Abstract-A trial site has been developed within a substation on the North East coast of Scotland for electrical testing high voltage composite cross-arms. A 400 kV transformer energizes two crossarms installed on a lattice tower oriented at 90 o from each other. A custom made protection system has been designed to keep the equipment within operating limits and minimize potential damage from faults. The purpose of the trial is to monitor the electrical performance of the cross-arms by measuring the leakage current on the surface of the insulating members. Weather monitoring equipment that includes a weather transmitter, a present weather detector and a solar sensor is used to correlate electrical behavior with specific weather phenomena. Cameras overlooking the cross-arms provide information regarding pollution accumulation and snow accretion. A data acquisition and control platform is responsible for recording the measurements. The monitoring system is capable of compiling and transmitting wirelessly a summary of the leakage current and weather information every five minutes.
Power supply utilities are continuously working to maintain reliable and efficient electrical networks that meet the growing demand for electricity. This is a complex task in which appropriate maintenance, refurbishment and replacement policies for all the assets are critical. Optimising business processes through these constitutes a key challenge of balancing service quality and stakeholder value. Here we present two frameworks that can be used to effectively condition monitor both ethylene propylene diene monomer (EPDM) and silicone rubber (SiR) composite insulators during their lifetime in service. The frameworks are tools to assist asset management decision making. The first framework is derived from a generalized dielectric ageing framework and a more specific one on composite insulators that points out the elements that govern composite insulator materials' ageing on power transmission and distribution lines. The second framework defines four aged states in relation to the risk to failure that a composite insulator has in service before its replacement. Properties of materials that can be measured in order to identify ageing are reviewed. The techniques available as engineering tools for measuring these properties are introduced. These are distinguished as techniques that can be carried out on-line and off-line, and as destructive and non-destructive tests. These techniques are then reviewed in the context of monitoring and maintaining reliable and efficient operation of power networks.
A number of EPDM insulators have been taken from service on a 132 kV system after eight years in a harsh environment and have been examined. Fortuitously three different insulator designs are available and compared. Two of the insulators were installed in a vertical orientation and one in the horizontal. The insulators are characterized visually, electrically and for hydrophobicity. They have been found to be fit for purpose, but show extensive superficial ageing, in particular blackening, of the polymer surfaces. No severe degradation has been identified. In particular there is evidence of discharge activity around the prominent longitudinal mould lines on all the insulators.
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