Dear student
The kWh meter It measures the amount of electrical energy used by the consumer in kWh.
the main fuse regulates the entr of electricity into the homes. if the amoun of electricity which is more and would damage electrical appliances when passes through themain fuse, the main fuse melits due to the heat generated and hence the connection of house hold appliances is cut out with the high electricity and thus the appliances are saved from damage, just at the cose of a fuse wire.
regards