Electrician teacher, if the neutral wire is not grounded, connect the wire directly

The neutral point is not grounded, and the voltage between phase zero is still 220V. As for whether it will work? I'll give you an example:

I have seen a family whose zero line was broken, and he connected the zero line directly to the water pipe, and the light was still on, which showed that the line was OK but it was quite unsafe. Because in the current three-phase four-wire power supply system, the neutral point of the transformer is grounded to lead to the neutral wire and PE line.

The neutral line has the following functions:

1. It is used to connect to the equipment that uses the phase line voltage.

2. It is used to conduct unbalanced current and single-phase current in three-phase system.

3. It is used to reduce the voltage offset of the neutral point of the load.

PE wire has the following functions:

Protect personal safety and prevent electric shock accidents in the event of electric shock and live housing. The metal shell of the exposed conductive part of the equipment is connected to the grounding point of the neutral point of the power supply through the protective wire PE. When the electrical equipment is single-phase grounded, a single-phase short circuit is formed, so that the protection device of the equipment or system acts, the faulty equipment is removed, and the person is prevented from being electrocuted.

So from a safety point of view, the neutral point must be grounded!

The neutral wire should be a grounding protection line, which is required for general household appliances and mechanical equipment; As long as people can touch the electrical equipment must have a neutral protection line, when the equipment leakage, with a neutral protection line leakage voltage will be grounded through the wire, causing the protection gate to be de-energized, so as to protect personal safety, if not, the leakage of electrical appliances will have a certain voltage when people come into contact with the person to cause personal injury.

The middle line can be grounded, or it can not be grounded, when the middle line is grounded, there is a certain danger for people to touch the one-phase line, and when the middle line is not grounded (when the insulation level is high), when the person touches the one-phase line, the basic thing.

According to the national electrical energy standard, the neutral wire after RCD is not allowed to be grounded, so as to prevent the external circuit of the human body from becoming a dielectric circle, which poses a threat to people's safety. The IEC standard refers to the conductor that is loaded with multiphase unbalanced currents as the neutral (N-wire), which is often referred to as the "zero wire". Earthing refers to the neutral point of the power system and electrical installation, the exposed conductive part of the electrical equipment and the external conductive part of the device are connected to the earth through conductors.

It can be divided into working grounding, lightning protection grounding and protective grounding.

The working grounding is set by the operation needs of the power system (such as the neutral ground), so under normal circumstances, there will be a long-term flow of current through the grounding electrode, but only an unbalanced current of a few amperes to tens of amperes. In the event of a grounding fault in the system, there will be thousands of amperes of working current flowing through the grounding electrode, but the current will be cut off by the relay protection device, even if it is a backup protection, the action is generally within 1s. Lightning protection grounding is a grounding designed to eliminate the dangerous effects of overvoltage, such as the grounding of lightning rods, lightning wires and lightning arresters.

The lightning protection grounding will only flow under the action of lightning impact, and the lightning current amplitude flowing through the lightning protection grounding electrode can reach tens to hundreds of thousands of amperes, but the duration is very short. Protective grounding is to slow down the grounding set up to prevent equipment from endangering personal safety due to insulation damage and live, such as metal shells, reinforced concrete poles and metal towers of power equipment. Protective grounding will only allow current to flow through if the insulation of the equipment is damaged.

Difference Between Neutral Grounded and Ungrounded:

The interference is different, the nature is different, and the single-phase ground fault is different. Neutral point grounding, due to the single-phase short-circuit current is very large, switches and electrical equipment to choose a large capacity, and can also cause system instability and interference with communication lines and other problems. The neutral point is not grounded, because the single-phase grounding current is limited, the neutral point is not grounded and the system has less interference to the communication; In addition, single-phase grounding can operate for a period of time, which improves the reliability of power supply.

Neutral point grounding, the system of neutral point grounding belongs to a larger current grounding system, generally the current through the grounding point is larger, which may burn out the electrical equipment. The neutral point is not grounded, and the system with the neutral point not grounded belongs to the smaller current grounding system, and the current through the grounding point is generally smaller, and the electrical equipment will not be burned out.

Neutral point grounding, when a single-phase grounding fault occurs in the neutral point grounding system, due to the existence of a short-circuit circuit, the grounding phase current is very large, and the protection device will be started to trip. When a single-phase grounding fault occurs in a neutral point ungrounded system, the fault point will not produce a large short-circuit current due to the neutral point being not effectively grounded, so the system is allowed to operate with faults for a short time. <>