NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
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NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
Author: Noyafa–CCTV Tester
Guangdong Cable Fault Detection - Capacitance Current Determination Method Detailed Explanation of Capacitive Current Determination Method: During the operation of the cable, there is capacitance between the core wires and between the core wires to the ground. The capacitance is evenly distributed, and the capacitance is linearly proportional to the length of the cable. Capacitance Current Determination Method Guangdong Cable Fault Detection - Capacitance Current Determination Method Detailed Capacitance Current Determination Method: During the operation of the cable, there is capacitance between the core wires and between the core wires to the ground. The capacitance is evenly distributed, and the capacitance is proportional to the length of the cable. The linear proportional relationship, the capacitance current measurement method is based on this principle, and it is very accurate for the determination of the cable core wire disconnection fault. The measurement circuit is shown in Figure 4. The equipment used is a 1-2kVA single-phase voltage regulator, a 0-30V, 0.5-level AC voltmeter, and a 0-100mA, 0.5-level AC mA meter. Measurement steps: ① First, measure the capacitance current of each phase core wire at the head end of the cable (the applied voltage should be kept equal) Ia, Ib, and Ic.
②Measure the capacitive current Ia of each phase core at the end of the cable′, Ib′, IC′By checking the ratio of the capacitance of the intact core wire to the broken core wire, the approximate point of the broken wire distance can be initially determined. ③According to the capacitance calculation formula C=1/2πIt can be known from fU that C is proportional to I when the voltage U and frequency f remain unchanged. Because the f (frequency) of the power frequency voltage is unchanged, as long as the applied voltage is kept unchanged during measurement, the ratio of the capacitance to the current is the ratio of the capacitance.
Assuming that the total length of the cable is L, and the distance between the breakpoints of the core wire is X, then Ia/Ic=L/X, X=(Ic/Ia)L. During the measurement process, as long as the voltage remains unchanged, the ammeter reading is accurate, the total length of the cable is accurately measured, and the measurement error is relatively small.
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