How to design Bay Control Unit (BCU) in a substation automation system

Bay Control Unit (BCU)

The main function of BCU is to monitor the whole system remotely away. The status of primary equipment or auxiliary devices can be obtained from auxiliary contacts. Therefore it is possible to detect and indicate both the OPEN and CLOSED position or a fault or intermediate circuit-breaker or auxiliary contact position.

In addition to the monitoring functions, BCU also support all control functions that are required for operating medium-voltage or high-voltage substations. The main application is reliable control of switching and other processes.

With integrated logic, the user can set, via a graphic interface, specific functions for the automation of switchgear or substation. Functions are activated via function keys, binary input or via communication interface.

Every switching operation and change of breaker position is kept in the status indication memory.

The switch command source, switching device, cause (i.e. spontaneous change or command) and result of a switching operation are retained.

Command processing

All the functionality of command processing is offered. This includes the processing of single and double commands with or without feedback, sophisticated monitoring of the control hardware and software, checking of the external process.

Control actions using functions such as runtime monitoring and automatic command termination after output are also included.

IEC 61850

The International Electrotechnical Committee (IEC) Technical Committee (TC) 57 was established in 1964 because of an urgent need to produce international standards in the field of communications between the equipment and systems for the electric power process, including telecontrol, teleprotection, and all other telecommunications that control the electric power system.

The new communication standard IEC 61850 is introduced in Substation Automation replacing almost all traditional wires by serial communication. Based on mainstream communication means like Ethernet it provides a high flexibility regarding communication architectures.

The goal of the standard is interoperability. Up to now, the communication for SA was based on proprietary serial communication mechanisms complemented with conventional parallel copper wiring.

The latter is used especially from the process to the switchgear. With the advent of IEC 61850 there is a comprehensive global standard for all communication needs in the substation being introduced now.