Surge Diverters in 33KV Switch Yard

The correct people to ask are the suppliers of the surge equipment!

The questions you ask tell me that you are not the person to undertake this. Get a company with qualified and registered high voltage engineers that can issue certificates of compliance to city and country laws on electrical installation and safety regulations. These Voltages are not the place to try and educate yourself. Get the correct people to do it and then ask the questions you need answers for. Learn from that. You get people in the industry that do this work every day that knows what works best for the longest time that they can put their signature on without come backs, use them.

From your question, i understand that there is a 33 kv switchyard and there are two 33/3.3 kv Transformers connected with overhead lines. If this is true, you need to connect Surge arrester at 3.3 kv overhead line for each phase between phase to earth. Also you may require to connect Surge Arrester at 33 kv side terminal box of Transformer depending upon whether it is connected with long /short cable. For surge arrester selection see ABB web page.

The lightning surge could travel through power line and damage the transformers. Hence, it is the practice to connect surge arresters / divertors at the 33kV terminals of the transformer which are supplied by overhead power line).

The surge arrester shall always be connected in all three phases (phase-to-earth). After all, the surge could travel through any phase.

It is important for good protection that the surge arrester is as close to the transformer as possible.

The rating of the surge arrester depends on the system earthing.

This is not a job for a weekend quarterback or engineer in training.

You should be able to do this job without consulting an unknown group on the 'Net.

Consult the manufacturer and request an on site engineer if required.

I think most contributors here will gladly advise on other things,but with the potential of disastrous results no one wants to be a party to the outcome.

No offense intended,but this is a case of what you don't know CAN hurt you and others.

I have seen a switch yard melt down.. puddles of molten steel from I Beams and blast damage far away from the site.

Literally millions of dollars of direct and collateral damage.

Be safe,not sorry.

The lightening arrestor can be mounted at the incoming point of the switch-yard. It will protect both the transformers from lightening surges. It is general practice to install lightening arrestor at the point where line terminates in the switchyard.