Correct Answer - Option 2 : Delta/delta connections
Merz-price differential protection scheme:
- Merz-price differential protection is nothing but a percentage differential protection.
- It works under the principle of the circulating current scheme.
- Merz-price differential protection is used to protect the transformer from internal short circuits, Internal ground faults, and inter-turn short circuits.
The CTs connection in the Merz-price protection:
CTs are connected to every phase of the system.
In order to nullify the phase shift of the Power transformer (PT), The Current transformers (CT) connected in a reverse configuration.
Configuration of PT
|
Configuration of CTs on primary and secondary of PT respectively
|
Y – Y
|
∆ - ∆
|
Y - ∆
|
∆ - Y
|
∆ - Y
|
Y - ∆
|
∆ - ∆
|
Y - Y
|
The star-star power transformer is protected by the current transformer having delta/delta connections.