2014年3月29日星期六

Jack knowledge about cable:knowledge of control cable

Power cables for transmission and distribution of electrical energy in the power system features a large trunk, the control cables from the distribution point of the power system to power transmission lines connected directly to the power supply of various electrical equipment appliances. Rated voltage power cables 0.6/1kV and more generally, control cables mainly for 450/750V. The same specifications as power cables and control cables in the production, power cable insulation and sheathing thickness thicker than the control cables. Control cables for the mining industry, energy and transportation sectors, for AC rated voltage of 450/750 volts control, protection circuit and other occasions of PVC insulated, PVC sheathed control cable.
Features
1. DC resistance:. 20 ℃, 0.4mm copper, less than or equal 148Ω/km, 0.5mm copper, less than or equal 95Ω/km.
2.insulated electrical strength: 1min 1kv no breakdown between the conductor and shield conductor 1min 3kv no breakdown
3 Insulation resistance: each wire with the rest of the grounding wire core, control cables greater than 10000MΩ.km, HYAT cable than 3000MΩ.km.
4 Capacitance: mean 52 ± 2nF/km
5 FEXT defense degree: the average power is greater than the specified combinations 150kHZ 69dB/km.
And the performance difference between the power cable
(A) control cables are cables for electrical equipment, cables and power cables are five categories of the two.
(B) The standard is 9330 control cable, power cable is standard GB12706.
(C) control cable color insulated cores are generally black and white printing, and low-voltage power cables are generally separations.
(D) control cable cross section are generally not more than 10 square feet, the main
power cable transmission of electricity, are generally large cross-section.
Due to the above reasons we talked about, power cable specifications generally large, large 500 square (conventional manufacturers can produce a range), then a large cross-section of the manufacturers generally do relatively little, while the control cable cross-section is generally small, generally not more than 10 square maximum.
Speaking from the cable core power cable according to claim grid, typically up to 5 cores, and the control signal transmission control cable, the number of cores is more, according to the standard in terms of number of core 61, but can also be produced according to the user requirements .
Precautions
Control wiring cable installation considerations:
1 roof. Cables are not only exposed to direct sunlight or ultra-high temperature, a standard LAN cable can be applied, it is recommended to use the pipeline. Ultraviolet (UV) - do not apply to cable without UV protection within direct sunlight environment.
2 external walls. Avoid direct sunlight walls and man-made damage. Heat - the temperature in a metal cable duct or trunking is high, many polymeric materials at such temperatures will reduce the service life.
3 pipes (plastic or metal). As in the pipeline, attention to thermal damage and metal pipes plastic pipe. Mechanical damage (Zhi ڮ f cost??) - Cable repair is very expensive, at least every two discontinuous point terminated.
4 vacant application / aerial cable. Consider sag and tension cables. Whether the cable is exposed to direct sunlight.
5 directly in the trench laying underground cables, control of this environment is minimal. To install the cable channel regularly check the extent of dry or wet. Grounding - If you need to control the cable shield grounding must comply with the appropriate standards.
6. Underground pipes. In order to facilitate future upgrades, cable replacement and surface pressure and ambient isolation to isolate the pipeline paved, paved the pipeline is a better way. But do not hope the pipeline will always be kept dry, it will affect the cable types to choose from. Water - Water twisted pair cable LAN cable capacitance will increase, thereby reducing the resistance and cause problems in the near-end crosstalk.
Maintenance
Control cable price formula as follows: Weight of copper in copper calculated X: silk warp ÷ 2 = square root of the number 1.25X1.25X3.14 = X then copper wire X0.89X +10% processing fee.
Calculation of cost price control cables
Square X1.83 = X then the weight of copper in copper + armored price (weight X0.4 yuan / kg) = cost price +10% processing fee
The price of the cable = manufacturing material costs + fixed costs + taxes + service fee + profit
Manufacturing materials cost = material costs * (1 + material consumption) (material cost is the theoretical value calculated)
Fixed costs vary according to each company's situation, generally including production wages, management salaries, utilities, repairs, depreciation, rent costs, transportation costs
Control cable line failures are common mechanical damage, insulation damage, wet insulation, insulation aging deterioration, over-voltage, cable overheating failure. The failure occurs when the line should be cut off the power cable fault, find the point of failure, the fault inspection and analysis, and repair and testing, the mutilation of circumcision, upon failure to eliminate before power is restored.
Above to introduce the performance characteristics of the control cables, precautions and maintenance of knowledge, as well as more control cable inspection knowledge to understand a lot of hope that we own!

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