NUCL 5120
DESIGN OF NUCLEAR PLANT
SYSTEMS
AC POWER DISTRIBUTION
Wednesday, February 27th 2019
Muhammad Rahman
B.Eng in Electrical Engineering
Content
• Power distribution schematic
• Why high voltage transmission
• Medium voltage substation and components
• Low voltage distribution system and components
• Low voltage ACB Protection system
• Breaker specification
• Question and Answer
Power distribution schematic
Step up to 5000kV
Step down to 5000V
5000V
Why high voltage transmission
The main reason power is transmitted high voltage is for the high efficiency.
There are huge power losses when electricity transmitted long distances
using a conductor.
High voltage over transmission is lower the current and the lower conductor
resistance losses.
Power distribution is divided in three level based on transmission and
distribution. High voltage (HV), Medium voltage (MV) and Low voltage (LV)
Each level of distribution has specific protection system for the safety of the
equipment, load and as a whole power distribution system.
Medium voltage substation and components
Typically 600V-69kV substation is
medium voltage
Substation consists of
Transformer, High tension
switchgear, Low tension
switchgear, disconnector switches,
fuses and relays
Typical Medium voltage substation single line diagram
Low voltage distribution system and components
The low voltage distribution system
also can be number of steps depends
on protection and reliability
requirements. The steps are 1- Main
distribution panel, 2- Distribution
panel and 3- Sub distribution panel
up to the household load.
The main distribution panel has
incoming breaker, busbar system and
out going breaker. Also there are
fuses and relays to make sure the
protection for the load and for the
system has been ensured.
Low voltage Air Circuit breaker (ACB)
protection system.
The low voltage Air circuit breaker give
protection for
1- Over current
2- Earth fault
3- Short circuit current
4- under voltage and over voltage protection
Breaker specification
Question and Answer
Thank you