In short. Emergency temporary power restores essential loads after a failed transformer, cable, switchboard or permanent generator. Speed matters, but the first useful step is identifying what has failed, which loads must come back first and where a rental set can be connected safely without back-feeding the fault or the DISCOM network. An enquiry with the voltage, critical loads, largest motor and site access lets the right set be mobilised the first time.
Identify what has failed
The failed element decides how temporary power can be connected. A DISCOM feeder outage leaves the site’s own transformer and switchboards healthy, so a rental set can feed the LT board through an existing changeover. A failed distribution transformer leaves the LT board usable but its incomer dead. A switchboard fire or flashover removes the normal connection point entirely, and the rental set must feed sub-boards or critical feeders directly. A failed permanent generator only removes the standby source, which is a different level of urgency again.
| Failure | Immediate question | Likely temporary arrangement |
|---|---|---|
| DISCOM supply lost for a long period | Is the existing DG absent, failed or undersized? | Rental set into the DG incomer or changeover |
| Transformer failure | Is the LT board healthy and isolated from the HT side? | Rental set to the LT main incomer |
| Main LT board damaged | Which outgoing feeders are intact? | Temporary panel feeding critical circuits directly |
| Cable fault | Can the faulted section be isolated? | Local set at the affected building or load |
| Standby generator breakdown | How long is the repair? | Rental set as replacement standby, possibly bridging power |
Never energise an unresolved fault
A rental generator is not a way to test whether a damaged board will hold. Before connection, the site’s responsible electrical person should confirm that the faulted equipment is isolated and locked off, that the DISCOM incomer is open so the set cannot back-feed the grid, and that the circuits being restored have been checked for insulation resistance where damage is possible. Protection set for utility fault levels may not clear a fault on generator supply quickly, so a cautious restoration is safer than a fast one. Changeover principles are set out under rental ATS.
Restore in priority order
Emergency restoration rarely needs the whole connected load. Agree the priority list with the facility: life safety and fire systems, then critical process or IT, then cooling and essential services, then everything else if capacity permits. Restoring in steps also manages the first load step. Motors restarting together, UPS batteries beginning to recharge and chillers coming back at once can demand far more than the running load, and a set sized only for running kW may trip. The load-shedding logic in load shedding applies directly.
Mobilisation and site practicalities
Availability depends on the size needed, where the set is and the route to site. A small or medium set on a trailer can move quickly within Hyderabad; a large set needs a suitable vehicle, a crane or hydraulic lift, and a clear, level position near the connection. Confirm access width, overhead obstructions, ground conditions after rain, and the cable length from the set position to the connection point before the vehicle leaves. Bring cables, a temporary panel and fuel for the first day with the set, rather than finding out on arrival that they are missing. Sizing guidance is on generator rental.
When emergency becomes bridging
A transformer replacement or switchboard rebuild often takes weeks, not days. Once the emergency set has run for more than a few days, review the arrangement as a longer-term installation: proper cable protection, refuelling contracts, service intervals, earthing checks and a defined end condition. That transition is covered on bridging power.
Sizing for the restoration step
The estimate does not need to be perfect, but it should be honest. A hospital wing near Secunderabad might need 60 kW of lighting and essential sockets, a 30 kW medical gas and vacuum plant, and a 45 kW chiller (illustrative). Running load is 135 kW, about 170 kVA at 0.8 power factor. The chiller compressor start can briefly add more than its running current several times over, so restoring it last, after the other loads are stable, lets a 200 kVA set carry the duty, whereas switching everything on together would call for a larger set. A clear restoration order is often worth more than extra kVA.
Related photographs and videos
Common mistakes
- Asking only for a kVA figure. The set arrives without the right cables, panel or connection plan and restoration waits.
- Connecting before the DISCOM incomer is isolated and locked. When the grid returns the generator is paralleled unintentionally, with serious damage and danger to line staff.
- Switching all loads on together. The restart surge trips the set and the site loses supply a second time.
- Treating a weeks-long repair as an emergency throughout. Temporary cabling and fuel arrangements degrade into an unmanaged hazard.
What to send us
Call or WhatsApp with the site location, what has failed, the supply voltage and phases, the critical loads with an estimate of their kW, the largest motor, and photographs of the connection point and the access route. An estimate is useful if it is labelled as one. Then follow up through the generator rental enquiry so the details are recorded for the hire.
Questions engineers ask
How quickly can an emergency generator be on site?
It depends on the size, the set’s current location, the distance and access to the site. Small and medium sets within the city can often be mobilised the same day, while large sets need lifting equipment and route planning. Sending complete details at the first call is what shortens the time most.
What size generator should I ask for in an emergency?
Ask for one that carries the loads you must restore, not the whole site. Add the running kW of those loads, allow for the largest motor start, and divide by 0.8 to get kVA. If unsure, describe the loads and let the supplier size the set.
Can a rental generator connect to my existing ATS?
Often yes, if the ATS is healthy, rated for the set and its generator-side terminals are accessible. The phase rotation and control wiring must be checked, and the existing permanent generator isolated if it is faulty.
Who is responsible for safe connection?
The site’s authorised electrical person is responsible for isolating the faulted equipment and permitting the connection. The rental team is responsible for the set, its cables and the work it performs. Agreeing these boundaries before energisation is part of a safe emergency response.
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
- 1–2 MVA generators
- 2 MVA and above generators
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.