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Li W.,Hunan Electrical Power Dispatch and Communication Bureau | Chen J.,Hunan Electrical Power Research Institute | Jiang M.,Hubei Engineering University | Hu Z.,Hubei Engineering University | Cheng X.,Hubei Engineering University
Dianwang Jishu/Power System Technology | Year: 2012

The influences of zero-sequence mutual inductance between the two circuits and capacitive current on zero-sequence current compensation coefficient were analyzed while the two circuits of double circuit transmission lines on the same tower are operated independently. A mathematical model of ground distance protection was derived, and based on traditional ground distance protection a new method to set zero-sequence current compensation coefficient was proposed, i.e., the zero-sequence current compensation coefficient was regarded as the sum of original zero-sequence current compensation coefficient, additional zero-sequence current compensation coefficient and additional capacitive current compensation coefficient, meanwhile the computing formulae of the three zero-sequence current compensation coefficients were given. Results of PSCAD-based simulation showed that when the setting range was eighty percent of total length of the transmission line and the fault occurred at the end of the transmission line, the fault position could be reflected by the proposed method more precisely than by traditional methods, besides, the first zones within the protection regions measured from both ends of the transmission line could be overlapped, thus the performance of ground distance protection for double-circuit transmission lines on the same tower could be improved. Source


Yang L.,Hunan University | Zhang W.,Hunan Electrical Power Dispatch and Communication Bureau | Zhou Y.,Hunan Electrical Power Dispatch and Communication Bureau | Liao F.,Hunan HDWL Electrical and Information Technology Co. | And 3 more authors.
Dianwang Jishu/Power System Technology | Year: 2011

To avoid the adverse effects of load transfer, power supply interruption and small power sources in 220 kV power supply region on bus load forecasting, a method to indirectly forecast bus load is proposed. Firstly, the bus-supplied load is transferred into ideal load located in the region supplied by this bus; then regarding this ideal load as historical load data, the bus load is forecasted by system load forecasting algorithm to attain preliminary forecasting result, meanwhile the values of influencing factors in the forecasted day are obtained; finally, discarding various values of influencing factors from the preliminary forecasting result, the bus-supplied load is indirectly forecasted. Case study results show that applying the proposed method to the bus load forecasting under the condition that there are small power sources in the bus-supplied region, the bus load forecasting results are much accurate than those forecasted by direct forecasting method in which the bus-supplied load is taken as historical load data. Source


Li W.,Hunan Electrical Power Dispatch and Communication Bureau | Tang J.,Hunan Electrical Power Dispatch and Communication Bureau | Yu Y.,Hunan Electrical Power Dispatch and Communication Bureau | Hu Z.,Hubei Engineering University | And 3 more authors.
Dianwang Jishu/Power System Technology | Year: 2011

Based on the simultaneously measured data of three-phase voltages and currents at both ends of transmission line by global positioning system (GPS), an approach to measure positive-sequence parameters of HV transmission line, in which the simultaneously measured two-terminal information of voltages and currents of transmission line is used, is proposed. The procedures of measuring positivesequence parameters as well as calculation formulae for positive-sequence impedance and capacitance, in which the influence of distributed capacitance is taken into account, are given, and the hardware structure of the measuring system is described. Results of simulation and actual measurements show that the proposed approach is feasible. Source

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