SEL-710-5 Motor Protection Relay Synchronous Motor Control and Protection, Broken Rotor Bar Detection, and Arc-Flash Detection Major Features and Benefits The SEL-710-5 Motor Protection Relay provides an exceptional combination of protection, monitoring, control, and communication in an industrial package. ➤ Standard Motor Protection and Control Features. Protect low- or medium-voltage three-phase motors, as well as variable frequency drive (VFD) fed 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, phase reversal, breaker/contactor failure, positive temperature coefficient (PTC) thermistor over temperature, phase, negative-sequence, residual ground instantaneous, and inverse-time overcurrent elements. Implement load control, star-delta starting, two-speed control, and forward/reverse start control. Other standard features offered by the SEL-710-5 include broken rotor bar detection, rotor slip calculation, virtual speed switch, motor coast time, Schweitzer Engineering Laboratories, Inc.

undervoltage, overvoltage, underpower, reactive power, phase reversal, power factor, frequency, loss of potential, and RTD-based protection. As many as 10 RTDs can be monitored using an internal RTD card or as many as 12 RTDs when using an SEL-2600 RTD Module with the ST option. ➤ Optional Synchronous Motor Protection and Control. Use the SEL-710-5 with an optional synchronous motor/differential card (SYNCH/3 DIFF ACI) that provides starting control, power factor or reactive power closed loop regulation control, and loss-of-field, out-of-step, loss-of-synchronism (pull-out), field resistance,...

ANSI NUMBERS/ACRONYMS AND FUNCTIONS ADDITIONAL FUNCTIONS 1 Copper or Fiber-Optic “Optional Feature • Eight Programmable Pushbuttons With Two Tricolor LEDs Each • Advanced SELogic Control Equations • 32 Programmable Display Messages • Mirrored Bits Communications • Forward/Reverse Control • Reduced Voltage Starting • Two-Speed Motor Control • Breaker Wear Monitoring • VFD Motor Protection • Arc-Flash Protection1 • Differential Protection1 • Synchronous Motor Control and Protection1 *Optional Functions-Select When Ordering **IRIG-B is only available on models without PTC Input Schweitzer Engineering...

The SEL-710-5 protection and control features depend on the model selected. The models are configured with current/voltage input cards on Slot Z and specific option cards on Slot E in the relay. Slot Z cards are assigned a two-digit code beginning with the number 8 in the SEL-710-5 Model Options Table (MOT). For example, 81 in the MOT for Slot Z indicates a SELECT 4 ACi/3 AVI card with 3-phase ac current inputs (1 A nominal), neutral ac current input (1 A nominal), and 3-phase ac voltage inputs (300 Vac). Slot E cards are assigned a two-digit code beginning with the number 7 in the SEL-710-5...

> Two residual overcurrent (50G) elements. These elements use calculated residual (3I0) current levels from phase currents for ground fault detection. > Two neutral-overcurrent (50N) elements. These elements operate on neutral content for three-phase input. Use the 1 A or 5 A rating, or the 2.5 mA rating for sensitive neutral-current applications for high- impedance and ungrounded applications where currents are very low. Time-Overcurrent Elements One level of the inverse time element is available for phases A, B, C, and negative-sequence overcurrent. Also, two levels of inverse time elements...

Arc-Flash Protection An arcing short circuit or a ground fault in low- or medium-voltage switchgear can cause very serious equipment damage and personal injury. They can also cause prolonged and expensive downtime. The best way to minimize the impact of an arc-flash event is to reduce the detection and circuit breaker tripping times. Conventional protection may need several cycles to detect the resulting overcurrent fault and trip the breaker. In some cases, there may not be sufficient current to detect an overcurrent fault. Tripping may be delayed hundreds of milliseconds for sensitivity and selectivity...

Broken Rotor Bar Detection (BBD) The SEL-710-5 detects broken rotor bars in induction motors by analyzing the current signatures under sufficient motor load conditions. BBD determines broken bars using the relative magnitudes of the signals at the sideband frequencies caused by the broken bars, with respect to the signal magnitudes at the system frequency. This normalization allows the algorithm to identify rotor failures independent of the motor characteristics. This function provides the following features for motor monitoring and protection. ➤ A broken rotor bar detection (BBD) element that...

will reset when the parameter drops below the upper level setting for one second. When the selected parameter drops below the load control lower setting level for one second, the auxiliary relay assigned to LOADLOW will operate. The auxiliary relay will reset when the parameter is above the lowerlevel setting for one second. You can use this feature to control the motor load within set limits. Synchronous Motor Protection and Starting Control The SEL-710-5 provides two levels of field over- and undervoltage, field over- and undercurrent, and field resistance protection. Also, loss-of-field (40),...

Schweitzer Engineering Laboratories, Inc.

Table 2 Metering Capabilities (Sheet 2 of 2) Event and Motor Start Reporting Event reports and the SER simplify post-fault analysis and improve understanding of simple and complex protective scheme operations. In response to a user selected trigger, the voltage, current, frequency, and element status information contained in each event report confirms relay, scheme, and system performance for every fault. Decide how much detail is necessary when you request an event report (e.g., 1/4-cycle or 1/32-cycle resolution and filtered or raw analog data). The relay stores as many as 5 of the most recent 180-cycle,...