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

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

Remote controlled partial discharge acquisition unit

Online partial discharge (PD) analysis for underground high voltage cables has major advantages over the offline techniques. Online techniques usually involve PD data acquisition, storage and post-processing of the data. However, the data acquisition process can be time consuming and troublesome because of design procedures and protocols required before commencement of data acquisition. This paper presents a robust remote controlled partial discharge acquisition unit for underground high voltage cable networks. This system is uniquely designed to incorporate the difficulties of accessibility, especially for remotely located substations. Real field data from a 33kV network is included in the paper

Evaluation of the EMC environment generated by a static var compensator

Describes an evaluation of the EMC environment generated by a static var compensator

Analyses of partial discharges in dielectric samples under DC excitation

The main focus of the paper is to develop a better understanding of partial discharges under DC excitation. Partial discharges studied will initially be limited to discharges from well-defined discharge sites. These include corona, surface discharges and internal voids. The samples are first tested under AC excitation as a sense check to ensure the samples yield the expected PD events. The samples were then subjected to DC excitations where the PD events were recorded and subsequently analysed. A number of analysis techniques will be applied to potentially enable the identification and classification of the type of PD event occurring in the DC system under investigation

A comparison of AC and DC partial discharge activity in polymeric cable insulation

The majority of PD monitoring is performed on cables operating under AC conditions, however, the increasing use of high voltage DC links, for subsea, or long land-based connections provides motivation for the increased use of PD monitoring on cables operating under HVDC. However, despite the increased intensity of research into PD in HVDC cables, there are significant knowledge gaps, preventing the practical application of PD monitoring techniques to HVDC cables. This paper seeks to partially address these gaps in knowledge, by presenting results obtained from PD measurements on artificial voids created in polymeric cable insulation under both AC and DC conditions. This work was presented at the 21st IEEE International Pulsed Power Conference

External lightning protection system for wind turbine blades - aerodynamics.

Many wind turbine blade manufacturers have installed lightning protection systems (particularly the down conductor) internally. Having the down conductor internally within the blades would indeed preserve their aerodynamic performance. However, the blades are, as a consequence, vulnerable to damage and burn resulting from lightning strikes. Owing to this, the authors believe that by having the down conductor on the external surface of the blade, the incidence of blade damage would be reduced. The authors have not found any literature in the public domain that quantifies the effect of having an external down conductor on the aerodynamic performance. Hence, in this paper, a study of the effects of an externally mounted lightning conductor has been undertaken. Simulation studies were carried out using the computational fluid dynamics numerical method available in the COMSOL Multiphysics software package. The results of studies on single conductor arrangement have shown that the degradation on aerodynamic performance is least at the trailing edges of the blade. However, it may not be adequate for lightning protection. Therefore, using a similar numerical modelling methodology, simulations were extended and investigated on multiple conductor arrangements where conductors? locations were varied on an aerofoil surfaces. The results of the aerodynamic modelling suggested that a four conductor arrangement may be the best option as it gives more coverage for lightning protection of the wind turbine blades while still having the least reduction (of around 25%) on lift to drag ratio

Lightning protection for a temporary structure in open area

The current lightning protection systems are well proven and widely deployed for general situation. However, the methodology may be inadequate when applied to various situations especially in open area because the current BS EN and international standards do not cover guidance or procedures for lightning protection in open areas. The fundamental principle of lightning safety is ‘No place outside is safe when thunderstorms are in the area!’ The purpose of this research is to provide an outline of the lightning protection system strategy for the protection of life, livestock, sensitive equipment and property in open areas. The research proposes alternative methodology that can be used in open area for safety rather than the No-Notice personal backcountry lightning risk reduction process. Based on the results a suitable protection mechanism shall be developed to concept stag

Practical experience from industry on the lightning protection of solar PV modules

This paper reports the practical experience from industry on the performance of the lightning protection of solar PV modules, which are necessarily installed in the open. The conventional practice as per the current industry experience is to use the support frame of the solar PV module for the passage of the lightning current should it be struck. Hence, the support frames are bonded to the lightning protection system installed. This leaves other parts of the PV modules vulnerable to direct lightning strikes with the result of the lightning current flowing through the DC cable rather than the lightning protection tapes that are bonded to the frame. This, therefore, results in the electronic AC/DC invertor being subject to the direct lightning current and against which they are not protected. The paper will provide examples of such incidents and will consider and discuss how best to avoid such penetration of direct lightning in future installations. The paper will also recommend that the industrial experience be considered during the next update of the Standard when referring to protection of solar PV modules against lightning. With the current global initiative to maximise renewable energy systems it is even more important to ensure that the systems are fail safe and can last their economic life thereby delivering the desired savings