Causes of Electrification of Neutral Line of Diesel Generator

1.What is a zero line charged?

The output cable connecting the three-phase AC diesel generator is divided into zero line, live line and ground line, of which the sign letter of the zero line is N; The symbol letter of the fire line is L; The symbol letter of the ground wire is E; The symbol letter for zero line grounding is PE, and the symbol letter for the integration of zero line and ground wire is PEN. The pressure difference between the live wire and the zero wire is maintained in a sinusoidal oscillation pattern. Due to the same potential between the ground wire and the zero wire, the pressure difference between the live wire and the ground wire is also maintained in a sinusoidal oscillation pattern. When you feel that the zero line is not charged because it is grounded, and when you come into contact with the zero line on the ground because there is no potential difference, there will be no current generated. So there is a feeling that the zero line is not charged.

The zero wire and the live wire are originally from the power source, and the positive direction of the current is from one end, passing through external devices, and entering from the other end, forming a circuit. The difference between a zero wire and a live wire is that one of the two terminals of the power supply is connected to the ground. The neutral line is connected to the neutral point of the Diesel generator and the grounding electrode of diesel generator, which means that the resistance from the neutral line to the neutral point and grounding electrode of the Diesel generator is very small, and the resistance from your body to the ground is much greater than that from the neutral line to the ground.

When the human body comes into contact with a live wire, the person is standing on the ground, and the current from the live wire flows into the ground or the neutral wire through the human body, causing an electric shock accident. However, if the person comes into contact with the neutral wire, they will not be electrocuted. Connect the shell of a conductive electrical appliance to the ground wire. In the event of leakage, the current will flow directly into the ground wire without passing through the body, thus avoiding electric shock accidents.

2.Reasons for zero line electrification

1. Generator leakage

The body of the diesel generator is a conductive material. If there is leakage, the current will flow to the zero line of the diesel generator. This usually occurs after the diesel generator is aged or damped, resulting in damage or deterioration of insulation materials.

2. Winding open circuit or short circuit

The winding of diesel generator may be open or short circuited due to long-term use or vibration and other factors. This will cause the current to flow to the zero line of the diesel generator, making it live.

3. Zero wire connection error

Some manufacturers confuse the zero line with other lines when designing diesel generating set, so that some wires that should have been connected to other lines are reversed from the zero line. In this way, the current will pass through the zero line of the diesel generator.

4. Poor grounding

The neutral line of Diesel generator needs to be grounded. If the grounding is poor, the neutral line will be electrified. This situation is usually caused by reasons such as excessive grounding resistance or disconnection of grounding lines.

5. Capacitor fault

If the capacitor in the generator malfunctions, it will cause current to leak out of the capacitor, causing the zero line to be charged. The cause of capacitor failure may be aging, overload, etc.

3.Solution to zero line electrification

1. Replace insulation material

Check the insulation of the Diesel generator to ensure that the insulation material is not damaged. If the fuselage leaks electricity, the insulation material needs to be replaced to reduce the flow of current to the zero line of the Diesel generator.

2. Repair winding

In case of open circuit or short circuit of the winding, the winding shall be repaired to prevent the current from flowing to the zero line of the diesel generator.

3. Replace the zero line

If there is a problem with the wrong connection of the zero line, it is necessary to separate the zero line from the line that should be connected. If there is a problem with the zero line, it can be replaced with a new one to avoid the electrification of the diesel generator zero line.

4. Check grounding

(1) Check the grounding of diesel generator to ensure that the grounding resistance is not greater than 4 ohms. If the grounding resistance is too high, measures such as increasing the number of grounding wires or replacing the grounding electrode can be taken.

(2) Once the zero line is disconnected, the electrical equipment that uses protective grounding will lose its protective effect. Once the equipment leaks electricity, it will cause personal electric shock. Even if the equipment does not leak electricity, the zero line itself carries dangerous voltage that makes the equipment shell live, which can also cause personal electric shock accidents. Therefore, the distribution line should be repeatedly grounded, and the grounding resistance of repeated grounding should not exceed 10 Ω. The renderings are shown in Figures 2 and 3.

5. Replace the capacitor

Capacitors play a very important role in brushless generators, as they can improve the stability of generator, protect surrounding electronic devices, and also improve the efficiency of the generator. Therefore, whether it is normal or not occupies a very important position. If a capacitor malfunction is found, it should be replaced in a timely manner.