Sel 551 - Section 1: Introduction and Specifications; Overview

Date Code 20110408 Instruction Manual SEL-551 Relay
Section 1
Introduction and Specifications
Overview
The SEL-551 Overcurrent Relay and Reclosing Relay provides overcurrent
protection and up to four shots of reclosing in one compact package. The relay
measures phase and neutral currents—no voltages.
SEL-551 Feature
Highlights
➤ Numerous Phase, Ground, and Negative-Sequence Overcurrent
Elements
➤ Multiple-Shot Reclosing Relay with Sequence Coordination
➤ Enhanced SELOGIC
®
Control Equations to Create Traditional
or Advanced Schemes
➤ Local/Remote Control Logic to Enable/Disable Schemes,
Operate Circuit Breakers, etc.
➤ Sequential Events Recorder (SER) Report and Event Reports
Stored in Nonvolatile Memory
➤ Hardware Options for Rear-Panel Terminals, Output Contacts,
and Serial Communications Port
➤ Demand Ammetering
Use the SEL-551 for
Overcurrent
Protection in New
Installations and
Retrofits
➤ Utility Distribution Feeders—includes reclosing
➤ Industrial Distribution Feeders—includes connections for a
core-balance current transformer
➤ Distribution Buses—includes fast bus trip scheme
➤ Transformer Banks—includes connections for a separate
neutral current transformer
➤ Other Power System Apparatus—capacitors, reactors, circuit
breakers, etc.
Differences Between
the SEL-551/SEL-551C
Relays
The SEL-551C Relay differs from the SEL-551 Relay in the following major
areas:
➤ Different I/O mix.
SEL-551 SEL-551C
5 output contacts
(OUT1–OUT4, ALARM)
3 output contacts
(OUT1–OUT3)
2 input contacts
(IN1, IN2)
6 input contacts
(IN1–IN6)