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Re: [RFI] Power Line Noise in Indonesia

To: rfi@contesting.com
Subject: Re: [RFI] Power Line Noise in Indonesia
From: Pete Smith <n4zr@contesting.com>
Date: Mon, 19 Jul 2004 13:44:39 -0400
List-post: <mailto:rfi@contesting.com>
At 10:14 AM 7/19/2004, W8JI wrote:
Slack spans with bell insulators were by far the largest
single problem at HF.

Defective insulators are a very deep pitch with little
effect from moisture, or they may actually get worse when
wet. In general most of the defective parts were bad either
wet or dry.

I actually found considerably more loose clamps and wires
than bad insulators. I don't think I found more than one or
two bad insulators out of thousands of noise complaints,
although we would sometimes change out really old bells with
newer polymer insulators since the new insulators could
tolerate having slack in the spans. ( The polymer insulators
were a long fiberglass core with a flexible plastic ribbing
to increase leakage path.)

Around here, slack spans are commonly and deliberately used whenever the positioning of poles will not permit adequate guying. Until recently the power company used standard taut span hardware for them, resulting in exactly the scenario Tom describes. I have gone around with the power company guys and shown them how these almost always are noisy, and (to their credit) they have made a big effort to replace them with rigid insulators (mounted on a steel bracket).

My favorite power pole noise involved a lightning arrestor that was mounted to the pole with two lag bolts. A woodpecker had undermined the wood at the tip of one of them, causing it to become loose, and the electrical field at that distance from the primary was high enough that arcs were occurring between the loose bolt and the bracket, even though neither was directly connected to the line. The lineman told me that it is now standard practice to attach these arrestors with only a single lag bolt; they would rather see them hanging from the line if a bracket bolt came loose, instead of having subtle problems like this.

73, Pete N4ZR
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