Nowadays, computer control is one of the most cost effective solutions for improving reliability, optimum operation, intelligent control and protection of a power system network. Having advanced data collection capabilities, SCADA system plays a significant role in power system operation.

SCADA Systems for Electrical Distribution

Typically, at distribution side SCADA does more than simply collecting data by automating entire distribution network and facilitating remote monitoring, coordinate, control and operating distribution components just like in Smart Grid System.

Before knowing distribution automation using SCADA, let us look at what exactly SCADA is and its functioning and what they do in the distribution system.

What is SCADA?

What is SCADA?

Supervisory Control and Data Acquisition or simply SCADA is one of the solutions available for data acquisition, monitor and control systems covering large geographical areas. It refers to the combination of data acquisition and telemetry.

SCADA MAster Control Station Center

SCADA systems are mainly used for the implementation of monitoring and control system of an equipment or a plant in several industries like power plants, oil and gas refining, water and waste control, telecommunications, etc.

SCADA in Distribution System

In this system, measurements are made under field or process level in a plant by number of remote terminal units and then data are transferred to the SCADA central host computer so that more complete process or manufacturing information can be provided remotely.

This system displays the received data on number of operator screens and conveys back the necessary control actions to the remote terminal units in process plant.

Components of Typical SCADA System

The major components in SCADA system are

Remote Terminal Units (RTUs)

RTU is the main component in SCADA system that has a direct connection with various sensors, meters and actuators associated with a control environment.

These RTUs are nothing but real-time programmable logic controllers (PLCs) which are responsible for properly converting remote station information to digital form for modem to transmit the data and also converts the received signals from master unit in order to control the process equipment through actuators and switchboxes.

Master Terminal Units (MTUs)

A central host servers or server is called Master Terminal Unit, sometimes it is also called as SCADA center. It communicates with several RTUs by performing reading and writing operations during scheduled scanning. In addition, it performs control, alarming, networking with other nodes, etc.

Communications System

The communication network transfers data among central host computer servers and the field data interface devices & control units. The medium of transfer can be cable, radio, telephone, satellite, etc. or any combination of these.

Operator Workstations

These are the computer terminals consisting of standard HMI (Human Machine Interface) software and are networked with a central host computer. These workstations are operator terminals that request and send the information to host client computer in order to monitor and control the remote field parameters.

Automation of Electrical Distribution System

SCADA Distribution Automation

Modern SCADA systems replace the manual labor to perform electrical distribution tasks and manual processes in distribution systems with automated equipments. SCADA maximizes the efficiency of power distribution system by providing the features like real-time view into the operations, data trending and logging, maintaining desired voltages, currents and power factors, generating alarms, etc.

SCADA performs automatic monitoring, protecting and controlling of various equipments in distribution systems with the use of Intelligent Electronic Devices (or RTUs). It restores the power service during fault condition and also maintains the desired operating conditions.

SCADA improves the reliability of supply by reducing duration of outages and also gives the cost-effective operation of distribution system. Therefore, distribution SCADA supervises the entire electrical distribution system. The major functions of SCADA can be categorized into following types.

  • Substation Control
  • Feeder Control
  • End User Load Control

Also read: Fault Current Limiter and Their Types

Substation Control using SCADA

In substation automation system, SCADA performs the operations like bus voltage control, bus load balancing, circulating current control, overload control, transformer fault protection, bus fault protection, etc.

Substation Control using SCADA

SCADA system continuously monitors the status of various equipments in substation and accordingly sends control signals to the remote control equipments. Also, it collects the historical data of the substation and generates the alarms in the event of electrical accidents or faults.

The above figure shows the typical SCADA based substation control system. Various input/output (I/O) modules connected to the substation equipment gathers the field parameters data, including status of switches, circuit breakers, transformers, capacitors and batteries, voltage and current magnitudes, etc. RTUs collect I/O data and transfers to remote master unit via network interface modules.

The central control or master unit receives and logs the information, displays on HMI and generate the control actions based on received data. This central controller also responsible for generating trend analysis, centralized alarming, and reporting.

The data historian, workstations, master terminal unit and communications servers are connected by LAN at the control center. A Wide Area Network (WAN) connection with standard protocol communication is used to transfer the information between field sites and central controller.

Thus, by implementing SCADA for substation control eventually improves the reliability of the network and minimizes the downtime with high speed transfer of measurements and control commands.

Also read: Why Nuclear Power is It The Last Option in Most Countries?

Feeder Control using SCADA

This automation includes feeder voltage or VAR control and feeder automatic switching. Feeder voltage control performs voltage regulation and capacitor placement operations while feeder switching deals with remote switching of various feeders, detection of faults, identifying fault location, isolating operation and restoration of service.

Feeder Control using SCADA

In this system, SCADA architecture continuously checks the faults and their location by using wireless fault detector units deployed at various feeding stations. In addition, it facilitates the remote circuit switching and historical data collection of feeder parameters and their status. The figure below illustrates feeder automation using SCADA.

In the above typical SCADA network, different feeders (underground as well as overhead networks) are automated with modular and integrated devices in order to decrease the number and duration of outages. Underground and overhead fault detection devices provide accurate information about transient and permanent faults so that at the remote side preventive and corrective measures can be performed in order to reduce the fault repeatability.

Ring main units and Remote Control Units (RTUs) of underground and overhead network responsible for maintenance and operational duties such as remote load switching, capacitor bank insertion and voltage regulation. The entire network is connected with a communication medium in order to facilitate remote energy management at the central monitoring station.

Also read: Primary and Secondary or Backup protection in a Power System

End User Load Control Automation by SCADA

End User Load Control Automation by SCADA (AMR)

This type of automation at user end side implements functions like remote load control, automatic meter reading and billing generation, etc. It provides the energy consumption by the large consumers and appropriate pricing on demand or time slots wise. Also detects energy meter tampering and theft and accordingly disconnects the remote service. Once the problem is resolved, it reconnects the service.

The above figure shows a centralized meter data-management system using SCADA. It is an easy and cost-effective solution for automating the energy meter data for billing purpose.

In this, smart meters with a communication unit extract the energy consumption information and made it available to a central control room as well as local data storage unit. At the central control room, AMR control unit automatically retrieves, stores and converts all meter data.

Modems or communication devices at each meter provide secure two-way communication between central control and monitoring room and remote sites.

Also read: Comparison between AC and DC Transmission System

Advantages of Implementing SCADA systems for Electrical Distribution

  • Due to timely recognition of faults, equipment damage can be avoided
  • Continuous monitoring and control of distribution network is performed from remote locations
  • Saves labor cost by eliminating manual operation of distribution equipment
  • Reduce the outage time by a system-wide monitoring and generating alarms so as to address problems quickly
  • Improves the continuity of service by restoring service after the occurrence of faults (temporary)
  • Automatically improves the voltage profile by power factor correction and VAR control
  • Facilitates the view of historian data in various ways
  • Reduces the labor cost by reducing the staff required for meter reading

Programmable Logic Controller (PLC), also referred to as programmable controller, is the name given to a type of computer commonly used in commercial and industrial control applications.


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PLCs differ from office computers in the types of tasks that they perform and the hardware and software they require to perform these tasks.

While the specific applications vary widely, all PLCs monitor inputs and other variable values, make decisions based on a stored program, and control outputs to automate a process or machine. This course is meant to supply you with basic information on the functions and configurations of PLCs with emphasis on the S7-200 PLC family.


Basic PLC operation

The basic elements of a PLC include input modules or points, a Central Processing Unit (CPU)output modules or points, and a programming device. The type of input modules or points used by a PLC depend upon the types of input devices used. Some input modules or points respond to digital inputs, also called discrete inputs, which are either on or off. Other modules or inputs respond to analog signals.

These analog signals represent machine or process conditions as a range of voltage or current values.

The primary function of a PLC’s input circuitry is to convert the signals provided by these various switches and sensors into logic signals that can be used by the CPU. The CPU evaluates the status of inputs, outputs, and other variables as it executes a stored program. The CPU then sends signals to update the status of outputs.

Output modules convert control signals from the CPU into digital or analog values that can be used to control various output devices.

The programming device is used to enter or change the PLC’s program or to monitor or change stored values. Once entered, the program and associated variables are stored in the CPU. In addition to these basic elements, a PLC system may also incorporate an operator interface device of some sort to simplify monitoring of the machine or process.

In the simple example shown below, pushbuttons (sensors) connected to PLC inputs, are used to start and stop a motor connected to a PLC output through a motor starter (actuator). No programming device or operator interface are shown in this simple example.


Hard-Wired Control

Prior to PLCs, many control tasks were performed by contactors, control relays and other electromechanical devices. This is often referred to as hard-wired control.

Circuit diagrams had to be designed, electrical components specified and installed, and wiring lists created. Electricians would then wire the components necessary to perform a specific task. If an error was made, the wires had to be reconnected correctly. A change in function or system expansion required extensive component changes and rewiring.


Advantages of PLCs

PLCs not only are capable of performing the same tasks as hard-wired control, but are also capable of many more complex applications. In addition, the PLC program and electronic communication lines replace much of the interconnecting wires required by hard-wired control.

Therefore, hard-wiring, though still required to connect field devices, is less intensive. This also makes correcting errors and modifying the application easier.

Some of the additional advantages of PLCs are as follows:

  • Smaller physical size than hard-wire solutions.
  • Easier and faster to make changes.
  • PLCs have integrated diagnostics and override functions.
  • Diagnostics are centrally available.
  • Applications can be immediately documented.
  • Applications can be duplicated faster and less expensively.

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Function block One of the official and widely used PLC programming languages is Function Block Diagram (FBD). It is a simple and graphical way to program any functions together in a PLC program. Function Block Diagram is easy to learn and provides a lot of possibilities.
As one of the official PLC programming languages described in IEC 61131-3, FBD is fundamental for all PLC programmers. It is a great way to implement everything from logic to timers, PID controllers etc.
Most engineers love FBD because it is graphically a very common way to describe a system. Engineers like to put things in boxes. And that is exactly what the concept of function block diagrams is.
In this tutorial I will introduce you to some of the basic principles of FBD programming and the function blocks.

What is Function Block Diagram?

From systems engineering you might already know something also called function block diagrams. PLC function block diagram is not that different from it. What FBD offers is a way to put functions written with many lines of code into boxes.
Thereby we can easily connect them, to make a bigger PLC program.
As with ladder logic and structured text, function block diagrams or FBD is described in the standard IEC 61131-3 by PLCOpen. Most PLC programs are written with some amount of FBD. Because, even though you might write your functions in structured text. You still, most of the times, have to connect those functions.

Function Blocks

In FBD all functions are put into function blocks. They all have one or more inputs and outputs. The function of the block is the relation between the state of its inputs and outputs.
Here’s how a simple function block could look like:
Function block illustration in FBD

Function block illustration in FBD
The function block is illustrated with a box. In the middle of the box is often a symbol or a text. This symbol represents the actual functionality of the function block.
Depending on the function there can be any number of inputs and outputs on the function block. You can connect the output of one function block to the input of another. Thereby creating a Function Block Diagram.
There are many standard function blocks provided in FBD.But you can also make your own function blocks. Often, you will have to use the same piece of code in your PLC program multiple times. It could be a function for controlling a valve, a motor etc. With function blocks you can make a function block specific for a motor and use it several times.

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Combining function blocks to make a basic function block diagram

VFD is a power electronics based device which converts a basic fixed frequency, fixed voltage sine wave power (line power) to a variable frequency, variable output voltage used to control speed of induction motor(s). It regulates the speed of a three phase induction motor by controlling the frequency and voltage of the power supplied to the motor.
Since the number of pole is constant the speed Ns can be varied by continuously changing frequency. Variable Frequency Drive
Related pages
Variable Frequency Drive or VFD

Working of Variable Frequency Drive

Any Variable Frequency Drive or VFD incorporates following three stages for controlling a three phase induction motor.

Rectifier Stage

A full-wave power diode based solid-state rectifier converts three-phase 50 Hz power from a standard 220, 440 or higher utility supply to either fixed or adjustable DC voltage. The system may include transformers for high voltage system.

Inverter Stage

Power electronic switches such as IGBT, GTO or SCR switch the DC power from rectifier on and off to produce a current or voltage waveform at the required new frequency. Presently most of the voltage source inverters (VSI) use pulse width modulation (PWM) because the current and voltage waveform at output in this scheme is approximately a sine wave. Power Electronic switches such as IGBT; GTO etc. switch DC voltage at high speed, producing a series of short-width pulses of constant amplitude. Output voltage is varied by varying the gain of the inverter. Output frequency is adjusted by changing the number of pulses per half cycle or by varying the period for each time cycle.
The resulting current in an induction motor simulates a sine wave of the desired output frequency. The high speed switching action of a PWM inverter results in less waveform distortion and hence decreases harmonic losses.

Control System

Its function is to control output voltage i.e. voltage vector of inverter being fed to motor and maintain a constant ratio of voltage to frequency (V/Hz). It consists of an electronic circuit which receives feedback information from the driven motor and adjusts the output voltage or frequency to the desired values. Control system may be based on SPWM (Sine Wave PWM), SVPWM (Space Vector modulated PWM) or some soft computing based algorithm.

Induction Motor Characteristic under Variable Frequency Drive

In an induction motor induced in stator, E is proportional to the product of the slip frequency and the air gap flux. The terminal voltage can be considered proportional to the product of the slip frequency and flux, if stator drop is neglected. Any reduction in the supply frequency without a change in the terminal voltage causes an increase in the air gap flux which will cause magnetic saturation of motor. Also the torque capability of motor is decreased. Hence while controlling a motor with the help of VFD or Variable Frequency Drive we always keep the V/f ratio constant. Now define variable ‘K’ as, For operation below K < 1 i.e. below rated frequency we have constant flux operation. For this we maintain constant magnetization current Im for all operating points. For K > 1 i.e. above rated frequency we maintain terminal voltage V rated constant. In this field is weakened in the inverse ratio of per unit frequency ‘K’. For values of K = 1 we have constant torque operation and above that we have constant power application. vfd

Merits of using Variable Frequency Drives

Energy Saving

Primary function of VFD in industry is to provide smooth control along with energy savings. The variable speed motor drive system is more efficient than all other flow control methods including valves, turbines, hydraulic transmissions, dampers, etc. Energy cost savings becomes more pronounced in variable-torque ID fan and pump applications, where the load’s torque and power is directly proportional to the square and cube of the speed respectively.

Increased Reliability

Adjustable speed motor-drive systems are more reliable than traditional mechanical approaches such as using valves, gears, louvers or turbines to control speed and flow. Unlike mechanical control system they don’t have any moving parts hence they are highly reliable.

Speed Variations

Beyond energy saving, applications such as crushers, conveyors and grinding mills can use the motor and VFD’s packages to provide optimal speed variations. In some crucial applications, the operating speed range can be wide, which a motor supplied with a constant frequency power source cannot provide. In the case of conveyors and mills, a VFD and motor system can even provide a “crawl” speed foe maintenance purposes eliminating the need for additional drives.

Soft Starting

When Variable Frequency Drives start large motors, the drawbacks associated with large inrush current i.e. starting current (winding stress, winding overheating and voltage dip on connected bus) is eliminated. This reduces chances of insulation or winding damage and provides extended motor life.

Extended Machine Life and Less Maintenance

The VFD’s greatly reduce wear to the motor, increase life of the equipment and decrease maintenance costs. Due to optimal voltage and frequency control it offers better protection to the motor from issues such as electro thermal overloads, phase faults, over voltage, under voltage etc. When we start a motor (on load) with help of a VFD, the motor is not subjected to “instant shock” hence there is less wear and tear of belt, gear and pulley system.

High Power Factor

Power converted to rotation, heat, sound, etc. is called active power and is measured in kilowatts (kW). Power that charges builds magnetic fields or charges capacitor is called reactive power and is measured in kVAR. The vector sum of the kW and the kVAR is the Apparent Power and is measured in KVA. Power factor is the ratio of kW/KVA. Typical AC motors may have a full load power factor ranging from 0.7 to 0.8. As the motor load is reduced, the power factor becomes low. The advantage of using VFD’s is that it includes capacitors in the DC Bus itself which maintains high power factor on the line side of the Variable Frequency Drive. This eliminates the need of additional expensive capacitor banks.

Slip Power Recovery

The fundamental power given to rotor by stator is called air gap power Pg. The mechanical power developed is given by The term ‘sP’ is called slip power. Slip power recovery SchemeIf the slip is very large i.e. speed is low then there is ample waste of power, a common example is kiln drives of cement industry. This power can be saved through slip recovery scheme. In this scheme slip power is first collected through brushes of WRIM. This slip power recovered is then rectified and inverted back to line frequency and is injected into supply through coupling transformer. The scheme is shown in figure below.

Applications of Variable Frequency Drive

  1. They are mostly used in industries for large induction motor (dealing with variable load) whose power rating ranges from few kW to few MW.
  2. Variable Frequency Drive is used in traction system. In India it is being used by Delhi Metro Rail Corporation.
  3. They are also used in modern lifts, escalators and pumping systems.
  4. Nowadays they are being also used in energy efficient refrigerators, AC’s and Outside-air Economizers.

SCADA Market will grow at CAGR of 6.6% from 2017 to 2022 to be worth $13.43 billion by 2022. Key driving factors for SCADA market are increased demand for industrial, increasing adoption of cloud, increasing infrastructure development, and rising adoption of Industry 4.0 using SCADA system.

The SCADA market is expected to grow at a CAGR of 6.6% between 2017 and 2022 to be worth USD 13.43 billion by 2022. The key driving factors for the growth of the SCADA market are increased demand for industrial mobility for remotely managing the process industry, increasing adoption of cloud computing in SCADA system, increasing infrastructure development in terms of smart cities and transportation, and rising adoption of Industry 4.0 using SCADA system. However, the high investment cost for setting up of SCADA system, and declining and fluctuating oil and gas prices are considered to be the major restraints for the SCADA market.
Remote terminal unit is expected to hold a major share of the market by 2022. The digital and analog parameters of the field or plant such as the open or close state of a nozzle or the temperatures of particular equipment are monitored with the help of an RTU, which further transmits the data to a central monitoring station of SCADA system. The major share of RTU in the SCADA market is attributed to its ability to enables efficient decision-making for the operator.
The services market is expected to hold the largest size of the SCADA market in 2017. Due to continuous development in technologies used in manufacturing processes and increasing demand for variation in the products, the demand for services of SCADA is increasing. Services in SCADA also include increased security system and latest technology adoption, which enable the SCADA system to remain up to date according to new changes.

The market for the water and wastewater application is expected to grow at the highest rate between 2017 and 2022. SCADA systems are used in water treatment plants as well as in wastewater treatment for constantly monitoring and regulating the water flow, reservoir levels, and pipe pressure, among others. The treatment of water and wastewater requires large amounts of energy; SCADA helps reduce this energy consumption and automates system operations.
The SCADA market in the APAC region is expected to grow at the highest rate between 2017 and 2022. The demand for SCADA systems is very high in APAC owing to the increase in the number of manufacturing plants in various sectors such as power and pharmaceuticals. The implementation of automation is increasing in APAC because of the rising demand for high-quality products along with increased production rates. It also helps in the reduction of labor costs and human interference.

Breakdown of the profiles of primary participants for the report has been given below:

  • By Company Type: Tier 1 = 54%, Tier 2= 26%, and Tier 3 = 20%
  • By Designation: C-Level Executives = 56%, Directors = 28%, and Others = 16%
  • By Region: North America = 42%, Europe = 30%, APAC = 23%, and RoW = 5%

The key players in the SCADA market include ABB (Switzerland), Alstom (France), Emerson Electric Co. (US), General Electric Co. (US), Honeywell International Inc. (US), Iconics Inc. (US), Omron Corporation (Japan), Rockwell Automation Inc. (US) Schneider Electric SE (France), Siemens AG (Germany), and Yokogawa Electric Corporation (Japan).

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A PLC is a Programmable Logic Controller. In other words, it is an industrial computer used as a standalone unit and can be used in a network of PLCs to automatically control a process or perform a specific function. To take information from the outside world such as temperature of a liquid, level in a tank, speed of an object etc, PLC uses different forms of connected sensors. Future of industrial automation would be great if automation people use PLC to control processes. However, the real world signals are transformed into electrical signals by the external sensors and relayed to the PLC that turn processes the electrical signals and uses them to complete its pre-programmed task.

PLCs are used in various places and many of the previous automation processes have been upgraded. This upgraded automation has more flexibility and is simple to alter also. This in turn lends itself to have a more efficient and portable process. On the other hand, PLCs come in various varieties. The sensors connected to the PLCs are smarter than in earlier years. PLC has a great impact on future of industrial automation as the name indicates; it is a programmable logic controller. We are controlling the devices using automation and using PLC programs can be logically done. PLC is mainly designed for multiple input and output arrangements and it can withstand extreme temperatures with resistance to vibration and impact.
Let us understand the following topics in future of industrial automation article:

  • Latest trends in industrial automation
  • Scope of plc programming
  • Future scope of industrial automation
  • Latest plc technology
  • New technology in industrial automation

Latest trends in industrial automation
Latest trends in industrial automation include increased use of analytics, growing use of PLCs, PACs, and increased cloud-based supervisory control and data acquisition (SCADA) systems. These trends will influence the industrial automation control market, according to a report. The report also predicts that these trends will also result in an eight percent compound annual growth rate (CAGR) for the Asia-Pacific region, but the trends are likely to be seen globally. Automation industry is moving towards a future of unparalleled productivity spurred by superior energy efficiency, better design and operator visualization, and rigorous safety standards.

Scope of plc programming
PLCs are continuously growing and evolving to be the best option for a variety of industrial automation applications. Scope of plc programming is increasing rapidly because of greater programming flexibility and ease, scalability, more memory, smaller sizes, very high-speed (gigabit) Ethernet, and built-in wireless features. PLCs are getting benefits from USB technology and thus make it easier than ever before to get online, program, and monitor your control systems. PLC programming will evolve, and with the availability of smaller micro and mini USB connectors, you can expect to see this option on more of the smaller PLCs. In the future, PLCs will continuously evolve while adapting technology enhancements in communications, hardware, and software.

Future scope of industrial automation
Future scope of industrial automation would be good enough as every technology is involved with automation techniques. It is the use of various control devices such as PC’s, DCS, and PLCs to control various operations of an industry without significant intervention from humans and to provide automatic control performance. In industries, there would be a set of technologies that are implemented to get the desired performance or output, making the automation systems most essential for industries. On the other hand, industrial automation involves usage of advanced control strategies such as cascade controls, control hardware devices and other instruments for sensing the control variables etc.

Latest PLC technology
Latest PLC technology helps to monitor and control distributed server/multi user applications. It also provides a comprehensive and accurate picture of operations, meeting the demands of multiple stakeholders including maintenance, engineering, operations, and production information technology (IT). Reliable and robust functionalities can be obtained using the latest technologies of PLC. These technologies enable you to take advantage of visualization, mobility and other new technologies, meeting various challenges in process, discrete applications and delivering critical visibility when you need it.

New technology in industrial automation
New technology in industrial automation is the driver of progress for companies. From the conception to the introduction of the collaborative robots, we have seen a major change in the technological developments continuously shape the industrial automation landscape. These new technologies in automation industry will shape industry in the year ahead. However, global automation industry has been progressing and enhancing functionalities. Risk to security has enhanced interest in open-source software maintained by an active community eager to fix errors.

Future of PLC in industrial automation has been rising since 1947 and most of the industries including automation are using PLCs and install control systems to reduce the manual labour and improve the precision and efficiency. PLCs are very popular because of their precision.

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