SCT4xxx | Differential current transformers

Differential current transformers measure residual/fault currents (also called ground fault currents or insulation leakage currents), that can be used to determine the insulating state of machines and whether they require maintenance and repairs to prevent emergency shutdowns. Real-time monitoring of fault currents in the power supply enables the state of the electrical insulation to be evaluated based on actual measured values, while the long-term trend of the fault current value can be used for maintenance planning. This means that residual current monitors (RCMs) can detect faults in a timely manner and increase the availability of power supplies or plants at a much lower cost than conventional, expensive, and time-consuming high-voltage insulation testing.

These fault currents can originate from various sources, such as insulation faults, insulation leakage currents, capacitive displacement currents, or EMC filter leakage currents. While some fault currents are in a ‘normal’ range, others are causes or signs of deteriorating insulation that can lead to abnormal heat dissipation, short circuits, and – in the worst cases – fires and personal safety hazards.