Enhanced Motor Protection—Protect low- or medium-voltage three-phase motors with an enhanced thermal model that includes locked rotor starts, time-between-starts, starts-per-hour, antibackspin timer, load loss, current unbalance, load jam/stalled rotor, breaker/contactor failure, frequency, and overcurrent elements, including phase, negative-sequence, residual ground instantaneous, and inverse-time elements. Implement load control, star-delta starting, forward/reverse start control, and two-speed control. Use the SEL-710 with optional voltage and differential current inputs to include rotor slip calculation, differential overcurrent (87M), undervoltage, overvoltage, underpower, reactive power, phase reversal, power factor, and loss-of-potential protection.

RTD and PTC-Based Thermal Protection—Connect as many as ten resistance temperature detectors (RTDs) directly to the relay’s optional RTD input card to monitor stator winding, bearing, ambient, or other motor operating temperatures. Free up space for other relay options by using the external SEL-2600 RTD Module to collect up to 12 unique operating temperatures and to send those temperatures back to the relay over a communications link. RTD alarm and trip thresholds provide flexible backup protection and can also be used to bias the thermal model or to form a voting scheme to confirm mitigation decisions. Select the optional positive temperature coefficient (PTC) thermistor over-temperature input when thermistors are used as thermal backup measurement devices.

Reliable Protection in Harsh Environments—The SEL-710 operates in extreme conditions, with an operating temperature of –40° to +85°C (–40° to +185°F), and it is designed and tested to exceed applicable standards, including vibration, electromagnetic compatibility, and adverse environmental conditions. In addition, the SEL-710 is ATEX- and Underwriters Laboratories (UL) Class I, Division 2-certified for use in hazardous and potentially explosive environments.

Overcurrent Protection—Provide backup overcurrent protection on motor feeders with inverse-time and instantaneous overcurrent elements. The SEL-710 provides complete overcurrent protection, including phase, negative sequence, residual, and neutral overcurrent elements.

Metering and Monitoring—Metered quantities include phase voltages and currents; sequence voltages and currents; power, frequency, and energy; and maximum/minimum logging of selected quantities. The relay stores as many as 19 of the most recent 64-cycle event reports or 77 of the most recent 15-cycle event reports in nonvolatile memory. The relay also monitors and alarms when measured conditions are beyond allowable thresholds. For example, circuit breakers experience mechanical and electrical wear every time they operate. With each breaker operation, the relay integrates measured currents and increments the breaker operation counter. When the result of this integration exceeds the breaker wear curve threshold, the relay alarms via output contact, communications port, or front-panel display. This kind of information allows timely and economical scheduling of breaker maintenance.

Integration and Automation—Select from up to nine communications protocols, as many as four independently operated serial ports, copper or fiber Ethernet ports (single or dual), powerful relay logic, and programmable front-panel options to integrate the SEL-710 into high-performance systems of protection, automation, and control.