCES IN CONTINUOUS PARTIAL
                DISCHARGE MONITORING


                          Patrick Fleming : IPEC Ltd
                            Colin Smith : IPEC Ltd
                  Matthieu Michel : EDF Energy Networks Ltd




Patrick Fleming-UK-Session RT1B-Paper 0276                    1
      Vienna 21-24 May 2007




 INTRODUCTION
 There is a growing interest in partial discharge monitoring technology:-
 For Distribution Network Operators
      •The reliability of the ageing asset base
      •Quality of Supply
      •Regulation of Customer Interruptions (CI)
      •and Customer Minutes Lost (CML).
 For highly critical consumers
      •Need for extremely reliable power supply.
      •Critical services that cannot be disrupted
      •consequential losses running into millions of pounds.


Patrick Fleming-UK-Session RT1B-Paper 0276                           2
                   Vienna 21-24 May 2007


                                   Typical Age Profile for Substations in UK

                 1200



                 1000


                  800
  No of Panels




                  600


                  400



                  200


                    0
                         1950-55


                                   1955-60


                                             1960-65


                                                       1965-70


                                                                     1970-75


                                                                               1975-80


                                                                                         1980-85


                                                                                                   1985-90


                                                                                                             1990-95


                                                                                                                       1995-00
                                                                 Year of Manufacture



                 In the UK, only 15% of substation panels have been installed in the last
                 40 years,85% of panels have reached or exceeded their design life

Patrick Fleming-UK-Session RT1B-Paper 0276                                                                                       3
      Vienna 21-24 May 2007




           For Cables there is a similar story:

           •Of 13000km of cable in the London area,
           •3500km was installed before 1955
           •and 6000km installed between 1955 and 1975.
           •Only 3500km of the network in the last 30 years.




Patrick Fleming-UK-Session RT1B-Paper 0276                     4
      Vienna 21-24 May 2007




   The problem facing DNOs:
        • Wholesale replacement is financially impractical
        • A “wait until it fails” policy is unacceptable
        • The regulator has set targets for CML and CI
        • A method of prioritising the replacement is required.




Patrick Fleming-UK-Session RT1B-Paper 0276                        5
      Vienna 21-24 May 2007




   Partial discharge (PD) is a key indicator of failure in MV and HV
   equipment
        • This is well documented in the literature
        • A growing understanding of the role PD has in cable failure
        • Continuous monitoring of PD yields diagnostic data
        • Extensive trials have been undertaken by EDF Energy over
        the last 6 years.




Patrick Fleming-UK-Session RT1B-Paper 0276                              6
      Vienna 21-24 May 2007


                     Progression of automatic monitors




                                                Advanced Substation
                                                Monitor       2007


                              OSM v3 2004
   OSM v1 2000

Patrick Fleming-UK-Session RT1B-Paper 0276                            7
      Vienna 21-24 May 2007



                   Partial Discharge Knowledge Process




Patrick Fleming-UK-Session RT1B-Paper 0276               8
      Vienna 21-24 May 2007




          Monitoring screen showing the criticality of all circuits
Patrick Fleming-UK-Session RT1B-Paper 0276                            9
      Vienna 21-24 May 2007




    Screen showing the criticality of circuits for a selected monitor
Patrick Fleming-UK-Session RT1B-Paper 0276                              10
      Vienna 21-24 May 2007




      Four case studies are presented:
           • A substation supplying a London Airport

           • Switchgear in a semiconductor
               manufacturer.

           • Monitoring of periodic variation of PD

           • Example of cable replacement



Patrick Fleming-UK-Session RT1B-Paper 0276             11
      Vienna 21-24 May 2007




   They show examples where:
        • Costly unscheduled outages have been avoided

        • Equipment failure is detected at an early stage

        • Continuous monitoring provides key information

        • Asset replacement is driven by data from
           permanent monitoring.




Patrick Fleming-UK-Session RT1B-Paper 0276                  12
      Vienna 21-24 May 2007




                                Case Study 1:
                                Airport Substation Monitor:
                                Uses Airborne Acoustic monitors to “listen
                                to” PD on the VMX switchgear

Patrick Fleming-UK-Session RT1B-Paper 0276                              13
      Vienna 21-24 May 2007




      Case Study 1:
      1 out of 5 adjacent panels is showing abnormal behaviour



Patrick Fleming-UK-Session RT1B-Paper 0276                       14
      Vienna 21-24 May 2007




     Case Study 1:
     The abnormal behaviour is seen to be following the humidity
     trace.
     On day 160 the PD ceases when the equipment is replaced.

Patrick Fleming-UK-Session RT1B-Paper 0276                         15
      Vienna 21-24 May 2007




Case Study 2:
Freescale Semiconductor.
IPEC ASM monitoring
cables and switchgear
using CTs and CCs




Patrick Fleming-UK-Session RT1B-Paper 0276   16
      Vienna 21-24 May 2007


    Case Study 2:
    Discharge activity initiated in an air insulated switchgear
    coming in bursts,
    some of which were brief, others lasting several hours.
    Intermittent PD developed over a period of 3 weeks
    On a Saturday local and remote alarms were triggered by SMS
    The Equipment was switched out of circuit
    Re-commissioned on the following Monday morning




Patrick Fleming-UK-Session RT1B-Paper 0276                        17
      Vienna 21-24 May 2007




   Case Study 2:
   This graph shows the final
   burst of activity.

   The equipment was taken out
   of service, the breakers
   replaced. The damage from
   the discharge can be seen.



                                             Consequential cost of failure
                                             would have been several
                                             million GB£.



Patrick Fleming-UK-Session RT1B-Paper 0276                                   18
      Vienna 21-24 May 2007




   Case Study 3:
   PD activity on a cable circuit in London over a 1 week period:
        •Highest levels being recorded over night.
        • Impossible to detect with daytime inspection and spot testing
        •The automatic monitor showed the cyclic activity
        •Data shows a cyclic dependence on Load
        •Continuous Monitoring gave a clear view of the trend

Patrick Fleming-UK-Session RT1B-Paper 0276                           19
      Vienna 21-24 May 2007




    Case Study 4:
    Increase in PD activity occurring over a period of about 7 weeks.

Patrick Fleming-UK-Session RT1B-Paper 0276                          20
      Vienna 21-24 May 2007




    Case Study 4:
         PD waveshape indicated a distant fault
         Problem located 800m away using Off-line VLF Mapping
         A cable section was removed and analysed.
         The investigation showed traces of carbonisation
         After re-energisation, the discharges had stopped.


Patrick Fleming-UK-Session RT1B-Paper 0276                      21
      Vienna 21-24 May 2007




    CONCLUSION

    The growing interest in PD Monitoring is driven
       • by the ageing asset base and
       • pressure to reduce Customer Interruptions
       • and Customer Minutes Lost.

    For Critical Users the driver is security of supply
        • Reducing downtime
        • Avoiding consequential loss

    The long term trial of this equipment on the EDF Energy
    networks has shown the value of continuous monitoring.
        • For reducing CI and CML
        • as a tool for providing information for asset management

Patrick Fleming-UK-Session RT1B-Paper 0276                           22

				
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