Short Circuit Current Calculation. Dispatcher Training Simulation Module Improvements

The development of large-scale power system network and the power market has given DTS an increasingly significant role in the power system simulation. The calculation of short-circuit current is an important and basic module of DTS, whose precision and speed has a direct impact on the fixed-value calculation in relay protection as well as the precision of transient stability calculation in dynamic simulation. Based on the process of short-circuit current calculation, this paper attaches an emphasis on improving the methods of mathematic model formulation and current calculation, with an aim to optimize the performance of short-circuit calculation to meet the emerging demands in the operation and simulation of modem power system. In addition, it is useful for DTS that improving the method of input data acquisition, then this paper also take it into account.A key step in the calculation of short-circuit current is the formation of nodal impedance matrix. There are two traditional methods for this problem, both of which had received wide application in different periods. When it comes to the question of which one is better, the conclusion turns out to be varied under diverse circumstances. It will be illustrated in this paper that under identical conditions, adding transmission line algorithm has a substantial predominance over bus admittance matrix algorithm in terms of calculation speed, which lays the foundation of former's position in the calculation of short-circuit current.The traditional adding transmission line algorithm has two major shortcomings, which can be effectively improved by comparing bus relationship degree and increasing branches not truely connected to ground. These two methods can resolve the problem of too much redundance in calculation so as to step up calculation efficiency.The ultimate purpose of short-circuit calculation is branch current calculation. Compared with entire-network calculation, calculation by-class is capable of tremendously reducing its occupancy of memory so that branch current calculation is applied exclusively to the branched severely affected by short-circuit faults. The speed of calculation can thus be raised.Lastly, this paper takes the power network in Shanxi region as an example for calculation. The results calculated respectively by programs before and after optimization are compared and analyzed in respect of the precision and speed of short-circuit current calculation. Results show that the program after three parts of optimization can improve the performance of calculation to some degree, especially in the speed of calculation.