<p style="text-align:justify"><span style="font-size:14px">Current flowing through transmission lines ranges from100 amp to 1000 amp under normal operating conditions. This current is required to be measured. Also, it is required to measure power, energy, kVAR (MVAR) etc. No measuring instrument can handle this large current. Hence this current is stepped down to appropriate value (1 amp or 5 amp) which can be conveniently and safely measured by measuring instruments. </span></p>

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<p style="text-align:justify"><span style="font-size:14px">Moreover, when fault occurs in the power system, it is sensed by the protective relays, the relay will operate, give signal to the breaker which will interrupt the fault current to protect the power system. This fault current is required to be stepped down [as it is 3 to 10 times (or even more) the CMR (Continuous Maximum Rating)] to a value which a protective relay can handle.</span></p>

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<p style="text-align:justify"><span style="font-size:14px">This stepping down of the current is carried out by the current transformer. These current transformers have single primary winding but 2, 3, 4, 5 or more (according to requirement) number of cores and secondary windings to feed to measuring instruments and protective relays. The core requirement for measurement and different protections are different. Hence, multicore C. T.s as shown in figure 5.1 are used.</span></p>

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<p style="text-align:justify"><span style="font-size:14px"><img alt="" src="https://edupmquestionhelp.s3.ap-south-1.amazonaws.com/hint/uploads/images/16194205811619420581.jpg" style="height:1469px; width:800px" /></span></p>