Back to the Basics Event Analysis Using Symmetrical Components

Transcription

1 Back to the Basics Event Analysis Using Symmetrical Components Amanvir Sudan Schweitzer Engineering Laboratories, Inc. 218 SEL Motivation Overview Back to Basics Introduction Symmetrical components refresher Event analysis using symmetrical components Case studies Conclusions 1

2 Introduction Symmetrical Components Usage Short-circuit calculations Protective elements (67G, 59Q, 49, and so on) Impedance-based fault location Fault identification Event analysis Symmetrical Components Refresher I a1 I a2 I a I b I c I c1 I b1 I b2 I c2 Positive-sequence currents Negative-sequence currents I I I I A a a1 a2 I I I I B b b1 b2 I I I I C c c1 c2 Zero-sequence currents 2

3 E 1 I 1 V 1 Symmetrical Components Refresher I 2 V 2 3R F Z I I = I 1 = I 2 V Symmetrical Components Refresher I 1 I 2 = I 1 I 1 Z E 1 V 1 V 2 E 1 V 1 V 2 V 3R F I 2 I 3

4 General Event Report Analysis Captured fault oscillography Relay hard-coded algorithm User-set relay settings Numeric Logic Event Report Analysis Using Symmetrical Components Captured fault oscillography Anatomy of power system Relay location in power system 4

5 Symmetrical Components-Based Approach 1. Using system one-line diagram, build positive-, negative-, and zero-sequence network diagrams 2. Connect networks based on known or expected fault location and type 3. Using basic circuit theory, reduce connected networks to calculate sequence currents at relay location Symmetrical Components-Based Approach 4. Calculate phase currents at relay location and verify they match phase current waveforms recorded in event report (similar procedure applies for voltages) 5. If calculated phase currents do not match event report phase currents, change expected fault location and type, and repeat procedure from Step 2 5

6 Symmetrical Components-Based Approach Can Be Used to Accomplish Several Tasks Explain nature of fault waveforms that may not resemble classic waveforms Estimate fault location Determine or verify impedance values of various power system elements Case Study 1 System equivalent source 69 kv W1 87T W2 51 Main kv Feeder 1 51 Feeder 2 B-CØ fault 6

7 Secondary Amperes 87T Relay Fault Oscillography 4 69 kv-side 2 currents IAW1 IBW1 ICW kv-side currents IAW2 IBW2 ICW Time (ms) Sequence Network Connection E 1 SYS I 1 I 1 V 1 V 1 SYS I 2 V 2 I 2 = I 1 V 2 7

8 Sequence Currents I I ' I I ' I I A I 1 3 I 2 3 I I 3 I 3 A 1 1 I I 9 A 1 Sequence Voltages V ' (V I Z ) V ' (V I Z )

9 Phase Currents and Voltages A V 3V I Z 9 I I 9 A 1 B 1 1 V 2I Z 27 I 2I 18 B 1 C V 3V 18 I Z 9 I I 9 C 1 Phasor Diagram V C V A I B I C I A V B 9

10 Secondary Amperes Case Study 2 F4 5 kv 34.5 kv Load F1 ac Solar 1 System equivalent source F3 F2 ac dc Solar kv W1 87T W2 W3 Load dc 87T Relay Fault Oscillography.4 5 kv-side currents IAW1 IBW1 ICW kv-side currents IAW2 IBW2 ICW2 IAW3 IBW3 ICW3 51N Time (ms) 66 1

11 Kilovolts Primary Amperes Feeder Relay Oscillography C1 56 Feeder relay oscillography IA IB IC VA_kV VB_kV VC_kV VA_kV.Mag VB_kV.Mag VC_kV.Mag C-phase undervoltage element picks up for about 3 cycles 2:3: AM 64 Time (ms) E 1 F3, F4 F2 F1 T5 LOAD Case Study 2 Fault Possibilities T5 LOAD Z T5 Z Z Z LOAD Z F3, F4 F2 F1 11

12 E 1 F3, F4 I 1 T5 Case Study 2 Sequence Network Connection I 2 I 2 T5 I I Z I F3, F4 I T5 Z I Z Z I = I 1 = I 2 1Ø System equivalent source 23 kv High-side breaker Capacitor bank Case Study 3 W1 IBW4 W3 87T W2 5/51 OPEN 34.5 kv PV1 PV2 PV3 PV4 ac ac A-GØ fault ac ac dc dc dc dc Solar 1 Solar 2 Solar 3 Solar 4 12

13 Secondary Amperes Primary Amperes PV2 5/51 Relay Fault Oscillography G 51P 67G1 67P :56: PM 25 Time (ms) IA IB IC IAMag IB.Mag IC.Mag VA_kV VB_kV VC_kV 87T Relay Fault Oscillography R TRIP1 87R2 87R3 87BL 15 11:56: PM 25 Time (ms) IAW1 IBW1 ICW1 IBW4 23 kv-side currents and neutral CT current IAW2 IBW2 ICW kv-side currents 13

14 Case Study 3 87T Relay Secondary Circuit Wiring A B C A From PV1 CT Z PV2 CT IAW2 I FAULT From PV3 CT A B C Z From PV4 CT Z C B A A-G fault N From 23 kv high-side breaker CT A B C IAW2 Missing connection From capacitor bank CT From neutral CT dot polarity N 87T IAW1 IBW1 ICW1 Relay IAW2 IBW2 ICW2 IAW3 IBW3 ICW3 IAW4 IBW4 ICW4 E 1 T23 I 1 I 1 Case Study 3 Sequence Network Connection I 2 T23 I 2 I 23 I Z T23 Z Z Z T23 I I I I 14

15 Case Study 3 Sequence Current Calculations I = I = I = I + I T T23 m I I m= Z Z T23 Z I m I T23 IAW I 2 T23 IBW1 1 I 1 ICW1 2 T23 1 I2 IAW m I 2 IBW1 1 I ICW1 2 I 1 IAW ( m ) I IBW ( m ) I ICW ( m ) I m 1 IBW ICW IAW 2 m IAW1 = 21.9 IBW1 = ICW1 = m 2 3 m 1 m.25 Conclusions Event Reports Performance report card Hold valuable information about power system 15

16 Conclusions Event Report Analysis Using Symmetrical Components Provide holistic view of power system Explain non-classic fault waveforms at relay location Estimate fault location Determine or validate power system element impedance, or build relationships between fault oscillography and element impedance Questions? 16