Wide Area Travelling Wave Fault Location Algorithm And Its Formal Verification

Rapidly and accurately locating the fault distance can reduce therepairing time for the permanent fault, and eliminate potential risks to avoidtransient fault happening. It has important significance to ensure powersystem stability and economic operation. Travelling wave fault location(TWFL) method has been widely applied in the power system because of itswide applicability and high accuracy. However, the existing TWFL systememploys the double ends method and doesn’t make use of the neighboringsubstations data. If one of its data acquisition equipment at both ends of a linefails to capture the fault transient, it will fail to give out fault location result.To record the fault transient reliably, traveling wave fault location equipmentis usually set to be more sensitive than relays and so will record more thanjust fault transients. The source of disturbances that do not trigger the relay,can be determined using the recorded traveling wave data. These disturbancesare normally associated with defective insulators which utilities can focus onreplacing during routine maintenance to avoid future problems. With the rapidgrowth of travelling wave fault location equipments, the wide area travellingwave fault location (WA-TWFL) network is formed. The neighboringsubstations data can be used to increase the reliability and accuracy of TWFLsystem. But TWFL equipments installed at substations may be supplied bydifferent manufacturers using different data models and incompatiblecommunication protocols.Based on the analysis of the wide area travelling wave propagation andthe travelling wave fault location methods, main achievements weresummarized as follows: (1) A WA-TWFL algorithm that only uses fault initial travelling wavearrival time and free from operation signal is proposed. The algorithm firstdetermines the valid calculation area of the monitored network to decreasecalculation scale and uses the shortest path and the extended double endsmethod to get possible fault point. Then, the faulty line and the distance tofault can be identified by using the judgment rules.(2) The single end travelling wave fault location method is usuallydifficult to discriminate the reflection wave of fault point. A reflection waverecognition algorithm based on construct fault waveform is presented. Thealgorithm employs wavelet transform to detect possible fault point in powersystem. Using the real time network topology and possible fault point, thetravelling wave propagation waveform can be constructed. By comparing theconstructed waveforms and real recorded waveform, the reflection wave offault point can be identified. The simulation verifies its correctness, and thefield application proves the feasibility of this method.(3) For the WA-TWFL algorithm that doesn’t use the operation signal,the preliminary selection of travelling wave arrival time and disturbance lineidentification are the key problems of the algorithm. The formal analysis andverification method was introduced. Applying linear temporal logic (LTL), thelogic of these two problems are analyzed and verified. The logic model ischecked by SPIN, which is a model verification tool. It ensures the logicalcompleteness of the WA-TWFL algorithm.(4) The travelling wave fault location equipment’s CIM model is firstbuilt. By using the modeling technique of IEC61850, the TWFL functions aredecomposed and defined. Based on the analysis of traveling wave faultlocation system’s communication interface and its data, the travelling wavefault location logic node RTFL is presented. The traveling wave fault locationequipment information model and mapping to MMS are studied to support theopen communication and interoperability.(5) Based on the analysis of the WA-TWFL master station’s architectureand functional requirements, the master station is developed. By using formal analysis and verification method, the reliability andcorrectness of the WA-TWFL system are effectively improved. The filedapplication results show the feasibility and effectiveness of the proposedWA-TWFL algorithm and the reflection wave recognition algorithm. Thedeveloped WA-TWFL system has been put into operation in the powersystem.The WA-TWFL algorithm makes use of the traveling-wave data ofvarious substations across the monitored network and therefore has betterreliability than the conventional double-end method. And the algorithm usesonly traveling-wave data, and does not require information from protectionrelays and so can be used not only to locate faults that cause replay operations,but also the location of incipient faults which only produce small disturbances.By analyzing the disturbance-traveling wave, utilities can focus on the weakpoints during routine maintenance to avoid problems, and thereby increase thereliability of power supply.