Prediction of switching transients in high voltage air-insulated substations

Describes the process of prediction of switching transients in high voltage air-insulated substations

Computation of transient electromagnetic fields due to switching in high voltage substations

Switching operations of circuit breakers and disconnect switches radiate transient electromagnetic fields within high-voltage substations. The generated fields may interfere and disrupt normal operations of electronic equipment. Hence, the electromagnetic compatibility (EMC) of this electronic equipment has to be considered as early as the design stage of substation planning and operation. Also, microelectronics are being introduced into the substation environment and are located close to the switching devices in the switchyards more than ever before, often referred to as distributed electronics. Hence, there is the need to re-evaluate the substation environment for EMC assessment, accounting for these issues. This paper deals with the computation of transient electromagnetic fields due to switching within a typical high-voltage air-insulated substation (AIS) using the finite-difference time-domain (FDTD) method

A frequency-based RF partial discharge detector for low-power wireless sensing

Partial discharge (PD) monitoring has been the subject of significant research in recent years, which has given rise to a range of well-established PD detection and measurement techniques, such as acoustic and RF, on which condition monitoring systems for highvoltage equipment have been based. This paper presents a novel approach to partial discharge monitoring by using a low-cost, low-power RF detector. The detector employs a frequency-based technique that can distinguish between multiple partial discharge events and other impulsive noise sources within a substation, tracking defect severity over time and providing information pertaining to plant health. The detector is designed to operate as part of a wireless condition monitoring network, removing the need for additional wiring to be installed into substations whilst still gaining the benefits of the RF technique. This novel approach to PD detection not only provides a low-cost solution to on-line partial discharge monitoring, but also presents a means to deploy wide-scale RF monitoring without the associated costs of wide-band monitoring systems

Time domain analysis of switching transient fields in high voltage substations

Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

Development of an integrated low-power RF partial discharge detector

This paper presents the results from integrating a low-power partial discharge detector with a wireless sensor node designed for operating as part of an IEEE 802.15.4 sensor network, and applying an on-line classifier capable of classifying partial discharges in real-time. Such a system is of benefit to monitoring engineers as it provides a means to exploit the RF technique using a low-cost device while circumventing the need for any additional cabling associated with new condition monitoring systems. The detector uses a frequency-based technique to differentiate between multiple defects, and has been integrated with a SunSPOT wireless sensor node hosting an agent-based monitoring platform, which includes a data capture agent and rule induction agent trained using experimental data. The results of laboratory system verification are discussed, and the requirements for a fully robust and flexible system are outlined

UHF diagnostic monitoring techniques for power transformers

This paper initially gives an introduction to ultra-high frequency (UHF) partial discharge monitoring techniques and their application to gas insulated substations. Recent advances in the technique, covering its application to power transformers, are then discussed and illustrated by means of four site trials. Mounting and installation of the UHF sensors is described and measurements of electrical discharges inside transformers are presented in a range of formats, demonstrating the potential of the UHF method. A procedure for locating sources of electrical discharge is described and demonstrated by means of a practical example where a source of sparking on a tap changer lead was located to within 15 cm. Progress with the development of a prototype on-line monitoring and diagnostic system is reviewed and possible approaches to its utilization are discussed. New concepts for enhancing the capabilities of the UHF technique are presented, including the possibility of monitoring the internal mechanical integrity of plant. The research presented provides sufficient evidence to justify the installation of robust UHF sensors on transformer tanks to facilitate their monitoring if and when required during the service lifetime

Monitoring contamination level on insulator materials under dry condition with a microwave reflectometer

Current techniques used for monitoring the levels of contamination on high voltage insulators, such as leakage current and infrared, are not effective in dry conditions since they require the surface of the insulator to be wetted by fog, rain or snow. If a buildup of contamination occurs during a prolonged dry period prior to a weather change there will be a significant risk that flashover may occur before there is time to implement preventative maintenance. Previous work has demonstrated the use of microwave radiometry to determine the levels of contamination on an insulator material under dry conditions, however practical applications are limited by low sensitivity. This paper reports the development of a novel technique based on microwave reflectometry to detect the power levels reflected from the surface of the insulator material. The level of contamination is then determined as a function of received power. A theoretical model establishes the relationship between equivalent salt deposit density levels on insulator surface and the dielectric properties of the contamination layer. A Finite Difference Time Domain (FDTD) model is used to simulate the total loss as a function of the contamination level. Experimental results verify the FDTD model and demonstrate the sensitivity of the reflectometer system to be approximately 100 times greater than the radiometer system. Therefore, the reflectometry system has considerably greater potential for practical applications to provide advance warning of the future failure of insulators under dry conditions for both HVDC and HVAC systems

Feasibility study on application of microwave radiometry to monitor contamination level on insulator materials

This paper introduces a novel method for monitoring contamination levels on high voltage insulators based on microwave radiometry. Present contamination monitoring solutions for high voltage insulators are only effective in predicting flashover risk when the contamination layer has been wetted by rain, fog or condensation. The challenge comes where the pollution occurs during a dry period prior to a weather change. Under these conditions, flashover can often occur within a short time period after wetting and is not predicted by measurements taken in the dry period. The microwave radiometer system described in this paper measures energy emitted from the contamination layer and could provide a safe, reliable, contactless monitoring method that is effective under dry conditions. The relationship between equivalent salt deposit density and radiometer output is described using a theoretical model and experimentally verified using a specially designed X-band radiometer. Results demonstrate that the output from the radiometer is able to clearly distinguish between different levels of contamination on insulator materials under dry conditions. This novel contamination monitoring method could potentially provide advance warning of the future failure of wet insulators in climates where insulators can experience dry conditions for extended periods

A technoeconomic assessment of microalgal culture technology implementation for combined wastewater treatment and CO2 mitigation in the Arabian Gulf

A technoeconomic assessment (TEA) has been conducted of the feasibility of large-scale application of microalgal culture technology (MCT) to the combined mitigation of CO2 emissions from flue gases and nutrient discharges from wastewater in the Arabian Gulf. The assessment has incorporated the selection of the algal species and MCT technologies, the extent of nutrient removal, and the biomass/biofuel production rate. The cost benefit of the abatement of pollutants (in the form of CO2 and nutrient discharges) was included by assigning appropriate credits to these contributions. The overall economic viability was quantified as the break-even selling price (BESP) of the generated biocrude, taken to be the price at which the product must sell to cover the operating expenditure (OPEX). Based on available information and optimal operational conditions, the BESP was calculated as being $0.544 per kg biomass, equating to$0.9 L−1 for the extracted biocrude, the credited items contributing ˜14% of this figure. The BESP was found to be most sensitive to the algal growth rate μ, the BESP changing by ±24% in response to a ±20% change in μ. Whilst the terms of reference of the study are limited to OPEX contributors, the potential for sustainability associated with the innately reliably high levels of natural light in the Gulf region appear to provide auspicious circumstances for large-scale implementation of MCT. For emerging economies with a comparable climate but without a mineral oil-based economy a greater financial benefit from the proposed scheme would arise

Radio Location of Partial Discharge Sources: A Support Vector Regression Approach

Partial discharge (PD) can provide a useful forewarning of asset failure in electricity substations. A significant proportion of assets are susceptible to PD due to incipient weakness in their dielectrics. This paper examines a low cost approach for uninterrupted monitoring of PD using a network of inexpensive radio sensors to sample the spatial patterns of PD received signal strength. Machine learning techniques are proposed for localisation of PD sources. Specifically, two models based on Support Vector Machines (SVMs) are developed: Support Vector Regression (SVR) and Least-Squares Support Vector Regression (LSSVR). These models construct an explicit regression surface in a high dimensional feature space for function estimation. Their performance is compared to that of artificial neural network (ANN) models. The results show that both SVR and LSSVR methods are superior to ANNs in accuracy. LSSVR approach is particularly recommended as practical alternative for PD source localisation due to it low complexity