SCADA stands for supervisory control and data acquisition. It is a kind of process control software application program. SCADA is a central control system consisting of network interfaces controllers, input / output, software and communication equipment. SCADA systems are used in the industrial process to track and manage equipment including manufacturing, development and production. Gas and oil supply, electrical power water distribution are among the infrastructural processes. Public utilities include the airport, bus system. The SCADA system takes meter reading and regularly checks sensor status so it requires minimal human interference.
Within large industrial organizations, a large number of processes exist. Every system you need to control is very complex due to the different output from each computer. The SCADA system used to collect data from remote area sensors and instruments. This data is then processed and presented in a timely manner by the computer. The SCADA system gathers the data (such as leakage occurred on a pipeline) and passes the information back to the system while sending the alerts that leakage occurred and shows the information in a logical and coordinated manner. The SCADA system has been used to run on operating systems like DOS and UNIX.
Generic SCADA systems include both components of hardware and software. SCADA software should be load on the computer used for analysis. The hardware component receives data from the input and for further analysis it is fed into the system. SCADA system contains a hard disk that records and stores the data in a file after which the human operator prints it as needed.
Who Uses SCADA?
SCADA systems are used by public and private sector industrial organizations and businesses to monitor and maintain efficiency, distribute smarter decision-making data, and communicate system issues to help mitigate downtime. In many different types of businesses, SCADA systems work well because they can vary from basic setups to massive, complex installations. SCADA systems are the backbone of a number of modern industries, including:
- Food and beverage
- Oil and gas
There are some forms of SCADA systems running behind the scenes almost anywhere in today’s world: maintaining refrigeration systems in the local supermarket, ensuring efficiency and security in a factory, meeting quality standards at a wastewater treatment plant, or even monitoring your energy consumption at home.
The SCADA systems consist of hardware and software unit. A server is used to run SCADA programs. Desktop computers and displays function as HMI linked to the server. Major components of a SCADA system are:
- Master Terminal Unit (MTU)
- Remote Terminal Unit (RTU)
- Communication Network
Master Terminal Unit (MTU)
MTU is the SCADA system’s core. It includes a processor, PLC, and network server to help MTU connect with RTUs. MTU starts communicating, collecting and saving data, interfacing with operators and communicating data to other systems.
Remote Terminal Unit (RTU)
Every Remote Terminal Unit (RTU) is connected to sensors and actuators as it is used in the field sites. RTU collects information from these sensors and sends the data to MTU. RTUs are equipped with storage capacity. So, when MTU sends the appropriate command, it stores the data and transmits the data. Recently developed units include sophisticated systems, which use PLCs as RTUs. This helps to transfer and manage data directly without any MTU signal.
Network means a link. It is defined as a link between RTU in the field and MTU in the central location, when you tell a communication network. The wired or wireless bidirectional communication channel is used for the purpose of networking. Also various other form of communication such as fiber optic cables, twisted pair cables, etc. are use.
As discussed earlier, SCADA software plays a significant role in the whole process analysis. There are several big manufacturing companies who work exclusively on SCADA software. There are many factors to be looked upon before the SCADA software is selected and implemented. To mention a few,
Software’s lifespan: Since you’re going to invest a lot to get the software, it’s always better to check if the technology is going to last down the lane from 5 to 10 years.
Information Request: This is a business term used to define manufacturer and distributor information. If you purchase software from a specific vendor, he / she should be able to provide technical support whenever necessary.
Historian Software: The word historian means that the software should save time stamped information that can be used for future reference purposes. Therefore, your software should be able to handle field data and log the same.
SCADA technology: As we all know, software is rapidly growing to meet our needs. When you’re talking about innovation, it doesn’t mean that you always have to use the latest technology on the market. Alternatively, choose a system that can stay stable and secure for a longer period of time.
Alarm Supervision and Management: Almost all SCADA systems have an alarming function that comes with developed software. It’s necessary to configure the alarm. There are two types of alarm system: system-defined alarm that is controlled by the system on its own and user-defined alarm that is operated by the user.
In automating complex systems, SCADA has made extensive use of characteristics such as versatility, reliability and scalability. In the real world, there are countless applications where SCADA has already been successful in providing alternatives to monitoring and control across a wide range of industries, from energy production to agricultural systems. SCADA is widely used in the chemical, gas, water, communications and electrical systems sectors.
Electric Power Generation, Transmission, and Distribution
Electrical utilities detect current flow and line voltage using SCADA devices, monitor the operation of the circuit breaker and take parts of the power grid online or offline.
SCADA systems are used to manage industrial automation and robots and to track processes and quality control.
Mass transit and Railway Traction
Transit officials use SCADA to regulate electricity for subways, trams, and trolley busses; to automate rail traffic signals; to track and locate trains and busses; and to control doors of railway crossing.
Water, Waste Water Utilities and Sewage
Use SCADA, state and local water systems monitor and control the flow of water, tank levels, pipe pressure and other variables.
Thermal Power Plants
The majority of thermal power plant operating inspections are automatic. Occasionally, however, manual action may be required. Therefore, the plant is equipped with monitoring and alarm systems that alert plant operators significantly from their normal range when certain working para counter deviates. In thermal power plants, demand for greater reliability and efficiency is growing. The power plant needs continuous inspection and tracking after regular intervals. As human employees calculate at different stages, there may be chances of errors. Automation is needed to improve the overall efficiency of the power plant to improve reliability. Automation is developed by using PLC & SCADA, which reduces the mistakes of human workers. A full cycle is supervised using the SCADA method.
Forestry, Pulp and Paper Industry
SCADA devices are also used by the forestry, pulp and paper industry. The industry has ample uses for SCADA, ranging from automation & process control, energy management, drive control, power protection, enclosure systems, and safety.
SCADA devices are used throughout the paper supply chain–including in the wood yard, chippers, evaporators, digesters, refiners, cleaners, drying and pressing machines, and paper machines, of course. By using established SCADA systems, this complex processing of trees to paper is automated from end to end.
Difference Between PLC and SCADA
When you first learn about control engineering, SCADA and PLCs can easily be confused. You will often hear in the same breath the terms “PLC” and “SCADA.” They are distinctly different from each other, even though they are related.
A PLC is a Programmable Logic Controller. This is essentially a rugged mini-computer that sits inside a panel in the field, with a bunch of inputs and outputs leading into the PLC from field devices. The PLC will monitor the status of these inputs (e.g. a motor speed) and will programmatically output various signals to control these field devices (e.g. stop the motor) depending on the program inside.
SCADA platforms are sitting on top of PLCs. PLCs are almost always part of a SCADA network. Usually, information that is logged and stored in a SCADA device is acquired through PLC communication. The PLC will continue to run its program, read inputs and write outputs. The SCADA system is used to keep a log of these inputs and outputs ‘ historical status that can be used for data analysis or auditing. The capacity of PLCs for long-term data storage is limited.
Although it is possible to program SCADA systems to control certain aspects of the field, this is usually an undesirable situation. Ideally, the PLC should run independently and be able to handle any situation it encounters programmatically. That is often not the case because of the complexities of the real world. In these cases, operator feedback is needed for these semi-autonomous systems to function properly.
Thus, the level of “control” that the operator interacts with on the SCADA screen (i.e. HMI) is generally much lower than the control that a PLC executes. Anything that can be easily programmed into logic (e.g. if the flow rate is higher than 100 meters / second, STOP the pump) is programmed into the PLC.
SCADA systems are therefore used mainly for monitoring and collecting information, with control functions being used in unusual or complicated circumstances. SCADA enables operators (and control systems engineers) to see from a distance an overview of the facility, allowing them to react to any unusual situation. It should be noted that a SCADA system includes PLCs that will be communicated with by SCADA technically.
A PLC sits in the field and reads field inputs (e.g. stopped conveyor belt) and writes outputs (e.g. start conveyor belt) depending on how it is configured. A PLC is part of a SCADA network, receiving and executing asynchronously certain commands from SCADA (e.g. operator commands to stop the pump) and reading as a source of data from a SCADA network.
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