<p style="text-align:justify"><span style="font-size:14px">The installed power generation capacity of Gujarat state is about 25000 MW and that of India is around 371000 MW. This electricity is transmitted through transmission lines and finally distributed to consumers.</span></p>

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<p style="text-align:justify"><span style="font-size:14px">The equipment for generation, transmission and distribution of electric power are very costly. The cost of 2&nbsp;&times;&nbsp;660 MW (two generating units of 660 MW each) coal based super thermal power plant with its super critical boilers, turbine stages, all auxiliaries, coal handling, ash handling, ESPs (Electrostatic precipitators) etc. is approximately Rs. 7500 crores. Cost of transmission of power ranges from Rs. 30 lakhs per km to Rs. 6.75 crores per km (depending on voltage of transmission ranging from 66 kV to 765 kV and depending on whether it is a single circuit line or double circuit line). Cost of 15.75/220 kV, 250 MVA, three phase power transformer is around Rs. 15,00,000. Thus, equipments are very costly.</span></p>

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<p style="text-align:justify"><span style="font-size:14px">As discussed, faults and abnormalities are inevitable and generally not under our control. These faults and abnormalities will damage the equipment of power system and if protective actions are not taken, such costly equipment will be badly damaged.</span></p>

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<p style="text-align:justify"><span style="font-size:14px">The protective gear (or switchgear) isolates the faulty section from remnant of the healthy system. This is known as clearing the fault. Rectifying or repairing the faulty equipment, if need be, is a different task to be handled by maintenance technical staff. How do the components of switchgear do this function fast and selectively? We will answer this question in about 13 chapters to follow.</span></p>