The term Working Voltage means the maximum voltage that any device can withstand without getting damaged or burnt off, keeping in mind factors like reliability and safety of the device and circuits for proper operation.
If the power is transmitted to a long distance there exist the desirability of using high voltage. It is also necessary that with the AC systems the load power factor should be as near to unity from an economic point of view. The heavy currents are more difficult to handle than high voltages.
Considerable savings in the cost of the conductor material are possible when the voltage is high. Although the much economy and cost of the installation can be effected in the conductor material by employing extra high voltages and as a result the cost of insulation of conductors whether overhead or underground, increases.
By adopting high voltages, the electrical separation or clearances between the conductor is to be increased. This is done to avoid electrical discharge. The mechanical supporting structure becomes more difficult and expensive.
The other problem arises with higher working voltage are the insulation of the equipments, corona effect, radio and television interference, etc. Ultimately the insulation costs of the transformers, switchgear and other terminal equipment increases drastically. These problems of corona and radio interference becomes very serious at the extra high working voltage. The working voltage should be considered on the basis of future requirement of load
Thus, higher the voltage the more costly is the line. The voltage level of a system is therefore governed by the two major factors. They are as follows:-
- The amount of the power to be transmitted
- The length of the transmission line.