This document discusses PLC-based load management. It begins with an introduction and provides a block diagram of a load management system. It then discusses what a PLC is and how it can be programmed using ladder logic to implement load management. Specifically, it explains how a PLC can be programmed to read data from an overcurrent relay and control contactors connecting different power sources to maintain regular load balancing. Key advantages of using a PLC for this application include flexibility, simple wiring, and communication capabilities.

1. PLC Based Load Management
Guidance By:
Dinesh Saini
Asst. Professor,
Electrical Department, BKBIET
Presented By:
Manish Kumar
11EBKEX028
Divya Saini
11EBKEX016
Aishwarya
11EBKEX002

2. Content
 Introduction about Load management
 Block diagram of Load Management
 About PLC
 Programming in PLC(Ladder logic)
 Advantage and short-comings

3. What is Load Management ?
Load Management is the "proper management of load“ which
means balancing the electrical power supply with the
variations in the load and its behavior. As we all know that
there are generation stations connected in parallel to each
other to ensure continuous supply of power to the load. In the
LOAD Management, there are contactors and the closing /
opening of these Contactors maintain the Load management.

4. How to do Load Management ?
Since electric power can not be stored and used later , so
Electricity is produced, distributed and consumed by the Load
simultaneously and this is the place where Load Management
comes into Action.
Also as the Load demand is not fixed so we have to design the
system keeping in mind the Maximum Load Condition. As for
example when the Induction Hardening Machine is started then
there is a sudden increase in the load by 400 - 600 % , so we
have to keep in mind all these behavior of loads. There are
many ways for Load Management but here we will focus on PLC
based Load Management.

5. PLC Programming for Load Management ?
To do Load Management using DG Sets, we will need an
overcurrent relay that will tell us all the data regarding current
and it will help us to determine the load value. The overcurrent
relay output will be connected with PLC input MODBUS. We
have made this PLC program for Load Management and using
ALLEN BRADLEY PLC. There are two sections in PLC program ,
one is for reading data from overcurrent Relay and other is for
PLC logic. PLC logic will provide required output to ensure
regular load management by connecting with busbars through
contactors.

6. Block diagram of load management

7. What is PLC ?
A Programmable Logic Controller (PLC) is an industrial
computer that accepts inputs from switches and sensors,
evaluates these in accordance with a stored program, and
generates outputs to control machines and processes.
PB1
LS1
INPUTS
M1
M2R
LOGIC OUTPUTS
M1
SOL
Block Diagram of a Control System

8. Major Components of a Common PLC
PROCESSOR
POWER
SUPPLY
I M
N O
P D
U U
T L
E
O M
U O
T D
P U
U L
T E
PROGRAMMING
DEVICE
From
SENSORS
Pushbuttons,
contacts,
limit switches,
etc.
To
OUTPUT
Solenoids,
contactors,
alarms
etc.

9. Major Components of a Common PLC
 POWER SUPPLY
Provides the voltage needed to run the primary PLC components
 I/O MODULES
Provides signal conversion and isolation between the internal logic-level signals inside
the PLC and the field’s high level signal.
 PROCESSOR
Provides intelligence to command and govern the activities of the entire PLC systems.
 PROGRAMMING DEVICE
used to enter the desired program that will determine the sequence of operation and
control of process equipment or driven machine.

10. What' happens in an operating cycle
Based on the data in
the output image file
the PLC energises or
de-energises it’s output
circuits,controlling
external devices.
1.Input
Scan
2. Program
Scan
3. Output
Scan
START
-
- -
-
PLC
OPERATING
CYCLE
TYPICALLY
1 to 25 ms.
During the input scan PLC
examines the external input
devices -On or Off.
The status of the inputs is
temporarily stored in an input
image memory file.
The PLC scans the instructions in the ladder
logic program,uses the input status from the
input image file & determines if an output will
be energised.The resulting status of the outputs
is written to the output image memory file.

11. Inputs and outputs of PLC
INPUTS
 Pushbuttons
 Selector Switches
 Limit Switches
 Level/Pressure/Temperature
Sensors
 Photoelectric Sensors
 Motor Starter Contacts
 Relay Contacts
 Transducers/Transmitters
 Encoder
OUTPUTS
 Relay
 Motor Starters
 Solenoids Valves
 Control Relays
 Alarms
 Lights
 Fans

12. Programming in PLC
 Ladder Logic
 Structured Text
 Sequential functional chart
 Functional Block Diagram
 Instruction List

13. Programming in PLC
 Ladder Logic
 Structured Text
 Sequential functional chart
 Functional Block Diagram
 Instruction List

14. Ladder logic
 Ladder Logic is a graphical system of symbols and terms.
 Those who are not familiar with relay wiring. Diagram, can easily learn it.
 In ladder logic, we have to translate all of the items we're using into symbols
the PLC understands

15. Advantages
Simple wiring
Flexibility in programming and reprogramming in the Plant.
Low space
Wider functions like high speed counters, etc.
Faster Scan Time.
Simpler installation.
Economic in cost.
Minimum maintenance.
Ability to communicate with HMI/MMI
Programmable troubleshooting aids which reduce
downtime

16. Short-comings
 Difficulty with changes or replacements.
 Difficult to find error hence require skillful workforce.
 When problem occurs, hold up time is indefinite.

17. References
 http://en.wikipedia.org/wiki/Load_management
 http://ab.rockwellautomation.com/Programmable-Controllers/MicroLogix-1100
 https://www.energyvortex.com/files/PLCCaseStudy.pdf
 http://www.plcedge.com/plc-architecture.html
 Automating Manufacturing Systems with PLC by Hugh Jack.
 http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Ladder_logic.html

18. Thank You