A partial discharge test platform for power cable frequency conversion series resonance

Abstract

The invention discloses a partial discharge test platform under power cable frequency conversion series resonance, comprising: a frequency conversion power supply, an excitation transformer, a voltage divider and a reactor; the frequency conversion power supply generates a sine wave at a resonant frequency, and the excitation transformer boosts the output voltage, The reactor and the cable test product constitute an inductance-capacitance series resonant circuit, and the voltage divider measures the high voltage terminal voltage of the cable test product; the partial discharge sensor, current transformer, acquisition unit and data processing unit; the acquisition unit collects the output signal of the voltage divider, local The output signal of the discharge sensor and the output signal of the current transformer; this platform is based on the propagation characteristics of the cable partial discharge signal, and uses the ultra-high frequency sensor to detect the pulse interference signal generated by the variable frequency power supply as a reference, and the high frequency current detects the pulse signal flowing through the cable grounding line As the main signal, through the comparison of the two signals, the filtering of the pulse signal and the extraction of the partial discharge pulse signal are realized.

Description

technical field [0001] The invention relates to the field of insulation state and fault diagnosis of electrical equipment, in particular to a partial discharge test platform under variable frequency series resonance of power cables. Background technique [0002] Cross-linked polyethylene (XLPE) power cables have been widely used in urban transmission and distribution networks in my country due to their excellent electrical and mechanical properties. In order to ensure the safety and reliability of power cable operation, the insulation performance of newly completed power cable projects must be tested through withstand voltage tests. The frequency conversion series resonance withstand voltage method is considered to be the most effective withstand voltage test method because of its small equipment power, good equivalence with power frequency, and high feasibility of on-site implementation. In addition, the industry standard recommends that partial discharge test be carried o...

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Problems solved by technology

[0003] Compared with the existing technology, it is found that the Chinese utility model patent with the patent number CN00259594.X and the name "Variable Frequency Resonant Power Supply" discloses a frequency-variable resonant power supply based on SPWM modulation, which has small size and high efficiency, but it is generated by switching devices. The key to partial discharge detection under this condition is the extraction of partial discharge pulses; the patent number is CN201210010921.7, and the Chinese invention patent named "Cable Partial Discharge Signal Detection System and Method" provides a A partial discharge testing method based on a series frequency modulation resonant system, which uses detection impedance to test partial discharge signals, and uses the high-pass and low-resistance characteristics of the detection impedance method to suppress power frequency and resonant low-frequency signals, but the pulse interference generated by the frequency modulation power supply Contains a wide range of frequency domain components, and there are still some interference signals that cannot be filtered out by this method, thereby interfering with the test results; in order to further suppress the interference generated by the variable frequency power supply, the patent No. CN201210190992. The Chinese invention patent of series resonance voltage withstand partial discharge test method adopts the frequency conversion power supply of square wave modulation mode, limits the interference signal in the phase interval of the second and fourth quadrants, and uses the characteristic that the partial discharge signal appears in the first and third quadrants to conduct partial discharge tests. However, the harmonic deviation of the test system will increase the reactive power output of the variable frequency power supply and the amplitude of the interference pulse

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