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Selection of cables and wires for explosive environments should comply with the following regulations: (Shared by Shenzhen ZhongNuo Testing Technology Co., Ltd.)
In explosive environments, the rated voltage of insulated conductors and cables used for low-voltage power and lighting circuits should be higher than or equal to the working voltage, with U0/U not less than the working voltage. The rated voltage of the neutral line should be equal to the phase voltage and should be laid in the same sheath or protective tube.
(2) In explosive hazard zones, except within distribution panels, wiring cabinets, or metal conduit wiring systems, uninsulated wires should not be used as supply and distribution lines.
(3) Copper-core cables should be used in Zone 1. In Zone 2, copper-core cables are recommended, except for intrinsically safe circuits. When aluminum-core cables are used, their cross-sectional area must not be less than 16 square millimeters, and copper-aluminum transition joints should be used for connections with electrical equipment. Circuits installed in explosive dust environments in Zones 20 and 21, as well as in areas with severe vibration within Zone 22, must use copper-core insulated conductors or cables.
(4) The technical requirements for wiring of cables in explosive environments, excluding the circuit of this pressure safety system, shall comply with the provisions of Table 5.4.1-1.
(5) Technical requirements for steel pipe wiring in explosive environments with voltages below 1000V, excluding circuits of intrinsic safety systems, shall comply with the specifications in Table 5.1.1-2.
(6) In explosive environments, the selection of insulated conductors and cable cross-sections shall comply with the requirements of Tables 5.4.1-1 and 5.4.1-2, as well as the following provisions:
1) The conductor's allowable current carrying capacity should not be less than 1.2 times the rated current of the fuse element and 1.2 times the set current of the long-time delay overcurrent trip coil of the circuit breaker, except for the situation specified in clause 2 of this article.
2) The long-term allowable current for the auxiliary line of squirrel-cage induction motors with voltage less than 1000V should not be less than 1.2 times the rated current of the motor.
(7) When installing overhead or bridge-mounted cables, flame-retardant cables are recommended. Plastic sheathed cables without armor can be used when the installation method employs bridges that prevent mechanical damage. Non-armor cables can also be installed in cable trenches within Zones 2 and 22, provided there is no risk of damage from rodents or insects.

Basic knowledge for explosion-proof electrical installation includes the following points:
Explosive material classification, grouping, and the categorization and area range division of explosive hazard sites.
Explosive gases should be classified based on their Maximum Experimental Safe Gap (MESG) or Minimum Ignition Current Ratio (MICR), and grouped by their ignition temperature. Combustible dusts, categorized by their conductivity, can be divided into conductive and non-conductive types, and grouped by their low ignition temperature. Hazardous areas with explosive risks are divided into two categories: gas explosion hazardous areas and dust explosion hazardous areas. These areas are further classified into three zones (0, 1, and 2) based on the frequency and duration of the presence of explosive gas environments. Hazardous areas with combustible dust/air mixtures are categorized into three zones (20, 21, and 22) based on the frequency and duration of their occurrence and the thickness of the dust layer.
Section II: Selection of Explosion-Proof Electrical Equipment for Hazardous Areas.
The selection principle for explosion-proof electrical equipment is safety and reliability, as well as economic rationality. It should be selected based on the grade of the explosive hazardous area and the category, level, and group of the explosive hazardous materials. Refer to the specific selection table in standard AQ3009-2007.
Section 3: Installation of electrical wiring and explosion-proof electrical equipment in hazardous explosive areas.
Installation methods for electrical wiring in explosive gas environments can be divided into cable wiring and conduit wiring methods. Electrical wiring should be laid in areas with lower explosion hazards or at a greater distance from the source of release, avoiding locations prone to mechanical damage, vibration, corrosion, dust accumulation, and those with hazardous temperatures. When avoidance is not possible, preventive measures should be taken. The low-voltage cables or insulated conductors used must have a rated voltage higher than the working voltage of the circuit and not less than 500V. Insulated conductors must be installed within conduits. For more details, refer to training courses on explosion-proof electrical installation, maintenance, and repair.
IV. Inspection and Maintenance of Explosion-Proof Electrical Equipment in Hazardous Areas.
To minimize the ignition hazard of electrical equipment in hazardous areas, initial inspections should be conducted before the equipment is put into operation and during the handover acceptance of the project. Continuous supervision and regular inspections should be carried out to ensure the electrical equipment remains in good condition for long-term use in hazardous areas. The initial and regular inspections should be entrusted to safety production testing and inspection institutions with explosion-proof qualifications.
Inspections and maintenance of explosion-proof electrical equipment should be conducted by qualified personnel meeting specified criteria. These individuals must undergo training covering topics such as explosion-proof types, installation practices, relevant regulations and procedures, as well as the general principles of hazardous area classification. They should also receive appropriate continuing education or regular training and possess relevant experience and trained qualifications. Continuous supervision and periodic inspections should be implemented. Maintenance requirements should propose reasonable corrective measures and equipment replacement procedures.

Basic Standards for Explosion-Proof Electrical Construction (Shared by Shenzhen ZhongNuo Inspection Technology Co., Ltd.)
Explosion-proof electrical installation differs from standard electrical installation due to the increased explosion-proof requirements of its environment. In accordance with industry standards, an environment where air is mixed with gases, vapors, mist, or dust, and upon ignition, the combustion can spread to the entire unburned mixture, is termed an explosive environment. An area where explosive gas environments or flammable dust environments are present in large quantities or are expected to occur, necessitating special preventive measures for the structure, installation, and use of electrical equipment, is called a hazardous area. Explosion-proof electrical installation refers to a task that meets the requirements for explosion-proof electrical equipment, conditions, and personnel, and involves working in explosive environments and hazardous areas, emphasizing strength.

Basic Requirements for Explosion-Proof Electrical Installations in Hazardous Areas (Shared by Shenzhen ZhongNuo Inspection Technology Co., Ltd.)
1. Oil-immersed equipment should be used under conditions of no vibration, no tilt, and fixed installation.
2. When using non-explosion-proof equipment for mechanical transmission as partition walls, the following regulations should be adhered to:
The room for installing electrical equipment should be separated from the explosive hazardous area by a solid wall made of non-combustible materials.
(2) Transmission shafts should be sealed through partition walls with gland packing or equivalent sealing measures.
(3) The exit of the electrical equipment room should lead to an environment free of explosive hazard areas.
(4) When the room where the equipment is installed must be connected to an explosive environment, the explosive environment should be maintained at a relative positive pressure.
3. Electrical circuits and equipment in explosive environments, excluding inherently safe circuits, should be equipped with overload, short-circuit, and grounding protection. Electrical equipment that cannot experience overload does not require overload protection. Motors in explosive environments, in addition to the necessary protection as required by current standards, should also be equipped with phase failure protection. If the automatic shutdown of electrical equipment could pose a greater danger than the ignition risk, an alarm device should be used instead of the automatic shutdown device.
4. In emergency situations, appropriate measures should be taken at suitable locations outside of hazardous areas to disconnect the power to the equipment. Continuous-running equipment should not be included in the emergency shutdown circuit and should be installed on a separate circuit to prevent the occurrence of additional hazards.
5. The design of transformer stations, sub-stations, and control rooms shall comply with the following regulations:
Transformer stations, distribution stations (including distribution rooms, etc.), and control rooms should be located outside of explosive atmosphere environments. When they are in a positive pressure room, they can be situated in Zones 1 and 2.
(2) For explosive gas environments heavier than air, the equipment floor of electrical and instrumentation in power substations, distribution stations, and control rooms located in the additional 2 zone of the explosion hazard area should be elevated 0.6 meters above the external ground level.
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