Selection Of Booster Cable Material To Determine The Safety Of Medium Voltage System
At present, China's urban power grid pressure system generally refers to 6-10 kV system, part of the region has 20 kV system. The medium voltage system receives power from the high voltage transmission system by step-down, directly to the medium voltage user, or then to the low pressure system after the step-down, from the low pressure system to the low voltage user. Therefore, the medium voltage system is connected to high voltage transmission system and millions of users important bridge. Like the human body sent to the brain and limbs of the capillaries, once blocked, the body will be paralyzed. A person must have a healthy body, must ensure that blood vessels flow. A city power grid to normal operation, must ensure that all levels of voltage lines flow, and the pressure system in the grid accounted for a large proportion, and directly connected with the user, so the safety and reliability is particularly important. So, aluminum alloy booster cable is suitable for China's power grid system?
1) aluminum alloy conductor of the six indicators that conductivity, tensile strength and creep resistance, melting point, thermal expansion coefficient, anti-oxidation corrosion, anti-electrochemical corrosion and copper are very different. And these six indicators is the conductor as a power transmission safety and energy efficiency assurance. From the six indicators, aluminum and aluminum compared to no significant progress.
2) At present, some aluminum alloy booster cable manufacturers proposed to use aluminum alloy booster cable instead of copper booster cable solution is to increase the aluminum alloy booster cable cross-sectional area of 1.6 times the copper, so as to achieve the same conductivity with copper. However, in addition to the conductivity, aluminum alloy conductor tensile strength and creep resistance, melting point, thermal expansion coefficient, anti-oxidation corrosion, anti-electrochemical corrosion and other five indicators are not due to increase the cross-section has changed, so aluminum and aluminum alloy Than the risk of copper did not decrease.
3) aluminum alloy booster cable to increase the cross-section of the solution is a theoretical algorithm, and in practice to increase the cross-section after the channel cost, booster cable spacing requirements, the row of aperture increases the cost of one or two specifications increase And the actual problem, the booster cable bending radius increases, the corner hole and the entrance hole area increases, the booster cable capacitance current increases with the booster cable cross-section increases, after the capacitor current increases in accordance with the provisions of power safety, but also need to take the appropriate Measures and so on. Because of these uncertainties, it is an uncertainty whether the aluminum alloy booster cable can, in practice, be able to add a 1.6x cross section to the copper booster cable according to the theoretical algorithm.
4) Aluminum models used in the manufacture of aluminum booster cables in North America are AA1350 and AA8030. AA1350 began for power transmission lines, and later used in residential buildings, but the effect is very unsatisfactory, and finally replaced with copper booster cable. AA1350 lessons used in the failure of power transmission lines should arouse our full attention.
5) AA8030 compared to AA1350 in mechanical performance has improved, mainly creep resistance has greatly improved, but no significant changes in other characteristics, it was later used in the residential area. AA8030 developed in North America for 40 years is also limited to residential construction, and did not enter the field of power transmission. In addition, the European countries, Japan and other developed countries have not carefully studied the use of aluminum alloy booster cable. So that the aluminum alloy booster cable market is very limited, technically no advanced, is a very limited market space technology. This should cause China's power users attach great importance.
6) In addition to the above problems, aluminum alloy booster cable connector terminal problems, to produce qualified high investment costs of aluminum alloy, the establishment of the corresponding standard regulatory system, aluminum alloy booster cable joint construction specifications and other issues.
7) from the grid to run, the city of low-voltage system is the highest proportion of fault system, the summer high load period is particularly serious, coupled with booster cable fault repair time is long, restore the transmission slow, the user loss, to the power supply enterprises bring great pressure, The call for high reliability equipment is high. In addition, from the safety, reliability, power supply capacity, equipment life, ease of construction and maintenance, copper booster cables are better than aluminum alloy booster cable.
In short, the aluminum alloy booster cable is a large investment risk, the market space is limited, the user safety and reliability of a low degree of protection products. Whether China is to be introduced into the grid pressure system, it is worth pondering.