Open Breaker Function ............................................................................................................................ 4-5

Stub Bus Trip ........................................................................................................................................... 4-5

Weak Feed Trip ........................................................................................................................................ 4-6

Reclose Initiate Logic ............................................................................................................................... 4-6

High Set Overcurrent Elements ................................................................................................................ 4-6

Fault Locator ............................................................................................................................................ 4-7

Faulted Phase Selector ............................................................................................................................ 4-7

Differential Protection Disable .................................................................................................................. 4-8

Optional Backup Functions ............................................................................................................................. 4-8

Distance Protection .................................................................................................................................. 4-8

Backup Protection Disable ....................................................................................................................... 4-8

Sensitive Directional Ground Overcurrent Unit .......................................................................................... 4-8

Out of Step Trip and Out of Step Block Logic ........................................................................................ 4-12

Loss of Potential (LOPB) ....................................................................................................................... 4-13

Loss of Current Monitoring ..................................................................................................................... 4-13

Section 5

Testing

Introduction .................................................................................................................................................... 5-1

Equipment Needed ......................................................................................................................................... 5-1

Test Setup ...................................................................................................................................................... 5-1

Current and Voltage Inputs ....................................................................................................................... 5-1

Analog Input and Front Panel Metering Test ................................................................................................... 5-1

Contact Input Subsystem Test ....................................................................................................................... 5-2

Relay Output Subsystem Test ........................................................................................................................ 5-3

Communication Subsystem Test .................................................................................................................... 5-3

9600 bps Audio Tone Option .................................................................................................................... 5-3

56/64 kpbs Digital Communication Option ................................................................................................ 5-3

Functional Tests - Current Differential System ............................................................................................... 5-4

Single Unit Loopback Test - Internal Faults .............................................................................................. 5-5

Single Unit Loopback Test - External Faults ............................................................................................. 5-8

Dual Unit Back to Back Test - External Faults ......................................................................................... 5-8

Dual Unit Back to Back Test - Internal Faults .......................................................................................... 5-9

Functional Tests - Optional Backup System ................................................................................................. 5-10

Phase to Ground Units ................................................................................................................................. 5-10

Zone 2 Phase-Ground Element Without Reverse Reach ......................................................................... 5-10

Zone 2 Phase-Ground Element With Reverse Reach ............................................................................. 5-13

Zone 3 Phase-Ground Element Without Reverse Reach ......................................................................... 5-16

Phase to Phase Units ............................................................................................................................ 5-18

Zone 2 Phase-Phase Element ................................................................................................................ 5-18

Zone 3 Phase-Phase Element ................................................................................................................ 5-20

3-Phase Units ........................................................................................................................................ 5-21

Zone 2 3-Phase Units ............................................................................................................................. 5-22

Zone 3 3-Phase Units ............................................................................................................................. 5-23

Out of Step System Functional Tests ........................................................................................................... 5-24

In-Service Checks ........................................................................................................................................ 5-26

Potential and Current Circuits ....................................................................................................................... 5-26

Current Differential Checks ........................................................................................................................... 5-27

Table of Contents

ABB REL 356 Current Differential Protection

Page vii

Table of Contents