Introduction and Application of SCADA in Improving Efficiency of Complex Processes

Introduction and Application of SCADA in Improving Efficiency of Complex Processes Animesh Verma, Student Electrical Engineering, DEI-Agra

Abstract—SCADA monitoring and control can save for you a lot of money and increase profitability. But your SCADA implementation can be a sinkhole of cost overruns, delays and limited capabilities. This Term Paper will explain the essentials of SCADA technology, give you guidelines for evaluating SCADA Technology and help you decide what kind of SCADA system is best for your needs. Further this paper extends towards optimizing the cost of SCADA equipments by using the best set of components. A brief discussion of the components of SCADA and their specific application, scope gives a insight to this new concept. Implementation of SCADA as case study on Power system example over IEEE reliability test system along with the analysis algorithm explains details for SCADA system restrains and future prospects and challenges in this area. Index Terms— PLC, RTU, RIO, SCADA

I. INTRODUCTION SCADA is not a specific technology, but a type of application. SCADA stands for Supervisory Control and Data Acquisition, any application that gets data about a system in order to control that system is a SCADA application. A SCADA application has two elements:  The process/system/machinery you want to monitor a control. This can be a power plant, a water system, a network, a system of traffic lights, or anything else.  A network of intelligent devices that interfaces with the first system through sensors and control outputs. This network, which is the SCADA system, gives you the ability to measure and control specific elements of the first system. You can build a SCADA system using several different kinds of technologies and protocols. This white paper will help you evaluate your options and decide what kind of SCADA system is best for your needs. Where is SCADA Used? You can use SCADA to manage any kind of equipment. Typically, SCADA systems are used to automate complex industrial processes where human control is impractical systems where there are more control factors, and faster moving control factors, than human beings can comfortably manage. Around the world, SCADA systems control: • Electric power generation, transmission and distribution: Electric utilities use SCADA systems to detect current flow and line voltage, to monitor the operation of circuit breakers, and to take sections of the power grid online or offline. • Water and sewage: State and municipal water utilities use SCADA to monitor and regulate water flow, reservoir levels, pipe pressure and other factors. • Buildings, facilities and environments: Facility managers use SCADA to control HVAC, refrigeration units, lighting and entry systems.

• Manufacturing: SCADA systems manage parts inventories for just-in-time manufacturing, regulate industrial automation and robots, and monitor process and quality control. • Mass transit: Transit authorities use SCADA to regulate electricity to subways, trams and trolley buses; to automate traffic signals for rail systems; to track and locate trains and buses; and to control railroad crossing gates. • Traffic signals: SCADA regulates traffic lights, controls traffic flow and detects out-of-order signals. As I’m sure you can imagine, this very short list barely hints at all the potential applications for SCADA systems. SCADA is used in nearly every industry and public infrastructure project — anywhere where automation increases efficiency. What’s more, these examples don’t show how deep and complex SCADA data can be. In every industry, managers need to control multiple factors and the interactions between those factors. SCADA systems provide the sensing capabilities and the computational power to track everything that’s relevant to your operations. What’s the Value of SCADA to You? Maybe you work in one of the fields I listed; maybe you don’t. But think about your operations and all the parameters that affect your bottom-line results: •Does your equipment need an uninterrupted power supply and/or a controlled temperature and humidity environment? •Do you need to know — in real time — the status of many different components and devices in a large complex system? •Do you need to measure how changing inputs affect the output of your operations? •What equipment do you need to control, in real time, from a distance? •Where are you lacking accurate, real-time data about key processes that affect your operations? Real-Time Monitoring and Control Increases Efficiency And Maximizes Profitability Ask yourself enough questions like that, and I’m sure you can see where you can apply a SCADA system in your operations. But I’m equally sure you’re asking ―So what?‖ What you really want to know is what kind of real-world results you can expect from using SCADA. Here are few of the things you can do with the information and control capabilities you get from a SCADA system: •Access quantitative measurements of important processes, both immediately and over time •Detect and correct problems as soon as they begin •Measure trends over time •Discover and eliminate bottlenecks and inefficiencies •Control larger and more complex processes with a smaller, less specialized staff. A SCADA system gives you the power to fine-tune your knowledge of your systems. You can place sensors and

controls at every critical point in your managed process (and as SCADA technology improves, you can put sensors in more and more places). As you monitor more things, you have a more detailed view of your operations and most important, it’s all in real time. So even for very complex manufacturing processes, large electrical plants, etc., you can have an eagleeye view of every event while it’s happening and that means you have a knowledge base from which to correct errors and improve efficiency. With SCADA, you can do more, at less cost, providing a direct increase in profitability. II. DETAILED WORKING OF SCADA SYSTEMS A SCADA system performs four functions: 1. Data acquisition 2. Networked data communication 3. Data presentation 4. Control These functions are performed by four kinds of SCADA components: 1. Sensors (either digital or analog) and control relays that directly interface with the managed system. 2. Remote telemetry units (RTUs). These are small computerized units deployed in the field at specific sites and locations. RTUs serve as local collection points for gathering reports from sensors and delivering commands to control relays. 3. SCADA master units. These are larger computer consoles that serve as the central processor for the SCADA system. Master units provide a human interface to the system and automatically regulate the managed system in response to sensor inputs. 4. The communications network that connects the SCADA master unit to the RTUs in the field. The World’s Simplest SCADA System The simplest possible SCADA system would be a single circuit that notifies you of one event. Imagine a fabrication machine that produces widgets. Every time the machine finishes a widget, it activates a switch. The switch turns on a light on a panel, which tells a human operator that a widget has been completed. Obviously, a real SCADA system does more than this simple model. But the principle is the same. A full-scale SCADA system just monitors more stuff over greater distances.

Figure 1(a), 1(b) showing the simplest SCADA system and the components of SCADA respectively

Let’s look at what is added to our simple model to create a full scale SCADA system: A. Data Acquisition First, the systems you need to monitor are much more complex than just one machine with one output. So a real-life SCADA system needs to monitor hundreds or thousands of sensors. Some sensors measure inputs into the system (for example, water flowing into a reservoir), and some sensors measure outputs (like valve pressure as water is released from the reservoir). Some of those sensors measure simple events that can be detected by a straightforward on/off switch, called a discrete input (or digital input). For example, in our simple model of the widget fabricator, the switch that turns on the light would be a discrete input. In real life, discrete inputs are used to measure simple states, like whether equipment is on or off, or tripwire alarms, like a power failure at a critical facility. Some sensors measure more complex situations where exact measurement is important. These are analog sensors, which can detect continuous changes in a voltage or current input. Analog sensors are used to track fluid levels in tanks, voltage levels in batteries, temperature and other factors that can be measured in a continuous range of input. For most analog factors, there is a normal range defined by a bottom and top level. For example, you may want the temperature in a server room to stay between 60 and 85 degrees Fahrenheit. If the temperature goes above or below this range, it will trigger a threshold alarm. In more advanced systems, there are four threshold alarms for analog sensors, defining Major Under, Minor Under, Minor Over and Major Over alarms. B. Data Communication In our simple model of the widget fabricator, the ―network‖ is just the wire leading from the switch to the panel light. In real life, you want to be able to monitor multiple systems from a central location, so you need a communications network to transport all the data collected from your sensors. Early SCADA networks communicated over radio, modem or dedicated serial lines. Today the trend is to put SCADA data on Ethernet and IP over SONET. For security reasons, SCADA data should be kept on closed LAN/WANs without exposing sensitive data to the open Internet. Real SCADA systems don’t communicate with just simple electrical signals, either. SCADA data is encoded in protocol format. Older SCADA systems depended on closed proprietary protocols, but today the trend is to open, standard protocols and protocol mediation. Sensors and control relays are very simple electric devices that can’t generate or interpret protocol communication on their own. Therefore the remote telemetry unit (RTU) is needed to provide an interface between the sensors and the SCADA network. The RTU encodes sensor inputs into protocol format and forwards them to the SCADA master; in turn, the RTU receives control commands in protocol format from the master and transmits electrical signals to the appropriate control relays. C. Data Presentation The only display element in our model SCADA system is the light that comes on when the switch is activated. This obviously won’t do on a large scale — you can’t track a light

board of thousand separate lights, and you don’t want to pay someone simply to watch a light board, either. Areal SCADA system reports to human operators over a specialized computer that is variously called a master station, an HMI (Human-Machine Interface) or an HCI (Human- Computer Interface). The SCADA master station has several different functions. The master continuously monitors all sensors and alerts the operator when there is an ―alarm‖ — that is, when a control factor is operating outside what is defined as its normal operation. The master presents a comprehensive view of the entire managed system, and presents more detail in response to user requests. The master also performs data processing on information gathered from sensors — it maintains report logs and summarizes historical trends. An advanced SCADA master can add a great deal of intelligence and automation to your systems management, making your job much easier. D. Control Unfortunately, our miniature SCADA system monitoring the widget fabricator doesn’t include any control elements. So let’s add one. Let’s say the human operator also has a button on his control panel. When he presses the button, it activates a switch on the widget fabricator that brings more widget parts into the fabricator. Now let’s add the full computerized control of a SCADA master unit that controls the entire factory. You now have a control system that responds to inputs elsewhere in the system. If the machines that make widget parts break down, you can slow down or stop the widget fabricator. If the part fabricators are running efficiently, you can speed up the widget fabricator. If you have a sufficiently sophisticated master unit, these controls can run completely automatically, without the need for human intervention. Of course, you can still manually override the automatic controls from the master station. In real life, SCADA systems automatically regulate all kinds of industrial processes. For example, if too much pressure is building up in a gas pipeline, the SCADA system can automatically open a release valve. Electricity production can be adjusted to meet demands on the power grid. Even\ these real-world examples are simplified; a full-scale SCADA system can adjust the managed system in response to multiple inputs.

III. EVALUATION OF SCADA SYSTEMS AND HARDWARE SCADA can do a lot for you but how do you make sure that you’re really getting the full benefits of SCADA? Evaluating complex systems can be tricky — especially if you have to learn a new technology while still doing your everyday job. But you’ve got to be able to make an informed decision, because the stakes are incredibly high. SCADA system is a major, business-to-business purchase that your company will live with for maybe as long as 10 to 15 years. When you make a recommendation about a permanent system like that, you’re laying your reputation on the line and making a major commitment for your company. And as much as SCADA can help you improve your operations, there are also

some pitfalls to a hasty, unconsidered SCADA implementation: • You can spend a fortune on unnecessary cost overruns • Even after going way over budget, you can STILL end up with a system that doesn’t really meet all your needs • Or just as bad, you can end up with an inflexible system that just meets your needs today, but can’t easily expand as your needs grow so let’s go over some guidelines for what you should look for in a SCADA system. What to Look for in a SCADA RTU Your SCADA RTUs need to communicate with all your onsite equipment and survive under the harsh conditions of an industrial environment. Here’s a checklist of things you should expect from a quality RTU:  Sufficient capacity to support the equipment at your Site but not more capacity than you actually will use. At every site, you want an RTU that can support your expected growth over a reasonable period of time, but it’s simply wasteful to spend your budget on excess capacity that you won’t use.  Rugged construction and ability to withstand extremes of temperature and humidity. You know how punishing on equipment your sites can be. Keep in mind that your SCADA system needs to be the most reliable element in your facility.  Secure redundant power supply. You need your SCADA system up and working 24/7, no excuses. Your RTU should support battery power and, ideally, two power inputs.  Redundant communication ports. Network connectivity is as important to SCADA operations as a power supply. A secondary serial port or internal modem will keep your RTU online even if the LAN fails. Plus, RTUs with multiple communication ports easily support a LAN migration strategy.  Nonvolatile memory (NVRAM) for storing software and/or firmware. NVRAM retains data even when power is lost. New firmware can be easily downloaded to NVRAM storage, often over LAN — so you can keep your RTUs’ capabilities up to date without excessive site visits.  Intelligent control. As I noted above, sophisticated SCADA remotes can control local systems by themselves according to programmed responses to sensor inputs. This isn’t necessary for every application, but it does come in handy for some users.  Real-time clock for accurate date/time stamping of reports.  Watchdog timer to ensure that the RTU restarts after a power failure. What to Look for in a SCADA Master Your SCADA master should display information in the most useful ways to human operators and intelligently regulated your managed systems. Here’s a checklist of SCADA master must-haves:  Flexible, programmable response to sensor inputs.  Look for a system that provides easy tools for programming soft alarms (reports of complex events that track combinations of sensor inputs and date/time statements) and

soft controls (programmed control responses to sensor inputs).  24/7, automatic pager and email notification.  There’s no need to pay personnel to watch a board 24 hours a day. If equipment needs human attention, the SCADA master can automatically page or email directly to repair technicians.  Detailed information display. You want a system that displays reports in plain English, with a complete description of what activity is happening and how you can manage it.  Nuisance alarm filtering. Nuisance alarms desensitize your staff to alarm reports, and they start to believe that all alarms are nonessential alarms. Eventually they stop responding even to critical alarms. Look for a SCADA master that includes tools to filter out nuisance alarms.  Expansion capability. A SCADA system is a long term investment that will last for as long as 10 to 15 years. So you need to make sure it will support your future growth for up to 15 years.  Redundant, geo diverse backup. The best SCADA systems support multiple backup masters, in separate locations.. If the primary SCADA master fails, a second master on the network automatically takes over, with no interruption of monitoring and control functions.  Support for multiple protocols and equipment types. Early SCADA systems were built on closed, proprietary protocols. Single-vendor solutions aren’t a great idea vendors sometimes drop support for their products or even just go out of business. Support for multiple open protocols safeguards your SCADA system against unplanned obsolescence. Now that you know about the SCADA application and its components, you’ll want to know where the sensors come in. Sensors used in SCADA systems can be discrete or analog.

Good SCADA systems will support your custom ―safe zone‖ and alert you automatically if the sensor detects conditions outside of that range. In more advanced systems, there are four threshold alarms for analog sensors, defining Major Under, Minor Under, Minor Over and Major Over alarms. These userdefined values will help you to distinguish the severity of alarms by indicating when a monitored analog has passed a certain value, such as a major temperature high that threatens your equipment. Know Exactly “How Much” with Analog Monitoring Analog monitoring is highly valuable, as it conveys specific environmental levels, fuel levels, and battery voltages from analog sensors. Near real-time readings of these continuous values provide a much clearer picture of your network than you can achieve with discrete alarm points alone.

Discrete vs. Analog Alarms

1) Commercial Power - This is a simple way power SCADA sensors. However, when remote sites experience a power outage, so do your sensors. They are also unprotected against a power surge.

Some sensors detect conditions that are reported as an ―on‖ or an ―off‖ (called a discrete input or digital input). That ―on‖ and ―off‖ originate as an on/off, such as a door sensor, or can represent an analog value that crosses a threshold. Other sensors measure more complex situations where exact measurement is important. Not every alarm condition can be represented by an ―on‖ and ―off‖. Analogs provide you with the ability to monitor environmental factors that affect your operations. These inputs can answer the question of ―how much?‖. Common examples of analog values include temperature, battery voltages, humidity, and many more. By knowing when these factors cross critical thresholds and by seeing their rate of change, you can take action before these conditions affect your network. As an example, you might bring in a portable generator if your batteries run low. For most analog measurements, you ideally want to keep the value between a bottom and top level. For example, you might want the temperature in a server room to stay between 60 and 72 degrees Fahrenheit. If the temperature goes above or below this range, you need to be notified.

Analog Sensors Show You Exactly What’s Happening in Your Network One of the primary advantages of using analog sensors for environmental monitoring is the ability to monitor shifting analog values in near real-time. This gives you insight into how the temperature, humidity, or battery voltage is rising or dropping at a site, allowing you to dispatch your technicians most effectively. It helps you make fast, prioritized decisions. For example, your discrete alarm notifies you of 2 hot more sites. One site is at 74 degrees, while the other has reached 118 degrees. How do you know which to fix first? Levels measured by analog sensors can have critical effects on essential equipment - and when your network uptime is threatened, you want all the information you can get. Powering Your Sensors You have an important choice to make when deciding how to power the sensors for your SCADA system. Here are your two major options:

2) RTU Power - The ideal way to provide power to your sensors is through a secure, redundant power supply. Using your SCADA remotes as the power supply for your sensors offers a big advantage. Your sensors are protected from commercial power failures because they’re running on the same protected battery power as your SCADA remotes. Establish Critical Thresholds and Receive Alarms when They’re Crossed Basic SCADA systems almost never include analog inputs, so you’ll never be able to measure exact values. Analog sensor support gives you the key advantage of complete visibility. For example, suppose you are measuring the temperature of a remote site. Under normal conditions, the building’s heating and cooling system will keep the temperature within an acceptable range. But if climate control fails and your equipment is threatened, will you have enough information to make the right decisions?

As an example, you might set up 4 different threshold values: 1) When the temperature is below 45 degrees, page a technician and notify the Network Operations Center (NOC) with a major alarm. A value this low might indicate that the heater is not working at all. 2) When the temperature is below 60 degrees, notify the NOC with a minor alarm. This may indicate that the heater is not functioning at full capacity. 3) When the temperature is above 90 degrees, notify the NOC with a minor alarm. This may indicate that the air conditioning unit is not functioning at full capacity. 4) When the temperature is above 100 degrees, notify the NOC with a major alarm. This may indicate that the air conditioning unit has failed - Equipment and services are in jeopardy. To ensure that you can react appropriately to rapidly fluctuating site conditions, it’s essential to choose the right SCADA system that features analog inputs that report realtime analog values. Analog Parameters and Scaling Once you’ve determined what your different threshold values need to be, you’ll want to be notified if they are crossed. But how can you make sure your alarm notifications arrive in native units (like ° F) that make sense? An advanced SCADA RTU uses analog scaling to convert voltage readings to the units you need, such as degrees. For example, let’s say you need to monitor outside temperature, and you’ve got a sensor with a measurable range of –4° to 167° Fahrenheit (–20° to 75° Celsius). The voltage for the analog channel is between 1 and 5 VDC for that sensor, and is reported as ° F. Here, 1 volt represents –4° F and 5 volts represents 167° F. Simply by inputting these two values into your remote, every notification you receive will be in ° F instead of meaningless voltages. Scale it once, use it forever. The Top 10 SCADA Sensors: 1.) Temperature Sensors - The most basic way to monitor temperature is a discrete threshold sensor. This is very similar to a simple home thermostat. You set a high-point threshold or a low-point threshold (one per sensor). When these presets are exceeded, you get a contact closure alarm, which translates to a basic high or low temperature alarm. The downside to this type of alarm is that if your threshold was set to 80°F, you could be at 81°F or 181°F - and all you wouldn’t be able to tell the difference! More advanced temperature sensors output analog values. Analog monitoring allows you to monitor fluctuating sensor levels at your remote sites. With the right SCADA system, you can use your analog readings to send alarms based on configurable thresholds. You can have different thresholds for low, critically low, high, and critically high. 2.) Humidity Sensors - Often, humidity monitoring is overlooked. But it is one of the key environmental alarms to monitor in every unmanned remote site. Looking at both internal and external humidity ranges, it’s very important to monitor what conditions your revenue-generating equipment

is operating in. If your environmental control unit failed and you didn’t have adequate monitoring of the humidity at your site, you would be completely unaware of the damage and would be too late in preventing equipment failure. Humidity can be monitored with both discrete and analog sensors, much like temperature. Where possible, look for a sensor that monitors temperature and humidity. 3.) Motion Sensors - The most critical element of physical site security is being able to detect intruders and receive an immediate alert. Motion sensors provide you with the instant information you need to react to an intruder before the real damage is done. Discrete motion sensors can even turn on a light and send an immediate intrusion notification when movement is detected in its field of vision. It’s very important to consider placement when installing motion sensors. Windows and other possible intrusion points should be protected by motion sensors. 4.) Liquid Level Sensors - Liquid level sensors can be used to monitor water towers and fuel tanks. This makes them especially useful for alarm circuits that control motor starters, contactors, solenoids, and relays. You should always know how much fuel you have before activating any piece of equipment. With a discrete liquid level sensor, you can configure the sensor to latch a contact closure when your liquid level has fallen below a critical line. This allows you to receive a notification when your water, fuel, or other tanks are low. Don’t risk running dry by ignoring the liquid levels of your machines and other equipment. 5.) Water Flow Sensors - Using water flow sensors gives you an accurate picture of your fluid flow rates. Most flow sensors can monitor water with an internal flowmeter or a flow datalogging device. At at water treatment plant, water flow is one item on a long list of data that must be collected during the treatment process. It’s important to find a reliable water flow sensor that produces accurate flow results and allows you to make quick decisions based on that data. 6.) Smoke Sensors - Smoke sensors are critical safety devices needed in every home, and the same principle holds true for your remote sites. There are many possible reasons a fire could break out at a site. Overheated equipment, electrical short, wildfire . . . the list goes on. In order to save your revenue-generating equipment, you need to know right away if smoke or fire is present at a remote site. Fires cause irreparable damage, and smoke sensors are your first line of defense. 7.) Door Sensors - Whether or not you’ve already experienced theft or vandalism in your network, your unmanned sites are vulnerable. While you might expect this type of criminal activity from strangers, an alarming amount of damage is done by employees, ex-employees, and outside contractors. Door sensors keep your revenue-generating equipment secure. You’ll know the moment someone tries to gain unauthorized access to one of your remote sites, or if an employee enters when they’re not supposed to. Without the protection a door sensor and other BAS sensors can provide, an unknowing technician could walk into a dangerous situation. 8.) Power Failure Sensors - The primary damage caused by a power outage is obvious: If commercial power and you don’t

have a reliable backup power supply, that site will eventually go dark. Dark sites mean network downtime, lost revenue, and frustrated customers. A power failure sensor will send an alarm when power is disrupted. This is a discrete sensor that outputs a contact closure when power is not detected for a user-defined amount of time. Most users want to receive a critical alarm after any failure lasting more than a few seconds. 9.) Current Sensors - You must always know whether your battery chargers, backup generators, and other power sources are outputting power. Analog current sensors tell you way more than, ―They’re outputting power‖. You’ll also know how much. Measuring AC/DC currents, current sensors isolate the sensor output from the conductor. These types of sensors are highly useful for motor drives, UPS systems, and battery supplies. 10.) Propane Tank Sensors - Monitoring your propane tanks can save you from running out of fuel. Some propane sensors send an audible alert when they’re running low. Depending on your tanks, a float sensor that gauges the propane remaining in your tank may be all you need. At sites where propane is the main fuel source, you may need advanced sensors that track gas usage rates and report back to an on-site RTU, like the Net Guardian, with the exact amount left. These type of analog sensors will allow you to order more propane for your tank before it runs empty. An empty propane tank means you have to wait for your next delivery from your supplier, and you may have to suffer without fuel for some time. Control Your Equipment Remotely with Control Relays Control relays allow you to remotely switch equipment on and off. They are simply a switch mechanism that can be activated remotely, no matter where you are located. This can be used for anything from light switches to generators to door locks and more. You’ll also want to make sure that your RTU supports both N/O and N/C so that if power fails, relay will return to intended operation. A sufficiently sophisticated master unit or RTU can run these controls completely automatically, without the need for human intervention. Of course, you can still manually override the automatic controls from the master station. In real life, SCADA systems automatically regulate all kinds of industrial processes. For example, if too much pressure is building up in a gas pipeline, the SCADA system can automatically open a release valve. Electricity production can be adjusted to meet demands on the power grid. You want to be able to monitor multiple systems from a central location, so you need a communications network to transport all the data collected from your sensors. Early SCADA networks communicated over radio, modem or dedicated serial lines. Today the trend is to put SCADA data on Ethernet and IP over SONET. For security reasons, SCADA data should be kept on closed LAN/WANs without exposing sensitive data to the open Internet. Real SCADA systems don’t communicate with just simple electrical signals, either. SCADA data is encoded in protocol format. Older SCADA systems depended on closed proprietary protocols, but today the trend is to open, standard protocols and protocol mediation. Sensors and control relays

are very simple electric devices that can’t generate or interpret protocol communication on their own. Therefore the remote telemetry unit (RTU) is needed to provide an interface between the sensors and the SCADA network. The RTU encodes sensor inputs into protocol format and forwards them to the SCADA master; in turn, the RTU receives control commands in protocol format from the master and transmits electrical signals to the appropriate control relays. Advanced SCADA Data Presentation: A real SCADA system reports to human operators over a specialized computer that is variously called a master station, an HMI (Human-Machine Interface) or an HCI (Human-Computer Interface). The SCADA master station has several different functions. The master continuously monitors all sensors and alerts the operator when there is an ―alarm‖ — that is, when a control factor is operating outside what is defined as its normal operation. The master presents a comprehensive view of the entire managed system, and presents more detail in response to user requests. The master also performs data processing on information gathered from sensors it maintains report logs and summarizes historical trends. An advanced SCADA master can add a great deal of intelligence and automation to your systems management, making your job much easier. IV. SECURITY OF SCADA In recent years, utility companies have undergone great changes in the way they run their businesses. The pressure to increase profits and reduce expenses has them integrating their SCADA systems with their business networks to streamline operations. The popularity of the Internet has customers requesting online access to their accounts as well as online bill payment, further increasing network exposure. In addition, utility companies have reduced costs by leveraging the Internet to facilitate core business operations such as outage management and procurement. The first step towards securing SCADA systems is creating a written security policy, an essential component in protecting the corporate network. Failure to have a policy in place exposes the company to attacks, revenue loss and legal action. A security policy should also be a living document, not a static policy created once and shelved. The management team needs to draw very clear and understandable objectives, goals, rules and formal procedures to define the overall position and architecture of the plan. Key personnel such as senior management, IT department, human resources and the legal department all should be included in the plan. It should also cover the following key components:  Roles and responsibilities of those affected by the policy  Actions, activities and processes that are allowed and those that are not allowed  Consequences of non-compliance A. Vulnerability Assessment A key aspect of preparing a written security policy is to perform a vulnerability assessment prior to completing the

written policy. A vulnerability assessment is designed to identify both the potential risks associated with the different aspects of the SCADA-related IT infrastructure and the priority of the different aspects of the infrastructure. This would typically be presented in a hierarchical manner, which in turn sets the priority to address security concerns and the level of related funding associated with each area of vulnerability. For example, within a typical SCADA environment, key items and the related hierarchy could be as follows:  Operational Availability of Operator Stations  Accuracy of Real-Time Data  Protection of System Configuration Data  Interconnection to Business Networks  Availability of Historical Data  Availability of Casual User Stations A vulnerability assessment also acts as a mechanism to identify holes or flaws in the understanding of how a system is architected and where threats against the system may originate. To successfully complete a vulnerability assessment, a physical audit of all the computer and networking equipment, associated software and network routings needs to be performed. A clear and accurate network diagram should be used to present a detailed depiction of the infrastructure following the audit. After defining the hierarchy and auditing the different system components, the next section highlights the areas of vulnerability need to be addressed, as they relate to each component, as part of the assessment process. B. Further Security Measures As previously mentioned, SCADA networks were once separate from other networks and physical penetration of the system was needed to perpetuate an attack. As corporate networks became electronically linked via the Internet or wireless technology, physical access was no longer necessary for a cyber attack. One solution is to isolate the SCADA network; however, this is not a practical solution for budgetminded operations that require monitoring plants and remote terminal units (RTU) from distant locations. Therefore, security measures need to be taken to protect the network, and some common security mechanisms apply to virtually all SCADA networks, which have any form of wide area (WAN) or Internet-based access requirements. The core elements are:     

Network Design Firewalls Virtual Private Networks (VPN) IP Security (IPSec) and Demilitarized Zones (DMZs)

C. Network Design – Keep It Simple Simple networks are at less risk than more complex, interconnected networks. Keep the network simple and, more importantly, well documented from the beginning. A key factor in ensuring a secure network is the number of contact points. These should be limited as far as possible.

While firewalls have secured access from the Internet, many existing control system have modems installed to allow remote users access to the system for debugging. These modems are often connected directly to controllers in the substations. The access point, if required, should be through a single point that is password protected and where user action logging can be achieved. D. Firewalls A firewall is a set of related programs, located at a network gateway server that protects the resources of a private network from outside users. A firewall, working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network, so that no incoming request can get directly at private network resources. In packet switched networks such as the Internet, a router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks to which it is connected. A router is located at any gateway (where one network meets another), including each point of presence on the Internet. A router is often included as part of a network switch. It is imperative to utilize a secured firewall between the corporate network and the Internet. As the single point of traffic into and out of a corporate network, a firewall can be effectively monitored and secured. It is important to have at least one firewall and router separating the network from external networks not in the company’s dominion. On larger sites the control system needs to be protected from attack within the SCADA network. Implementing an additional firewall between the corporate and SCADA network can achieve this aim and is highly recommended. E. Virtual Private Network (VPN) One of the main security issues facing more complex networks today is remote access. VPN is a secured way of connecting to remote SCADA networks. With a Virtual Private Network (VPN), all data paths are secret to a certain extent, yet open to a limited group of persons, such as employees of a supplier company. A VPN is basically a group of computers that interact as if they are on their own private network regardless of the actual structure of the physical network (e.g., the Internet, local LAN, wireless LAN, etc) upon which they actually exist. For example, there are a number of systems that allow the creation of networks using the Internet as the medium for transporting data. These systems use encryption and other security measures to ensure only authorized users access the network and data cannot be intercepted. Based on the existing public network infrastructure and incorporating data encryption and tunneling techniques, it provides a high level of data security. Typically a VPN server will be installed either as

part of the firewall or as a separate machine to which external users will authenticate before gaining access to the SCADA networks. F. IP Security (IP sec) IP Security (IP sec) is a set of protocols developed by the Internet Engineering Task Force (IETF) to support the secure exchange of packets at the IP layer. IP sec has been deployed widely to implement VPNs. IP sec can be deployed within a network to provide computerlevel authentication, as well as data encryption. IP sec can be used to create a VPN connection between the two remote networks using the highly secured Layer Two Tunneling Protocol with Internet Protocol security (L2TP/IPSec). IP sec supports two encryption modes: Transport and Tunnel. The Transport mode encrypts only the data portion (payload) of each packet, but leaves the header untouched. The more secure Tunnel mode encrypts both the header and the payload. On the receiving side, an IPSec-compliant device decrypts each packet. For IP sec to work, the sending and receiving devices must share a public key. This is accomplished through a protocol known as Internet Security Association and Key Management Protocol/Oakley (ISAKMP/ Oakley), which allows the receiver to obtain a public key and authenticate the sender using digital certificates. It is important during the selection process of network hardware such as routers, switches and gateways to consider the inclusion of support for IPSec security as part of the devices to enable the support of secure VPN connections. G. Demilitarized Zones (DMZ) Demilitarized Zones (DMZ) are a buffer between a trusted network (SCADA network) and the corporate network or Internet, separated through additional firewalls and routers, which provide an extra layer of security against cyber attacks. Utilizing DMZ buffers is becoming an increasingly common method to segregate business applications from the SCADA network and is a highly recommended additional security measure. V. APPLICATION OF SCADA IN POWER SYSTEM Analysis of Power System reliability provides a means of determining when power system failures or load curtailment’s occurring. SCADA failures are assumed to occur independently of load curtailment’s and occur when a power system Operator is unable to retrieve data from or issue controls to primary plant associated with one or more busses. In each case the controls or retrieved data is a necessary part of load restoration. Determining whether a bus is controlled or not, is done by analyzing, the availability of control paths through the SCADA system. This system is a detailed I model representing the master station, SCADA data communications network, remote terminal units and the data wide area network (WAN). Interest in SCADA reliability arose out of Trans Power’s adoption of new, centralized sub transmission SCADA architecture ((a) in Figure 2). This relies on a PC full

graphics terminal located remotely at each Area Control Centre (ACC) connected to National Control Centre (NCC).

Figure 2 Alternative area control centers SCADA architectures Trans Power previously had implemented distributed systems Similar to (b) in Figure 2 (control did not have 100% overlap). In each case the NCC acts as a standby backup facility for the ACC. This work was undertaken in response to concern over the apparent reduction in reliability caused by the removal of a master station and consequent dependence on a single master. Hence a comparison of the differences between these two architectures is presented as a detailed example of the application of the composite reliability analysis algorithm. This is based on using the IEEE reliability test system (IEEE RTS) and a model of one of Trans Power’s implemented ACC systems. A. Analysis Algorithm The objective of the analysis is to calculate the expected amount of unsupplied energy attributed to a SCADA failure. Taking an annual reference period we denote J to be the random variable representing the joint unsupplied energy in annual system minutes. Hence we want to derive E[J], the expected value of J. For a given system model, a single simulation will provide a sample as follows, assuming a

constant load. Then making a number of simulation runs will give an

estimate of E [J] from The quantity, joint load curtailments, is derived from the algorithm illustrated in Figure 3 and described below.

the best choice of SCADA system components according to the need problem. Security of SCADA is major hurdle and need to be handled with care with advanced encryption techniques. Application of SCADA to power system reliability problem suggests the efficient operation with increased reliability. Similarly various other areas also find the immense potentiate application of SCADA, such as railways, transport, generation, Water Management System, etc. With prime need of reliability and efficient optimized cost operation of big systems SCADA promises an advanced solution.

Figure 3. Flow chart for analysis algorithm 1. Generate a SCADA and power system state based on individual component reliability’s and determines which busses the Operator has control of. 2. If there are no power system failures then there will be no load curtailments. 3&4. If there is sufficient, available generation to meet the load then it may be possible to re-schedule this subject to circuit constraints. This is done using a dc load flow. 5. This step is based on the linear programme based optimal power flow (OPF) The OPF minimizes load curtailment by rescheduling generation subject to branch and generation capacities. 6. Compare whether loads curtailment and SCADA control failure has occurred at the same bus or busses. This is perhaps a harsh simplification. The real question at this step is whether, given a load curtailment. SCADA can restore the power system to full load? For example in Figure 5 if a load curtailment occurs at bus 7 due to a circuit outage on its feed from bus 8 then SCADA control would be required at both busses 7 and 8 to restore the load at bus 7. Whilst this is a straight forward example, analysis of this situation becomes more complex at more heavily meshed busses. Hence this is an area of ongoing study. 7. Accumulate the total power not supplied at busses where SCADA control has also failed. VI. CONCLUSION A brief startup of SCADA makes the concept of this new process to be suggested as emerging trend in control systems. And wise decision parameters were discussed in order to make

Figure4. SCADA communication topology for IEEE test System area 1

Figure5. IEEE reliability test system split into areas (loads and reactive power sources omitted)

REFRENCES (1) Bob berry,‖Key Scada Concepts,‖ white paper from DPS Telecoms Newyork. (2) ―Replacement of Programmable Logic Controls Agence Métropolitaine de Transport‖Ref/N. : AMTI06BS-0086-000, Section F-17010 Page I Rev 00 January, 2006 . (3) Divya, Ramya, Bhavani,Shalini, ―SCADA system in Visakhapatnam Stell Plant,‖ march 2009. (4)Anonymous,‖SCADA systems― http://www.amt.qc.ca/docs/appel/AMTI06BS_0086_000_DE V01_en.pdf?Aspx, Accessed on 15 April 2011. (5)Anonymous,‖ daata acquition using scada systems ― http://www.cscjournals.org/csc/manuscript/Journals/IJE/volu me3/Issue1. (6)Anonymous,‖ PLC and RTU comparison and basics ― http://www.motorola.com/web/Business/Products/SCADA%2 0Products/ Accessed on 13 April 2011. (7)Anonymous,‖ Risk mitigation systems, ―http://www.detectinc.com ,Accesse d on 14 April 2011. (8)―reliability analysis of electric utility Scada systems‖, A g bruce, member ieee, Trans Power NZ Ltd. (9) ―Securing an integrated scada system‖ Network security & scada systems whitepaper. (10)‖balaji viswanadh .g, Presentation on SCADA‖, Indian institute of technology delhi.