The arc suppression coil is an inductive coil with an iron core. It is connected between the neutral point of the transformer (or generator) and the earth to form an arc suppression coil grounding system. During normal operation, no current flows through the arc suppression coil. When the power grid is struck by lightning or a single-phase arc grounding occurs, the neutral point potential will rise to the phase voltage. At this time, the inductive current flowing through the arc suppression coil and the single-phase grounding capacitive fault current cancel each other out, making the fault current After being compensated, the residual current after compensation becomes very small, not enough to maintain the arc, so it extinguishes itself. In this way, the ground fault can be quickly eliminated without causing overvoltage.
In addition, the intermittent arc of the single-phase grounding of the neutral point ungrounded system is the main cause of the arc grounding overvoltage. Due to the compensation function of the arc suppression coil, the reignition of the arc can be basically prevented, thereby preventing the generation of intermittent arcs, and therefore, the arc grounding overvoltage will not be generated. It can be seen that the arc suppression coil has a certain effect on overvoltage protection.
The function of the arc suppression coil is to use the inductive current to compensate the capacitive current flowing through the grounding point. According to the different degree of compensation, it can be divided into three methods: full compensation, under compensation and over compensation.
1. Fully compensated
From the perspective of eliminating the arc at the fault point and avoiding arc overvoltage, this compensation method is the best. However, it is the condition that causes series resonance when it is fully compensated, so in practice, it is impossible to use a complete compensation method.
2. Undercompensation
The ground point current after compensation is still capacitive. When this method is adopted, the above-mentioned problems cannot be avoided. Therefore, the under-compensation method is generally not adopted.
3. Over compensation
The current flowing through the fault point after compensation is inductive. It is impossible for the overvoltage problem of series resonance to occur with this compensation method, so it has been widely used in practice.
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