1. Transient Analysis of Shunt Reactor Switching on 500kV System
Sze Mei ‘Cat’ Wong
Jayanth Ramamurthy
Sharma Kolluri
Entergy Services, Inc.
6/6/2014

2. Outline Background What is Transient Recovery Voltage (TRV)
Shunt Reactor at Entergy
Simulation Results using EMTP-RV
Summary

3. Background
Shunt reactors are used to compensate long EHV transmission lines in order to prevent steady state overvoltages.
Transient recovery voltage (TRV) is a big concern when switching large reactors.

4. Transient Recovery Voltage (TRV)

5. Shunt Reactor at Entergy
Entergy has installed two 70 MVARs reactor at one of the 500kV transmission station to give more flexibility to TOC (Transmission Operations Center) for controlling voltages
There are two 500kV transmission lines terminating at that station one is 50 miles long and the other is 180 miles long

7. Simulation Assumption
This study has been performed primarily from a shunt reactor de-energizing standpoint.
Transmission lines have been modeled as constant parameter lines.
The bus sections have been modeled using frequency dependence (FD) line to include the series inductance and resistive skin effect.
The damping resistor and stray capacitance of the shunt reactor have been modeled using information provided by manufacturer

8. EMTP Models
Equivalent sources were modeled at Station A, B and C along with their source impedances.
The constant parameter line model was used to represent the 500 kV lines between Station A – Station B and Station A – Station C.
Two 70 MVAR reactors were modeled on the line end of the circuit breaker on the Station A – Station C transmission line, while two 70 MVAR reactors were modeled on the bus at the Station C.

9. EMTP Models
The parameters of damping resistor, stray capacitance and the non-linear characteristics for the reactor are provided by manufacturer .
Non-linear characteristics of the reactor

10. EMTP Models
Chopping current is calculated based on the information provided by ABB engineer and IEEE C37.15.
ICH = λ*sqrt(NCt) where λ is 16x104, N is 2 with two interrupting units, and assume Ct is 2nF after adding load side capacitance to ground, ICH is calculated to be 10A.
It was applied in the 3 cases to demonstrate the effect of chopping current to TRV.

12. Simulation Results Case # Case Description TRV magnitude (kV peak)
TRV magnitude (p.u. peak)
TRV time to peak (µs)
Rate of rise of recovery voltage (kV / µs) 1
De-energize reactor without fault in the system
765.5
1.88
627
1.22 2
3 phase to ground short line fault near Station A end on Station A – Station C line
872.4
2.14
798
1.09 3
3 phase to ground short line fault near Station A end on Station A – Station B line
914.5
2.24
824
1.11 4
1 phase to ground short line fault near Station A end on Station A – Station C line
829.8
2.03
634
1.31 5
1 phase to ground short line fault near Station A end on Station A – Station B line
861.0
2.11
640
1.35

13. TRV Across Reactor Breaker for Case 1

14. TRV Across Reactor Breaker for Case 4

15. Simulation Results: Case # Case Description peak voltage of ITRV (kV)
time co-ordinate of ITRV (µs)
TRV magnitude (kV peak)
TRV magnitude (p.u. peak) 6
De-energize reactor without fault in the system with 10A chopping current
263.2
140
837.8
2.05 7
3PhG short line fault near Station A end on Station A – Station C line with 10A chopping current
226.9
121
1082.4
2.65 8
3PhG short line fault near Station A end on Station A – Station B line with 10A chopping current
225.9
120
1087.7
2.66

16. TRV Across Reactor Breaker for Case 8

17. Summary
Eight scenarios were simulated in EMTP-RV to determine TRV across the breaker used for switching the reactors.
According to IEC Table 26, for breaker rated 500kV, the TRV peak value for T10 test duty is 1031kV, TRV time to peak is 147 μs and Rate of rise of recovery voltage is 7 kV / µs.
The TRV peak voltage, TRV rise time and rate of rise of recovery voltage (R.R.R.V.) for the first five scenarios are in the range established in IEC Table 26.

18. Summary
However, the TRV peak voltages are above the range established in IEC Table 26 when chopping current was included in Case 7 and Case 8.
It is recommended to confirm with the breaker manufacturer that the breakers meet the IEEE / IEC standards on TRV and ITRV capability, and certify the type test shows that the breakers can successfully interrupt with the TRV shown in this study.

19. Q & A
Thank you!