Power cable voltage level classification
Divided by voltage level
1. Low-voltage cable: Suitable for fixed transmission on transmission and distribution lines with AC 50Hz and rated voltage of 3kV and below for transmission of electrical energy.
2. Medium and low voltage cable: (generally refers to 35KV and below): PVC insulated cable, polyethylene insulated cable, cross-linked polyethylene insulated cable, etc.
3, high-voltage cables: (usually 110KV and above): polyethylene cables and cross-linked polyethylene insulated cables.
4, ultra high voltage cable: (275 ~ 800 kV).
5, UHV cable: (1000 kV and above).
The main advantage
1 The area is small. Generally buried in the soil or laid in the indoor, channel, tunnel, the insulation distance between the lines is small, without poles and towers, covering a small area, basically does not occupy space on the ground.
2 high reliability. Due to the small impact of weather conditions and the surrounding environment, the transmission performance is stable and the reliability is high.
3 Has more favorable conditions for the development of ultra-high pressure and large capacity, such as low temperature, superconducting power cables.
4 large distributed capacitance.
5 less maintenance work.
6 The possibility of electric shock is small.
Reasons and countermeasures for failure of power cable
External damage: Damage to external forces may occur during the storage, transportation, laying, and operation of cables. In particular, buried cables that are already in operation are vulnerable to damage during the construction of other projects. Such accidents often account for 50% of cable accidents. In order to avoid such accidents, in addition to enhancing the quality of work in all aspects of cable storage, transportation, and laying, it is more important to strictly implement the groundless system.
Protective layer corrosion: Electrochemical corrosion of underground stray currents or chemical corrosion of non-neutral soils causes the protective layer to fail and lose its protective effect on insulation. The solution is to install drainage equipment in areas with stray electric current concentration; when the local soil on the cable line contains chemical substances that damage the cable lead, the cable should be installed in the pipe, and use neutral soil as the cable pad And cover, but also coated with asphalt on the cable.
Overvoltage and overload operation: Improper selection of cable voltage, sudden high pressure surges during operation, or long-term overload may damage the cable's dielectric strength and breakdown the cable. This needs to be stepped up by stepping up inspections and improving operating conditions.
Outdoor terminal head soaking: due to poor construction, insulation glue is not filled, the terminal head is soaked, and finally the explosion occurs. Therefore, it is necessary to strictly implement the construction process regulations and seriously accept and inspect; strengthen inspection and timely maintenance. The terminal head leaks oil, destroys the sealing structure, causes the draining of the impregnant at the end of the cable to dry, increases the thermal resistance, accelerates the aging of the insulation, easily absorbs moisture, and causes thermal breakdown. When it is found that the terminal head is leaking oil, inspections should be intensified, and when it is serious, the power should be cut off and redone.
Difference with control cable
The power cable is used to transmit and distribute the large-functional power in the main line of the power system, and the control cable directly transmits the power from the power distribution point of the power system to the power connection lines of various appliances and appliances. The rated voltage of the power cable is generally 0.6/1KV and above, and the control cable is mainly 450/750V. When power cables and control cables of the same specifications are manufactured, the insulation and sheath thickness of power cables is thicker than that of control cables.
(a) The control cables belong to the cables for electrical equipment, and the power cables are two of the five categories of cables.
(b) The standard for control cables is 9330, and the standard for power cables is GB12706.
(3) The color of the insulated wire core of the control cable is generally black and white, and the low voltage of the power cable is generally a color separation.
(4) The cross-section of the control cable will generally not exceed 10 square meters. The power cable is mainly used for power transmission and generally has a large section.
Explanation:
1. The following are the national standard, in addition to the national standard power cable, there are industry standards and local standards
2. The following are power cable standards and do not cover control cables, communication cables, etc.
3. The following are the latest versions, but some have already had updated versions of the discussion draft, but have not yet promulgated
4. Sorting is a bit messy, roughly sorted by cable and accessories, specifications, and test methods. There are too many standards in the test, only a part
GB/T 12706-2002 Extruded insulated power cables and accessories for rated voltages from 1kV (Um=1.2kV) to 35kV (Um=40.5kV)
GB11033-1989 Basic technical requirements for power cable accessories with rated voltage of 26/35 kV and below
GB/T 12976-1991 Copper core and aluminum core paper insulated power cable with rated voltage of 35kV and below
GB/T 11017-2002 110kV cross-linked polyethylene insulated power cable and its accessories
GB/Z 18890-2002 Rated voltage 220kV (Um=252kV) XLPE insulated power cable and its accessories
GB 9326-1988 Oil-paper insulated self-contained oil-filled cables and accessories for AC 330kV and below
GB 5013-1997 Rubber insulated cables of rated voltages up to and including 450/750V
GB 50217-1994 Electrical Engineering Cable Design Specification
GB 50168-1992 Specification for construction and acceptance of cable lines
GB/T 7594-1987 Wire and cable insulation and rubber sheath
GB/T 3048-1994 Test methods for electrical properties of wire and cable
GB/T 2951-1994 General test method for cable insulation and jacket materials GB/T 12666-1990 Wire and cable combustion test method
power cable
PVC insulated sheathed power cable
Model Name Application Range
VV
VLV PVC insulated PVC sheathed power cables are laid indoors, in tunnels and in pipelines. The cables cannot withstand pressure and mechanical external forces.
VV22
VLV22 PVC insulated steel tape armored PVC sheathed power cables are laid indoors, in tunnels and in direct-buried soil. The cables can withstand pressure and other external forces.
VV32
VLV32 PVC insulated thin steel wire armored PVC sheathed power cables are laid indoors, in mines, in water, and cables can withstand considerable tensile forces.
VV42
VLV42 PVC insulated thick steel wire armored PVC sheathed power cables are laid in vertical occasions such as shafts and underwater, and can withstand considerable axial tension.
ZR-VV
ZR-VLV PVC insulated PVC sheathed flame-retardant power cables are laid indoors, in tunnels and in pipelines. The cables cannot withstand pressure and mechanical external forces.
ZR-VV22
ZR-VLV22 PVC insulated steel tape armored PVC sheathed flame-retardant power cables are laid indoors, in tunnels and in direct-buried soil. The cables can withstand pressure and other external forces.
ZR-VV32
ZR-VLV32 PVC insulated thin steel wire armored PVC sheathed flame-retardant power cable is laid indoors, in the mine shaft, in water, and the cable can withstand considerable pulling force.
ZR-VV42
ZR-VLV42 PVC insulated thick steel wire armored PVC sheathed flame-retardant power cable is laid in the shaft, underwater and other vertical occasions, can withstand considerable axial tension.
ZR-VV32
ZR-VLV32 PVC insulated thin steel wire armored PVC sheathed flame-retardant power cable is laid indoors, in the mine shaft, in water, and the cable can withstand considerable pulling force.
ZR-VV42
ZR-VLV42 PVC insulated thick steel wire armored PVC sheathed flame-retardant power cable is laid in the shaft, underwater and other vertical occasions, can withstand considerable axial pull.
PVC insulated sheathed fire resistant power cable
Model Name
NH-VV PVC insulated and sheathed fire resistant power cable
NH-VV22 PVC insulated and sheathed steel tape armored fire-resistant power cable
Cross-linked polyethylene insulated power cable
Model Name
YJV
YJLV copper or aluminum core XLPE insulated, PVC sheathed power cable
YJV22
YJLV22 copper or aluminum core XLPE insulated, steel tape armored PVC sheathed power cable
YJV32, 42
YJLV32, 42 copper or aluminum core XLPE insulated, steel wire armored PVC sheathed power cable
Use description
Model/Copper Core Name Use
NA-YJV/NB-YJV cross-linked polyethylene insulated PVC sheathed type A (B) fire-resisting power cables can be laid in rooms, tunnels and pipelines where fire resistance is required.
NA-YJV22/NB-YJV22 cross-linked polyethylene insulated steel tape armored PVC sheathed type A (B) fire-resisting power cable is suitable for laying when buried in fire-resistant requirements, and is not suitable for pipe laying.
NA-VV/NB-VV PVC insulated PVC sheaths can be laid in rooms, tunnels and pipelines where fire resistance is required.
NA-VV22/NB-VV22 PVC insulated steel tape armored PVC sheathed type A (B) fire-resisting power cable is suitable for laying when buried in fire-resisting requirements, and is not suitable for laying in pipes.
WDNA-YJY/WDNB-YJY cross-linked polyethylene insulated polyolefin sheathed type A (B) halogen-free low smoke fire-retardant power cables can be laid in indoor, tunnels and pipelines where halogen-free, low-smoke and fire-resistant materials are required.
WDNA-YJY23/WDNB-YJY23 cross-linked polyethylene insulated steel tape armored polyolefin jacket A (B) halogen-free low smoke fire-resistant power cable suitable for laying halogen-free and smoke-free requirements when buried, not suitable for pipeline Laying inside.
1. Cables are classified by voltage level
Power cables are generally manufactured at a certain voltage level, and the voltage levels are 0.5kV, 1, 3, 6, 10, 20, 35, 60, 110, 220, and 330kV in this order. Among them, 1kV voltage grade power cables are used most. Power cables with voltage ratings of 3 to 35 kV are often used in main power supply lines in large and medium-sized buildings. The power cables with voltage ratings of 60-330kV are used in power transmission lines that are not suitable for overhead conductors, as well as for crossing rivers and seabeds. According to the crude voltage can be divided into low voltage cable (less than 1kV) and high voltage cable (greater than 1kV). From the aspects of construction technical requirements, cable joints, structural characteristics of cable terminations, and operation and maintenance, it is also divided into low-voltage power cables, medium-voltage power cables (1 to 10 kV), and high-voltage power cables.
2 cable according to the core section of the integral class
The conductive cable of the power cable is manufactured according to a certain class of nominal cross-sectional area, which is convenient for manufacturing and design and construction selection. The nominal cross-sectional area series of China's power cables are 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500, 600mm2, a total of 19 species. The nominal cross-sectional area of ​​the high pressure oil-filled cable series is 100, 240, 400, 600, 700, 845mm2 in total. Multi-core cables are based on the phase line with the largest cross section.
3. According to the number of conductors
The power cable has 5 cores of 1 to 5 cores. Single-core cable is used to transmit single-phase AC, DC and special occasions (high-voltage motor outlets). The oil-filled and gas-filled high-voltage cables with voltage ratings of 60kV and above are mostly single-core. The two-core cable is mostly used for transmitting single-phase alternating current or direct current. Three-core cables are used in three-phase AC power networks and are widely used in cable lines below 35kV. The four-core cable is used for low-voltage distribution lines, neutral grounded TT mode and TN-C mode power supply system. The five-core cable is used in the TN-S mode power supply system for low-voltage distribution lines and neutral grounding. Two cores and four cores are cables with a voltage below 1kV.
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