Motor protection relay

The SEL-701 Motor Protection Relay offers a comprehensive range of motor protection features including short circuit, load loss, load jam, and frequent starting protection as well as unbalance current and phase reversal protection.

In addition, the SEL-701 relay provides a motor thermal protection element that accurately tracks the heating effects of overloads and unbalance current. The integrated element calculates an estimate of the motor heat energy, based on the measured currents and motor characteristics. The estimate tracks changing conditions to protect the motor from thermal damage. The SEL-701's adaptive overcurrent element enhances the performance of the relay during extreme CT saturation conditions.

The relay is available with optional internal or external resistance temperature devices (RTD) modules. These inputs extend thermal protection to include direct temperature measurement to protect motor windings as well as motor and load bearings. The optional three-phase voltage inputs provide voltage and power-based protection and metering.

Detailed motor start and trend data provide the user with a real-time snapshot of how the motor and the load are working together - a useful tool for early detection of load problems. Load profiling data captured every 15 minutes can be used to indicate changes in the performance of the system, motor, or driven load.

Every time the motor starts, the relay stores a 60 s report detailing the motor currents, voltages (if included), and thermal model results.

The relay also calculates the accelerating time in seconds and records the maximum current magnitude and minimum voltage magnitude seen during the start. The relay stores the five latest start reports in non-volatile memory.

Modbus communications protocol is available as standard for seamless integration with SCADA or DCS.