The document discusses the objectives and operations of electric power systems. The key objectives are to provide continuous, quality service to users at minimum cost while minimizing environmental impact. Operations are divided into planning, control, and accounting. Planning optimizes resource allocation to meet peak demand at lowest cost. Control satisfies instantaneous load through economic dispatch and reserve calculation. Committing the most economical generating units based on costs and constraints is determined through unit commitment.

1. Electric Power System Operation
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
• Operational objectives of a power system have been to provide a continuous
quality service with minimum cost to the user. These objectives are:
• The term “continuous service” can be translated to mean “secure and reliable
service”
 First Objective: Supplying the energy user with quality service, i.e., at
acceptable voltage and frequency
 Second Objective: Meeting the first objective with acceptable impact
upon the environment.
 Third Objective: Meeting the first and second objectives continuously,
i.e., with adequate security and reliability.
 Fourth Objective: Meeting the first, second, and third objectives with
optimum economy, i.e., minimum cost to the energy user.
1

2. Integrated Objectives
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
• The direction of the arrows indicates the priority in which the objectives
are implemented
Interrelated objectives of operation of a power system
Economically constrained operation of a power system.
2

3. Task Division
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
 Operations planning
 Operations control
 Operations accounting
Interrelated tasks of planned scheduling operation
3

4. Operation planning
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
• The facilities of a large power system consist of many generating units,
transmission lines, transformers, circuit breakers, DC/DC converters & DC/ AC
converters which are to scheduled for orderly operation & maintenance
• The energy resources of a large power system consist of hydro, nuclear, fossil
power and renewable energy sources such as wind farm, photovoltaic and micro
turbines.
• These facilities are to be managed and utilized to satisfy load demand of a
power system.
• The load demand of a power system is cyclic in nature and has a daily peak
demand over a week period, weekly peak demand over a month period, and
monthly peak demand over a year period.
• Overall objectives of planned scheduling operation are to manage facilities and
optimize resources for satisfying the peak demand of each load cycle, such that
the total cost of operation is minimized.
4

5. Operation Control
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
• The primary functions of operations control are satisfying the instantaneous
load on a second-to-second and minute-to-minute basis. Some of these
functions are:
 Load Frequency Control
 On-Line Load Flow
 Economic Dispatch Calculation (EDC)
 Operating Reserve Calculation (ORC)
5

6. Operation Control……Contd.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
• Load Frequency Control (LFC). This function is also referred to as governor
response. As the load demand of the power system increases, the speed of
generators will decrease and this will reduce the system frequency. Similarly, as
system load demand decreases, the speed of the system generators would
increase and this will increase the system frequency. The power system
frequency control must be maintained for the power system grid to remain
stable.
• Online Load Flow (OLF): This function generally utilizes the output of network
topology, i.e. the real time network model, and the bus injections from state
estimation for purpose of security monitoring, security analysis and penalty
factor calculations. This function performs “if then condition” to determine the
possible system states (voltages) in face of system outages such as loss of a line
due to weather condition or sudden loss of a generator.
6

7. Operation Control……Contd.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
• Economic Dispatch Calculation: Economic dispatch calculation of a power
system determines the loading of each generator on a minute-by-minute basis so
as to minimize the operating costs.
• Operating Reserve Calculation: The objective of operating reserve calculation is
to calculate the actual reserve carried by each unit and to check whether or not
there is a sufficient reserve in a system. The operating reserve consists of
spinning reserve (synchronized), non-spinning reserve (non-synchronized), and
interruptible load.
7

8. Economic Dispatch
 With a given set of units running, how of the load much should be
generated at each to cover the load and losses? This is the question
of Economic dispatch.
 The solution is for the current state of the network and does not
typically consider future time periods.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
G
G
G
G
G
G
G
G G
8

9. Deciding which units to “commit”
 When should the generating units (G) be run for most economic
operation?
 Concern must be given to environmental effects
 How does one define “economic operation”? Profit maximizing?
Cost minimizing? Depends on the market you’re in.
G
G
G
G
G
G
G
G G
9
KONGUNADU COLLEGE OF ENGINERING AND
TECHNOLOGY, TRICHY Electric
Power System Operation

10. What is Unit Commitment?
 We have a few generators (units)
 Also we have some forecasted load
 Besides the cost of running the units we have additional costs and
constraints
 start-up cost
 shut-down cost
 spinning reserve
 ... and more
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
10

11. What is Unit Commitment?
 It turns out that we cannot just flip the switch of certain units on and use
them!.
 We need to think ahead, and based on the forecasted load and unit
constraints, determine which units to turn on (commit) and which ones to
keep down.
 Minimize cost, cheap units play first.
 Expensive ones run only .when demand is high.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
11

12. How Do We Solve the Problem?
 If a unit is on, we designate this with 1 and respectively, the off unit is 0.
 So, somehow we decide that for the next hour we will have "0 1 1 0 1" if we
have five units.
 Based on that, we solve the economic dispatch problem for unit 2, 3 and 5.
 We start turning on U2, U3, U5.
 When the next hour com.es, we have them up and running
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
12

13. To Come Up With Unit Commitment
 The question is, _how_ do we come up with this unit commitment
"0 1 1 0 1" ?
 One very simplistic way: if we have very few units, go over all combinations
from hour to hour
 For each combination at a given hour, solve the economic dispatch
 For each hour, pick the combination giving the lowest cost!
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
13

14. REFERENCES:
 Jeraldin Ahila M., “Power system operation and control”, Lakshmi
Publications, 2015.
 Kundur P., ‘Power System Stability and Control, Tata McGraw Hill
Education Pvt. Ltd., New Delhi,10th reprint, 2010.
 R3. Hadi Saadat, ‘Power System Analysis’, Tata McGraw Hill Education
Pvt. Ltd., New Delhi, 21st reprint, 2010.
 R4. Ramanathan V., “Power System Operation and Control,” Charulatha
Publications, 2015.
 R5. Gross C.A., “Power System Analysis,” Wiley India, 2011.
 Google and Wikipedia.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY Electric Power System Operation
14