Industrial Automation generally refers to the science and technology of process control and includes the control of chemical and petrochemical plants, Oil refineries, iron and steel plant, Power plants, cement mills, Paper pulp and paper mills water and waste water treatment plants and many other sectors. The basic objective of automation is identifying the information flow and manipulates the material and energy flow as given process in a desired way. PLC, SCADA,VFD and HMI plays an important role in automating industrial system. Automation of many different processes, such as controlling machines or factory assembly lines, is done through the use of small computers called as Programmable Logic Controller (PLC). This is actually a control device that consists of a programmable microprocessor, and is programmed using a specialized computer language. Today, Programmable Logic Controllers deliver a wide range of functionality, including basic relay control, motion control, process control, and complex networking, as well as being used in Supervisory Control and Data Acquisition Systems and Distributed Control Systems.