Should earthing of 66 kV transformer be linked with earthing of 11 kV alternator? 1

[SA07]

Hi
Our power plant consists of 2 units turbo-alternator/boiler. A sketch of the set-up is attached. Both units export power to the utility network. A company has done a discrimination of protection study and has recommended that the earthing of 66 kV transformer is linked with 11 kV earthing of alternator.
This is shown as red line on the sketch.
Can you plz confirm if this is correct?
By the way, can you plz confirm if all earthing points at 66 kV, 11 kV, 690 V, 400 V should be linked for such a power plant? Thks

 

[Kiribanda]

To avoid any transferred potentials due to GPR variations, everything should be bonded to the plant earthing system.
Do you have a drawing of the plant earthing system showing substation earthing & generator earthing?

 

[RRaghunath]

Neutral of individual equipment is earthed through dedicated electrodes which are in turn are connected to the station earth mat. All the individual earth mats such as the one in the switchyard and the one in the generating station as well as those small earthing systems in auxiliary buildings are all to be interconnected with redundant connections to prevent issues with GPR variation. Even the instrumentation earthing system, Lightning protection earthing system are interconnected with the station earth mat.

 

[SA07]

Thks for your reply