Abstract:
For the past few years, Junction transistors have been widely used for power system protection. Because of their reliability, long life and high speed of operation, they have replaced thermionic valves to a great extent. Only recently, Junction transistors have been used for phase comparison carrier protection. It is seen, that high frequency, high power transistors, which are not available, make it possible to obtain the required level of carrier output power.
One of the most important aspects of phase comparison system lies in the choice of relaying quantities. Selection of such a suitable network has been made, which produces all the relaying quantities simultaneously, while using only three main current transformers. Within this network means have been provided for an easy variation of the proportions of positive and negative sequence' components in the combined sequence output. A filter network has been used to eliminate the d.c. transient and harmonic components. Two successive equipments have been bull and thoroughly tes ted.
