Relay provides protected access

The need for flexible communications and convenient engineering access to settings and data is addressed by the rugged and reliable SEL-551C overcurrent/reclosing relay.

The need for flexible communications and convenient engineering access to settings and data is addressed by the rugged and reliable SEL-551C overcurrent/reclosing relay from Schweitzer Engineering Laboratories.

The new SEL-551C relay combines complete overcurrent protection and multishot reclosing to protect lines and equipment using a sensitive and secure mix of phase, negative-sequence, and ground overcurrent elements.

The SEL-551C relay enables easy integration into industrial protection and control schemes with Modbus RTU protocol.

A rear serial communications port is available as either an EIA232 or an EIA485 interface.

Also new, an optional front-panel EIA232 port allows easy connection for engineering functions such as changing relay settings and monitoring or downloading fault information.

"Providing communications access through a front-panel port is very helpful to system engineers and technicians", says Eric Sagen, SEL Distribution Product Engineer.

"Before, they could not plug their PCs into an EIA485 serial port or Modbus RTU on the back of a relay because a PC requires a different interface protocol".

"So, the optional SEL-551C relay front port enables users to plug their laptop right into the front of the relay in order to create or change settings, perform an evaluation or get event reports in order to see what happened before and during a fault and confirm that the relay tripped properly".

"All this can be done without disrupting communications at the back of the relay".

The SEL-551C relay also provides high-speed operation, even with high fault current and severe CT saturation, using the SEL adaptive overcurrent element for improved protective response.

Multiple-shot reclosing with sequence co-ordination enables utilities or industrial users to program up to a four-shot reclose sequence with reclose initiate supervision, skip-shot sequencing, and stall-open interval timing.

Six inputs and three outputs, all fully programmable, are available to meet a variety of application needs.

A wide operating temperature range (-40 to +85C) allows for installation in a control house or outdoor enclosure.

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