• Energy Research

Many fault-location algorithms rely on a simulation model incorporating network parameters which closely represent the real network. Estimations of the line parameters are usually based on limited geometrical information which do not reflect the complexity of a real network. In practice, obtaining an accurate model of the network is difficult without comprehensive field measurements of each constituent part of the network in question. Layer-peeling algorithms offer a solution to this problem by providing a fast “mapping” of the network based only on the response of a probing impulse. Starting with the classical “Schur” layer-peeling algorithm, this paper develops a new approach to map the reflection coefficients of an electrical network, then use this information post-fault to determine accurately and robustly the location of either permanent or incipient faults on overhead networks. The robustness of the method is derived from the similarity between the post-fault energy reaching the observation point and the predicted energy, which is based on real network observations rather than a simulation model. The method is shown to perform well for different noise levels and fault inception angles on the IEEE 13-bus network, indicating that the method is well suited to radial distribution networks.

This paper reports the results of a parametric study on the characteristics of electromagnetic (EM) waves propagated due to surface- and cavity-type partial discharges (PD) in materials using the finite-difference time domain (FDTD) method. First, the EM waves emitted by such discharges in material samples were measured using a broadband aperture antenna. The measurements showed that the frequency range of the measured signals lay within the ultra-high frequency (UHF) range, suggesting that by carefully choosing the UHF antenna characteristics and its location it might be possible to apply this method to characterize the PD-emitted waves; and hence, to potentially use it to detect and monitor PD defects. In this context, the FDTD simulations were used here to simulate the experimental set-up and examine the propagation characteristics of EM waves emitted by such discharges under uniform and non-uniform test electrode configurations. Using an approximation of the exciting PD current pulses, the electromagnetic field components and the voltage signals captured on a simulated monopole sensor were computed in the time domain at various locations. To explore the limits of the application of the UHF method for detecting these PD types, a parametric study was carried out to clarify how the captured signals are influenced by the PD intensity, the frequency content of the exciting PD pulse, the type of insulation material, the dimensions and the position of the UHF antenna. One of the challenges that needs further investigation is the accurate simulation of the actual PD current pulse produced by such discharges, and hence its frequency content, as there is limited or no measured data available. The results showed that while the amplitude of the captured EM signals increase with the PD intensity, no appreciable signal is detected when the PD pulse width is higher than about 4ns, which may not occur often in unbounded air insulated systems. Equally important is the location and orientation of the UHF sensor—the results showed improved sensitivity when the sensor is vertically polarized and placed in close proximity in the lateral direction with reference to the discharge path.

Power systems under expansion suffer from escalating fault levels that impact equipment integrity, operational flexibility, and the overall security of the system. The fault current limiter (FCL) is one of approaches used by utilities to limit fault current levels and in Dubai Aluminum (DUBAL) series current limiting reactors are currently used. However, more effective (FCL) topologies are sought and, in this paper, a case study is proposed using resistive high temperature superconducting fault current limiters (HT-SFCLs). The application of HT-SCFLs is aimed here at reducing short-circuit currents, while at the same time enhancing the stability and security of the network. The study involves analysis of three-phase and single-line-to-ground faults, evaluation of the voltage levels and total harmonic distortion (THD) levels at busbars considering different fault scenarios, and demonstrates how the use of HT-SFCLs at various locations improves the plant performance. The ideal HT-SFCL model is adopted for this analysis since the aim is to look at the steady-state performance rather than the transient performance. Comparison with series reactor FCLs which are currently installed in the plant show better performance with the proposed HT-SFCL. Voltage profile values and total harmonic content were also compared with measurement data available at the plant.

This paper investigates the possible options for achieving a substantial reduction in a substation footprint using air-insulated switchgear as a more environmentally-friendly alternative to gas-insulated substations that use SF6 gas. Adopting a new approach to surge arrester location and numbers, International Electrotechnical Commission (IEC) minimum clearances can be successfully selected instead of the maximum clearances as currently adopted by many utilities, as is the case in the UK. In addition, innovative alternative compact busbar arrangements using vertical and delta configurations have been proposed by the authors. A further opportunity for compaction is offered by the application of compact and integrated technology offered from several manufacturers. The full overvoltage control within the entire substation under any surge condition is a key aspect of the feasibility of this type of substation. This work demonstrates that the new design option can be an attractive alternative for future substation configuration with minimum footprint.