The Distinction between Prime Power and Standby Power in Diesel Generator Sets

Generally, the standby power rating of a diesel generator set is higher than its prime power rating. The prime power of a diesel generator set, also referred to as continuous power or long-running power, indicates the maximum output the unit can sustain continuously for 12 hours. In China, diesel generator sets are typically rated using this prime/continuous power specification.

The standby power, or maximum power, represents the overload capacity allowed within specific time constraints. According to standards, the generator can operate at 10% above its continuous power rating for up to 1 hour within any 12-hour period. For example:

• If a factory's diesel generator has a prime power of 400 kW, it can temporarily operate at 440 kW (standby power) for 1 hour within 12 hours.

• Conversely, if a generator is labeled with a 400 kW standby power rating, its actual continuous power capacity is only 360 kW. Operating such a unit continuously at 400 kW would constitute persistent overloading, significantly shortening equipment lifespan and increasing failure risks.

Therefore, optimal power selection should match actual power requirements plus approximately 10% reserve capacity. This ensures safe operation within the generator's continuous power range while accommodating temporary load fluctuations.