Transformer Installation

What do adjacent clauses 3.x.x say?

Is there a question? Or are you just making a statement for the sake of it?

OP said "Is it valid for all ratings when aggregate oil contents is less than 2000lit."

Sounds like a question.

As you can see from the following excerpt, the transformer rating does not factor into your decision, just the fact that the transformers contain certain quantities of oil. After all, the combustibility of oil does not care about the rating.

"...3.6.2 If two or more transformers are installed side by side, they shall be separated by fire-separation walls. Fire separation walls are deemed to be adequate from fire-safety point of view, even if oil capacity of individual transformers do not exceed 2 000 litres, and total capacity of all transformers installed side by side exceeds 2 000 litres. NOTE - Reference shall also be made to 4 of SP: 7 ( Part IV )-1970. and IS : 1641-19607..."

I suggest that you also pay heed to this:

"...3.3.2 It is recommended that the local authorities concerned in the administration of the rules and regulations in the matter of the layout and of the installation of the transformer should be consulted in regard to the rules and regulations that may be applicable..."

...not a bunch of strangers who may not be familiar with your particular installation.

IE rules 1956 Clause 52 191(e) gives clear guidence regarding installation of wall. You have to comply with the IE rules if the installation is in India.

When working in KSA, new 750Kva transformers were being installed, the designers/planners looked at 4 different standards from 4 countries. Aware of the many safety design requirements, and having 4 documents to consult, they tied themselves up in knots as they could not decide WHICH standard to adopt.

In the end the document with the highest spec won!

So find several specs, decide which has the higher spec, or the spec you can afford to implement, and go with it.

Fire separation walls are there to prevent the propagation of a fire which can be started by a transformer of any rating. It depends upon proximity to buildings, other plant, etc.

The containment should be of sufficient capacity to hold all the oil likely to be spilled.

Check with your local fire department to obtain clearance and also with your insurers.

CEA Regulations, 2010 - Measures relating to safety & electric supply (under Indian Electricity Act-1910, as amended in 2003) which supersedes IE Rule -1956 may please be referred. The relevant clauses are as under:

Clause 44 (2) (vii)

Where a sub-station or a switching station with apparatus having more than 2000 litres of oil is installed, whether indoor or outdoor, he should take the following measures, namely:-

(a) the baffle walls of four hours fire rating shall be provided between the apparatus.

(b) provisions shall be made for suitable oil soak pits and where more than 9000 litres of oil in any one oil tank, receptacle or chamber is involved, provision shall be made for the draining away or removal of any oil which may leak or escape from the tank, receptacle or chamber containing the same and special precautions shall be taken to prevent the spread of any fire resulting from the ignition of oil from any cause and adequate provision shall be made for extinguishing any fire which may occur

Clause 44 (2) (ix)

he shall ensure that the transformers of 10 MVA and above rating or in case of oil filled transformers with oil capacity of more than 2000 litres are provided with fire fighting system as per IS-3034:19993 or with Nitrogen Injection Fire Protection system.