SIIT Commemorative Publication (10 Years of International ...

10 Years of International Cooperation: FTI, Nippon Keidanren and TUSIIT Commemorative Publication, 2002entrance are economical. DA is the best solution tomonitor and control these parameters.4. Developed Algorithms for DistributionAutomation Application FunctionsDistribution networks are fed from alternativesources/substation feed-points for a reliable supply ofpower to consumers. In real time environmentdistribution network configuration changes dynamicallydue to switching. Real time network model depends onthe correctness of the network topology determined fromthe telemetered data. This research presents a networktopology processing (NTP) algorithm suitable fordistribution networks. A simple data structure fordistribution network connectivity information storage isproposed for efficient implementation of networktopology processing. The developed method has beentested on a large practical distribution network withseveral feeders (Thukaram et al, 1999a).An efficient load flow solution technique is required as apart of the distribution automation system for takingvarious control and operation decisions. A robust threephasepower flow algorithm is presented (Thukaram etal, 1999b). This method exploits the radial nature of thenetwork and uses forward and backward propagationtechnique to calculate branch currents and node voltages.The proposed method considers all aspects of threephasemodeling of branches and detailed load modeling.The merits of the method are, guaranteed convergenceeven for heavily loaded network with poor voltageprofile. The method has been tested on practicaldistribution systems with many feeders emanating fromthe grid substation with large number of nodes andbranches.The application of the proposed method was alsoextended to find optimum location for reactive powercompensation and network reconfiguration for planningand day-to-day operation of distribution networks(Jerome, 2001a).An efficient and robust state estimation solutionalgorithm has been presented (Thukaram et al, 1998).The algorithm is based on forward and backwardpropagation. The new methodology has been tested onsample systems to analyze distribution networks havinghigher R/X ratio of lines. The proposed method hasworked well regardless of the feeder r/x ratio while theconventional WLS method failed to give a solution inmost of the cases. Distribution state estimators (DSE)will also play a critical role in distribution managementsystem to estimate those real-time system states whichare unable to be obtained from the limited measurementinstruments in the distribution network. The success ofDAS largely depends on the availability of reliabledatabase of the control center and thus requires anefficient state estimation (SE) solution technique. Themethod estimates the line flows, node voltages and loadsat each node based on the measured quantities.Real-time control of the distribution system requires anestimate of the system states. Distribution, state estimatorestimates the current operating status of a distributionfeeder by using limited real-time SCADA data andhistorical load data. In modern energy managementsystem (EMS), a state estimation (SE) program processesa set of raw measurement data and provides a real-timeload flow solution which is the basis of the advancedfunction for system security monitoring and control. SEis based on the mathematical relations between thesystem state variables (node magnitudes and angles) andthe measurements. As the automation of powerdistribution progresses, it will become necessary to applystate estimation techniques as part of the DAS. SEsuitable for unbalanced three-phase radial distributionnetworks has been developed and tested on practicaldistribution network and presented (Thukaram et al,2000a).The SE cannot be executed without an adequate numberof measurements. The extension of the method to thenetwork observability analysis and bad data detection isalso discussed. The proposed method has been tested ona few sample and practical distribution networks withsimulated data for real-time measurements (Jerome,2001b).Unlike in transmission system, distribution networks maynot be provided with protective devices or circuitbreakers in each branch of the feeder. Although RTUsmay be installed at various nodes/branches of the feederfor various measurements, circuit breakers may be onlyat the substation/switching station in the network. For anyfault in the feeder, a large part of the feeder, may beisolated depending on the circuit breaker installation. Forthe purpose of speedy repair work and maintenance, it isimportant to find the exact fault location and type offault. An algorithmic approach for finding the locationand type of fault based on the three phase measurementsobtained for state estimation is presented. Results of thesimulated fault conditions on practical distributionsystems are also presented (Thukaram et al, 2000b).The advent and widespread use of high-powersemiconductor switches at the utilization, distribution andtransmission levels have made non-sinusoidal loadcurrents more common. Power quality engineering hasnow become a subject of more focused interest.Distribution Automation can improve the quality ofpower (Jerome, 2001c). When wave shapes are irregular,voltages are poorly regulated, harmonics and flicker arepresent, and then power utilization will be degraded.Power Quality enhancement trends has become a timelytopic in power engineering (Jerome, 2002)25