06.Double Busbar with Bus coupler + Bypass Isolator Configuration

What is busbar?
A busbar is a metallic conductor (usually copper or aluminium) used in substations to collect and distribute electric power. It connects multiple incoming and outgoing transmission lines and equipment like transformers within the substation.
Since the busbar is a critical node in the power system, any fault on it can cause widespread outages. Therefore, fast and reliable protection is essential.
Double Busbar with Bus coupler + Bypass Isolator Configuration
First, let's look at a simple representation of this busbar configuration. You can see Busbar 1 and Busbar 2 connected by a coupler. Additionally, each bay includes a bypass isolator across its circuit breaker.
Normal Operation
All these operations are carried out just like in a standard double busbar system with a bus coupler. This setup allows different switching options such as connecting all bays to Busbar 1, splitting them between Busbar 1 and Busbar 2, or connecting all bays to Busbar 2. It also allows smooth transfer of load from Busbar 1 to Busbar 2 and vice versa without interrupting the power supply. Lines and transformers can stay energized during these operations, as shown in the Double Busbar with Bus coupler configuration. 
Load transfer condition – with Transfer bus coupler when there is a breaker fault / Maintenance
In the previous scenario, the bay could not be operated in case of a breaker fault. To overcome this issue, a bypass arrangement is implemented.
In this setup, a bypass isolator is connected across the circuit breaker, and the breaker is isolated on both sides using disconnectors. This allows the faulty breaker to be bypassed safely and the bay to remain operational.
Operation Procedure:
  • Ensure all transfer isolators are open.
  • Close the transfer isolator for Line 2.
  • Close the disconnector for Busbar 2.
  • Open the disconnector for Busbar 1.
  • Close the transfer breaker after closing the transfer coupler disconnectors.
At this point, Line 2 bay is now connected to Busbar 1 through the transfer coupler.
The same procedure must be followed if any other bay's circuit breaker develops a fault. However, only one bay at a time can be operated in bypass mode, as per the busbar arrangement.
Advantages:
  • Higher reliable
  • Higher flexible
  • Less outage time
  • Very supportive for Protection coordination
Dis Advantages:
  • Very Higher cost
  • Very Higher space
  • Higher maintenance

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