Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question dated 2020-07-18

1 Neutral points of generators, transformers, and capacitor banks； 2 Secondary windings of current and voltage transformers ； 3 Chassis of lightning arresters, protective gaps, lightning rods, and coupling capacitors ； 4. Supports for insulators, wall-mounted bushings, high-voltage fuses, high-voltage circuit breakers, isolating switches, knife switches, etc ； 5 The enclosures of generators, transformers, motors, and capacitors, as well as the metal sheaths of power cables ； 6 Metal frames of distribution panels, switchgear cabinets, control panels, protection panels, and distribution boxes ； 7 The metal frames of indoor and outdoor electrical equipment, as well as the metal parts of reinforced concrete frames. 8. In general, electrical equipment in 380V three-phase four-wire low-voltage systems should be protected by zero connection. 9. Enclosure of the instrument control cabinet. 10. On-site instruments and solenoid valves

Neutral points of generators, transformers, and capacitor banks； Secondary coils of current and voltage transformers ； Chassis for lightning arresters, protective gaps, lightning rods, and coupling capacitors ； Bases for support insulators, wall-mounted bushings, high-voltage fuses, high-voltage circuit breakers, isolating switches, knife switches, etc ； The casings of generators, transformers, motors, and capacitors, as well as the metal outer sheaths of power cables ； Metal frames of distribution panels, switchgear cabinets, control panels, protection panels, and distribution boxes ； The metal frames of indoor and outdoor electrical equipment, as well as the metal parts of reinforced concrete frames.

In some cases, the casings or bodies of certain devices can be charged. The charge may be leakage current, induced electricity, or static electricity. Guide the charge into the ground through grounding.

Neutral points of generators, transformers, and capacitor banks； Secondary coils of current and voltage transformers ； Chassis for lightning arresters, protective gaps, lightning rods, and coupling capacitors ； Bases for support insulators, wall-mounted bushings, high-voltage fuses, high-voltage circuit breakers, isolating switches, knife switches, etc ； The casings of generators, transformers, motors, and capacitors, as well as the metal outer sheaths of power cables ； Metal frames of distribution panels, switchgear cabinets, control panels, protection panels, and distribution boxes ； The metal frames of indoor and outdoor electrical equipment, as well as the metal parts of reinforced concrete frames.

Neutral points of generators, transformers, and capacitor banks； Secondary coils of current and voltage transformers ； Chassis for lightning arresters, protective gaps, lightning rods, and coupling capacitors ； Bases for support insulators, wall-mounted bushings, high-voltage fuses, high-voltage circuit breakers, isolating switches, knife switches, etc ； The casings of generators, transformers, motors, and capacitors, as well as the metal outer sheaths of power cables ； Metal frames of distribution panels, switchgear cabinets, control panels, protection panels, and distribution boxes ； The metal frames of indoor and outdoor electrical equipment, as well as the metal parts of reinforced concrete frames.

Electrical equipment that must be grounded: 1. The neutral points of generators, transformers, and capacitor banks； 2 Secondary windings of current and voltage transformers ； 3 Chassis of lightning arresters, protective gaps, lightning rods, and coupling capacitors ； Electrical equipment that requires protective grounding: 1. Bases for insulators, bushings, high-voltage fuses, high-voltage circuit breakers, isolating switches, knife switches, etc ； 2 The enclosures of generators, transformers, motors, and capacitors, as well as the metal sheaths of power cables ； 3 Metal frames of distribution panels, switchgear cabinets, control panels, protection panels, and distribution boxes ； 4 The metal frames of indoor and outdoor electrical equipment, as well as the metal parts of reinforced concrete frames. In general, electrical equipment in 380V three-phase four-wire low-voltage systems should be protected by zero connection (grounding protection can also be used, but the two methods cannot be used together in the same system).

Grounding that is provided to prevent dangerous voltages, which may arise from accidents such as insulation failure on electrical meters and the metal parts of electrical equipment, from posing a threat to human safety, is called protective grounding. Those that are provided with protective grounding include: instrument panels and bases, enclosures for electrical instruments, distribution boxes, junction boxes, cable trays, conduit pipes, and the shielding layers of armored cables.

1 Neutral points of generators, transformers, and capacitor banks； 2 Secondary windings of current and voltage transformers ； 3 Chassis of lightning arresters, protective gaps, lightning rods, and coupling capacitors ； 4. Supports for insulators, wall-mounted bushings, high-voltage fuses, high-voltage circuit breakers, isolating switches, knife switches, etc ； 5 The enclosures of generators, transformers, motors, and capacitors, as well as the metal sheaths of power cables ； 6 Metal frames of distribution panels, switchgear cabinets, control panels, protection panels, and distribution boxes ； 7 The metal frames of indoor and outdoor electrical equipment, as well as the metal parts of reinforced concrete frames. 8. In general, electrical equipment in 380V three-phase four-wire low-voltage systems should be protected by zero connection. 9. Enclosure of the instrument control cabinet. 10. On-site instruments and solenoid valves

The exposed conductive parts of the following electrical equipment and appliances shall be connected to a protective wire (PE), to ground (in TT or IT systems), or to the neutral line (in TN systems). (1) Transformers, motors, electrical appliances, hand-held and mobile electrical appliances. (2) Transmission devices for electrical equipment. (3) The metal frame of the power distribution apparatus, and the frames of the power distribution panel and the protection control panel. (4) Metal protective tubes for distribution lines, metal wiring boxes for switches, etc.