The grounding resistance cabinet adopts neutral point grounding, which can reduce the transient overvoltage during single-phase grounding, eliminate the resonance overvoltage and arc grounding overvoltage, and the relay protection device can quickly select the fault line and cut off the fault point. Under the influence of grounding resistance cabinet, when non-metallic grounding occurs, the current flowing through neutral point and grounding point is greatly reduced compared with metal grounding. At the same time, the rise of sound phase voltage is also significantly reduced. The zero sequence voltage value is about half of that of single-phase metal grounding.
Grounding the neutral point through the resistance cabinet of the generator can limit the fault current to a moderate value. On the one hand, it can ensure the selectivity and sensitivity of relay protection. On the other hand, it should ensure that the fault point is not damaged as much as possible, and limit the transient overvoltage to within 26 times of the voltage of the normal line to neutral line, so as to prevent arc reignition and damage to the main equipment due to arc grounding overvoltage. At the same time, the damping of resistance plays an important role in preventing ferroresonance overvoltage.
According to different service conditions, the neutral grounding resistance cabinet can be divided into indoor type and outdoor type. The wire feeding mode can be upward movement, side entry and down exit, upward exit and downward entry and down exit. And adopt upward movement. In case of lateral entry and exit, the top of the cabinet is equipped with a through wall sleeve, and the top of the resistance cabinet is equipped with a lifting ring to facilitate hoisting. The resistor can be made of special alloy material or non-metallic special material valve plate.
After the neutral point grounding resistance cabinet is installed, when non-metallic grounding occurs, due to the influence of grounding address resistance, the current flowing through the grounding address and neutral point is significantly lower than that of metal grounding. At the same time, the rise of sound phase voltage is also significantly lower, and the zero sequence voltage value is about half of that of single-phase metal grounding. It can be seen that selecting neutral point to be grounded through resistance can reduce transient overvoltage, eliminate arc grounding overvoltage and partial resonance overvoltage during single-phase grounding, select simple relay protection equipment, quickly select fault line and cut off fault point.
The generator neutral point is grounded through resistance. The generator neutral point grounding resistance cabinet can limit the fault current to a certain appropriate value, improve the sensitivity of the relay protection device to tripping, and make the fault point only slightly burned, which can effectively prevent the ferromagnetic resonance overvoltage, so as to ensure the safe and normal operation of the generator in the generator neutral point grounding resistance cabinet.
Post time: Jun-20-2022