Hardware Components of SCADA systems


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A SCADA system can be implemented with the hardware and software components that constitute a whole SCADA system.

Using SCADA system the various application programs that can be implemented in power supply systems are fault location, load balancing, load shedding etc.

Now a detailed description of hard ware components, software components and application programs is given.

SCADA HARDWARE COMPONENTS

The components of a SCADA system are field instrumentation, remote stations, Communication Network (CN) and Central Monitoring Station (CMS).

Field instrumentation

Field instrumentation generally comprises sensors, transmitters and actuators that are directly interfaced to the plant or equipment and generate the analog and digital signals that will be monitor by the remote station.

Signals are also conditioned to make sure they are compatible with the inputs/outputs of the Remote Terminal Unit (RTU) or a Programmable Logic Controller (PLC) at the remote Station.

It also refers to the devices that are connected to the equipment or machines being controlled and monitored by the SCADA system. These are sensors for monitoring certain parameters and actuators for controlling certain modules of the system.

Remote stations

The remote station is installed at the remote plant with equipment being monitored and controlled by the central host computer.

This can be a RTU or PLC. Field instrumentation, connected to the plant or equipment being monitored and controlled, is interfaced to the remote station to allow process manipulation at a remote site. It is also used to gather data from the equipment and transfer it to the central SCADA system.

Communication Network

The Communication Network (CN) refers to the communication equipment needed to transfer data to and from different sites. The medium used can be cable, telephone, radio, and fiber optic or satellite communication system.

Central Monitoring Station:

The Central Monitoring Station (CMS) is the master unit of the SCADA system. Its function is collecting information gathered by the remote stations and generating necessary action for any event that is detected.

The CMS can have a single computer configuration or it can be networked to workstations to facilitate sharing of information from the SCADA system. It uses a Man Machine Interface (MMI) to monitor various types of data needed for the operation.

A MMI program runs on the CMS computer. A mimic diagram of the whole plant or process can be displayed onscreen for easier identification with the real system.

Each I/O point of the remote units can be displayed with corresponding graphical representation and the present I/O reading. Set-up parameters such as trip values, limits, etc. are entered on this program and downloaded to the corresponding remote units for updating of their operating parameters.

There are two typical network configurations for the SCADA systems. They are the point-to-point and the point-to-multipoint configurations. The point-to-point configuration is the simplest set-up for a telemetry system.

Here data is exchanged between two stations. One station can be set up as the master and the other as the slave. The point-to-multipoint configuration is where one device is designated as the master unit to several slave units.

The master is usually the main host and is located in the control room, while the slaves are the remote units. Each slave is assigned a unique address or identification number.