STANI MEMORIAL COLLEGE OF ENGINEERING & TECHNOLOGY
POWER SYSTEM DESIGN LAB
EXPERIMENT NO. 2
Aim: - Auxiliary power supply scheme for thermal power plant.
Apparatus Requirements: - Thermal Power Plant, Main Power Supply, Auxiliary Power
Theory: - The auxiliary power supply can be divided into two categories: Urgent Auxiliary Supply
and Service Auxiliary Supply.
The Urgent Auxiliaries are those which are associated with the running of a unit and whose loss
would cause an immediate reduction of the unit output.
The Service Auxiliaries are those whose loss would not affected the output until after a considerable
Precautions:1) Do not touch any live conductor.
2) Please keep distance from electrical equipments because voltage level very high i.e. 132 kV,
220 kV, and 400 kV.
Procedure:1) There should be two main sources of supply (I) from the grid via the station transformers, (II)
from the main generators via the unit transformers.
2) The urgent auxiliaries should be supplied from the unit transforms and the service auxiliaries
from the station transformers. Each generating unit should have a separate supply and the
failure of one unit should not affect the other.
3) The unit board and the station board should be interconnected for starting purposes and to
provide a supply in case the unit supply fails.
4) A standby supply should also be provided so that a unit can be brought back to service rapidly
in the event of a failure of one of the components in any of the normal supply circuits.
Result:- We have successfully studied about Auxiliary power supply scheme of thermal power
Ques. 1 How many categories are divided of auxiliary power supply?
Ques. 2 For which supply loss would cause an immediate reduction of the unit output?
Ques. 3 What is Thermal Power Plant?
Ans 1. Urgent Auxiliary Supply
Ans 2. The auxiliary power supply can be divided into two categories: Urgent Auxiliary Supply and
Service Auxiliary Supply.
Ans 3. A thermal power station is a power plant in which the prime mover is steam driven. Water is
heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes
through the turbine, the steam is condensed in a condenser and recycled to where it was heated.