3. Basics of
Transmission and Distribution
Power Generation
- The power generation has to be done by the plant
Power Transmission
- To send electricity far to the load
Power Distribution
- To distribute the electricity at the consumer level.
4. Typical AC Power Scheme Supply
1. Generating Station
2. Primary Transmission
3. Secondary Transmission
4. Primary Distribution
5. Secondary Distribution
8. Transmission above
66 kV on average is
feasible and safe
Faults anywhere in
the line are easy to
diagnose
Cheaper to build
and install.
OVERHEAD TRANSMISSION LINE
Advantages and Disadvantages of High Voltage Transmission Line
9. OVERHEAD TRANSMISSION LINE
String Efficiency
𝑆𝑡𝑟𝑖𝑛𝑔 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =
𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑎𝑐𝑟𝑜𝑠𝑠 𝒔𝒕𝒓𝒊𝒏𝒈
𝑵𝒐. 𝒐𝒇 𝒅𝒊𝒔𝒄𝒔 𝑖𝑛 𝑡ℎ𝑒 𝑠𝑡𝑟𝑖𝑛𝑔 × 𝑉𝑜𝑙𝑎𝑡𝑔𝑒 𝑎𝑐𝑟𝑜𝑠𝑠 𝑡ℎ𝑒 𝒏𝒆𝒂𝒓𝒆𝒔𝒕 𝒄𝒐𝒏𝒅𝒖𝒄𝒕𝒐𝒓
Methods of Improving the String Efficiency of an Insulator
By Using
Longer
Cross-arms
01
By
grading
the insulators
02
By using
a guard ring
03
10. OVERHEAD TRANSMISSION LINE
Corona Effect Phenomenon of violet glow, hissing noise and production of
ozone gas in an overhead transmission line.
Sag The difference in level between points of supports and the
lowest point on the conductor.
The tendency of alternating current to concentrate near the
surface of a conductor.
Skin Effect
Voltage Regulation
Transmission
Efficiency
The difference in voltage at the receiving end of a
transmission line between conditions of no load and full load.
At no load condition,
% 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑅𝑒𝑔𝑢𝑙𝑎𝑡𝑖𝑜𝑛 =
𝑉𝑅 − 𝑉𝑆
𝑉𝑅
× 100
At full load condition,
% 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑅𝑒𝑔𝑢𝑙𝑎𝑡𝑖𝑜𝑛 =
𝑉𝑆 − 𝑉𝑅
𝑉𝑅
× 100
The ratio of receiving end power to the sending end power
of a transmission line.
13. Types of Distribution System
Feeders Distributor
Service
Mains
It is a conductor
which connects
the sub-station to the
area where power is
to be distributed.
It is a conductor from
which tapings are
taken for supply to the
Consumers.
It is a conductor from
which tapings are
taken for supply to the
Consumers.
14. Classification of Distribution System
Types of Construction
• Overhead System
• Underground System
Nature of Current
• AC Distribution System
• DC Distribution System
Scheme Connection
• Radial System
• Ring Main System
• Inter-connected System
15. Requirements for Distribution System
Availability of Power on demand
Proper Voltage
Statutory limit of voltage variations should be ± 6%
Reliability
16. General Questions
What should be the percentage of frequency ups and downs?
- Should be within 2.5%, means (𝟓𝟎 𝑯𝒛 ± 𝟐. 𝟓%)
What is the best method for transmission and distribution?
- AC system is the best method for power generation and distribution and DC system for transmission.
If the value of the power factor is low, what are the problems in the system?
- If the value of power factor is low, more volume of conductors is required, line loss increases, power
system efficiency decreases, cost increases greatly, resulting in higher per unit cost.
17. [1] V.K. Mehta, Principles of power system, 14th ed. India: S CHAND & CO LTD., 2006. [Online].
Available: https://www.worldcat.org/title/1334718000
[2] A. Husain, Electrical Power Sytems. 2014.
[3] H. Saadat, Power system Analysis. 2010.
[4] Md. N. Islam, “ইলেকট্রিকযাে পাওয়ার িান্সমিশন ও মিমিমিউশন মিলেি,” VoltageLab,
Jun. 12, 2017. https://blog.voltagelab.com/িান্সমিশন/
References
