Traditional Culture Encyclopedia - Photography and portraiture - Arrester measurement principle and performance judgment of zinc oxide arrester live tester
Arrester measurement principle and performance judgment of zinc oxide arrester live tester
Arrester measurement principle
To determine whether a zinc oxide arrester is aging or affected by moisture, we usually observe the changes in the resistive current flowing through the zinc oxide arrester under normal operating voltage, that is, observing the resistive leakage current. Whether it increases is used as the basis for judgment.
The resistive leakage current often only accounts for 10% to 20% of the full current. Therefore, it is difficult to determine the changes in the resistive current of the zinc oxide arrester just by observing the changes in the full current. The resistive leakage current is separated from the total current.
This tester relies on the voltage reference signal to collect the reference voltage and arrester leakage current at high speed. Through the harmonic analysis method, it performs fast Fourier transform and calculates the resistive components (fundamental wave, harmonics) and capacitive components respectively. Portions etc.
Resistive current fundamental wave = full current fundamental wave·cosφ, φ is the phase angle difference between the full current and the voltage fundamental wave. As shown in Figure 17:
Figure 17
Judgement of arrester performance
(1) The fundamental wave component of the resistive current increases greatly, but the harmonic content does not increase When it is obvious, it usually shows severe pollution or moisture.
(2) When the content of resistive current harmonics increases greatly and the fundamental wave component does not increase significantly, it generally manifests as aging.
(3) Only when the arrester is uniformly degraded, the bottom capacitive current does not change. When uneven degradation occurs, the bottom capacitive current increases. When half of the arrester is degraded, the bottom capacitive current increases the most.
(4) Interphase interference has an impact on the test results, but does not affect the validity of the test results. The longitudinal comparison method of historical data can better reflect the operation of zinc oxide arresters.
(5) The performance of the arrester can be judged from the resistive current fundamental wave, or it can be more effectively judged from the current-voltage phase angle difference 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°: Performance <75° 75°~79° 79°~83° 83°~89° Φ Good among differences (6) Due to various manufacturers The product structures, materials, processes, etc. are different, so the arrester parameters are different. Therefore, there is no unified standard for the live test data of zinc oxide arresters.
Judgment can only be made based on comparison with the previous test results. When the test results double, the arrester should be taken out of operation and conducted laboratory tests to determine whether there is a problem with the arrester!
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