What must be grounded in electrical installations
Grounding of electrical installations
In electrical installations, it is necessary to ground the housings of transformers, electrical machines, apparatus, lamps, starting equipment, etc., metal boxes of mobile and portable power receivers, secondary windings of measuring transformers.
For current transformers installed in circuits with a voltage of 500 V and higher, the secondary winding must be grounded in one pole of the terminals.
In the case of voltage transformers, the neutral points are grounded, and when connecting their windings in an open triangle, the common point of the secondary windings.
The star-connected secondary windings of the voltage transformer can be earthed by a fault fuse.
It is also necessary to ground the frames of distribution boards, control boards, boards and cabinets, metal structures of switchgear, metal cable structures, metal boxes of cable joints, metal sheaths and shields of control and power cables, metal sheaths of wires , steel pipes for electrical wiring, hooks and pins of phase-exposed wires and other metal structures related to the installation of electrical equipment, reinforcement of reinforced concrete supports.
What does not need to be grounded in electrical installations
In electrical installations, they are not grounded:
- equipment mounted on grounded metal structures. The supporting surfaces at the point of contact of the equipment with the structure must be thoroughly cleaned to ensure electrical contact between them;
- boxes for electrical measuring devices (ammeters, voltmeters, etc.), relays, etc., mounted on boards, cabinets, as well as on the walls of the chambers;
- suspension fittings and pins of supporting insulators, covers and lighting fixtures when mounted on wooden poles of power lines and on wooden structures of open substations;
- railway tracks that go outside the territory of substations and switchgear;
- movable or opening parts on metal grounded frames and chambers of distribution enclosures, cabinets, doors, etc.