Bus Protection Features

Facing the threat of large-scale outages on the island of Grand Cayman, Caribbean Utilities Company chose SEL to fix failing bay controllers at its main substation. SEL’s solution saved the utility millions of dollars.

Caribbean Utility Thwarts Island-Wide Power Blackouts

Caribbean Utility Thwarts Island-wide Power Blackouts

This paper examines several common bus configurations, presents appropriate protection schemes for each configuration, and analyzes the protection scheme complexity, advantages, and disadvantages.

Bus Protection Considerations for Various Bus Types

In the early hours of the morning on a warm night in June, a group of engineers gathered in Georgia’s National Control Center. With quiet efficiency, they prepared to execute one of the most important tests the utility would ever perform, cutting the power to one of their most critical 500 kV transmission lines.

Innovation, Persistence, and a New Beginning

Two drastically different types of differential relays, one with a single set of very high-impedance inputs and another with multiple sets of low-impedance inputs, are available for bus differential protection. This paper discusses for each type of relay the concepts used, the pros and cons, and the importance that current transformer selection plays in applications.

Considerations for Using High-Impedance or Low-Impedance Relays for Bus Differential Protection

Busbar Protection

Bus protection products and systems provide complete primary and backup protection for all types of bus and switchgear arrangements. They are suited for use in utility-, industrial-, and commercial-scale power systems.

Features	SEL-387	SEL-487B	SEL-487E	SEL-587Z	SEL-787Z
Applications
Breaker Failure Protection	ƒ			ƒ
Bus Differential	ƒ
Transformer and Machine Current Differential
High-Impedance Bus Differential
Low-Impedance Bus Differential
Three-Phase Current Inputs	4	7/10/21 ‡	5	Common	4
Three-Phase Voltage Inputs		1	2
Protection
27/59 Under-/Overvoltage
46 Current Unbalance		ƒ
47 Voltage Unbalance			ƒ
50 (N,G) Overcurrent (Neutral, Ground)
50P Phase Overcurrent
50Q Negative-Sequence Overcurrent
51 (N,G) Time-Overcurrent (Neutral, Ground)
51P Phase Time-Overcurrent
51Q Negative-Sequence Time-Overcurrent
87 Current Differential
87Z High-Impedance Differential
Single-Pole Trip/Close
Three-Phase Differential Bus Zones	1	2/ 3/ 6 ‡	1	1	1
Check Zones		3
Instrumentation and Control
79 Automatic Reclosing		ƒ	ƒ
Dynamic Zone Selection
SELogic Control Equations
Nonvolatile Latch Control Switches
SELogic Remote/Local Control Switches
Display Points
Multiple Settings Groups
Substation Battery Monitor
Breaker Wear Monitor
Event Report (Multicycle Data)
Sequential Events Recorder
Instantaneous Meter
Demand Meter
Through-Fault Monitor
IEEE C37.118 Synchrophasors
Synchrophasor Real-Time Control
IEC 61850
Built-In Web Server
Simple Network Time Protocol (SNTP)
Rapid Spanning Tree Protocol (RSTP)
Mirrored Bits Communications
Parallel Redundancy Protocol (PRP)
IEEE 1588 Precision Time Protocol Verion 2 (PTPv2)
Time-Domain Link (TIDL™) Technology
Miscellaneous Features
Connectorized (Quick Disconnect) Available

Busbar Protection

Busbar Protection Relays

Overcurrent Protection Relays

System Components

Bus Protection Features