Neutral point grounding method selection - Solutions - Huaqiang Electronic Network

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The neutral point grounding method of the power system is a technical problem related to safety, power supply, personal equipment safety, communication interference, overvoltage, etc., and also involves economic issues such as power grid investment. Therefore, choosing a neutral point grounding method is a technology. Economic issues.
Neutral point is not grounded and the traditional arc-suppression coil is grounded to have high power supply, good safety for people and equipment, small communication interference, and low investment. It is more suitable for systems where the system is not large (the single-phase grounded capacitor current is within the scope specified by the regulations), the network structure is relatively simple, and the operation mode does not change much. Here, I would like to remind you that in the process of power grid development, the single-phase grounded capacitor current should be measured periodically. When the capacitor current exceeds the specified value, the neutral grounding method should be changed in time.
The neutral point is grounded by a resistor. The main advantage is that the overvoltage is small, and the system cable can choose a lower insulation level to save investment. For overhead line-based systems, most of the single-phase grounding is a transient fault, and this grounding method will trip regardless of the nature of the single-phase multi-phase fault, so the number of trips will be greatly increased. For cable-based distribution networks, single-phase grounding transient faults rarely occur in cables. To save cable investment, when the capacitor current reaches 150A or more, and the single-phase ground fault current is below 1000A, it should be grounded with a neutral point. .
From the point of view of limiting the hazard of single-phase ground fault current, the neutral point grounding in resonant mode (automatic tracking compensated arc suppression coil) is superior to other grounding methods, which is the trend of current neutral grounding. The resonant grounding method is not only suitable for systems with overhead lines, but also for cable-based systems or a mixture of the two. For example, in Berlin, the current reaches a current of 4000A, and the neutral point still uses resonant grounding. The arc suppression coil adopting the automatic tracking compensation is determined according to the comprehensive economic and technical comparison, wherein the thyristor tuned resonant grounding device (the arc suppression coil) adopts the short-circuit impedance transformer type controllable reactor and the power electronic technology. The arc suppression coils represented by the automatic tracking compensation are increasingly showing superiority. In the 10kV and 35kV systems of Hai'an Power Grid, the neutral point is mainly ungrounded. Only the 10kV in the southern suburbs and the 35kV system in Hai'an are installed with the traditional arc suppression coil grounding, but because of the substation. Increased, the capacitor current of the grid is very small, only a few amps, and the traditional arc suppression coil is difficult to adjust, and has been withdrawn from operation. In recent years, with the development of the power grid, we have adopted the automatic tracking compensation arc-suppression coil grounding in the neutral point of the new city 10kV system. Recently, we are also preparing to adopt the thyristor-regulated automatic in the neutral point of the 10kV system in the southern suburbs. Tracking compensation arc suppression coil grounding.