When conducting a power frequency reference voltage test, as long as the surface of the high-voltage arrester is partially cleaned, the influence of the current on the outer surface of the porcelain sleeve can be eliminated. When conducting a DC reference voltage test, the current on the surface of the porcelain sleeve must be shielded by wrapping a shielding ring, because the leakage current of the reference voltage is microampere level.
The solution during operation is to use a screen ring to separate it from the internal current. Currently, there are many forms of lightning protection rings, but the general requirement is that the dimensional shielding ring must be tightly wound, and the down conductor must be a lead with an insulating layer | or the lead must have a certain stiffness to avoid contact with the insulated base of the zinc oxide arrester and shunt the internal current.
The current in the inner wall of the porcelain sleeve and the insulating bracket is microampere under normal circumstances. If it gets damp or the insulating bracket is defective, the leakage current will increase significantly. When water gets wet due to poor sealing, the pain leakage current of the resistor sheet will increase and the insulation resistance will decrease. Most of the accidents caused by the exposure are flashover along the damp inner wall or axial flashover along the zinc oxide arrester resistor sheet, resulting in a short circuit to the ground. Zinc oxide arrester model resistor sheet current.
The current of the zinc oxide arrester resistor is milliamp level. The current Iz of the zinc oxide arrester resistor is composed of the capacitive component IC and the resistive component IT. Under the operating voltage, the capacitive component accounts for a large proportion, while the resistive component accounts for a relatively small proportion. When the external voltage is a sine wave, the capacitive current is also a sine wave.
The resistive current is in phase with the applied voltage. The waveform is nonlinear and is a distorted wave containing the fundamental wave and the higher-order i-harmonic wave. The positive resistive current is a non-positive 3-wave physics. In each half-wave, the left and right half-waves are symmetrical to the straight line perpendicular to the time axis through the half-wave top. It is composed of the fundamental wave and odd higher harmonics. Since the proportion of the positive current's harmonic is very small, the voltage-equalizing capacitor current can be ignored in the calculation of the i-harmonic current.
When the applied voltage is a sine wave, the capacitive component and the resistive component are both sine waves, which is consistent with the characteristics of the zinc oxide arrester capacitive device. The total current of the voltage equalizing capacitor is composed of the capacitive component and the resistive component.
