AC System Disadvantages Distribution & Transmission Lines

AC System Disadvantages

Alternating Current systems has the main advantages is that the voltage can be stepped up at generating end by means of step-up transformers to the required value for transmission and then steeped down at distributing end by means of step-down transformers for distribution with ease and efficiency.

The other advantages of ac systems are that electric power can be generated at high voltage easier and the maintenance of ac substations is easier and cheaper.

AC System Disadvantages in Distribution and Transmission Lines are given below:
  1. In case of overhead lines spacing between the conductors is to be kept more in order to provide adequate insulation and to avoid corona loss.
  2. More copper is required.
  3. Greater the length of transmission line more is the capacitance of the line. There is a continuous loss on account of charging current even though the line is open.
  4. The construction of transmission lines for ac systems is not so easy as for dc  systems.
  5. The alternators are to be synchronized before putting them into parallel.
  6. The variation in speeds of alternators are to be controlled within very low limits.

Distribution by ac system is undoubtedly superior to that by dc system as in ac system voltage control is easy by means of transformers.

The best method is to employ ac system for generation and distribution and dc system for transmission.

Transmission of electric power by dc system became possible because of introduction of mercury-arc rectifiers and thyratrons, which can convert ac into dc and vice versa efficiently and at reasonable cost.

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