In order to ensure personal safety and the needs of the power system, there are strict requirements for the grounding of the diesel generator set. There are three kinds of grounding methods: working grounding, protection grounding and protection zero. The purpose of grounding is as follows:
1. Grounding the work
Working ground is to ground the neutral point for the purpose of:
1) Reduce electric shock voltage. For the system with ungrounded neutral point, when one phase is connected to the ground and the human body touches one of the other two phases, the shock voltage is more than 1.7 times the phase voltage; For neutral ground systems, the shock voltage is reduced to close to or equal to the phase voltage.
2) Quickly cut off the faulty equipment. For the system with ungrounded neutral point, when a phase is connected to the ground, due to the existence of capacitance and insulation resistance in the wire and ground, the current path can be formed, and the grounding current is small, which is not enough to make the protection device operate and cut off the power supply, and cannot ensure personal safety. For the neutral point grounding system, when the ground current is large after a phase grounding, the protection device will quickly act to disconnect the fault point.
3) Reduce the insulation level of electrical equipment to the ground. In a system where the neutral point is not grounded, when one phase is grounded, the ground voltage of the other two phases will be raised to the line voltage. For a neutral ground system, when one phase is connected to the ground, the ground voltage of the other two phases is only close to the phase voltage, so the insulation level of electrical equipment and transmission lines can be reduced.
2. Grounding protection
Protective grounding is often used in low-voltage systems where the neutral point is not grounded, its role is: when the insulation structure of a winding of the motor has been damaged so that the shell is charged, if it is not grounded, the human body hits the shell, which is equivalent to single-phase electric shock, and the risk of electric shock may occur. If protective grounding is used, when the human body touches the shell, the resistance of the human body is in parallel with the grounding resistance, due to the resistance of the human body; Much higher than the ground resistance, the current through the human body is very small, there will be no danger of electric shock.
3. Protection connect to zero
Protective zero is often used in neutral ground low-voltage systems, its role is: when the insulation structure of a winding of the motor has been destroyed and connected with the shell, due to the use of protective zero, the formation of single-phase short circuit, quickly fuse this phase in the fuse, the shell will no longer live. Even when the body touches the shell before the fuse is blown, because the resistance of the body is much greater than the line resistance, the current through the body is also very small, and there is no danger of electric shock.
For more questions about the generator set, please call the Beidou Power team. More than ten years of professional production and sales of power generation equipment experience, more professional engineer team to serve you, choose Beidou power is to choose rest assured, welcome on-site factory inspection.
Post time: Dec-27-2024