PLC Based Load Management

Guidance By:

Dinesh Saini

Asst. Professor,

Electrical Department, BKBIET

Presented By:

Manish Kumar

11EBKEX028

Divya Saini

11EBKEX016

Aishwarya

11EBKEX002

Content

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

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.

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.

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.

Block diagram of load management

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

INPUTSM1

M2R

LOGIC OUTPUTS

M1

SOL

Block Diagram of a Control System

Major Components of a Common PLC

PROCESSOR

POWERSUPPLY

I MN O P D U UT L E

O M U OT DP UU LT E

PROGRAMMING DEVICE

From SENSORS

Pushbuttons,contacts,

limit switches,etc.

ToOUTPUT

Solenoids, contactors,

alarmsetc.

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.

What' happens in an operating cycle

Based on the data inthe output image filethe PLC energises or de-energises it’s outputcircuits,controllingexternal devices.

1.Input Scan

2. ProgramScan

3. OutputScan

START

-- -

-

PLCOPERATING CYCLETYPICALLY 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 willbe energised.The resulting status of the outputsis written to the output image memory file.

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

Programming in PLC

Ladder Logic

Structured Text

Sequential functional chart

Functional Block Diagram

Instruction List

Programming in PLC

Ladder Logic

Structured Text

Sequential functional chart

Functional Block Diagram

Instruction List

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

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

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

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

Thank You