Research on Single-phase Ground Fault Locating for Non-effectively Grounded System in Shanghai Weibin Wang Shanghai Municipal Electric Power Company, China Weibin Wang – China – Session 3 – 0084

Frankfurt (Germany), 6-9 June 2011 Contents Weibin Wang – China – Session 3 – 0084 Introduction 1 Traditional Ways to Find the Fault Spot 2 Fault Locating System 3 4 Conclusions 5 Actual Application

Frankfurt (Germany), 6-9 June 2011  Several neutral point grounding modes for 10kV grids in Shanghai  Low resistance (urban & Pudong districts)  Arc suppression coil (west district)  Ungrounded system (some small area)  Fault locating system is used in the west district Weibin Wang – China – Session 3 – 0084 Introduction

Frankfurt (Germany), 6-9 June 2011  Recently, parallel resistance has been added nearby the arc suppression coil to increase the selection accuracy of ground fault feeder Weibin Wang – China – Session 3 – 0084 Introduction

Frankfurt (Germany), 6-9 June 2011  Manual search method － time-consuming, laborious  Fault feeder selector － can’t locate the fault spot  Old fault indicator － can only locate the short-circuit faults, it can’t locate the ground faults Weibin Wang – China – Session 3 – 0084 Traditional Ways to Find the Fault Spot

Frankfurt (Germany), 6-9 June 2011 Traditional ways to find the fault spot  What is the key? － single-phase ground faults are the most frequent type of faults － traditional ways are not valid for locating single-phase ground faults － people’s requirement is rising, the demand of reliability is also rising  So, it is necessary to find a valid way to locate the ground fault quickly Weibin Wang – China – Session 3 – 0084

Frankfurt (Germany), 6-9 June 2011 Fault Locating System  Principle : signal injection method － first select the fault feeder － inform the master station － the parallel resistance will be put in and ablate it for 6 times － a characteristic current will be produced － indicators before the fault spot will detect the characteristic current, the indicators after the fault spot will not. － send data to the master station － the fault spot can be determined

Frankfurt (Germany), 6-9 June 2011  Action series: the duration time is 100ms, the interval time is 10s  Judgment : fault indicators capture the characteristics current ≥ 5 times  Factors: － In order to distinguish the characteristic current from the grid disturbance, put in and ablate the parallel resistance for several times － Considering the cooling of parallel resistance, the interval time should be enough Weibin Wang – China – Session 3 – 0084 Fault Locating System put in the parallel resistance ablate the parallel resistance t Ia 100ms 10s

Frankfurt (Germany), 6-9 June 2011  size :120*190*50mm  Installation － they are always installed evenly on trunk lines, and on each branch joints － hang it on the line, then rotate it 90 degree clockwise to close － rotate it counterclockwise to release, then take it down Weibin Wang – China – Session 3 – 0084 Fault indicators

Frankfurt (Germany), 6-9 June 2011  Functions － communication with the arc suppression coil controller － analyze and locate the fault spot, and flash it in GIS － management of fault indicators － display fault current wave － history data storage Weibin Wang – China – Session 3 – 0084 Master station

Frankfurt (Germany), 6-9 June 2011  GPRS: operation cost is high (so many indicators), RF technology: cheaper  indicators—repeater—transfer one by one--master station  433Hz, it is free  self-checking periodically Weibin Wang – China – Session 3 – 0084 Communication

Frankfurt (Germany), 6-9 June 2011 Actual Application  The system was tested strictly for many times in the lab  Applied to two 10 kV over-head lines － 54 fault indicators, 20 wireless repeaters － installation was ended in January  Result － so far, so good － part of the performance has been optimized Weibin Wang – China – Session 3 – 0084

Frankfurt (Germany), 6-9 June 2011  The fault locating system can locate single- phase ground faults, short-circuit faults, disconnection, etc  It takes full use of the existing parallel resistance, thus reduces the investment  A communication interface should be set up between the arc suppression coil controller and the master station of fault locating  In the future, we will still improve its performance, and use more widely in 10kV grids Weibin Wang – China – Session 3 – 0084 Conclusions

Frankfurt (Germany), 6-9 June 2011 Thank You! Weibin Wang – China – Session 3 – 0084