CEIG Approval for a Transformer Installation: Drawings, Tests and Energisation

A transformer that steps an 11 kV or higher supply down to 415 V needs the Electrical Inspector's attention before it is energised. Under the CEA safety regulations of 2023 you file drawings, produce the manufacturer's test certificates, complete site tests, and show the earthing, oil and fire provisions. Whether the inspector visits or you self-certify depends on the voltage your state has notified.

When does a transformer need CEIG approval?

Chapter VI of the CEA (Measures relating to Safety and Electric Supply) Regulations, 2023 covers installations of voltage exceeding 650 V, and a transformer fed at 11 kV or 33 kV sits squarely inside it. Regulation 45 then splits installations at a voltage that each state notifies. Above that notified voltage, the Electrical Inspector must inspect and test the installation before supply starts, or restarts after a shutdown of six months or more. At or below it, the owner inspects, tests and self-certifies, and files the report on the Schedule II form with the inspectorate.

The notified voltage is the state's to set, so do not assume the answer from another state's practice. Ask the state inspectorate which route applies to your connection voltage, and read our wider note on CEIG approval for factories for the state-by-state guides. Two situations always reopen the question: adding a second transformer or raising the rating of an existing one (regulation 45(6) requires written approval or self-certification for additions and alterations), and restarting a plant that has been shut for six months.

What goes into the drawing submission?

The inspectorate reviews the scheme on paper before the equipment is built. A transformer file is only as good as its single-line diagram, and the diagram must agree with the DISCOM sanction and the load schedule. These are the documents a reviewer normally expects; the exact list and forms are the state's.

What do the regulations require of the transformer itself?

Several rules in regulations 46 to 48 turn directly into design decisions, and they are cheaper to meet on paper than in a finished substation.

• Earthing of the neutral. Regulation 50(2) requires the neutral point of every transformer in a star-connected system with earthed neutral to be earthed through not less than two separate and distinct connections to the earthing system. The earthing system must keep touch and step potential within tolerable values (regulation 50(1)).
• Protection by rating. Regulation 47(2) requires a Buchholz relay, a pressure relief device, and winding and oil temperature protection, with alarm and trip contacts, on transformers of 1000 kVA and above. Differential protection is required from 10 MVA.
• Switching either side. Regulation 37(3) requires a linked switch with fuse, an air-break switch with fuse or a circuit breaker on the primary side of every transformer, with a circuit breaker required from 1000 kVA, and a circuit breaker of adequate rating on the secondary side (a linked switch with fuse is allowed there for supplier transformers below 1000 kVA).
• Interlocks. Isolators and their breakers are interlocked, isolators and earthing switches are interlocked, and where transformers run in parallel the secondary breaker of a transformer must trip when its primary breaker trips (regulation 47(1)).
• Clearances. Safety clearances follow the relevant standards, and the minimum working clearances in Schedule V apply to bare live parts in outdoor substations (regulation 46(2)).
• Outdoor fencing. An outdoor substation is fenced at not less than 1.8 metres, and the fence is earthed (regulation 51).

Oil-filled or dry-type: what changes at inspection?

The choice drives the civil work, the fire provisions and the questions the inspector asks. Regulation 46(2) is explicit on both types.

Spare oil may not be stored near oil-filled equipment (regulation 46(2)(vii)(c)), and cable trenches inside the substation must be filled with sand or similar non-inflammable material or covered with non-inflammable slabs. Decide the type before the layout is frozen, because the layout follows from it.

What tests come before energisation?

Regulation 48 sets the order. Before the Electrical Inspector approves, the manufacturer's test certificates for type, acceptance and routine tests are produced if required. New apparatus above 650 V cannot be commissioned until it has passed site tests under the relevant standards. Under regulation 45(5) the owner tests every circuit, other than an overhead line, to the testing voltage in regulation 48 and records the results for the inspector. The inspector may accept the manufacturer's certified tests for a particular item, and may ask for further tests before or after charging.

The supplier may energise the apparatus for those tests (the proviso to regulation 45(4)), but supply to the plant waits for written approval. In practice the site file holds insulation resistance, ratio and vector group checks, oil tests where relevant, relay secondary injection, interlock trials, and earth resistance for every pit and for the grid. Every earthing system, whether the supplier's or the consumer's, is tested for resistance on a dry day in the dry season at least once a year, with records kept for the inspector (regulation 50(8)).

How does this connect to the DISCOM?

The DISCOM will not connect an installation that needs inspector approval without it, and the DISCOM's metering arrangement must match the approved diagram. File the CEIG drawings in parallel with the DISCOM load sanction so neither department waits on the other. Our guide to HT connection and substation approval covers the DISCOM side, and the transformer sizing calculator gives a first kVA from connected load and demand factor before you commit to a rating.

How Secured Engineers helps

We design the substation in-house, so the single-line diagram, layout, earthing and protection scheme are drawn once and agree with each other. Fire NOC, CEIG and DISCOM net-metering filings are handled in-house by the same team, and MEPF and solar can sit under one contract. We work from our Noida (Delhi NCR) and Ludhiana offices, across 535+ projects in 18+ states, with 89.77% repeat clients. For a transformer file we review the drawings against regulations 45 to 51 before they go to the inspectorate, and we rectify gaps found in an existing installation.

If you have a transformer file ready or half built, send it to our CEIG approval team for a review of your file, message us on WhatsApp, call +91 70099 85817, or ask for a free proposal.