Zinc oxide arrester tester measurement principle and performance judgment - Database & Sql Blog Articles

Test - lowercase jpg

Kaixin micro test

Test probe P100-M3

1. Measurement principle After the input current and voltage are digitally filtered, the fundamental wave is taken out, and then the peak value of the resistive current fundamental wave Ir1p=Ix1p.cosφ is calculated by the projection method. Since the fundamental wave value is stable, the performance of the arrester is generally measured by Ir1p. The total current fundamental peak Ix1p is projected as Ir1p in the voltage fundamental U1 (E1) direction and Ic1p in the vertical direction, and φ is the current voltage fundamental phase angle, which includes the selected compensation angle (Fig. 7). Therefore, both φ and Ir1p can be used to visually measure MOA performance.

2. When the phase interference is measured in the field, the arrester is arranged in a word (Fig. 8), and the middle B phase affects the leakage current of A and C through the stray capacitance, so that the phase A φ decreases, the resistive current increases, and the phase C φ Increase, the resistive current decreases or even negative, this phenomenon is called phase interference (Figure 9). One method is to compensate for the interphase interference: assuming that the phase difference is 120° when Ia and Ic are not interfered, it is assumed that B has the same interference with respect to A and C phases; the voltage is taken as phase B, the current is taken as phase C, and φ1=φcb is measured; Take the current in phase A and measure φ1=φab; then the phase difference between phase C current and phase A current φca=φcb-φab; select the correction angle Dφ=(φca -120°) / 2, and this value is in the main The instrument can be placed in the menu; when the phase sequence is selected, the instrument will automatically perform angle compensation according to the selected phase sequence (A phase plus Dφ, phase B do not compensate, ie select 0, C phase subtracts Dφ), and it is not necessary to compensate for phase interference ( That is, the compensation angle is 0), and the arrester performance is judged from the trend of the resistive current. If allowed, you can only power up the phase to be measured to get absolute data. Laboratory measurements do not have to take into account interphase interference.

3. Lightning arrester performance judgment The arrester performance can be judged from the resistive current fundamental peak Ir1p, but it is more effective from the current voltage angle Φ, because 90°-Φ is equivalent to the dielectric loss angle. If the resistive current is specified to be less than 25% of the total current, the corresponding φ is 75°; when there is no phase interference:

When there is interphase interference, an error occurs:

The impact of this error should be taken into account in the actual measurement. Despite this interphase interference error, it is still feasible to judge the MOA performance. If only Ir1p is used, there will be several times of variation around 90°. It is better to look at the angle directly.