Transmission and Distribution
By
Dr S Sudalai Shunmugam Ph.D. (CPRI)
Assoc. Prof, Dept. of EEE,
BNMIT, Bangalore
✉: sudalaishunmugam@bnmit.in
Generator
Transformer
Vertical Structure of Conventional Power System
Source: SK Salman, Introduction to Smart Grid Concepts, Technology and Evolution
Varahi Underground Power House
Capacity – 460 MW (Karnataka's First Underground Power House)
Source: KSEB
Tehri Power House
Capacity – 24000 MW (Uttarakhand, Commissioned in 2006)
Source: PGCIL
Source: Ministry of Power
The conveyance of electrical power from
generating system to the consumer premises is
known as “Electrical Power System”
Components of Electrical Power System
kV – Kilo Volt
• Generating Station
- 6.6 kV, 11 kV, 33 kV
• Transmission System
- 66 kV, 132 kV, 220 kV, 400 kV, 750 kV,
1200 kV
• Distribution System
- 25 kV, 11 kV, 400 V, 230 V
POWER SYSTEM COMPONENTS
Generation Primary Transmission(132/220/400/765KV)
+/- 500 kV DC & +/- 800 kV DC
CB
X’mer
Power Plant (11/220kV) CB Bus-bar Steel Tower
220 kV Bus-bar
Primary Grid
Sending end SS (220/66 kV)
Commercial/ 66 kV
Industrial Transmission
Customer Secondary Transmission(66/132KV)
Distribution Transformer
Urban (11/0.415 kV) Primary Distribution
Customers
Secondary Distribution Secondary Grid
(66/33/11 kV)
Distribution
Underground Cable
Pole
To Other
Residential
Residential
66Kv
Customer Substations
Customer
Components of Electrical Power System
Generating Station
• Electrical power is generated by a 3 phase
alternators operating in parallel
• The nominal generation voltage in India is 11 kV
( It varies between 11 kV – 33 kV worldwide)
• For economic transmission of electric power, the
generating voltage (11 kV) is stepped up to 132
kV (or more) at the generating station using 3
phase power transformer
Components of Electrical Power System
Generating Station
• The choice/ level of the high voltage
transmission depends on the distance of power
transmission and economic constraints
(insulation problems, costs of switch gear, power
transformer)
Components of Electrical Power System
Generating Station
Components of Electrical Power System
Components of Electrical Power System
Components of Electrical Power System
Primary Transmission
• The electric power at 132 kV is transmitted by 3
phase 3 wire overhead system to the outskirts of
the city
Components of Electrical Power System
Primary Transmission
Components of Electrical Power System
Secondary Transmission
• The primary transmission line terminates at the
Receiving Station (RS) which usually lies in the
outskirts of the city
• At the RS, the voltage is reduced to 33 kV (or
less), by step down transformer
• From RS, the electric power is transmitted by 3
phase 3 wire system to various substations (SS)
located at the strategic points in the city
Components of Electrical Power System
Secondary Transmission
Components of Electrical Power System
Primary Distribution
• The secondary transmission line terminates at
the sub station (SS) where the voltage is reduced
from 33 kV to 11 kV, 3 phase, 3 wire system.
• The 11 kV lines run along the important road
sides of the city, forming the primary distribution
• Consumer (industries) with demand more than
50 kW are in general supplied with 11 kV supply
Components of Electrical Power System
Primary Distribution
Components of Electrical Power System
Secondary Distribution / Low Voltage Distribution
• These substations are located near
the consumer localities and the
voltage is stepped down to 400 V, 3
phase, 4 wire for secondary
distribution.
• Consists of three parts namely
Feeder
Distributor
Service Main
Components of Electrical Power System
Secondary Distribution
DS – Distribution Substation
AB
BC
CD Distributor Line
DA
Components of Electrical Power System
Secondary Distribution (DS) / LV DS
Feeders
• These are the conductors that carries bulk current to the
feeding points
• The size of the feeder is determined by the amount of the
current it carries
• No tappings are taken from the feeders, so that the current
remains constant throughout
Components of Electrical Power System
Secondary Distribution
Distributor
• These are the conductors used to transfer electrical power
from Distribution Station to the consumer end
• From the distributors, tappings are taken to provide supply to
the consumer
• The voltage drop along the distributors is the main criterion to
design the distributors
Components of Electrical Power System
Secondary Distribution
Distributor
Components of Electrical Power System
Secondary Distribution
Service Main
• are the small cables between the distributors and the actual
consumer premise
