ABOVE GROUND DETECTION AND INTERPRETATION OF TRANSIENT SIGNALS ON UNDERGROUND POWER DISTRIBUTION-SYSTEMS

A relatively simple system for recording any high voltage/current tran sients that occur on underground power distribution systems is describ ed. Experimental data resulting from faults on two different 15kV clas s URD sytems with helical neutrals is presented. A procedure for and d iscussion of the interpretation of the data is also presented in some detail. The most obvious application is for immediate fault location b ut the remarkable reproducibility of the data suggests other applicati ons. Background. This study was carried out mainly at a special facili ty constructed at Purdue University for studying-cable fault transient s on 15 kV class URD systems with helical neutrals. Figure 1 shows the concept of the system in a pictorial schematic. The transformers (pro vided by IPALCO) were located in the High Voltage Laboratory in a thre e compartment shielded roam, on either side of a frame in which faulte d cables could be inserted. The underground cables were led out and sp read over an adjacent area of the campus as suggested in Figure 2. Mor e details concerning the facility can be found in Reference 1. Perhaps the most noteworthy fact is the complexity yet essentially per feet r eproducibility of the experimental data. Much of the detail that looks like ''noise'' in a single test record shows up identically in all co rresponding test records. What some of the lesser features are telling us is so far not always clear, but the message is very consistent.