Polymer Housed Surge Arresters Research Articles

Aspects of moisture ingress in polymer housed surge arresters

Polymers have been extensively applied in the industry, especially in energy system e.g. due to their good processability and insulation properties. However, all polymers are permeable in different extent, which requires a good knowledge about the process of permeation through these materials. In this study the moisture dynamics of four different surge arresters were studied in several ways,—at first by analysing the moisture diffusion properties of the housing polymers and finally by testing the full arrester structures against moisture ingress. Housing polymer composites were evaluated using thermogravimetric analysis and differential scanning calorimetry while the polymers’ ability to withstand moisture diffusion was studied by water vapor transmission rate measurements. Moisture ingress behavior of the full surge arresters was examined by daily measurements of internal resistive leakage current along 30 days immersion test. Although correlations were found between the material composition and the diffusivity through the polymer, the moisture dynamic is deemed to be much more complex in the full surge arrester. Moisture permeation through separate housing material samples was typically high compared to internal leakage current formed in real arresters which highlights the main conclusion drawn,—internal structures and long term quality of interfaces are the key issues in preventing moisture induced degradation in metal oxide surge arresters.

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.

Specific Consideration on Superior Performance and Evaluation Methods of Polymer-housed Surge Arresters

It is very suitable to select the polymer materials for the housings of surge arresters (SAs), because the polymer materials are generally soft and light weight. Therefore, many kinds of polymer-housed SAs using various polymer materials have been developed, and expanding into many countries. Considering these backgrounds, the JEC technical report (JEC-TR) 23002-2008; polymer-housed surge arrester(1) has been established based on the existent relevant standards of arresters, such as JEC-2371-2003; Insulator-housed surge arresters(2) and IEC 60099-4 Edition 2.2, Metal-oxide surge arresters (MOSAs) without gaps for a.c. systems(3) in order to introduce the technology and provide a common guide for testing of polymer-housed SAs.According as the JEC-TR, the various new applications of the polymer-housed SAs, which are caused by superior advantages such as compact, light weight, safe failure mode, anti-seismic performance, anti-pollution performance and cost efficiency design, have been realized recently in Japan. Therefore, this paper gives specific consideration on the superior performance of the polymer-housed SAs and the evaluation methods of the polymer-housed SAs, because there are some issues in the existent standards to be solved.

열-기계적 스트레스가 폴리머 피뢰기의 전기적 특성에 미치는 영향

This paper describes the results of a study on the sealing integrity of polymer housed surge arrester based on the thermal mechanical test. The polymer housed surge arrester employs silicone insulating materials for its housing, instead of the conventional porcelain housing. The polymer housed surge arresters exhibited the highest sealing integrity because it is not air volume between the FRP(fiber reinforced plastics) module and the silicone housing. In accordance, the sealing integrity of station class surge arresters is investigated with moisture ingress test. And, the influence of sealing integrity was evaluated through such as measurement of the deflection, reference voltage, leakage current. In electrical characteristics, reference voltage decreased in the range of <TEX>$16.45{\sim}16.15\;kV$</TEX> with after thermal mechanical test. In contrary, despite the continued moisture ingress, the polymer housed surge arresters exhibited almost the same leakage current value and the resistive leakage current has risen slightly. As a results, It was thought that the polymer housed surge arresters shows good stability with sealing integrity.

Multistress accelerated aging of polymer housed surge arresters under simulated coastal Florida conditions

Long-term performance of polymer housed surge arresters under multistress accelerated conditions simulating coastal Florida service environment in the lab has been presented. Commercial 9 kV ethylene propylene silicone blend (EPSB) and silicone rubber (SiR) arresters were procured and used for this purpose. Multi-stress aging was used to realistically and meaningfully simulate the actual service environment that has the synergy of several environmental stresses. The various stresses applied include ultraviolet-A radiation (UVA), rain, heat, clear mist, and salt fog. Summer and winter weather cycles were designed to apply these stresses cyclically as they occur in the service environment. This method provides a comprehensive evaluation of the insulator, the hardware and its attachment. Coastal Florida conditions were chosen as the year-around warm temperatures and the high humidity challenge any insulating material, ceramic or polymeric. The evaluation was conducted for a period of 15 simulated service years of aging (15 lab-years) in the multistress accelerated aging chamber. Compared to the unaged (virgin) sample, the EPSB arresters showed chalking, reduced hydrophobicity, and reduction in hydrocarbon (CH) group molecules in the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements. The SiR arrester surfaces showed no noticeable changes in the FTIR measurements. However, scanning electron microscopy (SEM) micrographs indicated increased surface roughness and disintegration of the material for both the SiR and EPSB surfaces. Research results indicated that multistress accelerated tests are desirable since they reflect the real world.

Salt fog testing of polymer housed surge arresters

This paper deals with the evaluation of the insulation design of polymer housed surge arresters for distribution lines. Five commercial designs were tested in a salt fog chamber for 9 cycles using a cycle consisting of 120 hours of salt fog that was followed by a 48 hour rest period for a total of 1280 hours of salt fog. In these tests, the specification for the 1000-hour salt fog test in IEC 1109 for composite insulators was used as a guide. The results demonstrate that a comprehensive evaluation of the external and internal insulation design of polymer housed surge arresters can be obtained by performing a salt fog test, and as such, the test can be considered as a useful design test. Suggestions for improvements in the insulation design of all polymer housed surge arresters evaluated are given in the paper.

Watts loss of polymer housed surge arresters in a simulated Florida coastal climate

Polymer housed surge arresters, evaluated under accelerated conditions of a Florida coastal climate, are shown to exhibit an increasing watts loss characteristic with service life corresponding to the aging of their polymer housings. Surge arrester housings made of materials other than silicone rubber are shown to age more rapidly and, therefore, show significantly higher watts loss with service life. Lifetime energy costs of polymer housed surge arresters will need to factor in the watts loss of the housing due to wet surface contamination.

Multistress aging tests of polymer housed surge arresters

The combined stresses in multistress aging tests produce cumulative accelerated effects on polymer materials and surge arrester constructions that simulate typical service aging. The aging of polymer housed surge arresters is manifested by increased watts loss (internal, external or both), external flashover, or internal failure. Multistress testing is able to demonstrate deficiencies, with respect to aging, of surge arrester materials and designs, including the nature of interfaces in the insulation design. Therefore, multistress testing is believed to be a suitable test for evaluating the aging performance of surge arrester designs. Surge arrester housings made of materials other than silicone rubber are shown to age more rapidly and to require greater creepage distance than silicone rubber to maintain equivalent watts loss levels in multistress tests.