What happens when the generator stator is grounded?

Phenomena:

(1) The alarm bell rings and the “Generator Stator Grounded” light plate lights up. ?

(2) The voltmeter of the stator circuit insulation monitoring device has an indication. ?

(3) The water leak alarm device can work. ?

(4) When the primary fuse of the voltage transformer for protection is blown and the latch fails, the stator grounding protection will not work properly. Pay attention to the distinction.

(5) When the fundamental wave is triggered, the generator-transformer group is triggered and stopped. ?

(6) Third harmonic action signaling.

Treatment: ?

(1) The unit trips, checks the power switching situation of the installation and treats it as if the generator had tripped. Place the generator-transformer group for maintenancet contact maintenance to check the cause of the grounding. ?

(2) If the generator does not trip (the ground protection signal is in the signal position), check the voltmeter of the stator circuit insulation monitoring device and determine whether a grounding phenomenon occurs based on the operating conditions. ?

(3) Contact secondary team personnel to measure the secondary opening voltage of the TV generator and check the protection device. If the zero sequence voltage indication is higher than that of other units, it means that the unit is effectively grounded, and the appropriate duty manager and plant executives should be informed to request shutdown . ?

(4) Wear insulating boots to make a complete inspection of the generator body and lead wires to see if the primary and secondary plugs of the TV are damaged.loose, causing false signals, and check the neutral point of the generator in relation to the main network. transformer Carry out a detailed inspection of the output wires and high voltage side housing area of ​​the high voltage transformer to see if there is obvious grounding phenomenon (such as grounding caused by leakage water, etc.). ?

(5) If it is the third harmonic grounding, care should be taken to check and determine whether it is a protection malfunction. ?

Causes of generator stator grounding:

Stator coil leakage or water ingress causing degradation insulation; vibrations generated during operation of conductive wires cause damage to insulation; Condensation in the machine causes grounding; oil leaking from the bearing leads to insulation degradation; the updatingsingle-phase ground of the low-voltage side winding of the main transformer or of the high-voltage side winding of the transformer of the high-voltage installation, etc. .

Zero ground voltage is the voltage on the neutral wire n, which can also be thought of as the potential difference between the neutral wire n and the ground wire pe.

Since the ground wire voltage is zero under normal circumstances, the zero ground voltage is the voltage on the zero line, which is Upen as shown in the figure below. Upen=In*Rn, In is the current flowing through the neutral line and Rn is the resistance value of the neutral line.

The commonly used TN-S system (that is, the original three-phase five-wire system) is a power system that strictly separates the working neutral line N and the ground wire PE on the user side. The neutral line is generally not allowed again.

The distance ofenergy transport path determines the length of the neutral line. When the cross section of the neutral line remains unchanged, the length of the neutral line also determines the resistance value of the. neutral line. There is resistance on the neutral line. Once a current flows through the neutral line, zero ground voltage is generated.

Detailed information

On earth voltage, When a ground fault occurs in electrical equipment, the shell, ground wire and grounding body of the grounding equipment is equal to the zero potential point. The potential difference between them is called earth voltage when electrical equipment is earthed.

In the electrical system, ground voltage refers to the potential difference between the shell, ground wire and grounding body of the grounding equipment equal to the point of zero potential when a ground fault occurs in electrical equipment. Earth is generally defined as the point of zero potential.

Voltage can be divided into positive and negative. Consider the earth as the zero point of electric potential. The ground voltage of +220 V is the zero point voltage.

The neutral wire is the earth wire, which is considered the same as the earth, so the 0 V live wire is the high voltage wire at home, it is 220 V. standards different. Theoretically, you won't get an electric shock just from touching the live wire with your hand, because there should be no continuity.

Thus, the greater the radius of the moving fuse wire without load, the smaller the resistance burned, it is the square of the current multiplied by the value of the resistance and the time. heat is required to blow the fuse, the lower the resistance, the lower the ccurrent required is high.

Reference documents:

Reference documents: < /p>Baidu Encyclopedia - Zero Earth Voltage