The Carlisle Mosquito Online

Friday, October 15, 2004


NStar boosts circuit reliability
Momentary outages may be a thing of the past

I had almost forgotten that my old VCR starts flashing "12:00" after a power failure, but during the summer I kept getting reminded. Why wasn't I noticing the lights going out? Evidently most of these outages were very short.

I found out that my house was just one of many in Carlisle that was experiencing a rash of momentary power failures. A representative of NStar explained the situation to me as follows.

Tree branches falling through overhead wires can cause brief short circuits. And, as the Mosquito previously reported, so can pesky squirrels poking into where they shouldn't. In each such case, one of NStar's automatic circuit breakers not only opens the circuit for safety but also detects whether the fault clears by itself. If conditions are right, in a matter of seconds the "smart" breaker recloses and restores power. This action prevents a long-term outage requiring attention from a service crew.

A five-second outage, occurring during daylight or in the wee hours, can go completely unnoticed by a homeowner. But it does leave its mark by triggering those "12:00" flashers. According to NStar engineers sent in to investigate, the sensors on some of their smart circuit breakers were too sensitive. These breakers had been opening and reclosing in situations that should not have caused them to trip. I was assured by NStar that line crews followed up and adjusted the sensitivity downward.

As a further precaution, NStar's arborists made a fresh pass at tree trimming. (I restrained myself from asking whether the company had deployed any squirrel chasers to Carlisle. However, the representative did volunteer that metallic "squirrel guards" are indeed used on the overhead wiring here.) This summer's adjustments by NStar appear to be working. At my house the VCR has now kept perfect time for over a month.

A final note. Although dozens of people call NStar during a long-term blackout, almost no one reports momentary power failures. The company asks everyone to please do report them to the Customer Care Line: 1-800-592-2000. Subsequent analysis will indicate whether further system adjustments are needed and, if so, where in town.

2004 The Carlisle Mosquito