The basic purposes of graphite grounding and neutral grounding are twofold. Firstly, grounding is required according to the working requirements of the circuit; The second is to ensure the safety of personnel and equipment by grounding or zeroing. It can be divided into four types according to its function. A. Work grounding; b. Protective grounding; c. Protect the neutral connection; d. Repeatedly grounded.

Working grounding, in low-voltage power systems using 380/220V, generally involves four wires drawn from the power transformer, namely three phase wires and one neutral wire, which are used for power and lighting purposes. Three phase wires are used for power, and one phase wire and neutral wire are used for lighting. In such a low-voltage system, considering the reliable operation of electrical equipment and the safety of personnel and equipment under normal or faulty conditions, the neutral point of the system is generally directly grounded, which is called working grounding. The point connected by the three coils of the transformer, also known as the neutral line or zero line, is called the neutral point.

The role of work grounding: There are two functions of work grounding, one is to reduce the danger of grounding at the first phase; Stabilize the potential of the system, limit the voltage to a certain range, and reduce the risk of high voltage entering low voltage.

Protective grounding is a grounding method used to prevent the metal casing of electrical equipment, the structure of power distribution equipment, and line towers from being electrified and endangering personal and equipment safety. The so-called protective grounding is a protective wiring method that reliably connects the metal parts of electrical appliances that are not charged under normal circumstances but may be charged after insulation material damage or other situations (i.e. the metal structural parts that are insulated from the charged parts) to the grounding body with wires. So the application scope of protective grounding:

Protective grounding is applicable to ungrounded power grids. The editor of graphite grounding reminds everyone that in this type of power grid, regardless of the environment, any metal parts that may present dangerous voltage due to insulation damage or other reasons should be protected with grounding measures, unless otherwise specified, mainly including:

(1) Metal casings, bases, and transmission devices connected to motors, transformers, switchgear, lighting fixtures, and other electrical equipment;

(2) Metal or reinforced concrete structures for indoor and outdoor power distribution equipment, as well as metal barriers or fences near live parts;

(3) Metal frames or enclosures for distribution panels, control consoles, protective screens, and distribution cabinets (boxes);

(4) The metal shell of the cable joint box, the metal sheath of the cable, and the steel pipe for wiring;

In addition, metal towers and reinforced concrete towers of certain overhead power lines, as well as secondary coils of transformers, should also be grounded. The editor of graphite grounding reminds everyone that protecting the neutral point is to directly connect the metal parts of the equipment that are not charged under normal circumstances to the system through wires. Adopt protective grounding method to ensure personal safety and prevent electric shock accidents.

Working principle of protective zero connection:

Connecting the metal casing of electrical equipment to the neutral wire of the power grid is an electrical safety measure to protect personal safety. In a zero connected power grid with a voltage below 1000 volts, if the metal casing of electrical equipment is energized due to insulation damage or unexpected situations, resulting in a single-phase short circuit between the phase line and the neutral line, the protective device (automatic switch or fuse) on the line will quickly act to cut off the power supply, so that the metal parts of the equipment will not have dangerous voltage for a long time, which ensures personal safety. In a multiphase AC power system, the neutral point of the star connected winding is directly grounded to make it equal to the ground potential, which is zero potential. The wire drawn from the neutral point of the grounding is called the neutral wire. The editor of graphite grounding reminds everyone that on electrical equipment powered by the same power source, it is not allowed to use protective grounding for some devices and protective grounding for others (see grounding). Because when the protective grounding equipment casing is energized, if its grounding resistance r'D is large and the fault current ID is not sufficient to activate the protective device, the existence of the working resistance rD will cause a constant voltage U0=IDrD on the neutral line. At this time, the dangerous voltage U0 will remain on the protective grounding equipment casing for a long time, endangering personal safety.

The difference between working grounding and protective grounding

Work grounding - refers to the residual electricity generated during work. In order to prevent it from injuring people and allow it to be discharged into the earth, it is called work grounding; Any grounding required for equipment operation is called working grounding. If not connected, the device cannot operate. For example, the neutral point of a transformer is grounded.

The editor in charge of graphite grounding reminds everyone that it is actually a ground wire, which means that when one of the wires comes into contact with an object, the leakage protection switch can trip in time without injuring people, and it is called a protective neutral wire. Both wiring methods play an important role in protecting personal safety.

The difference between protective grounding and protective neutral grounding

Different principles

The editor of graphite grounding reminds everyone that protective grounding is to limit the voltage to ground after equipment leakage, so that it does not exceed the safe range. In high-voltage systems, protective grounding not only limits the voltage to ground, but in some cases, it also plays a role in prompting the operation of power grid protection devices; Neutral protection is the use of a neutral line to cause equipment leakage and form a single-phase short circuit, prompting the protection device on the line to operate and cutting off the power supply of the faulty equipment. In addition, in protecting the neutral grid, protecting the neutral line and repeated grounding can also limit the ground voltage when equipment leaks.

Applicable scope varies

The editor of graphite grounding reminds everyone that protective grounding is applicable to both high and low voltage power grids that are generally not grounded, as well as low voltage power grids that have taken other safety measures (such as installing leakage protectors); Protective grounding is only applicable to low-voltage power grids with a neutral point directly grounded.

Different line structures

The editor of graphite grounding reminds everyone that if protective grounding measures are taken, there can be no working neutral line in the power grid, only a protective grounding wire should be installed; If protective grounding measures are taken, a working neutral wire must be installed and used for grounding protection. The protective neutral wire should not be connected to switches or fuses. When a fuse or other disconnecting device is installed on the working neutral wire, a protective grounding wire or neutral wire must also be installed separately.