The optimum adjustment of motor protection relays in an industrial complex

n this paper a distribution network is considered supplying electricity to a number of factories belonging to one industrial complex. The costs of interruption may vary more than one order of magnitude from one factorY to another. The problem studied in this paper is how to adjust the time lags of the undervoltage protection relays in each factory in order to obtain a minimum in the total costs of interruptions of all factories together. By properly adjusting the time lags of the relays it may be provoked that factories with low interruption costs are disconnected from the network rather fast after the occurrence of a short circuit through which action the chance that a factory with high interruption cost is switched off is decreased.