Protection circuit and role of diesel generator
1. The reverse power phenomenon is caused by the different speed (frequency) and voltage of the diesel generator set, that is, one diesel generator set has positive power and the other diesel generator set has negative power. In other words, 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 a high voltage provides a reactive current and a reactive voltage to the unit with a low voltage (the unit's ammeter indicates positively), which is equivalent to adding a camera unit in the power supply system. The low-voltage unit becomes a large load at this time, receiving a large reactive current to maintain the voltage balance of the two units (the unit's ammeter reversely indicates). During monitoring, the voltage of one unit is increased, or the voltage of the other unit is increased, resulting in reverse current of one unit, and its operating current is about 20% of the rated current. Reverse relay action, trip, alarm, but does not stop.
2. Over current: The current generator set has a fixed rated power, and its overload capacity is very low, which is basically about 5% of the rated power. The allowable load time is 15-30 minutes, and the maximum is not more than 60 minutes. After this time, diesel The generator set will generate heat and the insulation of the wires will decrease, which will reduce the service life. Therefore, there is no special requirement when setting the overcurrent protection, and the overcurrent protection can be set at 110% of the rated current. During the load test, the current is brought to 110% of the rated current, and the overcurrent relay is activated. Trip, alarm, non-stop.
3． Over-voltage: When using diesel generator sets side by side, the power supply system is most afraid of oscillation. Once the voltage of the oscillating system increases, it is easy to cause insulation breakdown of the power equipment and power supply equipment, and paralyze the power supply equipment and power equipment. To this end, the diesel generators used in parallel are equipped with overvoltage protection, and the set value is 105% of the rated voltage is the best. Short circuit over voltage relay, trip and stop, alarm action.