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What You Need to Know About SCADA in Industrial Automation


Industrial automation is the use of computer-controlled devices such as Remote Terminal Units (RTUs), Computer Numerical Control (CNC), Programmable Logic Controllers (PLCs), etc. to control industrial systems in place of human labor. A typical industrial automation system incorporates an array of control elements that are effectively synchronized with each other to perform functions like sensing, monitoring, controlling, and supervising industrial processes and machinery.

These functional elements are divided into different levels, namely: (i) Field Level (Actuators & Sensors); (ii) Control Level (PLCs & PACs); (iii) Supervisory, Production Control Level (SCADA & DCS); (iv) Information and Enterprise Level (ERP & MES). This article focuses on supervisory control using SCADA, a key aspect in the automation of industrial systems spread out over an extensive geographical area.

What is a SCADA System?

The acronym SCADA stands for Supervisory Control and Data Acquisition. A SCADA system is an automation control system consisting of a combination of software and hardware components that enable the automation of industrial equipment, assets, and processes by capturing real-time operational data, mainly from remote locations.

The SCADA hardware components deployed in the field, such as sensors, gather the real-time operational data and feed it into controllers for processing, the processed data is then forwarded to other systems for presentation to plant operators in a timely manner via Human-Machine Interfaces (HMI). Essentially, SCADA connects input sensors monitoring field devices like valves, pumps, and motors to a remote or onsite centralized server. From the central server, the collected data is then analyzed and processed to control the necessary industrial process or machinery.

Note: SCADA systems include complex microprocessor-based control systems or PC-based data processing controllers that sense, process, and control various process variables like voltage, current, gas meter readings, liquid levels, pressure, temperature, flow, and distance simultaneously. These systems also make use of personal computers (PCs) that perform higher-level control operations such as set point computations, start-up, performance monitoring, diagnostics, troubleshooting, shutdown, and other emergency functions. For example, SCADA applications can sound alarms to warn operators of hazardous working conditions.

In summary, SCADA systems enable industries to:

  • Acquire/gather, analyze, and display real-time operational data
  • Control industrial processes either locally or at remote sites
  • Interact directly with industrial equipment such as input sensors, valves, motors, and pumps
  • Record and log all events for report creation or future reference
  • Implement a tag database containing tags or a distributed database that stores points across the entire plant. Each of these points represents an input or output value that’s being monitored or controlled by the SCADA system
  • Identify system issues in real-time

Key Components of a SCADA System

As previously stated, a SCADA system includes both software and hardware components.

SCADA Hardware

The hardware elements of a SCADA system are comprised of components deployed in the field to collect real-time operational data, and other related systems that enable data processing and which enhance industrial automation. Most SCADA systems have the following hardware components:

A) Field Sensors & Actuators

Sensors monitor and detect inputs from the factory machines and processes being controlled by the SCADA control system. These inputs can be physical elements such as heat, pressure, force, motion, or light, which are then converted into electrical signals by the sensors. On the other hand, actuators accept command signals and perform functions that control the mechanisms of the corresponding industrial processes or machinery.

For example, a pressure gauge or flow meter can function as a sensor, displaying the operating status of an industrial machine; while a control valve, dial, or switch can function as the actuator used to control the machine. Note, both field sensors and actuators are monitored and controlled by field controllers.

B) SCADA Field Controllers

These controllers interface directly with the field sensors and actuators. They are of two categories:

1) Remote Terminal Units (RTUs):

RTUs are microprocessor-based devices that monitor and control field equipment. They are present at geographically distributed remote locations to facilitate communication of various remote field equipment within the SCADA system, thereby supporting plant automation.

An RTU system consists of input & output hardware components and a communication interface for remote sensing and controlling ongoing industrial processes. In essence, the sole purpose of RTUs in a SCADA system is to send all the collected sensor data to the centralized SCADA control, for storage and monitoring purposes.

2) Programmable Logic Controllers (PLCs):

PLCs are ruggedized, solid-state computing devices used to control different electro-mechanical processes in automated manufacturing plants and other industrial facilities. A PLC system is comprised of a Central Processing Unit (CPU) or microprocessor, memory unit, power supply module, and dedicated I/O modules for the digital/analog inputs and outputs connected to it. Its CPU continuously monitors and collects data from the connected field input devices. It then processes the collected data, executes its programmed logic, and controls the corresponding field output devices based on the received input information and results of logic execution.

In SCADA systems, PLCs are directly interfaced with field sensors and actuators to control industrial processes and machinery, usually based on the preset standards for the processes and real-time telemetry data collected by RTUs. They are also networked with the SCADA supervisory computer system using high-speed connections for factory automation. For example, in remote SCADA applications like a large wastewater treatment facility, a high-speed wireless link can be used to connect PLCs directly to the SCADA supervisory system.

Note: RTUs use non-physical media/wireless transmission for data transfer, whereas PLCs rarely use wireless transmission instead they normally transfer data using communication cables. Also, RTUs are far more rugged than PLCs and they’re specially designed for remote I/O applications, meaning their geographic telemetry is more widely spread than that of PLCs. However, PLCs provide faster data transfer speeds compared to RTUs.

C) Supervisory Computers

These form the core of a SCADA system as they host the SCADA software, which controls all SCADA operations. They are used to gather real-time data from the connected field devices and to send control commands to those devices to control specific industrial processes. Also, they are responsible for communicating with the field controllers.

D) Human-Machine Interface (HMI)

Generally, HMI refers to a combination of software and hardware elements through which a plant operator interacts with field controllers. The HMI software enables operating personnel to manage industrial processes and control machinery through a computer-based Graphical User Interface (GUI). In SCADA systems, HMI acts as a platform–a touchscreen computer system–that allows users to view the SCADA data gathered from multiple RTUs and PLCs in a central control hub in an organized format. Also, if the process variables may require any changes, then operators can run appropriate programs or commands via the HMI.

Moreover, using the HMI platform users can modify the configuration settings of the field controllers and other devices within the SCADA system. Essentially, HMI functions as an operator window of the SCADA supervisory computer system. It consolidates and presents real-time data regarding the operating status of a SCADA-controlled industrial process to human operators. This data is presented in form of real-time trending graphs, mimic diagrams, event logging pages, and alarm displays. Also, via the HMI, operators can obtain reports and statistics based on the data collected from various SCADA field devices.

SCADA Software

Because SCADA is a centralized monitor and control system, the SCADA software is usually installed on a computer in a central monitoring hub of an industrial facility. It is a monitoring software that helps control the hardware components of the SCADA system and make a record of all the data collected from the connected remote field devices.   

SCADA software is also connected to supervisory computers, field controllers, graphical user interfaces such as HMI, and networked data communications to provide a broad overview of the industrial process being controlled. It serves as a sort of interface that consolidates plant data from various devices within the SCADA system onto a centralized control hub for assessment purposes. This allows plant operators to monitor and control automated industrial systems from multiple locations, including remote locations.

Note: You can install Computerized Maintenance Management System (CMMS) software on top of the SCADA software to further analyze the collected SCADA data and put it to better use. Also, the CMMS software assists in generating Corrective Maintenance (CM) work orders whenever the SCADA supervisory system receives any alarming readings of the process variables being monitored. A CM work order is simply a document that describes a problem, as well as the tasks that should be carried out to correct the outlined problem and the resources required to complete the stated tasks.

SCADA Network

This refers to the communication infrastructure that enables the SCADA supervisory computer system to communicate with field controllers (PLCs and RTUs) and field I/O devices (i.e. sensors and actuators). SCADA networks may utilize industry-standard or manufacturer-proprietary communication protocols, but both RTUs and PLCs are known to have embedded communication and control capabilities that support their autonomous functioning on the SCADA control system. Today, the most commonly used communication technology within SCADA systems is Industrial Ethernet.

Note: SCADA communication channels can either be digital or analog. Also, these channels transmit the collected data either spontaneously or in response to a data request from an upstream centralized or master station.

How Does a SCADA System Operate?

The basic architecture of a typical SCADA system begins with Remote Terminal Units (RTUs) or Programmable Logic Controllers (PLCs) that constantly communicate with an array of field devices (i.e. sensors and actuators) connected to factory machines. Communication networks and various end devices then route the data collected from the connected field devices to supervisory computers with installed SCADA software. The SCADA software processes the received data and presents it in real-time via HMI platforms, enabling users to analyze it and make important control decisions.

Most industrial facilities often implement a hybrid version of automated and direct SCADA control by creating programs that alert plant operators to any abnormal operating conditions. Using the real-time SCADA data consolidated in a centralized monitoring hub, the operating personnel can then make informed decisions on the appropriate control actions.

For example, let’s consider a SCADA system controlling an automated manufacturing facility. While in operation, the SCADA’s supervisory system identifies a batch of products showing a high percentage of errors and it quickly notifies an operator of the same with an alarm display. On receiving the error notification, the operator pauses the manufacturing process and reviews the SCADA system data via an HMI platform to determine the source of the problem. After evaluating the presented real-time SCADA data, the operator discovers that the machine responsible for producing that batch of products was malfunctioning, and requires servicing. Thus, the ability of the SCADA system to notify the operator of a product issue in real-time, helps him to resolve it promptly and prevent further production losses.

Also, operators can control and influence a SCADA environment without the need to directly respond to each event. Using customized logic-based instructions, an operator can designate a SCADA control system to perform specific actions when field sensors detect certain process anomalies. For example, if the rotating bit on a particular milling machine is likely to vibrate excessively, the SCADA software controlling the machine can be programmed to power down the machine whenever the bit’s vibration levels exceed a certain limit to avoid material wastage or potential harm to operators.

scada_b (37)” by Green_Mamba is licensed under CC BY-ND 2.0.

Applications of SCADA Systems

SCADA systems play a key role in advancing industrial automation due to their numerous benefits including graphically illustrating production processes via HMI, maintaining equipment efficiency, processing production data in real-time for quicker and smarter control decisions, and real-time communication of system issues via alarms and warnings, which significantly reduces system downtime. As a result, many industrial organizations, especially those with plant assets and machinery spread out over vast geographical areas, are largely implementing SCADA systems to improve their processes. Some of these industries include:

A) Electricity Generation, Transmission, and Distribution Utilities

SCADA systems are used in power plants to monitor every phase of electricity generation, i.e. from fuel input to electric power output in thermal power plants. The SCADA software enables such plants to respond almost instantaneously to fluctuations in power demand.

On the other hand, electric transmission utilities use SCADA systems to monitor and control the amount of electric power being transmitted over long-distance power lines. They also use SCADA for protection and safety purposes. For example, whenever an electric power transmission line experiences an electrical fault, the SCADA system in use is usually programmed to quickly clear the fault and restore power. In addition, electric distribution utilities use SCADA platforms to monitor and control power distribution lines and electrical substations.

B) Oil and Gas Industry

Unlike the SCADA platforms used in other applications like electric, telecom, and water systems, oil and gas SCADA systems do move physical substances through their infrastructure over a large geographical area. They are mainly used to monitor oil and gas wells, pumping sites, pipeline flow, and pumping pressure of distribution pipelines. Also, they’re used to monitor and control natural gas compressor stations.  In addition, SCADA software is necessary for safety purposes, as it can detect anomalies in the oil & gas systems and prevent disastrous events from happening.

C) Water Systems

SCADA systems are used to monitor and control water treatment plants, and water pumping at well sites. They are also useful in filling up overhead water storage tanks. In addition, SCADA platforms are employed in water distribution systems to control booster pumps to regulate the pressure of the water being delivered to customers.

D) Manufacturing Plants

Manufacturing facilities precisely use SCADA systems to control all plant operations. For example, the SCADA software can be used to monitor and regulate process variables such as temperature, humidity, flow, and pressure. It’s also useful in monitoring production lines and related machinery/equipment to ensure production goals (in terms of quality of products and production capacity) are being met. Moreover, SCADA systems are used to control assembly line robots and to manage parts inventory for just-in-time manufacturing.

E) Mass Transit Systems

Railways, tramways, and subways use SCADA systems to time their transit operations and to control their switches, thereby enabling cars and engines to pass each other safely. SCADA is also used to remotely control railroad crossing signals. In addition, automated traffic control systems rely on SCADA software to regulate traffic flow and improve road safety.

SCADA Security

SCADA security refers to the measures that have been put in place to protect SCADA networks from potential security threats. These networks are comprised of firmware, hardware, and software components, which make them vulnerable to different security threats including hackers, internal errors, malware, and terrorists.

SCADA systems were initially designed as isolated entities to be handled only by plant operators, system technicians, and engineers; thus, secure connections to public networks weren’t always prioritized, which left many SCADA platforms prone to cyber-attacks. Today, however, there are numerous preventive measures and standard protocols that must be implemented for an industrial organization to run a secure SCADA platform that’s operated by multiple users. Failure to correctly practice any of the instituted security checks and procedures would leave the SCADA system open to cyber-attacks and SCADA viruses.

One of the most effective practices for enhancing SCADA security is mapping all the systems and devices in the SCADA network. This involves documenting all the SCADA devices and systems connected to the internal network as well as to the Internet. Meaning that every bit of hardware, firmware, software, and application within the entire SCADA network is included in the generated map. The map is then used to identify major points of vulnerability and effectively counter potential security threats.

Also, governments and private companies have taken fundamental physical and cyber security measures to ensure the safety of SCADA networks used to control natural gas and oil pipelines, electricity grids, and water distribution systems, due to the critical roles and vulnerabilities of such SCADA networks. 

However, even with all the safety measures and practices being implemented to protect SCADA systems, some existing SCADA network designs still lack efficient authentication protocols in their operation. Thus, SCADA security is an aspect that continues to require more attention, and extremely secure SCADA systems should be developed. Because SCADA systems are real-time control systems and successful physical or cyber-attacks on such systems, particularly those used in key service industries, can cause serious consequences to many areas of society in terms of physical damage and loss of life.

This entry was posted on January 16th, 2023 and is filed under Uncategorized. Both comments and pings are currently closed.

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