Wide-area Current Differential Backup Protection Program

The relay protection system of electric grid in our country is adopted the main plus backup protection. For example, the transmission line main protection generally is the high frequency pilot protection based on the double ends electric quantity (transmission line) .The backup protection is depending on the single-end electric quantity to establish the multi-zone distance protection or the time-laddered over-current protection. With this mode, it is difficult to improve both the fault clearance speed and selectivity at the same time. It is all because these relays take decision based on their local inputs and data from remote units are rarely used in their internal logic.This thesis carries on a study to a new-type of wide area backup protection scheme. It utilizes the modern high-speed communication system and the GPS time synchronism technology to collect the sampling data of every breaker, and detects the fault area through the calculation of the real-time differential current, with a timer delay, referring to the response of the local main protection to decide that time situation-oriented tripping strategy. With the tools such as the target-oriented program design philosophy, the real-time topology and the tripping function, the new protection scheme is built up. Compared to the conventional backup protection, the proposed new scheme is with a much shorter fault clearance time and reduced tripping influence area for its that time fault extended situation based integrated protection, without the match problem of zones protection reach and setting time existing at the conventional protection. The scheme will be evaluated using theexample execution to a real power system.This thesis also provides a new wide-area protection design with the AGENT model application in the relay protection of power system. Based on AGENT model and with the aid of the modern communication technology, a new-type protection scheme is established. The protection design first uses the local AGENT to gather local electric quantity and state change information about the items in protected system, then executes the proper information combination and the necessary calculation, to get the fault detected and the primary isolated .if the original action isn't get the fault cleared, with the real time fault-extended situation and dynamic topology of the network, to activate the trends AGENT to search and the form that time fault situation against isolation area and the corresponding tripping strategy. Using AGENT software with the characteristics such as high flexibly scattering dispersed distribution around the network to use the needed information resources and also the getting the relevant information merged to solve a certain problem it can take advantage of the resources of the whole network to realize the optimized integrated protection function. The instance execution proves the virtues of the protection scheme.