In short. At 1 to 2 MVA the generator is one component of a power plant. The decisions that matter are made around it: 415 V or 11 kV generation, one set or several, how the neutral is earthed, how protection is graded, how thousands of litres of fuel are stored and kept clean, and how the heat of several engines is rejected. Procurement should follow a single-line diagram, a load study and a protection philosophy, not precede them.
From generator selection to plant design
A 1.5 MVA set delivers about 2087 A at 415 V; a 2 MVA set about 2782 A. Those currents demand large busducts, multiple parallel cables and 2500 to 3200 A air circuit breakers, and they bring fault levels that stress ordinary LV switchboards. The plant also carries a fuel system of several thousand litres, a cooling system rejecting more than a megawatt of heat, an exhaust that is a structural item, and a control system that starts, synchronises, shares load and sheds it. Buyers in this band, from data centres and pharmaceutical campuses to cement and steel plants across Telangana and Andhra Pradesh, treat the installation as an electrical project with a generator in it.
LV or MV generation
I = S / (√3 × V)
Here I is the line current in amperes, S is the apparent power in VA and V is the line voltage in volts. A 2000 kVA set produces 2782 A at 415 V but only 105 A at 11 kV (illustrative). That single comparison drives the choice. Generating at 415 V suits a plant whose loads are close by and whose existing switchboard can be extended; generating at 11 kV suits a campus where power must travel hundreds of metres, where several sets are paralleled onto a common bus, or where the DISCOM connection is already at 11 kV. The medium-voltage generator page covers alternator insulation, switchgear and protection at 11 kV, and the low-voltage generator page the busduct and breaker questions at 415 V.
| Factor | 415 V generation | 11 kV generation |
|---|---|---|
| Current for 2 MVA | About 2782 A | About 105 A |
| Switchgear | 3200 A ACB, busduct, high fault level | MV vacuum breaker panel, cables, lower fault current |
| Distance to load | Short runs only; voltage drop and cable cost rise quickly | Long runs practical |
| Transformer | None if loads are LV | Step-down transformers at each load centre |
| Paralleling several sets | Fault level grows with each set and can exceed LV switchgear ratings | Common MV bus accommodates many sets |
Protection philosophy
No protection settings table should be copied from one plant to another. Each generator needs its own breaker with overcurrent, earth fault, reverse power, loss of excitation, over- and under-voltage and frequency protection, and in a paralleled plant the bus-coupler and incomer relays must grade with the generator relays and with the DISCOM incomer. A generator’s fault contribution decays within cycles as its reactance rises from sub-transient to synchronous values, so overcurrent relays set for the DISCOM source may never see enough current from the generator to trip. Voltage-restrained overcurrent, differential protection on larger machines and a properly designed earth fault scheme are the usual remedies. The protection coordination page sets out the grading study that every plant in this band should have before energisation.
Neutral earthing
With several alternators on one bus, solidly earthing every neutral allows third-harmonic currents to circulate between machines and makes earth fault currents very high. The common approaches are a single earthed neutral selected by contactor with the others floating, a neutral earthing resistor on each machine to limit earth fault current to a few hundred amperes, or at 11 kV a resistance-earthed neutral sized to the cable charging current and the protection sensitivity. Each choice sets the earth fault relay settings and the touch voltage design. Earthing assumptions must never be carried over from another site; the soil, the transformer vector groups and the DISCOM arrangement differ. The earthing and neutral page covers the options and their protection consequences.
Fuel as infrastructure
A 2 MVA plant at full load burns around 350 to 400 litres of diesel an hour, so 24 hours of autonomy means 8000 to 10000 litres of usable fuel on site (illustrative). That is a bulk tank or tank farm with bunding, a filling point suited to a tanker, transfer pumps in duty and standby, day tanks at each set, level monitoring with alarms, water separation and a polishing loop, because diesel stored for months grows microbial sludge and collects condensate, and a single contaminated tank can stop an otherwise healthy plant. Consumption planning must follow the number of sets actually online and be revisited whenever an emergency runs beyond its expected duration. The fuel cleaning and polishing service exists because this is the most common cause of multi-set plant failures we see.
Cooling and the plant room
Several sets running together reject a very large quantity of heat. Set-mounted radiators need a plant room with openings measured in tens of square metres, arranged so that no set draws the discharge of another; remote radiators on the roof, or heat exchangers with a cooling tower, move the problem outdoors at the cost of pumps and pipework. The design condition is every set at full load on the hottest afternoon of May, not one set on a mild evening. Exhaust stacks for engines of this size are structural items with expansion bellows, supports and heights set by the CPCB stack height formula for the plant’s capacity; sets above 800 kW fall outside CPCB IV+ and under the emission norms for larger engines, and that must be confirmed per engine rating with the manufacturer.
Studies, commissioning and the project path
Procurement at this scale should be linked to a single-line diagram, a load study with motor-starting and load-flow checks, a fault level calculation, a protection coordination study, a control philosophy for starting, synchronising, load sharing and shedding, a fuel design and a commissioning plan. Commissioning should include individual set tests on load bank, synchronising and load-sharing tests between sets, protection injection tests, a plant-level heat run with all sets loaded and a simulated mains failure with the real load. For the next step in capacity, where architecture questions dominate completely, see 2 MVA and above.
Common mistakes
- Choosing 415 V generation for a 2 MVA plant with loads 300 metres away. Cable cost and voltage drop overwhelm the project and the switchboard fault level exceeds its rating.
- Copying protection settings from a similar plant. Relays either trip on motor starts or fail to clear generator-fed faults.
- Earthing every alternator neutral solidly. Circulating harmonic current heats the machines and earth fault relays trip without a fault.
- Finalising the electrical plant and then asking where the fuel tank goes. The tank ends up far from the sets with long pipe runs and no bund.
- Commissioning each set alone and never running the plant together. The first real outage reveals load-sharing instability and a room that overheats.
What to send us
Send the single-line diagram, the load list with the large motors and their starting methods, the required autonomy, whether generation is to be at 415 V or 11 kV, the redundancy requirement, and a site plan with the proposed plant location, fuel access and distances to the load centres. Tell us whether the plant will parallel with the DISCOM supply. Use the application engineering enquiry form and we will set out an architecture, a study list and the information we need from the manufacturers.
Questions engineers ask
At what capacity should I generate at 11 kV instead of 415 V?
There is no fixed point, but above about 2 MVA on one bus, or wherever power must travel more than a couple of hundred metres, 11 kV generation usually wins on cable cost, fault level and expandability. Below 1 MVA with nearby loads, 415 V is almost always simpler.
How many generators should a 2 MVA standby plant have?
For a critical facility, enough that the loss of one still covers the critical load, which often means three 750 kVA or 1000 kVA sets rather than two 1000 kVA sets. For a non-critical industrial standby, two sets is a common compromise.
What is a neutral earthing resistor for?
It limits the current that flows when a phase faults to earth, typically to a few hundred amperes, which protects the alternator windings from burning damage and makes the earth fault protection selective between machines.
Does CPCB IV+ apply to a 1500 kVA generator?
No. CPCB IV+ covers new diesel sets up to 800 kW, roughly 1000 kVA. Larger engines fall under the emission and stack-height norms for generators above 800 kW, and the applicable limits should be confirmed with the manufacturer and the state pollution control board for the specific engine.
Generators by rating
- Under 15 kVA generators
- 15–50 kVA generators
- 50–125 kVA generators
- 125–250 kVA generators
- 250–500 kVA generators
- 500–1000 kVA generators
- 2 MVA and above generators
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.