By hvhipot 
Professional terminology of partial discharge detector:
1. Time window (door unit)
The time window is a circuit device designed to prevent interference signals larger than partial discharge from entering the peak detection circuit. Because some interference will inevitably be introduced during actual tests, especially when doing tests on site, the use of time windows is even more important.
The working principle of the time window is to divide the elliptical scan time base into two parts: on (highlighted area) and cut off (unhighlighted area), and the discharge pulse is placed in conduction (highlighted area) by changing the position and width of the time window. , The interference pulse is set to cut-off (not highlighted area), at this time the meter reading is the discharge pulse value, and the interference will not affect the discharge pulse value regardless of the magnitude. If the two time windows are closed at the same time, the meter reading is the peak value of the pulse on the entire ellipse.
2. Apparent discharge calibrator
The apparent discharge calibrator is a standard electric quantity generator. Before the test, it outputs a certain fixed electric quantity plus the two ends of the sample to simulate the response of the partial discharge tester when the sample is discharged under this electric quantity. At this time, adjust the scale factor. Determine the range of the partial discharge detector to measure the apparent discharge of the sample under the rated voltage during the test. Since the discharge amount is measured indirectly after comparison with a standard electric quantity generator, rather than directly measured, the discharge amount is called “apparent discharge amount”. The calibration electric quantity generator is a necessary instrument for measuring partial discharge, and its performance parameters are directly related to the accuracy of the 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, decay time, internal resistance, pulse peak value, calibration capacitance value, etc.
The rise time of the voltage waveform of the calibration pulse voltage generator is the time from 0.1U0 to 0.9U0, and the decay time is defined as the time from the peak value to 0.1U0.
3. The amount of charge q
A certain amount of charge is injected instantaneously at both ends of the test sample so that the change in the terminal voltage of the test sample is the same as the change in the terminal voltage caused by the partial discharge itself. This injection amount is the apparent charge of the partial discharge.
4. Partial discharge
Partial discharge refers to the discharge at a partial location of the insulation, and it does not constitute a penetration breakdown of the entire insulation. It contains three types of discharge: internal discharge (inside the medium), creeping discharge (on the surface of the medium), and corona discharge (at the tip of the electrode).
5. Detect impedance
The detection impedance is a device that picks up the detection signal. In use, the appropriate detection impedance should be selected according to different test purposes and the type of test product to improve the sensitivity, resolution, waveform characteristics and signal-to-noise ratio of Partial Discharge Measurement.