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Voltage uprating is a reliable method for increasing the power transfer capability of an existing overhead line. It is essential to meet the primary air clearance requirements for power frequency, switching and lightning overvoltages while evaluating the suitability to uprate the line to a higher voltage level. In this paper, a method is discussed to establish the necessary clearance envelopes for...
In recent years, uprating of existing overhead power line has become a popular option for electric utilities to address increasing demand for power. Uprating overhead line by increasing voltage allows considerable increase in power transfer capability. This paper initially examines technical issues and conventional methods of uprating the voltage of overhead transmission lines. It then considers a...
This paper presents computation results of transient stresses during energization of an MSCDN in a 400 kV system. For validation purposes, transient voltages and currents were also estimated analytically before performing a full three-phase simulation using ATP/EMTP program. Following the circuit breaker closing, instantaneous overvoltage changes of high magnitude are observed across the reactor of...
While uprating an overhead line to a higher voltage level, it is often difficult to achieve the required clearance level for the uprated structure. Use of Transmission Line Arresters (TLAs) is an effective technique in controlling overvoltages and thereby, achieving the required clearance margin. In this paper, suitability of this technique in reducing the clearance margin is discussed. A case study...
With the known greenhouse effect of SF6-insulated substations, the aim now is to reduce the size of transmission substations using air-insulated designs. In this work, a 400 kV compact substation layout is proposed adopting the lower IEC basic insulation level and switching impulse level, and consequently reduced clearances. Simulation studies using EMTP are performed to evaluate the lightning and...
The voltage rating of overhead lines is determined by a combined consideration of the stress applied to the line and its electrical strength. In this investigation, the voltage uprating of an existing `L3' 275 kV transmission line to 400 kV is explored. Minimum air clearances for 275 kV and 400 kV lines are first reviewed and the IEC recommendations for insulation coordination were considered. The...
In this paper, an investigation of current distribution on tower lines under lightning and power frequency fault conditions is carried out. An equivalent circuit model of a 400 kV double-circuit transmission line was established using EMTP and two models of differing complexity were developed. The power-frequency earth fault was simulated by short circuiting one phase conductor to the earth wire while...
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