Contents. Reignition and Restrikes. Reactor Switching. Normal and Abnormal Transients. Normal and Abnormal Transients Reignition.

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1 Contents Reignition and Restrikes By :- Himanshu Bahirat EE5 : Power System Transients Date:- February, Normal and Abnormal Transients Reignition Reactor Switching Restrike Capacitor switching Three phase capacitor switching Grounded vs. Ungrounded banks Normal and Abnormal Transients Normal Transients Transients during energization Up to p.u. voltages No trapped charges assumed Capacitor Energization inrush currents and voltages Abnormal Transients During denergization Trapped charges Very high voltages and currents Current Chopping Interruption of currents Restrikes and Reignitions Reactor Switching Trapped Energy High Frequency oscillations of reactor voltage Dielectric Breakdown Rs Ls CB Vs SC Reactor

2 Circuit Breaker Current : Reignition Reactor Voltage :Reignition Interruption of circuit current with reignition 9 After Reignition [p.u] 7 5 Reignition : Current Reactor Side recovery Voltage : High frequency [ms] 5 (f ile Reactor_Switching_reignitions_P56.pl; x-v ar t) c:src -REACT [ms] 9. (file Reactor_Switching_reignitions_P56.pl; x-var t) v:react 8.88E [ms] 8.6 (f ile Reactor_Switching_reignitions_P56.pl; x-v ar t) c:src -REACT Reignition : Definition A reignition occurs when a current is interrupted at current zero and then re-establishes itself within one-eight of a power frequency cycle []. 9 Capacitor Switching Switching of normal load current Deenergization at system peak voltage Trapped charge on the capacitor Reignition region 8 6 V Ls CB V - Vs Cap Bank [ms] 5 (file Reactor_Switching_reignitions_P56.pl; x-var t) v:src c:xx-react

3 Capacitor Bank Trapped Voltage and TRV Restrikes and Voltage Escalation 8 6 [ka] 6 Trapped Voltage on Capacitor Bank after deenergization Circuit Breaker TRV [ms] 5 (f ile Restrike_Basics.pl; x-v ar t) v:capb v:capc - [ms] 5 (f ile Restrike_Basics.pl; x-v ar t) v :BUSB -CLRB v :BUSC -CLRC -6 6 [ms] 5 (file Restrike_Basics.pl; x-var t) v:capa c:busa -CLRA Voltage escalation with multiple restrikes Stored Voltage on Capacitor Bank increase with each restrike. ( st.p.u. nd 5 p.u Very high transient current spikes Restrikes : TRV Restrikes :Bus Voltage [ms] 5 (file Restrike_Basics.pl; x-var t) v:busa -CLRA 7.6E-6-7 [ms] 5 (f ile Restrike_Basics.pl; x-v ar t) v :BUSA

4 Restrikes :Ungrounded banks Capacitor Bank Voltage Restrikes :Ungrounded banks Circuit Breaker TRV [ms] 5 (file Restrike_Basics.pl; x-var t) v:capc v:capa 7.6E-6 7.6E-6 Higher trapped voltages than the case of grounded banks. Restrike on phase A results in escalation on phase c. First restrike trapped voltage increases to about.5 p.u - -5 [ms] 5 (file Restrike_Basics.pl; x-var t) v:busa -CLRA v:busc -CLRC 7.6E-6 7.6E-6 Restrike : Definition Restrike and Reignition: Comparison The term restrike is defined as a re-establishment of the current, one-quarter cycle or longer, following interruption of a capacitive current at a normal current zero []. 9 8 Reignition region Restrike region Restrike region [ms] 5 (file Reactor_Switching_reignitions_P56.pl; x-var t) v:src c:xx-react -9 [ms] 5 (file Reactor_Switching_reignitions_P56.pl; x-var t) v:src c:xx-react

5 Conclusions Abnormal transients are a result of trapped charges and energy. Reignitions and restrikes can lead to very magnitude transients. Multiple restrikes can damage circuit breakers and other equipments. Ungrounded Banks result in higher magnitude of transients than grounded banks. Can controlled with use of surge arresters. References. N. E. Dillow, I. B. Johnson, N. R. Schultz, and A. E. Were, "Switching Capacitive Kilovolt-Amperes with Power Circuit Breakers," AIEE Transactions, pp. 88--, 95.. R. D. Garzon, High Voltage Circuit Breakers:Design and Applications: Marcel Dekker, Inc.,996.. Shui-cheong Kam Modelling of Restriking and Reignition Phenomena in Threephase Capacitor and Shunt Reactor Switching. Allan Greenwood. Electrical Transients in Power Systems. Wiley, New York, NY.