Parallel Operation of Shunt Generators

Parallel Operation of Shunt Generators Points : Parallel Operation of Shunt Generators When two shunt generators are connected in parallel, they function together to supply power to a common load and they are completely stable whether or not their exact voltage versus current characteristics are identical. This is because of the drooping voltage-current characteristics of shunt generators. The circuit diagram for the operation of two shunt generators in parallel. Assume that generator A is in operation with switch SA closed and that the load it is delivering is about to be increased sufficiently to require the use of a machine of larger rating than A or the connection of a second generator to operate in parallel with A, The procedure for connection of two shunt generators in parallel is as follows:
1. Second generator B is brought up to rated speed by its prime mover. 2. The field switch SB2 is closed whereupon the voltage will build, assuring of course that all conditions for build up are satisfied.
3. The voltage of generator B2 is adjusted until it is equal to a slightly higher than that of generator A, the field rheostat of the incoming machine being manipulated for this purpose; special care should be taken that polarity of B is exactly same as that for A with respect to the load. i.e., the plus and minus terminals of the linking machine must be traced to the corresponding bus polarities across open switch SB.
4. With adjustment made and precautions taken as indicated, main switch SB is closed; this places generator B in parallel with A but the later still supplying the entire load and machine B running idle, i.e. floating.
5. To shift the load from A to B it is merely necessary to adjust the field rheostat of two generators simultaneously, cutting in resistance in the field circuit of A and at the same time cutting out resistance in the field circuit of B.