Diesel generator power can be defined as continuous operating power (COP), prime power (PRP), limited time operating power (LTP), and emergency standby power (ESP). Some drawings do not specify the specific power level when marking diesel generator power.Due to the varying power levels, this can cause difficulties during construction.
These four power levels represent the maximum power a generator can achieve under the manufacturer’s specified conditions. However, different power modes have different operating methods and average output power, as follows:
- Continuous operating power (COP): The maximum power a generator can continuously supply to a constant load with no restrictions on its annual operating time (a generator marked with a COP of 1000kW has an average output power of 1000kW).
- Prime power (PRP): The maximum power a generator can continuously supply to a variable load with no restrictions on its annual operating time. The permissible average output power over a 24-hour period should not exceed 70% of the PRP (a generator marked with a PRP of 1000kW has an average output power of 700kW).
- Limited Time Power (LTP): The maximum power a generator set can deliver to supply a constant load for 500 hours per year. This means that the maximum annual operating time at 100% LTP is no more than 500 hours (for a generator marked with LTP 1000kW, the average output power is 1000kW).
- Emergency Standby Power (ESP): The maximum power within a variable power range that a generator set can deliver for 200 hours per year. The average output power allowed within a 24-hour operating cycle should not exceed 70% of ESP (for a generator marked with ESP 1000kW, the average output power is 700kW).
Any diesel generator can be rated for one of four power levels, with the relationship being: COP < PRP < LTP < ESP. Suppose, based on actual load, a generator should have a COP of 1000kW, but the drawing only specifies 1000kW (without specifying the power rating). If the manufacturer provides a PRP of 1000kW during procurement, this will result in the actual average output power not meeting the required output power.
For Class A data centers, the output power of diesel generators can be selected based on either COP or 70% PRP.
Since most residential buildings have relatively short power supply periods and variable loads, the output power can be selected based on 70% ESP unless there are special circumstances.
