In short. Getting a DG set legally energised in Telangana or Andhra Pradesh is a sequence of nine steps, from load list to filed approvals. The order matters more than anything else. Prepare the drawings and earthing design before the set arrives, confirm your inspectorate route for the set’s capacity, settle the pollution-board position, then install, test, apply and energise. This page sets out each step, the documents it needs, who issues each one, and how long a well-run job takes.
Who this page is for: factory engineers, facility managers, builders and apartment associations installing a new, replacement or relocated DG set in Telangana or Andhra Pradesh.
Key facts
- Which authority governs what — emissions and noise, electrical safety, pollution-board consent, fuel storage — and when a notification applies is explained on our regulatory updates page. This page is the route itself.
- Under the CEA (Measures relating to Safety and Electric Supply) Regulations, 2023, installations above the notified voltage, and generating units above the capacity the state notifies, must be inspected and approved by the Electrical Inspector before supply starts, and again before supply restarts after a shutdown of six months or more. Installations at or below the notified voltage are tested and self-certified instead. Any addition or alteration, such as a replacement set, must be approved or self-certified before it is connected.
- Whether your set goes to the Electrical Inspector or is self-certified depends on the voltage and generating-unit capacity notified by the state government. These thresholds are set by notification and revised from time to time.
- Connected installations are periodically inspected, or self-certified, at intervals the state sets, which may not exceed five years.
- Under the central pollution board’s 2016 classification of industries, stand-alone DG sets with a total capacity of 1 MVA or less, fitted with acoustic enclosures and an adequate stack, may be exempted from consent management. The exemption is applied by each state board, and the classification has since been revised, so confirm the current position with the Telangana or Andhra Pradesh board. Sets in a consented industry are declared in that consent.
- A well-prepared job takes about 4 to 6 weeks from order to energisation. Most delays come from drawings started after the set arrives.
The route, step by step
Step 1: Size the set and fix the scope
Start from a load list, not the old set’s rating: the connected loads, which ones must run on generator, the largest motor, and any UPS or VFD loads. The output of this step is a rating, a duty (standby or prime), a changeover method (manual interlocked switch, AMF or ATS) and a decision on whether the job is new, a replacement or a relocation. All three need approval before energisation.
Step 2: Fix the location
Check the proposed position against the highest flood level, ventilation, fuel tanker access, exhaust route and stack height, fire separation and neighbours. Record the building height h, because the stack height follows H = h + 0.2 × √kVA, where H and h are in metres. Engines above 800 kW follow a separate, stricter stack rule under the emission standards, and a consent order can set a higher figure. Our site planning checklist gives the dimensions to survey.
Step 3: Write compliance into the purchase order
Require current emission and noise approval certificates matching the engine serial, a factory test certificate, and the changeover or AMF panel’s test certificate. Compliance then becomes a contract condition, checked at delivery, not a hope.
Step 4: Prepare the drawings and the earthing design
This is the step that decides your timeline. Before the set arrives, prepare:
- a single-line diagram showing generator, breaker, changeover or ATS, protection, cable sizes and the point of connection
- an earthing layout with separate body and neutral pits, conductor sizes and the design resistance
- a site or room layout showing the set, fuel tank, exhaust route, stack height and clearances
Step 5: Confirm your inspectorate route
Ask the jurisdictional office of the Electrical Inspectorate in Telangana or Andhra Pradesh which route applies to your capacity this year. Is it Inspector certification or self-certification? Is drawing approval needed before installation starts? Which forms and portal are in use? Note the answer, the date and the officer in your file. The route decides whether you wait for an inspection or certify after your own tests.
Step 6: Settle the pollution-board position
- Consented industry: declare the new or changed DG capacity to the Telangana or Andhra Pradesh pollution control board as a change to your Consent for Establishment or Operation, with stack height and sampling-port details.
- Stand-alone set within the exemption conditions: confirm with the board’s regional office that the exemption applies, then write a short note for the file stating the rating, the enclosure, the stack height, the expected operating hours and the date of that confirmation, so the basis of the exemption is on record.
- Above 1 MVA: expect to apply for consent in its own right. Ask the regional office early.
Step 7: Install with a licensed contractor and test everything
A licensed electrical contractor, or a person holding the right certificate of competency, carries out and signs for the work. Before any application, run and record:
- insulation resistance of the alternator and the cables, with test voltage and temperature
- earth resistance of each pit, with instrument and method
- changeover interlock: proof that the generator cannot back-feed the utility supply
- protection trips, phase sequence and AMF or ATS function
Step 8: Apply, certify and energise
Submit the prescribed form with the drawings, equipment list, test reports, the contractor’s completion certificate and licence, and any declarations the state requires. Under the Inspector route, wait for inspection and approval. Under the self-certification route, certify as prescribed. Then commission on load. A load-bank run is the best proof of capacity if the building load is light.
Step 9: File it and diarise the next inspection
Put the approval or certificate, every test report and the as-built drawings in the set’s file. Diarise the periodic inspection at the interval the state sets, which is never more than five years. Diarise again whenever you plan a modification, or a shutdown of six months or more.
Documents, who issues them, and at which step
| Document | Prepared or issued by | Needed at step | Goes to |
|---|---|---|---|
| Load list and rating calculation | Owner’s engineer or service engineer | 1 | Your file; supports the drawings |
| Emission and noise approval certificate copies; factory test certificate | Manufacturer, via the supplier | 3, checked at delivery | Your file; shown at inspection |
| Single-line diagram | Designer, contractor or service engineer | 4 | Inspectorate application |
| Earthing layout and calculation | Designer, contractor or service engineer | 4 | Inspectorate application |
| Site or room layout with stack height | Designer or contractor | 4 | Inspectorate; pollution board where applicable |
| Note of inspectorate route and date | Owner | 5 | Your file |
| Consent amendment, or exemption-basis note | Owner | 6 | Pollution board, or your file |
| Insulation, earth, interlock and protection test reports | Contractor or service engineer | 7 | Inspectorate application |
| Contractor’s completion certificate and licence copy | Licensed contractor | 7–8 | Inspectorate application |
| Approval before energisation, or self-certification record | Electrical Inspectorate, or owner | 8 | Your file; supply side if asked |
| Commissioning and load-bank report | Service engineer | 8 | Your file |
As your service engineers, we can prepare the technical documents the application needs: load calculation, single-line diagram, earthing design and test records, protection settings, and the commissioning and load-bank reports. The application itself is made by the owner, or the owner’s licensed contractor, through the inspectorate’s prescribed process.
Which steps apply to your job
| Job | Steps 1–4 | Step 5 (inspectorate route) | Step 6 (pollution board) | Watch for |
|---|---|---|---|---|
| New small set (up to about 62.5 kVA) for a shop, clinic or office | All, kept short | Likely self-certification, if the threshold allows | Exemption-basis note | Interlocked changeover; proper earthing |
| 125–500 kVA standby for an apartment block or hospital | All | Inspector approval likely; drawings first | Exemption-basis note, if within the conditions | Fire NOC review of the DG room and day tank |
| Any size inside a consented factory | All | As per threshold | Consent amendment | Stack port and monitoring conditions |
| Replacement with a different rating | All; old approval does not carry over | Fresh approval or certification | Update the consent if consented | Re-size the changeover and cables |
| Relocation, or reconnection after a shutdown of 6 months or more | Steps 2, 4 and 7 again | Fresh approval before energisation | Update the consent if consented | Re-test earthing and insulation |
| Multi-set plant or above 1 MVA | All, plus synchronising drawings | Inspector approval | Consent normally required | Acoustic room and ventilation design |
Worked example (illustrative): a 250 kVA replacement at a Hyderabad engineering unit
The site. A machining unit in an industrial area west of Hyderabad holds Consent for Operation. It is replacing a 160 kVA set with a 250 kVA set in a ground-floor DG yard beside its 9 m high building.
- Week 0, steps 1–3. The load list confirms 250 kVA with motor-starting margin. The order specifies current approval certificates matching the engine serial and an AMF panel with mechanically and electrically interlocked changeover.
- Week 1, step 2 arithmetic. Stack height H = 9 + 0.2 × √250 = 9 + 0.2 × 15.81 = 9 + 3.16 = 12.2 m.
- Week 1–2, step 4. Full-load current = 250,000 ÷ (1.732 × 415) = 348 A, so the single-line diagram shows a 400 A four-pole changeover and a cable sized for 348 A plus the route’s derating. The earthing layout shows two body pits and two neutral pits.
- Week 2, steps 5–6. The inspectorate confirms that Inspector approval applies at this capacity. The replacement is reported to the pollution board as a change in DG capacity, with stack details.
- Week 3–4, step 7. Installation and tests. One neutral pit reads above design, so it is improved with an additional electrode and retested before the application goes in.
- Week 4–5, step 8. The application is filed with the complete set of documents, then the inspection, approval and commissioning on load follow.
- Step 9. Everything is filed, and the next periodic inspection is diarised.
What made it fast: the drawings and the earthing design existed before the set arrived, so the one retest happened before the application rather than after a rejection.
Exceptions and cautions
- Inspectorate thresholds, forms and portals change by notification. Confirm the current position for your capacity and district every time. Never rely on last year’s job, or on any supplier’s memory, including ours.
- Paralleling with the grid, even momentarily for closed-transition changeover, needs the distribution company’s technical approval as well as the inspectorate’s.
- Bulk diesel storage above the exempt quantity needs its own licence, and in buildings the fire department’s review covers the DG room and the day tank. Settle both before ordering a larger tank or moving the set.
- Rental sets connected for long periods to a building’s distribution should be treated as installations: interlocked, earthed and recorded.
Common mistakes
- Energising a replacement set on the old set’s approval.
- Ordering the set first and starting drawings after delivery.
- Earthing that shares pits with lightning protection, or has no test values on record.
- A changeover without interlocking, which leaves a real risk of back-feeding the utility line and endangering line staff.
- Routing the exhaust to roof level without working out the required stack height.
- Not recording the inspectorate route and date, then repeating the enquiry on the next job.
What to send us
Send the set’s rating or your load list, the site address and district, the building height, a photograph of the proposed DG location, and whether the unit holds pollution-board consent. Our service engineers will map your job to the nine steps and prepare the technical documents the application needs. Use the generator sales enquiry for a new set, or the service enquiry for a replacement or relocation, or WhatsApp 98852 01608. We work across Telangana, Andhra Pradesh and every district within about 300 km of Hyderabad, with project support across India.
Questions engineers ask
Does every DG set need Electrical Inspector approval?
Not always. Installations above the voltage notified by the state, and generating units above the capacity it notifies, need the Electrical Inspector’s approval before energisation. Installations at or below the notified voltage are tested and self-certified by the owner. Check the current Telangana or Andhra Pradesh thresholds for your set before you plan the job.
Can I reuse the approval of the old generator for a new one?
No. A replacement set is an addition or alteration to the installation, and it must be approved by the Electrical Inspector or self-certified, as the thresholds require, before it is connected.
Do I need pollution-board consent for a standby set in an apartment block?
Usually not for a stand-alone set. Under the 2016 classification, stand-alone DG sets totalling 1 MVA or less, with acoustic enclosures and an adequate stack, may be exempted from consent management. The classification has since been revised and each state board applies it, so confirm with the Telangana or Andhra Pradesh board. Larger sets, and sets in consented industries, are handled through consent.
Who applies for the approvals: the supplier or the owner?
The manufacturer holds the emission and noise approvals for the model. The owner, or the owner’s licensed contractor, applies to the Electrical Inspectorate and deals with the pollution board where consent applies. Your supplier or service engineers can prepare the technical documents those applications need.
How long does the approval route take?
Typically about four to six weeks from order to energisation when the drawings and earthing design are ready before the set arrives. Starting drawings after delivery, or a failed earth test found at inspection, can add several weeks.
How high should the exhaust stack be?
Use H = h + 0.2 × √kVA, where h is the building height in metres. A 250 kVA set beside a 9 m building needs about 12.2 m. Engines above 800 kW follow a separate, stricter stack rule, and any higher figure in your consent applies.
How often is a DG installation inspected after approval?
Periodically, at the interval the state sets, which may not exceed five years. Installations above the notified voltage are inspected by the Electrical Inspector; those at or below it are tested and self-certified by the owner. Keep your earthing and insulation test records current between inspections.
Related pages
- Regulatory updates: which authority governs what
- India genset emission norms
- The DG set document file
- Generator noise on site: measurement and zone limits
- Generator site planning checklist
- DG set earthing, step by step
- DG breaker, changeover and cable size chart
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer. Last updated 5 November 2026.