How to use a megohmmeter to simply measure the quality of primary detuning on site

The primary detuning device is used in 6-35kv neutral point ungrounded system and is connected in series between the voltage transformer and the neutral point. It can limit the overvoltage caused by ferromagnetic resonance and the overcurrent flowing through the high-voltage transformer when single-phase grounding or arc grounding occurs.

Made of SiC nonlinear material, it has the characteristics of good heat dissipation, small size, large heat capacity, etc. It is used in a variety of voltage transformers.

Many users on site mainly use multimeters for measurement. Since the voltage of the multimeter is low, some use 9V batteries, some even use 3V batteries, and SiC is a nonlinear material, the error is large. Many use digital multimeters, and the internal resistance is different, so the error will be greater.

The simple method is to use a megohmmeter: a 500V megohmmeter, or a 1000V megohmmeter.

(1) For a 10kV primary detuning device, at 500V, the current is about 4mA and the resistance is about 125KΩ; at 1000V, the current is about 10mA and the resistance is about 100K.

(2) For a 35kV primary detuning device, at 500V, the current is about 0.35mA and the resistance is about 1400KΩ; at 1000V, the current is about 1mA and the resistance is about 1000K.

If the measurement is within this range, it means that the primary detuning device is not damaged and can continue to be used. If it has been used for a long time, simply follow this process to perform precise measurement.