What Is Apparent Magnitude?

Apparent discharge, according to "People's Republic of China Electric Power Industry Standard DL 417-91", refers to the injection of a certain amount of charge across the test part of a partial discharge of electrical equipment, so that the change in the terminal voltage and the terminal voltage during partial discharge The same amount. The amount of charge injected at this time is called the apparent discharge of the partial discharge, and is expressed in pico-cues (pC).

Apparent discharge, a special term for partial discharge test of power equipment, refers to the injection of a certain amount of charge across the test piece of partial discharge of the power equipment, so that the change in the terminal voltage of the sample is the same as the change in the terminal voltage during partial discharge. The amount of charge injected at this time is called the apparent discharge of the partial discharge, and is expressed in pico-cues (pC).

In fact, the apparent discharge is not equal to the actual discharge at the test point, which cannot be measured directly. The voltage waveform generated by the current pulse caused by the discharge of the test sample at the measurement impedance terminal may be different from the waveform caused by the injection pulse, but it can generally be considered that the response values read by the two quantities on the measuring instrument are equal ^[1]

The unit of partial discharge is PC. Generally, when conducting a partial discharge test, the background interference of the test site should not be too large. Generally, the background partial discharge of the transformer test site cannot exceed 2-3PC. Then use a square wave generator to calibrate the PD. Ensure that the transformer is effectively grounded before the partial discharge test ^[2]

Calibration power generator is an indispensable instrument for measuring partial discharge. Its performance parameters are directly related to the accuracy of test results.
The apparent discharge calibrator is composed of a calibration pulse voltage generator and a calibration capacitor in series. Its parameters mainly include: pulse waveform rise time. The rise time of the voltage waveform of the calibration pulse voltage generator is from 0.1U0 to 0.9U0, rather than directly measured. Therefore, the discharge amount is called "apparent discharge amount", pulse peak value, calibration capacitance value, etc. At this time, adjust the scale factor. , Determine the range of the partial discharge detector, and simulate the response of the partial discharge tester when the test sample is discharged at this power. The apparent discharge calibrator is a standard power generator. Before the test, it outputs a fixed power plus the test product. End ^[3] .