Bridging Power

In short. Bridging power is rental generation that runs a site for weeks or months while a permanent supply or asset is unavailable, such as a delayed DISCOM connection, a transformer on order or a generator being replaced. Because the set becomes the prime source, select it on a prime or continuous rating, plan maintenance during the hire, secure the fuel supply, engineer the installation as semi-permanent and define the end condition before the start.

What bridging power covers

Common cases in Telangana and Andhra Pradesh include a new factory ready to produce before its HT connection is energised, a load expansion waiting for an enhanced contract demand, a failed transformer with a long lead time, and a standby generator replacement where the old set is removed before the new one is commissioned. In each case the temporary set is no longer standby. It carries the site for most or all of the day, and that changes how it is chosen and run.

Rating for the duty

A standby rating applies to a set used only during utility outages for limited hours. A bridging set runs as the main source, so its prime rating, typically around 90 percent of standby, or its continuous rating is the figure that matters. Average load should sit in a sensible band, roughly 40 to 80 percent of prime rating, because long running below about 30 percent leads to wet stacking and poor fuel economy, while running at the limit leaves nothing for motor starting. Where the load will grow, several sets or a synchronised plant let capacity follow demand. See generator paralleling.

Maintenance without losing the site

Engines need oil, filter and inspection at intervals measured in running hours, often 250 to 500 hours depending on the engine; a set running around the clock reaches that in two to three weeks. Decide in advance how the service is done: a second set that carries the load while the first is serviced, a short planned outage at a quiet time, or a synchronised plant where one unit can drop out. The permitted interruption should be written into the hire scope. Preventive maintenance practice is set out in preventive maintenance.

Fuel and cost over a long duration

Over months, diesel cost exceeds the hire cost by a wide margin, so measured consumption against kWh delivered is worth tracking from the first week. Fuel supply needs a contract rather than ad hoc orders, and the reserve should survive a delayed delivery. Sizing tank and reserve follows the method on rental fuel tanks. Note that new diesel gensets up to 800 kW supplied in India must meet CPCB IV+ emission norms, which affects which rental sets can be deployed for long-term prime duty.

Avoid temporary permanence

An installation engineered for three weeks becomes risky if it quietly runs for nine months. Cables laid on the ground get damaged, extra loads are added without checks, and earth electrodes dry out. Set a review date: if the bridge is extended, the installation is inspected and upgraded to suit the new duration.

Long bridges also deserve monitoring. A simple remote controller reporting load, running hours, fuel level and alarms lets the owner see problems before they become outages, and gives a factual record of energy delivered. Monsoon conditions matter too: a set sitting on bare ground for months needs a raised plinth, drainage and a weatherproof cable entry. On a plant that will grow during the bridge, agree in advance how added load is assessed, because the margin that existed at handover disappears quietly as new machines are connected.

A worked check helps (illustrative). A new unit in an industrial estate near Hyderabad expects 350 kW average and 450 kW peak for five months while its HT connection is completed. Two 320 kVA sets synchronised, each with a prime rating near 230 kW, carry the peak together and run near 75 percent at average load. When one set is serviced, the site sheds non-essential load to about 220 kW for the few hours involved. A single 625 kVA set would carry the load more simply, but every service would mean a full outage.

Plan the exit

Write down what ends the bridge: DISCOM energisation, transformer commissioning, or acceptance of the new generator. Agree how the permanent source is tested before load transfers, whether the change is a short break or a synchronised transfer, who removes the temporary equipment and how the final readings are recorded.

Common mistakes

• Selecting a bridging set on its standby rating. The engine is overrated for continuous duty and wears quickly or trips in the afternoon heat.
• Having no plan for routine service. The site either skips maintenance or takes an unplanned outage.
• Leaving a short-term cable installation in place for months. Mechanical damage and moisture create earth faults and fire risk.
• Not defining the end condition. The hire extends with no review and costs grow unnoticed.

What to send us

Send the reason for the bridge and its expected duration, the load profile across the day with any planned growth, the site single-line diagram and connection point, and the fuel arrangements you can support. Send a generator rental enquiry and we will propose sets, maintenance cover and an exit plan.

Questions engineers ask

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 D. Srinivas Reddy, Managing Partner and Service Engineer, Reddy Generators. Last updated 19 October 2026.