Comparative Investigation of Pollution Accumulation and Natural Cleaning for Different HV Insulators

Abstract

High Voltage insulators are scattered throughout any HV network and a single insulator fault may cause an excessive outage. Reliability is a key issue for electric power systems and fault-free performance of insulators greatly reflects on the reliability of the system. Environmental influence is rather important for the optimum selection of outdoor insulators and, therefore, field measurements provide valuable information. Utilities perform such measurements in order to decide upon the location/route of new HV installations (substations, lines etc) and also to optimize the selection, maintenance and replacement of already installed insulators. A rather interesting case in Greek territory is the island of Crete, due to the coastal development of the network and the local weather conditions. The Greek utility has employed a variety of remedies to cope with the pollution problem. Following the positive feedback after the installation on certain tower in the past, a large project to replace all ceramic insulators with new polymer ones of hydrophobic surface is now in progress. Polymer coatings have also been extensively applied on substations and also on certain areas/towers of the transmission network in the past. In order to investigate the pollution accumulation and the impact of natural washing on different insulator types, a series of periodical ESDD and NSDD pollution measurements were conducted in HEDNO’s TALOS High Voltage Test Station for a 3-months period. Multiple measurements were performed on each insulator every month in order to collect additional data. Five different insulators were selected based on the types historically used in the Cretan Network. Along with the standard glass disc profile, two strings of glass fog profile (the one coated with RTV) and two long-rod composite insulators of different shed profile and material were used. Results are presented and discussed in this paper.

Compact Solid-State Marx Generator for Repetitive Applications

“…The total time ܶ ை required to obtain the repetitive pulses across the load is the summation of charging time of Marx capacitors ‫ݐ(‬ ), high voltage time ‫ݐ(‬ ௩ ), and switch recovery time ‫ݐ(‬ ௦௪ ) as shown in (1). Equation (2) depicts the repetitive frequency (݂ ) which is the reciprocal of total time period.…”

“…The time required for Marx capacitors to charge to the input voltage is given by (3). Equivalent circuit of solid-state Marx while charging [1,2].…”

“…The total time period for any given Marx modulator is calculated by (1). The charging time ‫ݐ‬ required for capacitors to charge is calculated as 351µs from (3).…”

“…It has many applications in fusion research, high power pulsed lasers, air pollution control, food processing, etc. [1][2]. In conventional Marx generators, the repetitiveness of the Marx generator is limited by switches and the charging method used.…”

Hybrid Grey Wolf and Finite Element Method (GWO-FEM) Algorithm for Enhancing High Voltage Insulator String Performance in Wet Pollution Conditions

“…The presence of high electric field leads to corona discharges by ionizing the surrounding air of the insulator, resulting in energy losses, electromagnetic interferences, visible light, audible noise, and the destruction of materials by erosion [10][11][12]. When the electric field stress exceeds a threshold value, especially in the presence of pollution conditions [13], flashover of the insulator string may occur. Thus, finding the insulating string design that can reduce the critical value of the electric field at the triple junction region, and at the same time reduce the weight of the insulator constitutes, a considerable advantage for improving the performance of electrical networks.…”