Grounding standards for high voltage switchgear

1. In order to ensure the safety of maintenance personnel and equipment, all components in the circuit that need to be connected or provided for access should be grounded in advance, excluding detachable or withdrawable components that can be accessed after being separated from the high-voltage switchgear.

2. Dedicated grounding conductors should be provided in the full length extension direction of all high-voltage switch cabinets. If it is copper, the current density during the ground fault shall not exceed 200A/`mm^2', but the minimum cross-section shall not be less than 30`mm^2'. The grounding conductor should be equipped with a fixed terminal connected to the grounding grid, and there should be obvious Ground mark. If the grounding conductor is not copper, it should also meet the requirements of the same peak withstand current and short-term withstand current.

3. The peak withstand current and short-term withstand current that the grounding circuit can withstand should be suitable for the main circuit. The special grounding conductor should withstand the maximum short-term withstand current that may occur. The grounding bus and the conductor segment connected to it should be able to be selected after passing 87% of the rated short-circuit breaking current on the nameplate according to the method in Appendix B of this technical condition.

4. The metal frame of the high-voltage switch cabinet and the metal support of the high-voltage electrical components installed in the cabinet should be grounded in accordance with technical conditions and firmly connected to the dedicated grounding conductor.

5. Every component that can be isolated from the main circuit should be grounded, including grounding by switching the isolating switch to the closed position of the grounding switch.

6. Under normal circumstances, the metal parts that should be grounded in the withdrawable parts should maintain a good grounding connection under the conditions specified in the test, isolation position or isolation fracture (see DL/T 486), and when the auxiliary circuit is in any intermediate position When not completely disconnected.

The special grounding conductors between each high-voltage switchgear should be connected to each other and firmly connected through special terminals.