Abstract :
A paper was presented by the writer at the A. I. E. E. Spring Convention, held at Pittsburgh, April 24 to 26, 1923, and was published in the July 1923 issue of the Institute Journal, on the subject: ``Selective Relay System of the 66,000 Volt Ring of the Duquesne Light Company.´´ That paper described in detail the systems of relaying which are used to protect the Duquesne Ring for both short circuit and ground faults. That paper also described the service tests which were made on the ring to test the relay protection. Nearly a year has passed since the ring was put into operation with the protection described, and ample opportunity has been given to study the protective schemes under actual service conditions and to prove their practicability. This period of service has included one of the worst, if not the very worst, lightning seasons that has ever been experienced in the history of the Duquesne Light Company. Electrical storms in the Pittsburgh District, are unusually severe, both as to intensity and duration, due probably to the geographical location of the district, situated as it is at the junction of two rivers. Storms in this vicinity almost invariably seek the Ohio River Valley and follow it up to the point of junction of the Allegheny and Monongahela Rivers, after which they will continue up one of these streams. Storms of several hours duration are not at all uncommon during the height of the lightning season.
