This paper focuses on a systematic and cumulative statistical approach for identifying symptom parameters of incipient faults in distribution feeders. The proposed method aims at providing a tool for evaluating and identifying the best and highly correlated parameters to the faults so that they could be used for incipient fault detection and feeder condition monitoring. The Laplace test statistic is adopted for trend analysis of the event log of candidate parameters and applied to actual feeder event data for online detection and monitoring purposes.

Evaluation of feeder monitoring parameters for incipient fault detection using Laplace trend statistic

A feasibility study on the characterization of incipient insulator failure for distribution fault prediction is presented. In this study, real distribution data was collected and analyzed to isolate incipient failure signatures or parameters which were expected to show distinct behaviors before and after failure incident. Several signal analysis methods were applied to isolate the parameters and a new strategy of analysis, the event-date concept, was also applied to find a relationship between nonharmonic and high frequency signal activities and imminent insulator failures.

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A study on the characterization of the incipient failure behavior of insulators in power distribution line

This paper focuses on a systematic and cumulative statistical approach for identifying symptom parameters of incip- ient faults in distribution feeders. The proposed method aims at providing a tool for evaluating and identifying the best and highly correlated parameters to the faults so that they could be used for incipient fault detection and feeder condition monitoring. The Laplace test statistic is adopted for trend analysis of the event log of candidate parameters and applied to actual feeder event data for online detection and monitoring purposes. Index Terms—Condition monitoring, hazard function, incipient fault, Laplace test statistic, trend analysis.

Evaluation of Feeder Monitoring Parameters for Incipient Fault Detection Using

The degree of pollution of an insulator polluted rapidly under a saltwater spray is observed by measurement of the leakage current, which flows between electrodes fixed on the surface of the insulator, under 30 V ac voltage. Long rod insulators were used as samples. The relation between the leakage impedance and the equivalent salt deposit density (ESDD) of the insulators was obtained under several experimental conditions. As a result, the following was found (1) the effect of the wind velocity on the insulator is small, and is especially small when the distance between the electrodes is short, (2) the effect of the distribution of the saltwater drops on the insulator is small, and (3) the leakage impedance does not depend on initial dryness of the insulator surface (and the conductance is low) before the saltwater spray. It is important that the ESDD be above a certain value, and that the distance between the electrodes be short. Furthermore, it was shown that ESDD can be estimated fairly exactly from the leakage impedance.

Relation between leakage impedance and equivalent salt deposit density on an insulator under a saltwater spray

This paper represents experimental techniques to simulate the naturally polluted high voltage insulators, under conditions that simulate the desert environment. Usually, the IEC fog method is used for testing the polluted insulators of high voltage transmission lines, but it does not simulate them under the desert pollution environments. For that reason, in this paper two other suggested techniques are added to the IEC one. The first one is to explain the performance of the polluted insulators under the dew and the second one is to explain their performance under the simultaneous fog and dew. The results of these three tests are compared with each other under different surface polluted layer conductivities. The aim of this paper is to record the leakage current and the warning voltage under different simulation weather conditions that to monitor the insulator strings before the occurrence of the flashover that of course is useful for the efficient maintenance. Also, in this paper, an attempt to simulate the flashover of the insulator in the field condition (actual outdoor condition) is presented. Where, the surface of the insulator is polluted naturally over a relatively long period, while it is permanently under high voltage.

Experimental techniques to simulate naturally polluted high voltage transmission line insulators

Apparatus is developed for monitoring the leakage current drawn by an insulator chain of a power line in a polluted atmosphere. The apparatus senses the leakage current bursts by a novel current transformer arrangement. The apparatus counts the number of bursts, whose amplitude exceeds a critical level, occurring over a preset period. If this number reaches a critical value corresponding to a potentially dangerous intensity of the insulator pollution, the apparatus transmits an alarm signal to the service crew so that they would thus clean the power line insulators in time before a sudden line outage occurs, with the entailed excessive expense, loss of power supply and annoyance to customers. Line insulator cleaning is thus carried out only when necessary, which adds to the economy of the power system operation. The apparatus was designed, built and is currently being tested in the high voltage laboratory of Cairo University. Experience with it on actual power networks will be the subject of another paper.

M. Khalifa

Papers

A new monitor for pollution on power line insulators. Part 1: Design, construction and preliminary tests