Threading method and installation position of residual current sensor

- Apr 15, 2019-

Before the threading of the residual current sensor, the phase line, N line and PE line in the power grid should be separated. The phase line and the N line must pass through the residual current sensor together, and the PE line cannot pass through the transformer. In the system, if the N line does not pass through the transformer together with the phase line, once the three-phase load is unbalanced, a current will flow through the N line, and the detector detects the current signal, that is, a malfunction occurs.

The N lines between different circuits are not connected or grounded repeatedly. Otherwise, it will cause malfunction. When the system is running, the leakage current value is too large and an alarm occurs. A large part is caused by such a situation. If the PE line passes through the transformer together with the N line and the phase line, it will also cause the rejection or malfunction of the monitoring detector.

Not all residual current monitoring needs to penetrate the phase line into the transformer. The total residual current monitoring method of the TN-S system can be excluded. It can pass only one cable through the residual current sensor. The advantage of this method is that a small residual current sensor can be used to improve the measurement accuracy; in the later stage, if the transformer fails, the maintenance is convenient.

The residual current sensor should be installed in a place that is easy to access and keep away from strong magnetic fields. There is no problem with the installation of the transformer. The transformer can be hung directly on the cable or fixed in the distribution box. Installation and switching of the upper or lower end of the circuit breaker does not affect the monitoring of the protected line. However, in order to facilitate maintenance in the future, it is better to install at the lower port of the switch. It is not necessary to power off the upper switch during power-off maintenance, and only need to disconnect the switch at this