Diesel generator usage tips: What are the reasons for the grounding of the generator set?
Operating the diesel generator in accordance with the operating instruction manual can extend the service life of the unit. Next, let's take a look at the reasons why diesel generators should be grounded when in use.
1. Working grounding is to ground the neutral point. Its purpose is:
(1) Reduce the electric shock voltage. In a system where the neutral point of the generator set is not grounded, when one phase is grounded and the human body touches one of the other two phases, the electric shock voltage is more than 1.7 times the phase voltage; while for a system with a grounded neutral point, the electric shock voltage drops to close to or equal to the phase voltage.
(2) Quickly cut off the faulty equipment. In a system with an ungrounded neutral point, when one phase is grounded, due to the capacitance and insulation resistance between the conductor and the ground, a current path can be formed. The grounding current is very small, which is not enough to cause the protective device to operate and cut off the power supply, which cannot ensure personal safety; and For neutral point grounding systems, when one phase is grounded and the grounding current is large, the protection device will act quickly to disconnect the fault point.
(3) Reduce the insulation level of electrical equipment to ground. In a system with an ungrounded neutral point, when one phase is grounded, the ground voltage of the other two phases will rise to the line voltage; for a system with a grounded neutral point, when one phase is grounded, the voltage of the other two phases will rise to the line voltage. The ground voltage is only close to the phase voltage, so the insulation level of electrical equipment and transmission lines can be reduced.
2. Protective grounding
Generator set protective grounding is often used in low-voltage systems where the neutral point is not grounded. Its function is: when the insulation structure of a certain winding of the motor has been damaged and the shell is charged, if it is not grounded and the human body touches the shell, it is equivalent to a single-phase electric shock. Risk of electric shock may occur. If protective grounding is used, when the human body touches the shell, since the resistance of the human body is connected in parallel with the ground resistance, the resistance of the human body is much greater than the ground resistance, so the current passing through the human body is very small, and there is no risk of electric shock.
3. Protective connection to zero
Protective zero connection is often used in low-voltage systems where the neutral point is grounded. Its function is: when the insulation structure of a certain winding of the motor has been damaged and is connected to the shell, the protective zero connection is used to form a single-phase short circuit. The current can quickly cause this The fuse in one phase blows and the enclosure is no longer live. Even if the human body touches the casing before the fuse blows, the resistance of the human body is much greater than the resistance of the circuit, and the current passing through the human body is very small, so there is no risk of electric shock.
Use the generator set according to the correct operating procedures, maintain the generator set and replace diesel generator accessories in time according to the usage of the generator set; choose the generator set manufacturer according to the principle of shopping around and choosing a generator set manufacturer with strong comprehensive strength; follow the principle of using the generator set Choose the right brand of generator set based on the number and power of the electrical equipment, budget, and requirements for automation and cloud services.
