Theoretical And Experimental Research On Distribution Automation And Service Reliability

In today's competitive market, power utilities company are expected to provide good quality and reliable power supply at low cost to their consumers. Distribution Automation is the primary way to increase service with low system operational cost.Between 2003 and 2004, Haining Power Company improved and enhanced the Zhejiang Haining area medium voltage power distribution system by upgrading the network. The Author was involved in the design and construction of the Hongzha-Guangfu distribution automation system.The dissertation used part of the problems encountered during the course of the project, to discuss ways to improve and enhance power service quality and reliability from two perspectives, one problem in the area of fault location and the other is optimal switches location scheme.Automatic circuit breakers are generally employed in power distribution lines and are installed in series in the network, to separate feeders into several sectors, this makes it easier to locate and automatically disconnecting the part of the system in trouble to prevent excessive damage and to confine the trouble to the smallest possible part of the system, and simultaneously re-establishing service to other sectors unaffected by the fault within the shortest possible time.The traditional method of fault location has inherent inefficiency; this paper proposes a new method that utilizes fault generated high frequency current signals to ascertain fault locations.This method first analyzes the generation mechanism of the fault transient signal on the power line. The effect of that the components of power supply have on transient current is also discussed.Theoretical analysis and experiments have shown that the characteristics resistance of a feeder line can be changed by shunt connecting the band filter circuits on the feeder, thus strengthen the spectrum energy difference between the two sides of the filter. To achieve this, filters are installed on all the sectors of the power boundaries and tuned to the same resonance frequency.Further research work shows that the boundary of the faulted area has the most distinct difference in current energy, while on other locations the energy appears comparatively weak.Based on this a fault locator is designed, the kind of control unit is proposed to reduce the burden involved in calculating the transient current energy, and helps to improve the speed, reliability of the calculation and the overall performance.During the construction of the fault locator for the system, a multiples protection scheme was designed and used in the project to prevent the possibility of not isolating the faulty sector due to micro currents signals. The scheme adopts a transient signal based as a primary measure, a recloser based method as its standby. A high level of accuracy was achieved in isolating the faulted sector.Finally considering the local economic level, the scale of customer investment ability, the relationship between the power services company and the investors, this paper proposes an optimization method of planning adequate number of location of feeder switches on the distribution and automation system, the objective is to minimize the total reliability cost as a precondition for the required level of service reliability. The Generic Algorithm (GA) is used to overcome this objective, due to the short comings in the simple Genetic algorithm, the improved Multiple population Genetic Algorithms (MPGA) is introduced to enhance the searching efficiency.