40 MVA Transformer

Configurations for a 40 MVA Unit

The winding arrangement follows the voltage levels of the substation:

40 MVA Transformer Specification (Typical Data)

40 MVA Transformer Current Rating and Load Capacity

Full-load current follows the voltage level, so the same 40 MVA unit shows very different currents on each side. On a 110kV primary the line current is about 210A; on a 132kV primary it falls to about 175A; and on the 10.5kV secondary it rises to about 2,200A – which is why the low-voltage side of a unit this size is busbar connected rather than cabled.

40 MVA transformer load capacity in kW depends on the power factor of the connected load. At 0.8 power factor a 40 MVA transformer delivers about 32 MW; at unity power factor it can carry 40 MW. The kVA rating fixes the current and the heating limit, while the kW figure is what the load actually consumes – so when a project asks for 40 MW, the transformer is normally specified above 40 MVA unless the power factor is known to be high.

Full-load current by voltage level (40 MVA)

40 MVA Transformer Weight, Oil Capacity and Dimensions

A typical 40 MVA transformer weight is around 46-65 tonnes for transport, with the active part (core and windings) at about 40 tonnes and the insulating oil at about 20-23 tonnes. Units at this size are heavy, and transport limits often shape the design as much as the electrical data – which is why the shipping configuration and lifting points are agreed at order stage.

40 MVA transformer oil capacity is confirmed at order stage in tonnes or litres, because it depends on tank design, radiator area and cooling mode. 40 MVA transformer dimensions for this class commonly fall around 5,400-6,700 mm long, 4,150-5,300 mm wide and 4,300-5,800 mm high. Always confirm against the approval drawing, and check the route to site for bridge, crane and heavy-haul limits before the order is placed.

Typical 40 MVA transport data (confirm on approval drawings)

Losses, Impedance and Specification Choices

Loss level is the main technical decision on a 40 MVA unit because it is paid for over 25-40 years of service. At the 110kV class the no-load loss for this rating is typically between 17.8 kW and 25.8 kW depending on the loss level selected, and the load loss at 75°C is around 139-148 kW. Higher-grade core steel and larger conductor sections lower those figures but raise the purchase price.

Short-circuit impedance is normally 10.5% on the 110kV/10.5kV pair, and it has to be coordinated with the substation switchgear. A lower impedance gives better voltage regulation but raises the fault current the breakers must interrupt; a higher impedance reduces fault levels but increases voltage drop and load loss. Impedance is therefore confirmed against the network study rather than chosen in isolation.

Indicative loss data, 40 MVA 110kV class

40 MVA Transformer: 132 kV Substation Duty

In a 132kV substation the 40 MVA transformer is usually the step-down unit that converts transmission voltage to the local distribution level. A common arrangement is 132/33kV or 132/11kV, with the 132 kV substation busbar feeding the primary through a circuit breaker and disconnector, and the 33kV or 11kV side feeding the distribution switchboard.

Protection and monitoring for this duty normally include differential protection, overcurrent and earth-fault relays, Buchholz and oil-temperature devices, and tap-changer control. The unit is usually specified with an on-load tap changer so the secondary voltage can be held while the 132kV supply varies. On site it needs a bunded oil containment area and a fire wall to local substation practice.

Typical 132kV substation configuration

What 31.5/40, 30/40, 20/40, 32/40 and 40/50 MVA Mean

The paired figures seen in tender documents and datasheets describe dual ratings, not two different transformers. The 40/50 MVA transformer meaning is straightforward once the cooling suffix is understood: a 31.5/40 MVA transformer or a 40/50 MVA transformer is one unit with two declared capacities, where the lower figure is the rating with natural cooling (ONAN) and the higher figure is the rating with fans running (ONAF). Forced cooling removes more heat from the same windings, so the unit can carry more load without exceeding its temperature limits.

The same notation appears on a 30/40 MVA transformer, a 20/40 MVA transformer or a 32/40 MVA transformer entry, where the ratio is wider and the pair may instead describe a base rating against a short-time emergency rating – so always read the datasheet note rather than assuming. If a project calls up 40/50 MVA, state which figure the switchgear, cables and protection must be rated for: protection and fault level must follow the higher ONAF rating.

Reading dual-rating notation

40 MVA Transformer Price and What Drives It

The cost of 40 MVA transformer units is driven by the electrical specification rather than the MVA figure alone: voltage class, loss level, impedance, two- or three-winding construction, tap-changer type, cooling, bushings and protection accessories all move the number. A standard two-winding 110kV unit with off-circuit tapping sits at the lower end of the range, while a 132kV three-winding unit with OLTC, low-loss core and full monitoring sits at the upper end.

For budgetary planning, export-built 40 MVA 110kV class units typically land in the region of USD 250,000-650,000 depending on loss level, winding material and accessory package, before freight, duties and site works. For the 40 MVA transformer price in Pakistan, Africa and the Middle East, add freight, insurance and local clearing costs on top of the ex-works figure, and note that loss capitalisation rules can make a low-loss unit cheaper over its service life even when the purchase price is higher. To quote accurately we need the voltage combination, impedance, loss level, tap-changer type, cooling and destination port.

What moves the price – and what we need to quote

Larger Ratings: 400 MVA and 4000 MVA Transformers

Searches for a 400 MVA transformer or a 4000 MVA transformer point to a different class of equipment. A 400 MVA power transformer belongs to the 400kV transmission level – roughly ten times the capacity of a 40 MVA unit, with a 400 MVA transformer weight in the hundreds of tonnes and transport that needs specialised heavy-haul planning. On 400 MVA transformer price, budget several times the cost of a 40 MVA unit, since both the material content and the transport scope scale with capacity. A 4000 MVA machine sits at the largest end of generator step-up and ultra-high-voltage applications and is normally engineered as a one-off project unit.

Subian’s power transformer series covers 6,300-63,000 kVA at 110-132kV, which includes the 40 MVA rating and units up to 63 MVA. For ratings beyond that class, send the specification and we will confirm what can be built or supplied through our partner works, together with realistic weights, dimensions and lead times for the transport study.