Research On Set Of Severe Operation Condition For Intelligent System Of Protective Relay Setting

Relay protection devices are one of the most important the secondary equipment of power system, which play an extremely important role in safe and stable operation of power system. The calculation of the setting value is also an essential job of the power system in operation and management. At present, the setting calculation is completed mainly by computer-aiding. After a long period of development, the software of setting calculation has already been improved better, and played an important part in the practice of relay protection. In high voltage power grid, the setting value of some non-adaptive relay protection is ob-tained through the off-line calculation and keeps invariable in operation. In order to guarantee the device running correctly in the variable operating mode of the system, the setting calculation must take into account a variety of extreme operating modes. To achieve a reasonable extreme operating mode, it should first form the set of the extreme operating mode of the system according to the protec-tion to be calculated, then make fault calculation on all the operating modes. At last, select the extreme operating mode according to the value of fault calculation results.In order to achieve a comprehensive set of extreme operating mode reasona-bly and efficiently, a new method based on graph theory is proposed in this paper. By the comprehensive analysis of the loop network topology graph, first find all the simple loops which need to be protected by setting, that is, make out the re-searching scope of the set of extreme operating mode which is required by setting calculation. Then determine the direction of branch loop current in the loop by using the method of virtual branch loop, according to the current distribution of branch loop, acquire all the key branch loops responding to the protection in the simple loop, that is, to determine all the key branch loops which can make the protection loop open, its breaking is likely to make the system running in the ex-treme operating mode. Finally, make all the key branch loops and the common operating modes store to the set of operating mode according to the extent of pro-tection. Take the Cangzhou's local loop net as the research object, set up a com-plete operating mode set by using the algorithm proposed in this paper, by calcu-lating and analyzing, the method of building up the set of extreme operating mode is correct. At last, based on the algorithm proposed in the paper and the original intelligent system of protective relay setting, applying VC++6.0 as de-velopment tools, complete visual realization of the set of extreme operation modes. There is better consistency by comparing the results generated by the computer-aided software with the theoretical value.