1. Inverse work
The reverse power phenomenon is caused by the difference in the speed (frequency) and voltage of the generator set, that is, one generator set has positive power, while the other set has negative power. That is to say, the unit with negative power becomes a load at this time (this unit has low frequency and inconsistent speed). When the voltages are not the same, the unit with higher voltage provides a reactive current and voltage to the unit with lower voltage (the unit's ammeter indicates the positive direction), which is equivalent to adding a power adjustment unit in the power supply system. The unit with low voltage becomes a large load at this time and accepts a large reactive current to maintain the voltage balance of the two units (the ammeter of this unit indicates the reverse direction). During monitoring, the voltage of one unit is increased, or the voltage of another unit is high or low, causing a unit to have a reverse current, and its operating current is about 20% of the rated current. The reverse-acting relay operates, trips, and alarms, but does not shut down.
2. Overcurrent:
The current generator set has a certain rated power, its overload capacity is very low, basically about 5% of the rated power, and the allowable load time is 15-30 minutes, and the maximum is not more than 60 minutes. After this time, the generator set will generate heat. The wire insulation will be reduced, which reduces the service life. Therefore, if there is no special requirement when setting the overcurrent protection, the overcurrent protection can be set at 110% of the rated current. During the load test, bring the current to 110% of the rated current, and the overcurrent relay will act. Trip, alarm, non-stop.
3. Overvoltage:
When generating sets are used in parallel, the power supply system is most afraid of oscillations. Once the voltage of the oscillation system rises, it is easy to cause the insulation breakdown of the electrical equipment and the power supply equipment, and the power supply equipment and the electrical equipment are paralyzed. For this reason, the generator sets used in parallel are all equipped with over-voltage protection, and the setting value is 105% of the rated voltage is the best. Short-circuit the over-voltage relay, trip and shutdown, and alarm action.
