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This paper describes a case study to find the location of the voltage sag source at a petroleum industry where sags are causing undesired trips on critical loads. The network that supplies this industry is operated by basically two transmission and distribution utilities. Therefore, finding the location of the disturbance source is a first step in mitigation and decisive in allocating responsibilities.
Generally planar transformers experience significant capacitive coupling between the primary and secondary windings. A novel shielding configuration which overcomes the problems of conventional electrostatic shields is presented While the technique is focused on planar transformers, it is shown that similar benefits may be obtained with conventional transformers. The operation of the new shield relies...
In order to meet South Africa's future electricity demand, Eskom has initiated a process to evaluate the feasibility of various power generation options. Coal fired generating options are envisaged to remain a fundamental part of South Africa's power generation options. ISEP (integrated strategic electricity planning) indicated that new base load power generation will be required no later than 2011...
Exergy analysis of a 500 MWe steam turbine cycle is performed to identify the components that offer significant work potential saving opportunity. Criteria of performance relevant to the individual components are formulated. Exergy flows, exergy consumption due to irreversibilities and rational performance parameters for the turbine cycle and its components are computed by using plant operation data...
This paper investigates the effect of damping ratio zeta on the performance of Hinfin power system stabilizer (PSS). The bilinear transformation is used together with the Hinfin optimal control to design the Hinfin-PSS. Various zeta levels are obtained by varying the parameter |p1| of the bilinear transformation as guided by a certain rule-of-thumb. The effect of the variation in the zeta on sensitivity...
A dynamic fault current limiter (DFCL) based on a six-pulse thyristor rectifier is presented in this paper. With this device several possibilities are given to limit and even control fault currents. On the one hand it can switch off the limited fault current very fast by blocking the firing pulses on the other hand it is possible to have only a slight effect on the steady short-circuit current, if...
A spectral analysis of the electrical power draw of the two 5.2 MW motors driving a large grinding mill is performed to determine whether they are the source of a severe 55.8 Hz vibration. The applicable electrical and mechanical data was measured during October 2006 and recorded with a sample rate of 5 kHz over a few minutes. It is shown that the motors do not supply the mechanical system with any...
Voltage stability is one of the major concerns in competitive electricity markets. In this paper, RBF neural network is applied to predict the static voltage stability index and rank the critical line outage contingencies. Three distinct feature extraction algorithms are proposed to speedup the neural network training process via reducing the input training vectors dimensions. Based on the weak buses...
High voltage direct current (HVDC) is a technology used worldwide because of its tremendous advantages. Yet the HVDC technology is not well known and widely implemented in Africa. The purpose and aim of this paper is to introduce the HVDC technology to power utilities in Africa. The intended audience is engineers, system planners, technicians, managers, executives, economists, environmentalists, decision-makers.
There have been several cases of dielectric faults and failures in power transformers identified internationally that have been associated with system operation. This paper discusses UK examples and concludes the evidence indicates internal over- voltages arising from part winding resonance. These resonances are initiated by remote energisation, either intentionally or by the action of automatic re-energisation...
This paper describes the recent developments and proposals for Ancillary Services trading between Southern African Power Pool (SAPP) members. Ancillary services are the services, apart from energy, required to maintain reliability of the interconnected power system. Reactive power and operating reserve services maintain voltage and frequency of the interconnection within acceptable levels and in the...
China is currently pushing on constructing plusmn800 kV UHVDC power transmission projects. The Yunnan-Guangdong power transmission project to be built in 2009 will be the first UHVDC power transmission project around the world. The paper has presented insulation level and insulation coordination for the key equipment, which would be adopted in the Yunnan-Guangdong UHVDC Project. The research result...
This paper presents the basic structure parameters of 800kV DC composite insulator specimen and the pollution test scheme. The condition of 800kV DC composite insulator pollution test under whole 800kV voltage and whole structure dimension completed in STRI, which is completed first time in the world, is introduced. The study results indicate that the linear relation between the pollution flashover...
In the AC & DC hybrid system (ADHS) in China Southern Power Grid (CSG), many long-distance, huge-capacity transmission lines operate in parallel. So the reaction and performance of AC & DC system during faults and disturbances have great effect on the stabilization of ADHS. This paper sets up the detail PSCAD/EMTDC models of CSG and analyzes its dynamic performance under different kinds of...
A new approach to identify the nonlinear model of an induction machine using two generalized neurons (GNs) is presented in this paper. Compared to the multilayer perceptron feedforward neural network, a GN has simpler structure and lesser requirement in terms of memory storage which is makes it attractive for hardware implementation. This method shows that with less number of weights, GN is able to...
This paper investigates the performance of voltage regulating relays used to control on-load tap changing transformers in a meshed distribution system. Real-time digital simulation, together with hardware-in-loop connection of the actual relays, is used to investigate the performance of the relays under practical conditions in an actual distribution network. In particular, the paper focuses on the...
A simple graphical method (P. Kundur, 1993) could be used to obtain the appropriate shape and the correct complex plane location of the OOS polygons at locations where the swing traces a classical locus. The swing locus could, however, be greatly non-classical at certain locations in networks that have shunts (i.e. loads, voltage regulating shunts, etc) [1]. At locations where the swing locus is greatly...
The paper reports on research conducted in order to understand the contribution of bird streamers to transmission line faults under HVDC conditions. The research was initiated due to the lack of knowledge regarding this phenomenon under HVDC conditions. The experimental work was conducted on a model transmission line tower, which was used to suspend insulator strings of various configurations. Tests...
This paper describes the development of a detailed mathematical model of a representative study system to examine the impact of FACTS-based closed-loop control of AC power on the damping of sub synchronous torsional modes. The mathematical model is an adaptation of the IEEE first benchmark system for the study of subsynchronous resonance, extended to include a controllable series compensator and power...
A review of the condition assessment methods of porcelain insulators shows that there is motivation for further improvements particularly regarding applications in distribution systems. Acoustic and high frequency (HF) methods are quite attractive mainly due to better immunity to noise and the relative easiness with which they can be adapted to in-service monitoring applications. These methods have...
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