Connecting a part of a power system or electrical equipment to a grounding electrode through a grounding wire is called "grounding".
"Electrical device" is a combination of several interconnected electrical devices in a certain space. "Electrical equipment" refers to any equipment that generates, converts, transmits, distributes or uses electric power, such as motors, transformers, electrical appliances, measuring instruments, protective devices and wiring materials.
The grounding point in power system is generally neutral point, or it may be a point on the phase line. The grounding part of electrical equipment is the exposed conductive part. "Exposed conductive part" refers to the conductive part that can be contacted in electrical equipment. Under normal circumstances, it is not charged, but it may be charged under fault conditions, generally referring to the metal shell.
Sometimes, due to the need of safety protection, the conductive part outside the equipment is connected to the grounding wire for grounding. The "outer conductive part of the device" can also be called the outer conductive part, which does not belong to electrical devices, and is generally the metal pipes of water, heating, gas and air conditioning and the metal structures of buildings.
The outer conductive part can introduce an electric potential, usually a ground potential. The ground wire is a wire connected to the ground electrode. Grounding device is the floorboard of grounding electrode and grounding wire.
Any current that exceeds the rated current is called overcurrent. In general, the overcurrent caused by faults with negligible impedance between different potential points is called short-circuit current, and the current caused by metal short-circuit between phase line and neutral line is called single-phase short-circuit current.
The current generated by insulation damage is called fault current, and the fault current flowing into the earth is called grounding fault current. When the shell of electrical equipment is grounded and the insulation is damaged, it is called "shell collision" when the phase line contacts the metal shell, and the generated current is called "shell collision current". ?
Extended data:
Grounding precautions:
(1) grounding resistance-* * The grounding resistance of the grounding pile shall meet the requirement of smaller grounding resistance among all kinds of grounding.
(2) In order to prevent the mutual interference of grounding systems and ensure the insulation of buildings, the grounding bus bar should be shielded wire with insulating sheath, and one end of the shielding sheath should be grounded.
(3) Although the 3)DC ground, AC ground and safe ground are all connected later, it does not mean that they can be connected at will. Only after strict insulation can they be connected to the same pile according to the above requirements.
(4) In computer equipment, the DC ground and the chassis are safely grounded separately, because the DC ground and the chassis are strictly insulated and connected to the system ground piles respectively, but some computer chassis and DC ground are electrically connected together, and the workplace of AC equipment is strictly insulated from the chassis.
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