What are the operating modes of the neutral point in electrical systems?

Three methods: direct grounding of the neutral point, ungrounding, and grounding through an arc-suppression coil.

In the early days of our country, the grounding methods for the neutral point in power systems were classified into high-current grounding systems and low-current grounding systems. It is generally believed that a grounding system in which the grounding arc can extinguish itself is a low-current grounding system, while a grounding system in which the grounding arc cannot extinguish itself is a high-current grounding system. Since the magnitude of the grounding current cannot be clearly defined using the classification of neutral point grounding methods in power systems, it has been replaced with effective neutral point grounding systems and ineffective neutral point grounding systems. Effective neutral grounding systems include direct grounding and grounding through a low-value resistor or low-value reactor. Neutral point non-effective grounding systems include grounding through arc suppression coils, high-resistance grounding, high-impedance grounding, and ungrounding.