Based on transmission-line equations and the distributed parameter model, a new approach is proposed to accurately measure the zero-sequence parameters of long-distance double-circuit transmission lines using voltages...
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Based on transmission-line equations and the distributed parameter model, a new approach is proposed to accurately measure the zero-sequence parameters of long-distance double-circuit transmission lines using voltages and currents measured at the ends of lines. The mathematical model of the proposed method is explained in detail, and the differential equations of two coupled lines with different self parameters were solved for the first time with Laplace transform to obtain all of the zero-sequence parameters. And this approach is easy to implement since the measurement process is simple. PSCAD simulation experimental results of double-circuit 500 kV transmission lines with line lengths changing from 200 to 1000 km and a comparison of the measurement results between the proposed method and the traditional method are shown. Simulation experiments validate that whether the two lines are short or long, the new approach has high accuracy even if there is system white noise and interference from other coupled lines.
Based on the demand of real projects that new overhead wires are been erected on the running wires with power flow, if zero-sequence parameters of the wires are needed, zero-sequence signals of different frequencies a...
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Based on the demand of real projects that new overhead wires are been erected on the running wires with power flow, if zero-sequence parameters of the wires are needed, zero-sequence signals of different frequencies around the basic 50 Hz can be added to the newly erected ones to generate zero-sequence signals, avoiding the short-term power down of the running wires. This paper analyses the structure of multi-coupled lines with different voltage levels, builds "double-Π-shaped" zerosequence lumped-parameter circuit model, proposes a new algorithm based on variable-frequency electrical measurement to work out the zero-sequence parameters, including self-impedance, admittance and mutual parameters of the coupled lines. Simulation experiments for double circuit and triple circuit of different voltage levels are carried out in this paper. The simulation results reveal that the circuit models and zero-sequence parameter measurement algorithms are applicable to the zero-sequence parameters measurement of power system.
Estimation of line impedances is of great interest to power system engineers. Power utility companies use different software to calculate line impedances based on the conductor and structure types. However, the calcul...
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ISBN:
(纸本)9781728145471
Estimation of line impedances is of great interest to power system engineers. Power utility companies use different software to calculate line impedances based on the conductor and structure types. However, the calculated values cannot remain accurate due to atmospheric condition. Also, due to lack of communication between the line construction, maintenance, and other departments, a line conductor/structure may be partially/totally changed without notifying the affected departments. Various estimation methods are used to dynamically obtain line impedance values. The majority of these methods use phasor measurement units (PMUs) for the impedances estimation. These methods require PMUs in the substations and fail to measure zero-sequence voltages/currents due to inadequate zero-sequence components under normal operation. The estimation of zero-sequence impedances is even more challenging for parallel transmission lines which are mutually coupled. This study proposes a method for estimating the self and mutual zero-sequence impedances for mutually coupled transmission lines using recorded fault data by protective relays. Extensive simulation results in RSCAD/RTDS indicate that the proposed approach has high accuracy in estimating the self and mutual zero-sequence impedances as well as the fault location in parallel transmission lines.
For EHV/UHV transmission lines, the effects of distribution capacitance of lines on the parameter measurement can't be neglected. A new method of measuring the zerosequenceparameters of double-circuit EHV/UHV tr...
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ISBN:
(纸本)9781457705472
For EHV/UHV transmission lines, the effects of distribution capacitance of lines on the parameter measurement can't be neglected. A new method of measuring the zerosequenceparameters of double-circuit EHV/UHV transmission lines with mutual inductance based on distribution parameter model and GPS technology is proposed. The distribution parameter model of double-circuit transmission lines is established and the independent measurement cases for both live line and no live line measurement are given. The calculation formulae for solving the zero-sequence parameters of lines are derived. The parameter measurement for double-circuit EHV/UHV transmission lines from 300 km to 1600 km is simulated and compared with the traditional measurement method. Simulation results have validated that the new method can greatly improve the accuracy of the parameter measurement of EHV/UHV transmission lines.
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