Product Description

Advanced Generator Protection System

The SEL-400G offers primary and backup protection for generators of all sizes and types, including hydro, pumped-storage hydro, steam turbine, and combustion gas turbine generators. It combines generator, bus, and step-up transformer protection in one package, making the relay an economical solution for an entire generation unit.


Advanced protection functions, like transverse differential protection, provide turn-to-turn fault detection, which allows for earlier fault detection, limits damage to your generator, and helps you return to service faster. Adaptive differential protection and a wide frequency tracking range (5–120 Hz) improve protection security. Dual frequency zones and autosynchronization offer smooth synchronization to the grid.



Advanced Generator Protection—Two independent universal differential elements provide protection for the generator and GSU transformer in a single relay. With its 18 current inputs, 6 voltage inputs, and wide-range frequency tracking (5–120 Hz), the SEL-400G can be applied in a wide variety of generator configurations. In addition, its advanced antimotoring protection and loss-of-field protection elements further protect your generator.

Pumped Storage Logic—This feature enables pumped storage hydropower protection without the need for external relays to switch CT wiring, which lowers costs and improves reliability.

Stator Ground Fault Protection—Achieve passive and active ground fault detection across 100 percent of the stator winding. The stator winding ground fault protection elements include integrating timers that detect intermittent ground faults and isolate the generator before the fault evolves into a permanent fault.

Rotor/Field Winding Protection—Applying the SEL-2664 Field Ground Module and the SEL-2664S Stator Ground Protection Relay with the SEL-400G allows you to protect your system against rotor/field winding short circuits. With the field ground protection element, the first fault will trigger an alarm and a second fault results in a trip signal. This allows you to continue meeting your generating obligations and to schedule an outage at a preferred time. 

Simplified Settings Management—SEL Grid Configurator is a new configuration software tool that increases efficiency and improves settings insights. It features a spreadsheet-style editor, powerful protection visualization, comprehensive reporting, custom filters, and multiple-device settings management.

Communication and Integration—Quickly integrate the SEL-400G into serial- or Ethernet-based communications with IEC 61850, IEC 62439 PRP, Mirrored Bits communications, Modbus, DNP3, and other protocols.


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