Cables Charging current

Reduction of capacitive cable charging current in long motor cables... 

Interrupting an unloaded transmission or distribution line or a cable, i.e. interrupting a line charging current, which is capacitive and may lead the system voltage by nearly 90°. 

Voltage fluctuation caused by the charging current of cables is an important factor for the design of a wind farm. The voltage fluctuation can be simulated by steady-state analysis. In the analysis, the cable can be approximately expressed by a lumped parameter equivalent circuit. Since the steady-state behavior of a three-phase circuit is determined by its positive sequence component, the wind farm can be expressed by a single-phase circuit. 

Table 4.5a shows the analytical charging currents of the cables... 

Numerical simulations of a wind farm using the EMTP are explained in this chapter. Vbltage increase due to the charging current of the cables is easily obtained by the EMTP s steady-state analysis routine. The load-flow calculation option of the EMTP called FIX SOURCE enables an estimation of the steady-state behavior of the wind farm, which has plural generators. These techniques are applicable to a simulation of conventional grids. 

Electrostatic spraying is used in shops to coat conductive objects. It is very useful for odd-shaped objects such as wire fence, cables, and piping. An electrostatic potential of 60,000 volts on the object attracts oppositely-charged paint particles the spray can wrap around and coat the side of the object opposite to the spray gun. This technique produces very uniform finishes and has the least paint loss of the three methods. However, it is slow, requires expensive equipment, produces only thin coats, and is sensitive to wind currents. 

When there is no dedicated transformer and these circuits are connected on the system bus directly a large inductor will be essential at the incoming of the static circuits, sufficient to absorb the trapped charge within the transformer and the interconnecting cables up to the converter unit. The size of the inductor can be calculated depending on the size (kVA) of the distribution transformer, its fault level and the characteristics of its current limiting protective device. An inductor sufficient to absorb //, L of the transformer and the cables may be provided at the incoming of the sialic circuits. 

The installation costs for a single impressed current anode of high-silicon iron can be taken as Kj = DM 975 (S550). This involves about 5 m of cable trench between anodes so that the costs for horizontal or vertical anodes or for anodes in a common continuous coke bed are almost the same. To calculate the total costs, the annuity factor for a trouble-free service life of 20 years (a = 0.11, given in Fig. 22-2) should be used. For the cost of current, an industrial power tariff of 0.188 DM/kWh should be assumed for t = 8750 hours of use per year, and for the rectifier an efficiency of w = 0.5. The annual basic charge of about DM 152 for 0.5 kW gives about 0.0174 DM/kWh for the calculated hours of use, so that the total current cost comes to... 

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