Low-voltage distribution network line impedance estimation method

Abstract

The invention discloses a low-voltage distribution network line impedance estimation method. According to the method, synchronous time checking is realized based on a GPS, and four current channels and four voltage channels of a power quality analyzer are utilized; and two power quality analyzers with GPSs are installed at the head end and the tail end of a line respectively, synchronous measurement of phasor values of ABC three-phase neutral line fundamental voltages and phasor values of ABCN four-line fundamental currents at the head end and the tail end of the line is proposed, impedance parameters of a neutral line and a phase line in three-phase four-line low-voltage distribution network lines are accurately estimated based on measured values, and basic parameter data is provided forlow-voltage distribution network analysis, network loss calculation and power quality state acquisition.

Description

technical field [0001] The invention belongs to the technical field of power quality control and power system analysis, and in particular relates to a method for estimating line impedance of a low-voltage distribution network. Background technique [0002] In the three-phase four-wire low-voltage distribution network, there are a large number of single-phase loads, and the load types are diverse, which makes the load fluctuations large, and the three-phase unbalanced operation state is common. The unbalanced three-phase causes current to flow in the neutral line, and the line loss increases significantly. According to relevant statistics, the distribution network line loss accounts for more than 40% of the feeder loss, which accounts for a large proportion, which brings huge economic losses to power companies, hinders the economic development of power companies, and is not conducive to the implementation of energy conservation and emission reduction policies. With the lean ...

AI Technical Summary

Problems solved by technology

Three-phase imbalance causes current to flow in the neutral line, and the line loss increases significantly

[0003] At present, in order to obtain the impedance value of 110kV and above transmission lines, the on-site measurement method is generally used before the project is put into operation. Some literatures estimate the impedance parameters of transmission lines in operation based on the phasor measurement unit (PMU); PMU is used in 10kV distribution network to estimate line impedance parameters. PMU can only measure three-phase voltage, current amplitude and phase angle. The three-phase voltage used in the literature is the line relative to the "virtual ground" (zero potential). Phase voltage phasor value, and in the actual field measurement, 10kV line has many branch lines and branch lines, and the "virtual ground" required for measurement may not be found at the measurement point, so the parameter estimation error will be caused by improper measurement wiring. even wrong

Different from the high-voltage system, the structure of the main line, branch line and branch line in the low-voltage distribution network is complex, and the actual on-site construction design drawings are often seriously lacking, and it is difficult to carry out impedance parameter testing before on-site operation; in addition, in the three-phase four-wire system , There are different wiring forms such as TN-S, TN-C and TN-C-S for the connection of the neutral line and the protection line, and it is more difficult to find a suitable "zero potential" reference point for phase-to-earth voltage measurement on site

Moreover, the calculation of the neutral line current based on the test of the three-phase current will also cause the accumulation of measurement errors and increase the error of parameter estimation.

Therefore, there is currently no effective means to obtain the impedance parameters of the phase and neutral wires in the three-phase four-wire low-voltage distribution network

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