Monitoring, Control and Communications for Electrical Power Apparatus

Analysis of Partial Discharges Detected in 420kV Oil Impregnated Paper Bushings

Mark Tostrud

Dynamic Ratings, Inc

17th, May 2017

Monitoring, Control and Communications for Electrical Power Apparatus

Offline Power Factor Tests – 420 kV OIP BushingsBushing Date Tanδ at 10kV

C1 C2Capacitance at 10kVC1 C2

H1 Nameplate 0.31 439Commissioning 0.30 0.32 434 382729.11.14 0.26 0.32 438 3825

H2 Nameplate 0.30 438Commissioning 0.30 0.27 435 347129.11.14 0.26 0.50 436 3473

H3 Nameplate 0.39 443Commissioning 0.33 0.33 440 494629.11.14 0.34 0.29 442 4942

Monitoring, Control and Communications for Electrical Power Apparatus

Typical bushing and partial discharge monitoring system installation for high voltage reactors:• Bushing sensors installed in the

capacitive tap of the bushing –primary sensor for the system

• Rogowski coils installed near the bottom flange of the bushing –secondary sensor for the system

400kV 3 Phase 125 MVAR Shunt Reactor Bushing & PD Installation

Monitoring, Control and Communications for Electrical Power Apparatus

Phase 1 Bushing DGA Data

Date H2 CH4 C2H4 C2H6 C2H2 CO CO2

Bushing H1 (ppm)

April 15 2014 17 2 3 0 0 60 356

Nov 29 2014 625 46 0 7 0 95 513

Jan 7 2015 1262 88 4 16 0 95 515

Feb 14 2015 2378 147 1 26 2 104 512

Monitoring, Control and Communications for Electrical Power Apparatus

Phase 1 Bushing – Duval Pentagon 1Analysis

Monitoring, Control and Communications for Electrical Power Apparatus

400kV 3 Phase 125 MVAR Shunt Reactor PD Analysis – Bushing 1

Monitoring, Control and Communications for Electrical Power Apparatus

OIP Bushing - Lower Inner Porcelain Partial Discharge Signature

Lower porcelain contamination

Monitoring, Control and Communications for Electrical Power Apparatus

Phase 2 Bushing DGA Data

Date H2 CH4 C2H4 C2H6 C2H2 CO CO2

Bushing H2 (ppm)

April 15 2014 15 0 3 0 0 63 177

Nov 29 2014 47 2 0 1 0 110 249

Jan 7 2015 361 16 4 0 0 82 224

Feb 14 2015 1180 111 30 26 0 54 287

Monitoring, Control and Communications for Electrical Power Apparatus

Phase 2 Bushing – Duval Triangle 4 Analysis

Monitoring, Control and Communications for Electrical Power Apparatus

400kV 3 Phase 125 MVAR Shunt Reactor PD Analysis – Bushing 2

Monitoring, Control and Communications for Electrical Power Apparatus

Phase 3 Bushing DGA Data

Date H2 CH4 C2H4 C2H6 C2H2 CO CO2

Bushing H3 (ppm)

April 15 2014 42 0 4 0 0 77 526

Nov 29 2014 72 2 0 0 0 151 903

Jan 7 2015 50 2 2 0 0 123 891

Feb 14 2015 54 3 2 0 0 135 944

Monitoring, Control and Communications for Electrical Power Apparatus

Phase 3 Bushing – All gases are normal

Monitoring, Control and Communications for Electrical Power Apparatus

● Online partial discharge monitoring can successfully identify bushing health problems

● The phase resolved data patterns provide a useful information to assess the type of failure that may be occurring in the bushing

● Understanding the failure modes of the equipment being monitored can help users better analyze the data from the monitor

● Transformer and reactor designs can significantly influence the electrical fields to which bushings are subjected

● Bushings can degrade very rapidly and the use of an online monitoring system can provide the data needed to make an informed decision on the asset health

Conclusions

Monitoring, Control and Communications for Electrical Power Apparatus

Questions / Discussion