What are the transformer neutral point grounding mode and characteristics?

In the power system, the grounding mode of the transformer neutral point plays a vital role in the stable operation of the system. Different grounding modes have their own distinct characteristics, which profoundly affect each link of the power transmission.

Content

l Neutral point direct grounding: rapid protection under strong current

Neutral point direct grounding is a more common way, more common in 110KV level above the high voltage power system. When the system has a single-phase grounding fault, the neutral point and the ground short circuit current are directly connected to the earth. This is like the "emergency brake" in the circuit, prompting the protection device to move quickly and remove the fault phase at a very fast speed, so as to effectively avoid the expansion of the fault range. However, this high current characteristic also means that the insulation level of the equipment is quite high, after all, to bear the impact of short circuit instant strong current. But in terms of overall system stability, it can be fast when a failure occurs Decisions, to ensure the timeliness and reliability of power supply, to provide a solid backing for high voltage and large capacity transmission.

l The neutral point is grounded by the arc suppression coil: the small current maintains the continuity of power supply

In some medium voltage distribution networks, such as 35KV and below systems, the neutral point through the arc suppression coil grounding mode is often used. In normal operation, the arc coil does not work. Once there is a single-phase ground fault, the arc coil will immediately "appear". It takes advantage of its own inductive current and the grounding capacitor current to offset each other to greatly reduce the grounding fault current to a smaller value. In this way, the system does not have to immediately remove the fault phase, and can maintain a fault operation for a period of time, which greatly improves the reliability of power supply, and avoids large area power failure caused by frequent tripping, just like adding a "buffer band" to the power system to ensure residence The continuous stability of electricity consumption for civilian life and small industrial consumption is especially suitable for scenes with high requirements for power supply continuity.

l Neutral point is ungrounded: insulation challenges and adaptability

The neutral point unground mode is mainly used in some small, isolated power grid or special power supply areas. Under normal working conditions, the relative capacitance current is balanced, and the system can operate smoothly. However, once the single-phase ground fault occurs, because there is no direct grounding path, the grounding current is only the system to the ground capacitor current, and the value is relatively small. However, this also brings challenges. Long-term operation will increase the non-fault phase voltage to the line voltage, which puts forward higher requirements for the equipment insulation, and tests the ability of the equipment to withstand high voltage. This grounding method is low cost, under specific conditions, such as temporary power supply facilities, remote areas of the simple power grid, etc., can rely on simple The structure meets the basic power supply demand and shows a certain adaptability.

In Summary

To sum up, the transformer neutral grounding way have advantages and disadvantages, according to the voltage level of power system, power supply demand, operating environment factors reasonable choice grounding way, is to ensure the power system safe, efficient and stable operation of the key decision, as laying solid foundation for power transmission, supporting the whole power building.

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LuShan, est.1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase isolation transformers,electrical transformer,distribution transformer, step down and step up transformer, low voltage transformer, high voltage transformer, control transformer, toroidal transformer, R-core transformer;DC inductors, AC reactors, filtering reactor, line and load reactor, chokes, filtering reactor, and intermediate,high-frequency products.

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