Time Delay Relay for Arc Flash Protection

This time-delay relay is a microprocessor-controlled control switch relay engineered to address the arc flash safety concerns of manually operating high-fault-current power circuit breakers. When personnel initiate a local trip or close command at the front-panel push button, the relay delays the actual breaker operation by 10 seconds (factory adjustable), giving the operator time to leave the arc flash boundary and reach a safe standoff distance before the breaker actuates. A flashing LED annunciates the pending operation throughout the delay period, and an extended 4- to 5-second button-press requirement prevents accidental delay-mode entry.

The relay combines standard control switch functionality, local and remote operation, a mechanical trip/close flag, pistol-grip manual override, contact deck flexibility, and SCADA status output, with the added safety layer of delayed local actuation. Continuous contact rating is 30 amperes at 600 volts, with UL interrupt ratings of 25 A at 120 VAC, 15 A at 240 VAC, 6 A at 600 VAC, 3 A at 125 VDC, and 1 A at 250 VDC. Contact resistance is 10 milliohms maximum, and contact configurations include both break-before-make (non-shorting) and make-before-break (shorting) options.

Standard panel-mount patterns allow direct interchange with existing switchgear, minimizing retrofit work. Typical applications for this time-delay relay include medium-voltage substation control, industrial motor control centers with high available fault current, generator switchgear, and any breaker operation where NFPA 70E arc flash calculations call for enhanced operator safety during manual switching. The delay function can be halted and returned to normal instantaneous operation with a subsequent press of the delay button, giving operators mode-selection flexibility based on the specific breaker operation being performed.