Leakage Current Of Surge Arrester Research Articles

Development and Experimental Evaluation of Leakage Current Measurement Sensor for Electrical Power Apparatus

Abstract Leakage current measurement plays an important role in determining the healthiness of high voltage insulation of a power apparatus. High voltage (HV) insulation degrades due to electrical, thermal and mechanical ageing and their cumulative effects, and thus the leakage current of the insulation increase over a period of time. The accurate and real time measurement of leakage current enables the utilities to on-line access the healthiness of the insulation. This paper describes about the design, development, calibration and testing of a novel non-contact type passive leakage current sensor which can be used for monitoring of various electrical devices based on the analysis of the leakage current captured by the sensor. The developed sensor has been successfully used for measurement of leakage current in oil-filled HV bushings as well as in gas insulated surge arresters. The sensitivity of the developed sensor as per its design can be in the order of few milli amperes in case of bushing and in the order few micro amperes for surge arrester monitoring. The paper also reported a novel design of bushing adapter-sensor assembly for on-line measuring the leakage current in HV bushings without using the conventional capacitive or resistive tapping based measurements. Further, results covering experimental leakage current measurement on a 420 kV bushing using the developed adapter sensor assembly have also been presented. To establish capabilities of the developed sensor with optimized design parameters, laboratory measurements of leakage current on 420 kV and 145 kV GIS surge arresters have also been carried out and reported in the paper. Third harmonic content of surge arrester leakage current has also been estimated in-line with IEC requirement to assess the healthiness of the surge arrester. Finally, suitability of the developed sensor for leakage current measurement of above power apparatus equipment has also been analyzed and discussed.

Condition monitoring of electrical assets using digital IRT and AI technique

In this paper, an advancement approach considering an infrared thermography methodology is taken into account for pronouncing and diagnosing the fault persisting in the electrical equipment. This technology is mainly focused on non-contact and non-destructive property. It is a fast and reliable technique to inspect system without any interruption. In the field of the electrified area, maintenance and reliability of transmission and distribution system are one of the most critical issue which mostly suffers from few problems like loose connection, corrosion, and unbalanced loads. The loose connection arise the sag and corrosion on wire produce the more corona loss. In this paper, non-invasive method is employed to monitor the temperature of zinc oxide (ZnO) surge arrester. Surge arrester is utilized to analyze the hot region and exercise the watershed transform for the image segmentation and hot color mapping. Detection of hot regions is resembled through dark red color. Monitoring of surge arrester leakage current (SALC) is the main consideration to solve out the problems through infra-red thermo-gram (IRT) and artificial intelligence (AI) techniques. Artificial neural network (ANN) techniques utilized monitoring the condition of arrester within input constraints; arrester temperature, ambient temperature and humidity. These constraints are implemented to find out leakage current. The proposed method detects the hotness, hot region of the ZnO arrester and a relationship between the thermal characteristic and leakage current of surge arrester for condition monitoring.

Application of leakage current parameters for technical diagnostics of surge arresters

The work presents a method for the assessment of the technical condition of gapless surge arresters based on the analysis of the leakage current waveform and harmonic components distributions. In order to diagnose the arresters a measurement set was developed that can be used in a location where the arresters have been installed. The measurements are made by supplying the set from power network (on-line method) or from the external voltage source (off-line method). Based on the measurements of maximal, mean and harmonic components values of surge arrester leakage current, for the arresters from service, values of p 1 and p 2 coefficients are calculated, which are then related to the values of p 1E and p 2E coefficients determined for new arresters, included in the database. The introduction of p 1 and p 2 coefficients allows diagnosing different types of gapless surge arresters, irrespective of the voltage level of power network in which they were installed. The results of tests of selected surge arresters were presented - diagnosed with this method - which have been subject to different types of failure during operation.

Evaluation of ultraviolet ageing, pollution and varistor degradation effects on harmonic contents of surge arrester leakage current

Metal-oxide surge arresters are one of the most important equipments for power system protection against switching and lightning over-voltages. Surge arresters leakage currents increase by the operating time. In this study, the important factors on leakage current variations such as surface contamination, ultraviolet ageing and varistor degradation have been studied. To accomplish this purpose, experimental tests have been performed on various polymer housed surge arresters. Fast Fourier transform analysis has been performed on measured leakage currents. Results show that ultraviolet radiation and varistor degradation affect resistive harmonic components, especially the third and fifth harmonics. Moreover, it is observed that surface contamination has influence on fundamental harmonic variation more than ultraviolet ageing. In addition, combination of ultraviolet radiation and pollution had more effect on leakage currents. The investigation and the discussion of the results can be used to easily analyse arresters condition leading to effective schedule maintenance.

Low Current Transformer Utilizing Co-Based Amorphous Alloys

Metal oxide surge arresters have been widely used for protection of power system networks against overvoltages caused by atmospheric discharges or malfunction of devices connected to the network. During its operation, a surge arrester structure is degradated, which can be observed as an increase of a surge arrester leakage current. This paper presents an implementation of a new, high-permeability, Co64Fe4Ni1Si15B14 amorphous alloy as a current transformer for monitoring of a leakage current in low voltage surge arresters. The characteristics of the current transformer for different loads have been measured in the system using very sensitive current-voltage converter. Experimental results confirmed that low current transformer utilizing Co64Fe4Ni1Si15B14 amorphous alloy in annealed state gives a possibility to measure a leakage current about several μA with operating frequency 50 Hz. Moreover, the results indicate that the leakage current waveforms have a different shape than a pure sine wave voltage applied to the surge arrester enabling an evaluation of the device nonlinearity as a measure of its degradation by means of a resistive component of the leakage current.