Selective relay system of the 66,000-volt ring of the duquesne light company: Ground selector for ungrounded three-phase distribution systems: The distance relay for automatically sectionalizing electrical net works

R. N. Conwell: Mr. Sleeper's paper gives an example of one of the methods of determining whether relays are correctly set for selective operation. There is another method, that of keeping accurate records of relay operations in service, which will give equally good results but these are not obtained as promptly as by applying actual short-circuit tests. The expense, however, is much less and it is the only method applicable to those systems in which the transmission cannot be taken out of service for tests. Both methods must be preceded and followed by the same careful analytical study which Mr. Sleeper has given to his problem.