Tree Times The Charm: A Cultivated Approach To Targeted Trimming

Vegetation encroachment of overhead distribution lines is a common problem for electric utilities. Experience has shown these encroachments can be detected one to two years in advance by overcurrent assertions and/or trips in protective relays. The assertions are transient, usually lasting only a few cycles at most, so the protective relays often do not trip. Since no trip occurred, no engineering analysis of the records is carried out, and the data indicating an incipient event is wasted. Even when trips do occur, utilities often do not perform event analysis of momentary interruptions (single trip and reclose), so the data is still wasted. This paper presents a novel method for sensing encroaching vegetation using this transient relay data by a detection and filtering algorithm developed inside protective relays. The algorithm can send an encroachment alarm to engineering and/or system operators to start the process of locating the problem area for targeted, on-demand trimming. The encroachment alarm can be improved to precisely locate the encroachment location by using strategically placed fault indicators. The paper illustrates how using these indicators can refine the algorithm from three-phase detection down to the exact phase(s) involved and a small location bandwidth, ideal for targeting taps with known vegetation problems