DC grounding includes one-point grounding and two-point grounding:
One-point grounding may cause the protection and automatic installation to malfunction or refuse to operate, while two-point grounding may not only cause the relay protection, signal, and automatic device to malfunction or refuse to operate, but also may cause the DC fuse to blow, making the protection and automatic installation fail. When the power supply of the control circuit is lost, the two points of the same pole are grounded in the complex protection circuit, and some relays may be short-circuited, which may cause the tripping due to inability to act, which will lead to a leapfrog tripping, resulting in the expansion of the accident.
In the DC system, the DC positive and negative electrodes are insulated from the ground. When one pole is grounded, it will not cause any harm because there is no ground current path. However, long-term operation of one pole grounding is not allowed, because the same pole When another place is grounded, it may cause incorrect action of signal device, relay protection or control circuit. A point of grounding followed by another grounding will cause a DC short circuit.
If the DC positive pole is grounded, it may cause the malfunction of the relay protection. Because the general trip coils (such as the outlet intermediate relay coil and the trip and closing coils, etc.) are all connected to the negative power supply, if these circuits are grounded or poorly insulated, the relay protection will malfunction. The grounding of the negative electrode of the DC is the same as the grounding of the positive electrode. If there is a little more grounding in the loop, it may cause the relay protection to reject the action, and the accident will expand by leaps and bounds.
Grounding the two poles and two points at the same time will short-circuit the tripping or closing circuit, which may not only blow the fuse, but also burn out the contacts of the relay.