Th this slide we are going to discuss about load shedding and load scheduling in power system.

1. A Project Report On
Load Scheduling & Load Shedding
Submitted By:
Bijay Kumar Nayak
Branch : EEE
8th Semester
Regd No: 1501298205
Seminar Guide:
Prof. Sudhanshu Bhusan Pati
Department Of EEE
Gandhi Institute For Technology

2. Contents
 Introduction
 What is load
 Load Scheduling in Power Systems
 Need for load Schedule
 Methodology used in load Scheduling
 Load Shedding
 Effect of excess load
 Reason For Instability
 Advantages & Disadvantages
 Conclusion
 Reference

3. Introduction
 Now a days electricity
loads are increasing day by
day. So it is important to
manage the supply side for
optimal operation.

4. Load
 An electrical load is
an electrical component
or portion of a circuit that
consumes (active)
electric power. This is
opposed to
a power source, such as
a battery or generator,
which produces power

5. Load Scheduling in
Power Systems
 The electrical load scheduling is the process
of estimating the instantaneous loads
operating in an installation.
 The load schedule provides the load for the
particular installation in terms of apparent,
reactive and active power (kVA, kVAR and
kW) and usually carried out at the sub facility
area or at the switchboard.

6. Cont.
 The load schedule preparation should ideally be the first task to perform during the
electrical system design stage since it relates to the equipment sizes and other power
system requirements. In particular, it provides information about the equipment ratings
during normal and peak operations, thereby guiding the electrician in determining the
conductor sizes.
 Load scheduling is one form of load management action that allows companies to save
energy by minimizing their demand. In order to have an efficient load schedule operation,
the energy manager or business should conduct power logging and record all sessions
so as to measure the usage of energy over a specific time. This enables the consumer to
identify large loads that may be operating concurrently.

7. Need for load Schedule
 Preparing an electrical load schedule eases the work of
designing the system in terms of equipment sizing as well as in
power system studies. The process requires an understanding
o the installation, all the equipment that will be installed,
frequency of using the equipment and their importance or
criticality.
 The load schedule should ideally be started as early as is
practically possible in the design process. One requires an
idea of the main voltage levels required in the installation as
well as all other details of the function of the facility or building,
and the nature of process and non process loads.

8. Methodology used in load Scheduling
 There is no standard methodology and varying methods can be used based on type of installation and
person carrying out the load scheduling exercise. However, there are some basic steps which are
followed when creating the load schedule for the first time. This involves the collection of a list of
equipment, their design load ratings, expected operating and peak power consumption.
 Also required are some typical electrical load characteristics such a rated power, absorbed power, power
factor and efficiency. The loads are then classified according to some specific criteria which may differ
from one installation to the other.
 The loads are mostly classified using three parameters, the first criteria is according to voltage; the other
one according to load duty to show whether loads are standby, continuous, or intermittent. And lastly
according to load criticality based on whether they are normal loads, essential loads or critical loads. The
collected information is then used to calculate the individual and overall operating, design and peak
power at continuous, intermittent, and standby load duty.

10. Load Shedding
 Load shedding in electrical supply networks is a
controlled process in which the utility company
drops off part of the load in order to balance the
demand and the generated capacity. This is often
done whenever there is excess load on the
system. In standby generators, it involves
disconnecting or shedding some circuits to
prevent an overload condition.

11. Effect of excess load
 In power systems, an excess load puts a stress on the generating equipment. It slows down the
prime movers, associated generators and other parts of the system as they attempt to cope with
the excess load. This leads to a combination of events including power swings and overloads
which can cause the system becoming unstable. Some of the parts such as protection systems
may interrupt the supply due to the excess current resulting from the overload.
 The higher load may also lead to a lower generating and supply frequency. Even though the hydro
generating systems can tolerate up to 10% frequency change, the thermal generator’s operation
will be affected since they are more sensitive.
 The reduced frequency can damage the steam turbines as well as the frequency sensitive load. As
such, most generator systems incorporate under-frequency relays to automatically disconnect
some of the excess load.

12. Reason For Instability
 Inefficiency and lack of maintenance of generating and distribution systems
 Increased population
 Improved living standards
 Lack of planning

13. Load Shedding Procedures
 Utility companies use scheduled load shedding so that the available electricity is fairly
shared by the consumers. This involves switching off some parts of the electricity supply
network in a planned and controlled process. They alternate between different parts and time
schedules to ensure that at least everyone gets power at a specific time. By dropping off the
excess load, the power system remains stable.
 Some smaller generators such as those used in domestic applications have inbuilt load
shedding capabilities. This becomes necessary when these are used as standby generators,
in the event of a utility power outage, the emergency supply kicks in. And since all the
circuits and appliances are connected, the load demand may exceed the generator capacity.
When the load becomes too much, the generator sheds some of the smaller non-critical
circuits automatically in an attempt to reduce the load.

14. Advantages
 Prevents overloading and damage of the power generators
 Prevents instability and system collapse of the electrical generation
and distribution systems
 Ensures that consumers or parts of the network have power as
opposed to a total blackout.
 The planned schedules ensure that available capacity is shared
fairly and each consumer gets power at one time or another.
 It serves as a warning to the utility hence forcing them to increase
capacity, and efficiency so as to meet the demand.

15. Disadvantages
 Loss of production
 Increased crime due to darkness and
lack of jobs
 The utilities may not increased the
output
 Restoring the load may cause more
instabilities

16. Conclusion
 Electrical load scheduling is an essential practice that an electrical technician should carry out
at the initial stages of an electrical power installation. The load schedule provides data that is a
close estimate of the amount of power consumed for normal and peak loads and anything in
between
 Load shedding is one of the last things that a utility company should look at. It leads to
frustrated customers and loss of revenue for the consumers as production drops. In addition, it
may cause equipment damage.
 Electricity companies should ensure that they have enough capacity to meet normal and peak
demands. This can be achieved by planning for future electricity demand and progressively
upgrading the generating equipment, maintain existing systems, reducing transmission losses
and increasing efficiency in the entire system.

17. Reference
1. http://engineering.electrical-equipment.org/safety/reasons-load-shedding.html
2. http://engineering.electrical-equipment.org/electrical-distribution/load-scheduling-
power-systems.html
3. https://ieeexplore.ieee.org/document/7120135/
4. http://www.iitk.ac.in/npsc/Papers/NPSC2014/1569987285.pdf
5. http://www.nelsonmandelabay.gov.za/Council.aspx?pageID=202