Traveling Wave Relays. Fault Location

Transcription

1 Traveling Wave Relays Determining direction requires knowing when the remote terminal detects wave front. et: tr = remote time of detection ts = local time of detection tl = travel time for line Algorithm if ( ts-tr < tl then fault in zone else not 1 Read Selected papers link ault ocation 6001.pdf (SE 6089.pdf (SE review of methods.pdf (ABB Update Text Ch4ab.PD 1

2 ault ocation Standard equipment on microprocessor based relays Single ended is desirable cheap (packaged with relay fairly reliable does not require communications inherent with traveling wave and distance relays Time is on our side 3 ault ocation Significant Problems : ine configurations Strong zero-sequence mutual coupling Multiple remote terminals (most commonly three-terminal applications arge angle differences between power system sources and the protected line Non-transposed transmission lines Can be overcome using communications and time Heisenberg uncertainty principle applies 4

3 ault ocation Single Ended undamental: Single phase single end: Z = V/I EA Z S VA I A V R I Va = Ia ( mz1 + R = m ( Ia Z1 + Ia R Va Ia R Ia Z1 [ Va Ia] [( Ia Z1 Ia] Okay if R = 0 mz Accuracy of Z1 affects accuracy of calculation of m 5 ault ocation Single Ended Single line to ground faults for multi-phase lines Need to know Z1 and Z0 Works best for radial lines ( Va I a ( Z1 ( Ia k Ia0 Ia 0 [ Vbc Ibc] [ Ibc Z Ibc] ( Ground faults Phase faults 6 3

4 ault ocation Single Ended ault locating for multi-terminal lines Two approaches: With communications Without communications Start by writing loop equations (Ohm s law Ground fault Va = m ( Ia Z1 + I R I Z1 VSA SA S ESA R V I RA V RA IERA Z1 S VSA I SA I RA VRA E SA E RA Phase fault Vbc = m ( Iab Z1 + I R I Z1 VSB SB S E SB V BC Z1 S R I BC I RB VRB V RBC E RB E SC V SC I SC (1-mZ1 I RC V RC E RC 7 ault ocation Single Ended Single ended fault calculations for multiterminal lines Two simple methods simple reactance (been there done that algorithm based on work by Takagi Reactance method Measures apparent impedance S ( IaS + Ia0 K0 + ( IaS IaR R Va = m Z X apt 1 + Va X apt = Ia ( Z1 8 4

5 ault ocation Single Ended Works well Homogeneous systems ow fault resistance ow power flow Errors caused by R : Ignore or eliminate Ignoring assumes best case scenario Elimination Use negative sequence current [ Vas Ias ] [ Z1 ( Ias + k0 3 Ia0 Ias ] 9 ault ocation Single Ended Takagi method does not use I A* or I * R Uses complex conjugate of a superposition term Requires good pre-fault data T. Takagi, et. al., Development of a New Type ault ocator Using the One-Terminal Voltage and Current Data, IEEE Transactions on Power Apparatus and Systems, Vol. PAS-101, No. 8, August, 198. Superposition term: Iφpre-fault - Iφ post-fault α = ( I φ Iφ PRE _ AUT POST _ AUT 10 5

6 ault ocation Single Ended Ground faults are so important 90% faults involve ground. R has no value (unlike quadrilateral relay Any distortion of measurement of X is bad S ( IaS + Ia0 K0 + ( IaS IaR R Va = m Z 1 + [ Vas Ias ] [ Z1 ( Ias + k0 3 Ia0 Ias ] 11 ault ocation Single Ended Accuracy dependent on accuracy of estimate of I I is usually best estimate of I for both Phase and Ground faults. Not influenced by load Not a dependent on source impedance 1 6

7 ault ocation Single Ended Influence of non co-linear systems T is accurate at one fault location only A T = A T = ( Zs + Zr + Z I total = (( 1 m Z + Zr I local ( If ( Is Z1 Va S jt ( Ias e jt ( Ias + k Ia ( Ias e ault ocation Single Ended Alternate method to get T Communicate magnitude and angle of I between relays. I TOTA = I local + I remote. requires synchronizing relays sampling clocks any single quantity angle measurement made by either relay is relative to its own internal sampling clock. 14 7

8 ault ocation Multi-Ended Dilemma: Problem: Don t know I Solution: Share current measurements Problem: Data samples must be align Solution: Synchronizing using GPS (don t trivialize Requires additional equipment and relay capability Collect data at one terminal which serves as the reference bus Must know pre-fault V 1 and I 1 from all terminals 15 ault ocation Multi-Ended Adjustment angle computed Vr 1 and IIr 1 Vas + Re 1 = Var1 Ias1 Z1 ( Var1 = Re ( Vas1 + Re ( Ias1 Z1 ( Var1 = ( Vas1 + ( Ias1 Z1 1 ( Var 1 = Vr MEASURED tan Re( Var 1 φ ADJUST Once data is aligned, there are many ways to proceed 16 8

9 ESA ault ocation Multi-Ended Method #1: Assume single fault on line V source = V remote I I V RA Z1 VSA SA V S RA IERA R Z1 S VSA I SA I RA VRA E SA E RA Z1 S VSB I SB I RB VRB E SB E RB V BC R I BC V RBC Z1 S E SC V SC I SC (1-mZ1 I RC V RC E RC 17 ault ocation Multi-Ended Method #1 continued: Vr line drop = Ir Z and Vs line drop= Is Z is a function of the distance to the fault. equate the fault voltage from both line ends solve the distance to the fault V V = Vr 1 m = Vs m Z Is Relay at Bus S ( Z Ir ( Vs Vr Z Ir Z( Is + Ir Relay at Bus S Solve for m 18 9

10 ault ocation Multi-Ended Advantages of using V and I More difficult to determine Z 0 I 0 source from tapped loads I 0 from mutually coupling from parallel lines With that being said, why use I 0? Text assumes that there are thoes that do and offers some considerations