05.Double Busbar with Bus coupler 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
First, we look at the very simple representation of this busbar configuration, You can see Busbar 1 and Busbar 2 with a coupler. This is a common arrangement that is widely used.
Operation 1
In this case, all bays are connected to Bus-1, as shown in the operation and power flow diagram. Line 1 and Line 2 are energized, and Transformer 1 and Transformer 2 are also getting charged
Operation 2
In this case, Line 2 is connected to Busbar 2, and Line 1 is connected to Busbar 1. Transformer 2 is associated with Busbar 2, while Transformer 1 is connected to Busbar 1. You can refer to the power flow diagram for a visual representation
Load transfer condition - with bus coupler
Under load conditions, it is not safe to directly switch circuits from Bus-1 to Bus-2 or vice versa. This is because when attempting to operate the isolator, a potential difference between the two buses may exist. This can result in arc formation, which may damage the equipment.
To prevent this, a bus coupler breaker is used to ensure a safe transfer.
Bus Transfer Procedure:
Establish a Common Bus:
Close all relevant bus disconnectors.
Close the bus coupler breaker.
This action connects Bus-1 and Bus-2 into a common bus, eliminating any voltage difference.
Transfer the Load:
Open the bus disconnectors of the bus from which the bays are being transferred.
Open the bus coupler breaker.
At this point, all bays are successfully transferred from Bus-1 to Bus-2. The same procedure is followed to switch from Bus-2 to Bus-1.
Bay-wise Transfer (for Large Substations):
In most cases, especially when a large number of bays are connected in the substation, bay-wise transfer is preferred. This ensures better control, minimizes risk, and avoids full bus shutdown during the switching operation.
Operation 3
In this case, all bays are connected to Bus-2, as shown in the operation and power flow diagram. Line 1 and Line 2 are energized, and both Transformer 1 and Transformer 2 are also being charged.
Advantages:
Higher flexible
Less outage time
Very supportive for Protection coordination
Dis Advantages:
Very Higher cost
Very Higher space
Higher maintenance
Lower reliable if Breaker failure.
