An HT AVR transformer is a distribution transformer fitted with an on-load tap changer (OLTC) and an automatic voltage regulator (AVR) relay. When the HT grid voltage rises or falls, the relay moves the tap changer on load, so the LT output stays close to the set voltage without interrupting supply. SG Power HT AVR transformers hold the LT output within ±1%.
What it is: Copper-wound “two-in-one” HT stabilizer and transformer for 11, 22 or 33 kV, holding the LT output within ±1%, for indoor or outdoor installation, 500 kVA to 10 MVA.
Best suited for: Industrial plants on unstable HT supply, hospitals, data centres, process lines.
Stabilizes the 11, 22 or 33 kV supply and steps it down in one unit.
Automatic regulation on load: LT output within ±1%.
Removes the need for a separate HT or LT stabilizer, with no extra stabilizer losses.
Supplied with an AVR control panel in addition to the standard distribution fittings.
Suits long HT feeders where voltage is high or low at the far end.
| Parameter | HT AVR Transformer |
|---|---|
| Rating | 500 kVA to 10 MVA |
| Primary voltage | 11, 22 or 33 kV |
| Secondary voltage | 415 V or 433 V |
| Phase and frequency | Three phase, 50 Hz |
| Vector group | Dyn11 (or as specified) |
| Cooling | ONAN |
| Winding | Copper |
| Core | Step-lap CRGO core, as distribution |
| Voltage regulation | HT stabilization; LT output within ±1% |
| Impedance | As distribution |
| Losses | Low no-load and load losses per IS 1180; designed to BEE 4-star / 5-star levels |
| Temperature rise | Oil 35 °C; winding 45 °C |
| Insulation level | HV 95 kV BIL (11 kV system); LV 3 kV (1.1 kV system) |
| Design ambient | 50 °C, 100% humidity |
| Oil and protection | High BDV oil; moisture-resistant insulation; anti-corrosion, tropicalised finish |
| Standards | As distribution: IS 1180 (Part 1), IS 2026 |
| Fittings | As distribution, plus AVR control panel |
Off-circuit tap switch, Buchholz relay, oil and winding temperature indicators, cable box or bushings, and marshalling box are available as options. GA drawings, rating plate drawings and guaranteed technical particulars (GTP) are available on request.
Grid voltage swings, causing trips or machine damage
Long HT feeder with high or low voltage at the end
Textile, plastic and process industries: voltage-sensitive drives and machines
Hospitals and data centres: stable supply for critical loads
Manufacturing plants on an unstable HT supply
Our application engineers can size the unit for your load and supply. We also make servo voltage stabilizers, industrial rectifiers, chemical earthing electrodes for transformer neutral and body earthing, and lightning arresters for the substation.
More questions are answered on the transformers page, which covers kVA sizing, losses, testing and how to compare transformer manufacturers.
| Product | What it is | Best suited for |
|---|---|---|
| Distribution Transformer | Three phase, oil cooled (ONAN), 11/0.433 kV, 22/0.433 kV or 33/0.433 kV, 25 kVA to 500 kVA, step-lap CRGO core, copper wound | Utility-supplied factories, commercial buildings, housing, solar and pumping |
| LT Step-Down Transformer | 415 V down to 230 V, 110 V or as specified, 25 kVA to 2500 kVA, dry type or oil cooled | Lighting, controls, imported equipment, separate LT circuits |
| LT Step-Up Transformer | 415 V up to 690 V or as specified, 25 kVA to 2500 kVA | Motors and machines rated above 415 V, long LT cable runs |
| Dry Type Transformer | Three phase, ventilated, cast resin or VPI, 11 kV or 33 kV class, 25 kVA to 500 kVA, oil-free and fire-safe | Indoor substations, high-rise buildings, hospitals, malls, metro and data centres where oil is a fire risk |
| Furnace Transformer | Heavy-duty transformer feeding medium-frequency induction furnace panels, 25 kVA to 500 kVA, built for high currents and frequent short circuits during melting | Steel melting shops, foundries and alloy plants |
Send your kVA rating, HT and LT voltages, vector group and site location. Our engineers will reply with a techno-commercial offer, guaranteed losses, a GA drawing and the delivery schedule.