SEL-710-5/SEL-710 Motor Protection Relay

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

Functional Overview

SEL-710-5 SEL-710

14 Speed Switch 27 Undervoltage 37 (P,C) Underpower/Undercurrent 38 Bearing Temperature 40 Loss-of-Field 46 Current Unbalance 47 Phase Reversal 49P PTC Overtemperature 49R RTD Thermal 49T Thermal Model 50 (P,G,Q) Overcurrent (Phase, Ground, Neg. Seq.) 50N AF Arc-Flash Neutral Overcurrent 50P AF Arc-Flash Phase Overcurrent 50P LR Locked Rotor 50P LJ Load Jam 50N Neutral Overcurrent 51 (P,G,Q) Time-Overcurrent (Phase, Residual, Neg. Seq.) 55 Power Factor 59P Phase Overvoltage 60 Loss-of-Potential 66 Starts-Per-Hour 78 Out-of-Step 81 (O,U) Over-/Underfrequency 87 Current Differential 90 Load Control 50/51 Adaptive Overcurrent 85 RIO SEL Mirrored Bits Communications AFD Arc-Flash Detector BBD Broken Rotor Bar Detection DFR Event Reports—Motor Starts, Motor Operating Statistics ENV Optional SEL-2600 RTD Module HMI Operator Interface LDP Load Data Profiling LGC SELogic Control Equations MET High-Accuracy Metering RTU Remote Terminal Unit SDTM Slip-Dependent AccuTrack Thermal Model SER Sequential Events Recorder SM Synchronous Motor Control and Protection VAR Reactive Power VFD Variable-Frequency Drive Support * Optional

Front- and Rear-Panel Diagrams

Front		Rear

Multiple Applications

The SEL-710-5 Motor Protection Relay is a full-featured, multifunctional relay that provides complete ac induction and synchronous motor protection and control, including automatic starting. The SEL-710-5 can be implemented for a wide variety of applications, such as fans, blowers, compressors, air handlers, pumps, conveyors, chippers, crushers, screeners, feeders, augers, and bucket elevators.

Standard Motor Protection

Standard features include SEL’s trusted current-, voltage-, and thermal-based motor protection with current differential. The powerful thermal model dynamically calculates motor slip to provide precise temperature tracking with less time required between restarts and more time during the start sequence.

Synchronous Motor Protection and Starting

The SEL-710-5 provides two levels of field over- and undervoltage, field over- and undercurrent, and field resistance protection as an option. It provides automatic synchronization by applying the dc field voltage to the motor field at the correct slip frequency and rotor angle to lock the motor to synchronous speed. It also includes out-of-step and loss-of-field protection.

Arc-Flash Protection

Overcurrent-supervised arc-flash protection provides secure arc-flash tripping by operating when both arc-flash and overcurrent conditions occur. This important feature improves worker safety in areas where high fault current and high incident energy arc-flash events are possible.

Broken Rotor Bar Detection

The broken rotor bar feature detects and reports signature sideband frequencies—current signature analysis (CSA)—that occur in the presence of broken rotor bars. Early detection reduces maintenance costs and helps prevent associated thermal and mechanical damage contributing to catastrophic motor failure.

Flexible Communications

Advanced protocols, such as IEC 61850, DNP3, Modbus TCP/IP, Modbus RTU, Telnet, FTP, SNTP, and ASCII, support communication with legacy and modern supervisory and control systems.

Reliable Rugged Hardware

The SEL-710-5 operates in extreme conditions, with an operating temperature range of –40° to +85°C (–40° to +185°F), and is designed and tested to exceed applicable stan-dards, including vibration, electromagnetic compatibility, and adverse environmental conditions.