Materials and Equipment
High Voltage
Transmission of high-voltage lines in DC, unlike the widely used mode of transport using high-voltage line AC is a process for electricity transmission as a DC voltage of 100-1000kV.
In terms of investment costs DC stations are more expensive than those in AC, while the lines are much cheaper. Since costs are proportional to the distance lines, over a long distance power lines sanctioned DC become more efficient than AC. This limit is at about 30km with sea cables and about 500km at the overhead cables. The possibility of controlling the parameters of current switching circuits, the asynchronous network connections and efficient use of energy transmission by submarine cables, often leads to high voltage lines using DC at borders for energy transfer. Eoline generators parks offshore also require submarine cables due to the fact that their turbines are unsynchronized. The low cost of high voltage DC lines advantages the link between communities located far away from each other.
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Medium Voltage
By means of such equipment the distribution of electricity on large stretches is made effective. It also makes a great supply of electricity to individual consumers.
They are extremely common and used in the power system, both on the production of electricity and the distribution, connection points and power points as well as large industrial networks or individual users.
Energy needs of cities and densely populated areas are growing. Distribution systems are becoming larger. Often, estimates of energy through MV cables, to a certain part of the town are no longer affordable because of high energy requirements. It is therefore necessary to provide processing systems capable of connecting high-voltage transmission capacity at the medium voltage.
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Low Voltage
Low voltage equipment is built for rated voltages not exceeding 1000 V AC 1200 V direct current.They are used not only in central power stations, but also in industry and domestic sectors at a very large scale.
Classification of materials and low voltage electrical equipment can be made according to several criteria: by the way the current, after the rated voltage, rated current after by number of poles, etc..
By the way the current is AC or DC, the AC is AC single or three phase alternating current.
Standard nominal voltages below 1000V AC and 1200V DC are: AC – 24, 48,127,220,380,660,1000 V and DC – 24,48,125,400,800, 1200V.
Standardized nominal currents are: 3,6,10,16, 32.40, 63,80,100,160, 200, 315, 400, 630.1600, 2000, 2500 and 3150 A. As is standard transformer secondary current of 5 A.
Low voltage devices are built monopolar, bipolar, tripolar and tetrapolary. The first two options are designed to operate in single-phase AC or DC. Tri-and tetrapolary variants are built to work in three-phase alternating current.
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