MICROCOMPUTER-BASED TWO LEVEL SUPERVISORY CONTROL AND DATA ACQUISITION SYSTEM

Abstract

The industrial systems in which there are distinct units of operation, often unattended and which require supervision from a central facility, use supervisory control and data acquisition (SCADA), where in control centre operators can monitor and con-trol the devices at remote place. Functionally, SCADA consists in the acquisition of data from the controlled system, process-ing the data, displaying the processed data ata central computer system and giving the commands to operate devices at remote pla-ces from the control centre. A review of the developments in remote control, telemetry and supervisory control techniques since the World War II has been carried out. trends in communication with respect to the im-pact of the development of transistors, large automatic tracking antennas, phase locked FM detector and technologically superior communication mediams, are also looked at. The use of computers in SCADA is overviewed. A two level SCADA system has been developed in this project. For the hardware of the remote terminal unit (RTU) of this system, Intel 8085 micro-processor based card cage micro-computer system is used. With the help of different modules of the micro-computer system, various facilities of SCADA on RTU side are achieved. Data of analog and digital variables/quantities is acquired, integra-tion of variables in the form of pulses is carried out and the data is processed and relevant information, is displayed on CRT. Relevant information is sent to MCS also. Provision is made to enable the operator to give control commands from keyboard. The Master Control Station (MCS) is based on 80286 PC. It acquires relevant information from RTU at intervals. System con-figuration in the form of a mimic diagram is displayed along with the real time information. Hard copy of this display and data can be obtained on printer. The MCS issues control command for RTUs. The communication of information between RTU and MCS is done via RS 232 C link using the standard three wire configura-tion. A protocol for exchange of information between the two sta-tions, is designed in a manner as could ensure minimum error dur-ing communication. The entire software for the RTU is written in the assembly langauge of 8085. The control and communication software for the MCS has been developed in the assembly langauge of 8086 while Fortran-77 has been used for writing the display software in the MCS. Suggestions are made at the end for further work on the project. (