Littelfuse, Inc. has announced its RCD300M2 Differential Current Relay, designed to improve worker safety and protect equipment from dangerous electrical ground faults. To avoid nuisance tripping that occurs with conventional ground fault relays, maintenance workers tend to increase trip points above sensitive levels. However, this defeats the purpose of having a ground fault relay that is sensitive enough to protect workers from potentially life-threatening electric shock or Arc-Flash incidents. The RCD300M2 solves this problem by using unique technology that provides highly sensitive protection while avoiding nuisance trips and unnecessary equipment shutdown.

The new ground fault relay also provides features for automated monitoring and control in power distribution panels, switchboard installations, municipal utilities, elevators, new construction sites, and similar applications. The RCD300M2 ground fault relay features include an adjustable time delay (0-1.5s), fault indicator LEDs, and signal output to drive either a remote meter or PLC (programmable logic controller). This output gives the RCD300M2 both protective and predictive capabilities - leakages can be seen as they develop, and ground faults can be detected before they become critical.

The RCD300M2 ground fault relay is connected to a Littelfuse WKE Series current transformer (CT), and together they sense the fault current. Advanced filtering techniques are used to differentiate between fault current and typical noise or harmonic current. If the fault current exceeds the relay trip setting, it activates and sends a signal to disconnect high potential from the equipment. Seven different CT sizes are available for a wide range of wire gages and applications. In addition, the RCD300M2 can operate in a fail-safe mode by continuously checking the CT connection. If the CT circuit is broken, the RCD300M2 illuminates the "CT Fault" lamp and activates its disconnect relay, just as if a ground fault had occurred.