[RFI] Power Line Noise in Indonesia

[Pete Smith]

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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