Residual current monitoring is a technology capable of detecting fault currents in earthed power grids/electrical systems. Normally, in an electrical circuit, the sum of the currents flowing into the electrical consumers and the currents flowing out of the consumers is equal. This means there is no residual current. If a fault current flows through earth (PE) in an electrical circuit, e.g. due to faulty insulation of a cable or moisture penetrating a drive, the incoming and outgoing currents are of different magnitudes. This residual current is detected by a measuring current transformer and transmitted to the evaluation device. If a specified limit value is exceeded, the measuring device alerts the operator.

Waterworks and sewage treatment plants use numerous electrical consumers such as pumps and drives. Moisture or wetness getting in can cause fault currents in the supply lines or the consumers themselves, which can lead to pumps, drives or entire areas being shut down. Even a fault current of 30 mA will trip an RCD (residual current circuit breaker).

Since most of these fault currents do not occur spontaneously but are initially very small, they can be detected using residual current monitoring devices before the critical threshold of 30 mA is reached and the RCD trips. The monitoring devices are set to sound an alarm as soon as a specified limit value is exceeded.

This way, technical staff are informed of an electrical fault at an early stage, before the RCD trips.

The monitoring of electrical consumers using residual current measurement technology is continuous, i.e. 24/7/365. This means that operators always know the status of their electrical systems and consumers. If an error occurs, it is reported early on, long before the RCD shuts down individual consumers or entire system components.

Here is an overview of the advantages:

• Permanent monitoring 24/7/365
• Early detection of electrical faults, including alarm notification
• Avoiding spontaneous shutdown by RCD