Relay: Differential current relay improves worker safety

Littelfuse RCD300M2 differential current relay improves worker safety and protects equipment from electrical ground faults. If fault current exceeds the relay trip setting, it activates and sends a signal to disconnect high potential from the equipment. Here's how it avoids an arc flash. Links are provided to other power protection products.

12/31/2008



Littelfuse RCD300M2 differential current relay improves worker safety and protects equipment from electrical ground faults.

Des Plaines, IL – The Littelfuse RCD300M2 differential current relay improves worker safety and protects equipment from electrical ground faults. Unintended conductive paths from a high potential line to ground, allow electrical currents to pass through sensitive equipment components or through personnel who touch equipment housing with devastating results. About 90% of ground faults occur slowly due to dust buildup, moisture ingress, vibration, cable chaffing, or chemical and corrosive vapors, which lead to earth-leakage or residual-current ground faults that escalate to high-current levels. Annually, appoximately 150 fires and explosions in commercial and industrial buildings are caused by electrical grounding failures, with an average loss of more than $575,000 per event (per FM Global). The worst are dangerous arc-flash events.
To avoid nuisance tripping with conventional ground fault relays, maintenance workers tend to increase trip points above sensitive levels, which defeats the purpose of having a relay sensitive enough to protect workers from electric shock or arc-flash incidents. RCD300M2 uses technology that provides highly sensitive protection, avoiding nuisance trips and unnecessary equipment shutdown.
The relay is connected to a Littelfuse WKE Series current transformer (CT), and together they sense fault current. Advanced filtering techniques differentiate between fault current and typical noise or harmonic current. If fault current exceeds the relay trip setting, it activates and sends a signal to disconnect high potential from the equipment. Seven CT sizes are available for a range of wire gages and applications. RCD300M2 can operate in a fail-safe mode by continuously checking the CT connection. If the circuit is broken, it illuminates the CT Fault lamp and activates its disconnect relay, just as if a ground fault had occurred.
Features include automated monitoring and control in power distribution panels, switchboard installations, municipal utilities, elevators, new construction sites, and similar applications, plus an adjustable time delay (0-1.5s), fault indicator LEDs, and signal output to drive a remote meter or PLC. The output gives RCD300M2 protective and predictive capabilities; leakages can be seen as they develop, and ground faults can be detected before they are critical.
Specifications include adjustable trip setting: 10 mA to 3 A; relay supply voltage: 24 V ac/dc, or 120 V ac, 50-60 Hz; two form C alarm relay contacts: 1,100 V A switching capacity (closure); 5 A continuous current; 250 V rating; breaking capacity: 3 A @ 240 V ac (P.F. = 0.4), and 0.3 A @ 110 V dc (resistive load).
Also read about:

Omron industrial relays that have easy installation with new socket options

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Weidmuller expanded its relays with the Riderseries family, available in kits

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And see

Product Research on Power Protection Devices


Littelfuse

– Control Engineering News Desk
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