Fault Location Principles

Transcription

1 Group Presenter March 6, Slide ault Location Principles Dr. MURR MOHN SH Västerås, Sweden KTH/EH74 Lecture 4 Dr. Murari Mohan Saha was born in 947 in angladesh. He received.sc.e.e. from angladesh University of Technology (UET), Dhaka in 968 and completed M.Sc.E.E. in 97. During , he was a lecturer at the E.E. dept.,uet. n 97 he completed M.S.E.E and in 975 he was awarded with Ph.D. from The Technical University of Warsaw, Poland. He joined SE, Sweden in 975 as a Development Engineer and currently is a Senior Research and Development Engineer at, Västerås, Sweden. He is a Senior Member of EEE (US) and a ellow of ET (UK). He is a registered European Engineer (EUR NG) and a Chartered Engineer (CEng). His areas of interest are measuring transformers, power system analysis and simulation, and digital protective relays. He holds 35 granted patents and produces more than technical papers. He is the co-author of a book, entitled, ault location on Power Networks, published by Springer, January. Group March 6, Slide Contents ntroduction One-end fault location Two-end/Multiterminal fault location ault location on distribution networks ntroduction Conclusions nformation about book on ault Location Group March 6, Slide 3 Group March 6, Slide 4 ntroduction What is a ault Locator? t is a device or apparatus placed at one end of a station, which displays the distance to fault (in km or in % of line) following a fault in a transmission line. Line section length ault distance Line Relay ault Locator L Line Relay ntroduction When a fault occurs on a line (distribution or transmission), it is very important for the utility to identify the fault location as quickly as possible for improving the service reliability. f a fault location cannot be identified quickly and this produces prolonged line outage during a period of peak load, severe economic losses may occur and reliability of service may be questioned. ll these circumstances have raised the great importance of fault-location research studies and thus the problem has attracted widespread attention among researchers in power-system technology in recent years. Group March 6, Slide 5 Group March 6, Slide 6

2 Group ntroduction ntroduction ault location is a process aimed at locating the occurred fault with the highest possibly accuracy. ault locator is mainly the supplementary protection equipment, which apply the fault-location algorithms for estimating the distance to fault. When locating faults on the line consisting of more than one section, i.e., in the case of a three-terminal or multi-terminal line, the faulted section has to be identified and a fault on this section has to be located. fault-location function can be implemented into: microprocessor-based protective relays digital fault recorders (DRs) stand-alone fault locators post-fault analysis programs March 6, Slide 7 Group March 6, Slide 8 ntroduction ault locators versus protective relays differences related to the following features: Group March 6, Slide 9 accuracy of fault location speed of determining the fault position speed of transmitting data from remote site used data window digital filtering of input signals and complexity of calculations ntroduction General division of fault location techniques: Group March 6, Slide technique based on fundamental-frequency currents and voltages mainly on impedance measurement technique based on traveling-wave phenomenon technique based on high-frequency components of currents and voltages generated by faults knowledge-based approaches unconventional techniques (fault indicators installed either in substations or on towers along the line; monitoring transients of induced radiation from power-system arcing faults using both VL and VH reception ) Voltage & Current Measurement Chains Voltage & Current Measurement Chains POWER SYSTEM v p i p VTs CURRENT TRNSORMERS CTs v s i s Matching Transformers Matching Transformers nalogue ilters nalogue ilters /D v (n) /D i (n) Group March 6, Slide Group March 6, Slide

3 Group Voltage & Current Measurement Chains Voltage & Current Measurement Chains CVT u p HV C C L CR u i Tr -SC u s URDEN Voltage ( 5 V) 4 a 3 b c i p Rp L p R s L s i s 3 CT i r Rm i e i m Lm R L Time (ms) CVT transformation under a g fault on transmission line close to the relaying point March 6, Slide 3 Group March 6, Slide 4 Voltage & Current Measurement Chains Primary and recalculated secondary currents ( 4 ) i s Time (ms) i p One-end ault Location Possibility of CT saturation under unfavorable conditions: presence of d.c. component in primary current and remanent flux left in the core Group March 6, Slide 5 Group March 6, Slide 6 One-end ault Location Error Sources One-end ault Location Reactance Effect Combined effect of fault resistance R f and load for ground faults - reactance effect ncorrect fault-type identification Mutual coupling Line parameter uncertainty, especially zero sequence X R # X # R X R # _p L _p _p Line Relay ault Locator R f Line Relay R No pre-fault power flow R Pre-fault power flow from to R Pre-fault power flow from to

4 One-end ault Location lgorithm Compensating for Remote End nfeed Effect Line section length ault distance irst Stand lone Numerical ault Locator on Commercial Use E S p L (-p) L S E R ault Locator where: D U p R L (-p)l S D S L S One-end ault Location lgorithm Compensating for Remote End nfeed Effect One-end ault Location lgorithm Compensating for Remote End nfeed Effect Case of Parallel Lines U pl D p pk K R K R 3 S L L OP p L OM (-p) L S where: U K L S L L P R U K L K3 L S L S L S where: U pl R OMOP D (-p)(s SL) S D S SL One-end ault Location lgorithm Compensating for Remote End nfeed Effect Hardware Configuration One-end ault Location lgorithm Compensating for Remote End nfeed Effect ield Results Experienced nput signals from: Line protection Trip Phase selection Measuring transformers Currents Voltages ) ) Relay input nput transformers ilter low pass Multiplexer Hold circuit nalog/digital converter Micro processor Peripheral interface adapter Collection of in parallel lines Data and program memory Parameter setting nstallation Event Results Sweden, 3 kv, 76 km P-E fault, July km 67. km (error.8%) US, 38 kv, 3.3 km ive staged faults on parallel Maximum error of 3% lines, October 983 (without compensat.) 3 Spain, 4 kv, 35 km P-E fault, March 984 Displayed in the 93 to 99% of line range 93 to 99% 4 taly, 38 kv, 88.5 km P-E fault, ebruary % (no error) 6% of line 5 Norway, 45 kv, 9.3 km P-P fault, December % (error.5%) 77% of line 6 inland, kv, 3 km P-E faults, June 985 Displayed in the 78 to 9% of line range 78 to 9% (error max.4%) 7 ndia, 4 kv, 36 km P-E faults, December 987 (no error) 76 to 78% of line Led-indykator Telemeter output Printer output

5 Optimization of One-end ault Location E d L ( d) E L Optimization of One-end ault Location {i } L d {u } im: improving fault location accuracy by introducing compensation for shunt capacitances limiting influence of uncertain parameters on fault location accuracy to get simple formulae by applying generalized fault loop model and fault model Optimization of One-end ault Location Symmetrical components approach appears as very effective technique for transposed lines and fault location algorithm is formulated in terms of these components (positive-, negative- and zero-sequence) Optimization of One-end ault Location Generalized fault loop model: U _P d L _P R ( a a a ) V V V 3 a a V a V a V a b c d, R unknown distance to fault (p.u.) and fault resistance U _P, _P fault loop voltage and current (dependent on fault type) L line impedance for the positive-sequence,, symmetrical components of the ttotal fault current a exp(j / 3) a, a, a weighting coefficients (dependent on fault type) Optimization of One-end ault Location Optimization of One-end ault Location ault loop voltage and current (in terms of symmetrical components): ault loop voltage: U _P a U a U a U Total fault current can be expressed as the weighted sum of its symmetrical components: ault loop current single line: a _P a ault loop current parallel lines: _P a a a L L a L L m L a, a, a share coefficients (dependent on fault type) a a a a, a, a weighting coefficients (complex numbers), dependent on fault type and the assumed priority for using particular symmetrical components,,, zero-, positive- and negative-sequence components of total fault current, which are to be calculated or estimated

6 Optimization of One-end ault Location Optimization of One-end ault Location ault location formula: d d R K L L L K L ( a _P _P _P a ) M fter resolving into real/imag parts the unknowns: d, R are determined sh comp sh comp sh comp L U d comp comp comp _P ( n) L a a ( ) ( ) a ( ) n n n R ( a a a ) ( ) n L Compensation for shunt capacitances of the line: i comp i d sh ( n) il i( n) i U i U i U i comp th.5d( n) Y L ( n ) U comp th.5d Y ( ) L n ( n ) U comp th.5d( n) Y L ( n).5d Y th ( n) il i( n) U i i ( d ) sh ( n) il i( n) th ( n) ) il i( n).5( d Y i Optimization of One-end ault Location Example: 4kV, 3km line; a-g fault, d=.8 pu, R = Distance to fault (p.u.).8.6 No compensation d aver. =.786 p.u. Distance to fault (p.u.).8.6 With compensation d aver. =.83 p.u. ault Location on Parallel Lines with measurements at one-end ault time (ms) ault time (ms) Due to compensation the error decreases from.94% to.3% ault Location on Parallel Lines under vailability of Complete Measurements at One End ault Location on Parallel Lines under vailability of Complete Measurements at One End V L d Traditional one-end Ls for parallel lines apply the following standard input signals: phase voltages phase currents from the faulted line zero-sequence current from the healthy line (to compensate for the mutual coupling) Limitationss of the traditional one-end Ls: pre-fault measurements are required remote source impedance data has to be provided

7 Two-end ault Location One-terminal methods have some limitations due to necessity of taking simplifying assumptions Two-end ault Location Two-Terminal methods give better results but require communications Methods using Global Positioning Satellites (GPS) - synchronized phasors from both ends Methods requiring time-tagging of events - no synchronized phasors Low-speed communications needed for two-end fault location nalyze data from two ends at a third, more convenient site Two-end ault Location Synchronized Measurements Two-end ault Location Unsynchronized Measurements ~ d [p.u.] GPS ~ ~ d [p.u.] ~ R R MU MU MU MU L d, R L d, R Two-end ault Location Unsynchronized Measurements Two-end ault Location use of incomplete measurements Need for phase alignment: sampling interval T - LT t LT LT DETECTON T "" t t = t () LT DETECTON T "" t t = t t=t = ( t) Use of incomplete two-end measurements: two-end currents and one-end voltage (x +xv) one-end current and two-end voltages (x +xv) two-end voltages (xv) two-end currents (x)

8 Two-end ault Location use of: x +xv ault location (L) function added to current differential relay Use of two-end synchronised measurements of three-phase currents and additionally providing the local three-phase voltage Two-end ault Location use of: x +xv mmunity of fault location to saturation of CTs at one line side is assured by rejecting currents from saturated CTs SYSTEM d L {i } { } D REL {v } d, R L ( d ) L { } D {i } REL SYSTEM SYSTEM jδ e V jδ e d L L d, R ( d) L COMMUNCTON STUR. pre V SYSTEM Three-end ault Location Use of measurements: synchronized three-phase currents from all (,, C) ends three-phase voltage at ault Locator bus Three-end & Multi-end ault Location PROTECTVE RELY C C C C PROTECTVE RELY V L L RESULTS T C PROTECTVE RELY Solution ault location algorithm consists of three subroutines (SU_, SU_, SU_C) and the procedure for selecting the valid subroutine SYSTEM d V C L SU_ L RESULTS T SU_C SU_ d d C C SYSTEM C SYSTEM Selection of faulted line section General algorithm:. ault distance calculation assuming the fault to be on the T, T or TC segment: 3 different results. Selection procedure is based on checking the rejection conditions: fault occurring outside the section range calculated fault resistance has negative value correctness of the estimated remote source impedances

9 ault Location Example ault Location Example () PROTECTVE RELY C C C C a-g fault at the section T, d =.6 p.u., R C =.3 C V C PROTECTVE RELY L RESULTS L T C PROTECTVE RELY Network parameters: Line: L (.76 j.35), (.75 j.65) (/km) L CL. μ/km C μ/km.8 L System :, S ( j3.693) System : i S = is System C: i S = 3 is S (.59 + j6.5735) Distance to fault [p.u.] (d ) av = Post fault time [ms] (d ) av =.6933 (d C ) av =.676 T ault resistance [] SU_ (R ) V =.33 (R C ) V = Post fault time [ms] SU_ is selected as valid one our-end ault Location Use of measurements: synchronized three-phase currents from all (,, C, D) ends three-phase voltage at ault Locator bus SYSTEM C SYSTEM D ault Location in Distribution (Medium Voltage) Networks ntroduction ault location in MV networks differs from that in HV/EHV transmission lines When a current of a faulty line is not directly available in the L, certain error is introduced when assumed the current at the substation MV line may be multi-terminal and/or contain loops what creates problem in single ended fault location n the case of MV line, there are often loads located between fault point and the busbar. Since the loads change and are unknown to the L it is difficult to compensate of them ssues for Distribution Networks Network grounding ungrounded networks Peterson s coil resistance grounded Lack of measured data for tapped loads fault on a main or on a tap? Unbalanced network configuration and load Dynamic change in a network configuration Change in conductor impedance Multiple faults

10 lgorithm Structure ault-loop mpedance Measurement Digital ault Recorder or EMTP/TP simulator currents voltages Estimation of the impedance impedance Estimation of the distance distance Which feeder short-circuited? nformation from relays and/or Cs V V k V V k k kc k k k kc k m mpedance Measured at the aulty eeder Distance to ault Estimation Phase-phase fault loop: V k Phase-ground fault loop: k pp kpp V ph k kph kn kn kpp k k V V V pp k kn 3 kn k k kc Equivalent diagram of the cable segment with fault: l fk- sk- (-l fk- ) k- sk- k R f pk- pk, ault-loop impedances for fault at the considered node Scheme of the Considered Network 5 kv/ kv sys HV LV L EMTP/TP simulation with an Utility Network Vsys S V S Rg Rtg Substation grounding

11 Scheme of Distribution Network Distance to ault Calculation from the Recorded Data dea of the feeder model representation: Current measured at the faulty feeder: eeder.8 equivalent a equivalent b equivalent c equivalent d equivalent e grounding system connection No ile ault type Estimated Distance to ault, m 9734.MT - GMR-RURW m GMR-JCG m 9734.MT - ETR-GMR m MT - GMR-RURW m GMR-JCG m MT -G GMR-RURW m GMR-JCG m MT -G ETR-GMR m ctual fault at 8999 m Distance to ault Calculation from the Recorded Data Current measured at the substation: eeder.8 No ile ault type Estimated Distance to ault, m 9734.MT - GMR-RURW m GMR-JCG m 9734.MT - GMR-RURW m GMR-JCG m MT -G GMR-RURW m GMR-JCG m MT -G GMR-RURW m GMR-JCG m Comparison of EMTP/TP simulation with recorded Stage ault ctual fault at 8999 m EMTP Simulation: Comparison with Recorded Stage ault EMTP Simulation: Comparison with Recorded Stage ault

12 Conlusions enefits of ault Location Conclusions Quick elimination of permanent fault to: minimize outage time facilitate service and maintenance minimize production losses reduce cost Pinpointing of weak spots due to temporary fault to: assist patrol in finding excessive tree growth allow rapid arrival at the site of vandalism Conclusions ccurate fault location is key to improved operations and lower maintenance cost Selection of a fault location method depends on network configuration, communications, and requirements One-terminal methods have limited accuracy Two-terminal methods give higher accuracy nalysis at convenient site using data from existing µp devices The fault location algorithm can easily be expanded to cover lines with three-terminals and even more ault location algorithm for Medium Voltage Network is based on voltage and current phasor estimation. The algorithm was investigated and proved on the basis of voltage and current data obtained from EMTP/TP simulations as well as recorded at DR experiences ault Location on Power Networks ook Series Power Systems SSN 6-87 Publisher Springer London DO.7/ Copyright SN (Print) (Online) ault Location On Power Networks ault Location on Power Lines enables readers to pinpoint the location of a fault on power lines following a disturbance. The nine chapters are organised according to the design of different locators. The authors have compiled detailed information to allow for in-depth comparison. ault Location on Power Lines describes basic algorithms used in fault locators, focusing on fault location on overhead transmission lines, but also covering fault location in distribution networks. n application of artificial intelligence in this field is also presented, to help the reader to understand all aspects of fault location on overhead lines, including both the design and application standpoints. Professional engineers, researchers, and postgraduate and undergraduate students will find ault Location on Power Lines a valuable resource, which enables them to reproduce complete algorithms of digital fault locators in their basic forms.

13 Table of Contents. ault Location - asic Concepts and Characteristic of Methods. Network Configurations and Models 3. Power-line aults - Models and nalysis 4. Signal Processing for ault Location 5. Measurement Chains of ault Locators 6. One-end mpedance-based ault-location lgorithms 7. Two-end and Multi-end ault-location lgorithms 8. ault Location in Distribution Networks 9. rtificial ntelligence pplication References (35)