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Cable and wire introduction
Wires and cables refer to materials used for power, electrical and related transmission purposes. There is no strict boundary between 'wire' and 'cable'. Generally, products with a small number of cores, small product diameters, and simple structures are called wires, those without insulation are called bare wires, and the others are called cables. The ones without insulation are called bare wires, and the others are called cables; the ones with larger conductor cross-sectional area (greater than 6 square millimeters) are called large cables, and the smaller ones (less than or equal to 6 square millimeters) are called small wires and also called cloth. wire.
Wires and cables mainly include bare wires, cloth wires and power cables for electrical equipment, cross-linked cables and communication optical cables.
The complete naming is usually more complicated, so people sometimes use a simple name (usually the name of a category) combined with model specifications to replace the complete name. For example, 'low voltage cable' represents all PVC insulated power cables of 0.6/1kV level. . The type spectrum of the wire and cable is relatively complete. It can be said that as long as the standard type and specifications of the wire and cable are written, the specific product can be clarified, but what is its complete naming?
The naming of wire and cable products has the following principles:
1. What's included in the product name
(1) Product application occasion or size category name
(2) Product structure material or type;
(3) Important features or additional features of the product
Basically named in the above order, sometimes in order to emphasize important or additional features, write the features before or before the corresponding structure description.
2. The order of structure description
The product structure description is based on the principle from the inside to the outside: conductor --> insulation --> inner sheath --> outer sheath --> armor type.
Under the circumstance that will not cause confusion, some structural descriptions are omitted or abbreviated. For example, aluminum conductors are not allowed in automobile wires and flexible wires, so the conductor materials are not described.
Rated voltage 8.7/15kV flame-retardant copper core XLPE insulated steel tape armored PVC sheathed power cable
'Rated voltage 8.7/15kV'--application occasion/voltage grade
'Flame Retardant'-an emphasized feature
'Copper Core'-Conductor Material
'Cross-linked polyethylene insulation'--insulating material
'Steel tape armor'-armor layer material and type (double steel tape gap wrapping)
'Polyvinyl chloride sheath'-inner and outer sheath materials (the inner and outer sheath materials are the same, the inner sheath material is omitted)
'Power Cable'-the name of the product category
The corresponding model is written as ZR-YJV22-8.7/15.
The model composition and sequence of the wire and cable are as follows:
[1: Category, Use] [2: Conductor] [3: Insulation] [4: Inner Sheath] [5: Structural Features] [6: Outer Sheath or Derivatives]-[7: Use Features]
Items 1-5 and 7 are represented by pinyin letters, and polymer materials are represented by the first letter of the English name. Each item can be 1-2 letters; item 6 is 1-3 numbers.
The principle of omission in the model: Copper is the main conductor material used in wire and cable products, so the copper core code is written as T, except for bare wires and bare conductor products. Bare wires and bare conductor products, power cables, and electromagnetic wire products do not indicate major category codes, and electrical equipment wires and cables and communication cables are also not listed, but subcategory or series codes are listed.
Item 7 is a mark for various special use occasions or additional special use requirements, which are marked with pinyin letters after '-'. Sometimes in order to highlight this item, write this item to the top. Such as ZR- (flame retardant), NH- (fire-resistant), WDZ- (low smoke and halogen-free, corporate standard), -TH (for hot and humid areas), FY- (anti-termite, corporate standard), etc.
Number mark Armor layer Outer layer or outer sheath
cause of issue
1. External force damage. Judging from the operation analysis in recent years, especially in the high-speed economic development of Haipudong, quite a lot of cable failures are caused by mechanical damage. For example, non-standard construction during cable laying and installation can easily cause mechanical damage; civil construction on directly buried cables can also easily damage cables in operation. l Sometimes if the damage is not serious, it will take months or even years to cause the damaged part to be completely broken down to form a fault, and sometimes a short-circuit fault may occur if the damage is serious, which directly affects the safe production of the electric power unit and the power user.
2. The insulation is damp. This situation is also very common, and generally occurs at the cable joints in direct burial or piping. For example: unqualified cable joints and joints made in humid weather conditions will cause water or steam to enter the joints. Over time, water branches will form under the action of the electric field, which will gradually damage the insulation strength of the cable and cause failures.
3. Chemical corrosion. The cable is directly buried in the area with acid and alkali, which will often cause the cable armor, lead skin or outer sheath to be corroded. The protective layer suffers from chemical corrosion or electrolytic corrosion for a long time, resulting in the failure of the protective layer and the reduction of insulation. The cable is faulty. Chemical: The unit’s cable corrosion is quite serious.
4. Long-term overload operation. Overload operation, due to the thermal effect of the current, the conductor heating will inevitably be caused when the load current passes through the cable. At the same time, the skin effect of the charge, the eddy current loss of the steel armor, and the insulation loss will also generate additional heat, which will increase the temperature of the cable. During long-term overload operation, the excessively high temperature will accelerate the aging of the insulation, and even the insulation will be broken down. Especially in the hot summer, the temperature rise of the cable often leads to the first breakdown of the weak insulation of the cable, so in the summer, there are more cable faults.
5. The cable connector is faulty. The cable joint is the weakest link in the cable line, and the cable joint failures caused by the direct fault of the personnel (poor construction) often occur. In the process of making cable joints, if there are original nets such as insufficient joint crimping, insufficient heating, etc., the insulation of the cable head will be reduced, which will cause an accident.
6. Environment and temperature. The external environment and heat source where the cable is located can also cause the cable's temperature to be too high, insulation breakdown, and even explosion and fire.
7. The normal aging of the cable body or other reasons such as natural disasters.