Porcelain pin insulator field inspections

Porcelain pin insulator field inspections are research method. Noise level, weather conditions and results of the laboratory performance tests were the basis for the definition of the final recommended inspection procedure.

Porcelain pin insulator

Porcelain pin insulator field inspections:
The first part of the present research considered only high outage rate feeders. However, the second part of the research, aiming at determining the influence of the weather conditions, considered all the feeders. The maintenance crews frequently observed that when at least one insulator on a pole presented a doubtful withstanding condition there is at least one outage during daily rain activity. The second part of the research took into account some techniques previously developed to increase the area coverage and extend the inspection task. Therefore, during the second part of the research, the inspections were first carried out with the radio interference detector, the M 242 antenna tuned to 40 MHz, installed on a car roof, driven through parallel roads, close to the medium voltage lines. Once a noise was detected, the pole was closely inspected by means of a radio interference antenna.

All insulators of a chosen pole were removed and substituted by the equivalent post units and sent to the High Voltage Laboratory of the Federal University of Itajubá to be tested. The insulator manufacturer, manufacturing year, main design, position on the feeder and on the pole were recorded. A special data base was built up and finally, all the “in condition” insulators were submitted to laboratory testing.

As a result, approximately 19.2% of insulators that could be considered as being undamaged were tested at the high voltage laboratory. This figure was higher if compared to the first part of the research [1], in which 11.22% of undamaged insulators were removed and tested at the high voltage laboratory. This explains part of the differences observed in these two research studies between the success and error indexes of the detector antenna.

In order to try to avoid some previous drawbacks [1], the present research considers ground measurements of relative air humidity, local temperature, and wind speed. There may be some dissent about the fact that all the weather measurements were taken from the ground and no pole height correction factor was considered. However, as a field procedure, normally carried out by non-skilled personnel, this is the most practical solution.

The noise level, weather conditions and results of the laboratory performance tests were the basis for the definition of the final recommended inspection procedure, mainly for defining the cutting limit for the noise level.


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