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A small town with a demand of 800 KW of electric power at 220V is situated 15km away from an electric plant generating power at 440 V. The resistance of the two line wires carrying power is 0.5Omega//km. The twon gets power from the lines through a 4000 - 220 V step down transformer at a substation in the town. a) Estimate the line power loss in hte form of heat b) How much power must the plant supply, assuming there is negligible power loss due to leakage? c) Characterize the step up transformer at the plant |
Answer» Solution : POWER requirement of the twon is given by EI, where E is the voltage at the RECEIVING end of the line and I is the line current. Here `P=800xx1000W,E=4000V` then `I=(P)/(E)=(800xx1000)/(4000)=200A` (i) Line power loss `=I^(2)R=(200)^(2)xx(2xx15xx0.5)` `=600,000W=600kW` (ii) TOTAL power delivered by power plant `=800+600=1400kW` (iii) Voltage at sending end of line `="Receiving end line voltage "+" voltage drop in line"` `=4000+(IR)=4000+200(2xx15xx0.5)` `=4000+3000=7000V` `therefore"Step up transformer of "(7000V)/(440V)" is required"` |
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