SEL – 710-5 Motor Protection Relay

Protect asynchronous (induction) and synchronous motors with one SEL-710-5 Motor Protection Relay. Features include broken rotor bar detection and variable-frequency drive (VFD) support as well as options for arc-flash detection (AFD), differential protection, and synchronous motor protection. The synchronous option supports power factor regulation and includes, at no additional cost, a voltage divider accessory to interface with the motor excitation system.



The SEL-710 calculates thermal energy in the motor to determine maximum safe start times, with full motor protection. Accurate temperature tracking also minimizes the time needed between starts. Use the four programmable pushbuttons on the front panel for quick personalized control, with factory default start and stop functions. The SEL-710 provides protection for overcurrent, thermal overload, undercurrent, current unbalance, current differential, phase loss, ground fault, and over- or underfrequency, and much more. Choose from single or dual, copper or fiber-optic Ethernet as well as Modbus TCP, IEC 61850, Modbus Serial, EIA-232, EIA-485, Telnet, and File Transfer Protocol (FTP) communications. Pick one or multiple connections, including multiple Modbus sessions for custom configuration of your application. Trust the industry’s widest ambient operating temperature range, –40° to +85°C (–40° to +185°F). The SEL-710 withstands vibration, electrical surges, fast transients, and extreme temperatures, meeting stringent industry standards. A conformal-coating option for the printed circuit boards provides an additional barrier to airborne contaminants, such as hydrogen sulfide, chlorine, salt, and moisture. In addition, the SEL-710 is ATEX- and Underwriters Laboratories (UL) Class I, Division 2-certified for use in hazardous and potentially explosive environments.



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.

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