SCADA Knowledge Base

SCADA Introduction

What SCADA is - and How to Make It Work for You

What is SCADA
SCADA stands for Supervisory Control And Data Acquisition. While North Americans use this term to refer to distributed measurement and control systems that are larger in scale, the rest of the world applies this term to any application that performs Supervisory Control And Data Acquisition functions.

SCADA systems perform data collection and control at the supervisory level. Some SCADA systems only monitor without performing controlling functions, but these systems are still referred to as SCADA systems.

The History of SCADA
SCADA systems became popular in the 1960’s as the need to monitor and control remote equipment grew. Early SCADA systems used mainframe technology and required human operators to make action decisions and maintain the information systems. Because this increased the human labor cost, early SCADA systems were very expensive to maintain. Today, SCADA is generally much more automated, and consequently more cost-efficient.

The 2 Basic Components of SCADA
Any SCADA scenario involves 2 basic components

1. Things you want to monitor and control
2. Devices you will use to perform monitoring and controlling functions

As stated above, SCADA systems are used to collect data and control processes at the supervisory level. Therefore, one of the major components of a SCADA system is having something that you want to control. This could be a system or process, or even specific machinery. These SCADA-monitored elements could be just about anything, from an oil refinery plant, a power-generation system, an organization’s communication network, or even a simple switch.

To monitor and control these elements using a SCADA system, you will need devices to collect data from them and issue commands. This network of monitoring and control devices makes up your SCADA system. Using sensors (discrete or analog) and control relays, the system can collect information about processes and control individual pieces of equipment. The system is governed by a SCADA master, which collects data from monitoring devices and issues controls in response (either automatically or at the request of human operators).

Where You Can Use SCADA
While SCADA can be used to manage any kind of equipment, SCADA systems are typically for the automation of industrial processes where humans are unable to manage complex or rapid operations. These are often fast-paced processes dealing with extremely delicate and tiny parts and equipment that are simply too difficult for human operators to monitor with any consistent level of accuracy.

SCADA systems are often used by:

• Power companies: SCADA systems can be used to maximize the efficiency of power generation and distribution processes. More specifically, SCADA systems can monitor the power flow, power line voltage, circuit breaker status, and other electrical processes. SCADA systems can even be used to control individual sections of the power grid.
• Major Utility Companies: Both government and private utility companies use SCADA for water and sewage services. This includes collecting water use and distribution information, gauging supply levels, monitoring pressure readings, and other similar applications.
• Physical sites: SCADA systems can be used to control environmental factors at an organization’s physical sites. SCADA data collection functions can be used at facilities and buildings to monitor variables such as temperate, lighting, and entry systems. The control functions of SCADA systems can be used to maintain specific environmental elements at these sites, keeping refrigeration units online, maintaining specific heating levels, and more.
• Manufacturing companies: Production managers can use SCADA to monitor their inventory. They can use their SCADA system to regulate production machinery and implement quality control tests. SCADA can be very beneficial for just-in-time manufacturers by automating production so that demand is met exactly, which reduces inventory costs.
• Providers of mass transportation: SCADA can be used to regulate critical transportation processes, like providing power for all types of public transportation, as well as automating related equipment, including traffic lights and railroad crossing gates. SCADA systems can even be used to track the progress of individual vehicles within a transportation network, including individual buses on city streets, or cars on a specific subway line.

How You Can Use SCADA to Maximize Network Uptime
If you are unsure of the practical applications of a SCADA network monitoring system, review the following list of scenarios where a SCADA system can improve operational efficiency. If any of the following situations sounds like it could be your company, you need a SCADA solution to protect your mission-critical operations.

• You need a constant stream of power to operate your equipment
• You need to monitor, control, or respond to environmental factors, such as wind level or temperature at your site
• You need to constantly monitor the connectivity of different devices or other components of your large system
• You need to gather information that demonstrate the effects of input changes on your operational output levels
• You need the ability to remotely control equipment in real time
• You need reliable, real-time information reporting about mission-critical processes that affect overall output

SCADA System Operation
There are four parts common to every SCADA system:

1. Sensors (either digital or analog) and control relays - These are input/output devices that monitor and control the managed processes and equipment.
2. Remote telemetry units (RTU’s)- These are devices deployed in the field at specific sites and locations. RTU’s gather information locally from the sensors to report back to the SCADA master unit. RTU’s can also issue control commands to the control relays it communicates with.
3. SCADA master units- SCADA master units are the main, user-end component of the entire SCADA monitoring system. They are also sometimes referred to as the SCADA HMI (Human-Machine Interface). The master provides the central processing capability for the SCADA system. Master units connect the human operators to the system with a browser interface that allows the system operator to respond to data gathered from all parts of the network.
4. The communications network- The communication network provides the connection between the SCADA master unit and the RTU’s in the field. It is the all-important link between the far-flung elements of a geo-diverse operation.

1. Data collection- A SCADA system is composed of large numbers of sensors that collect inputs into a system, or measure the output levels of a system or process. The information collected by these sensors is collected by the RTU’s locally, and then forwarded to the SCADA master, where reports and alarms are presented to the network operator.

   Sensors can be classified as two types, either discrete or analog. Discrete sensors collect information about simple events, whereas analog sensors can provide more detailed information that can fall within a range of values, rather than a present/not present type of situation. Analog sensors are particularly useful in measuring environmental factors, such as temperature and humidity, battery levels, fuel levels, and more.

2. Communication of data across the network- To monitor geo-diverse operational systems from a centralized location, you need a communications network. This network provides you with a means to transport all information collected across the system. SCADA communications generally take place on Ethernet and IP over SONET. To alleviate security concerns when transporting sensitive data, communication of data should be done over internal LAN/WANs, not the public Internet.

   SCADA uses protocol communication methods, so input and output devices cannot interpret or create SCADA communications on their own. RTU’s interpret information from attached sensors and transmit it to the SCADA master (HMI). In turn, the RTU receives control commands in protocol format from the SCADA master, and forwards these commands to the appropriate control relays. This allows the SCADA master to control individual operational processes throughout the network from a single location

3. Information reporting- A SCADA system presents data to operators via the SCADA HMI (Human-Machine Interface). Along with presenting this data, the SCADA master station also performs many other tasks for network operators. The master continuously monitors all sensors and alerts the operator when there is a Change-of-State (COS) event within the managed system.

   The master presents a comprehensive view of the entire network of devices, and presents more specific information about the managed equipment and processes when the system operator requests it. The master also presents reports and summarizes historical trends of data gathered by the system.

4. System control functions- A SCADA solution with control functions can respond to COS events anywhere in the system by automatically issuing related, user-specified commands. If you have an advanced SCADA master, this can be done without any human intervention at all, resulting in instantaneous response to dynamic problems and threats. Advanced systems also allow overriding of automatic controls as the need occurs.

Building Your SCADA System
When building a SCADA system, it is important to identify criteria that will protect revenue and reduce costs for your company. When planning your yearly expenditures, you must budget for advanced monitoring and control equipment, as the revenue conservation and cost reduction provided by advanced SCADA systems can quickly cover the initial purchasing expense.

What to Look for in a SCADA RTU
SCADA remotes are a critical part of your SCADA monitoring system. You need RTU’s that can communicate with all your on-site equipment. Seek RTU’s that are durable, because they must be able to weather the harsh conditions of an industrial setting. When researching a SCADA RTU, make sure it has the following key features:

• Sufficient capacity to support your site equipment- You want an RTU that will support your growing monitoring needs. However, you shouldn’t purchase a remote that provides more capacity than you can ever reasonably expect to need. Look for a vendor that provides you with many capacity choices. Then, select one for each site that meets your monitoring needs and fits within your allotted budget.
• Rugged construction to withstand extreme environmental conditions- Harsh industrial environments can take a toll on your equipment. Nonetheless, your SCADA system needs to be the most reliable element in your operation. You need remotes that can stand up to extreme conditions, and provide you accurate and reliable monitoring - no matter what environmental factors are in effect. Choose a remote with rugged construction to get the durability you need from a SCADA monitoring system.
• Reliable, constant power supply- You need your SCADA system up and running every minute of every day. Your RTU should support battery power in addition to two power inputs. Choose an RTU that will give you the network visibility you need no matter what.
• Mutiple communication ports- Adaptable network connectivity is as critical to SCADA operations as a power supply. A secondary serial port or internal modem will keep your RTU online even when your primary communication fails. RTU’s with multiple communication ports also support a cost-efficient LAN migration process, ensuring that your equipment will have a long-life, even as your network architecture changes and expands.
• Control functions- Advanced SCADA remotes can control local systems by utilizing programmed responses to sensor inputs. This will come in handy if you ever face an unforeseen outage, or other network problem that can be simply and quickly corrected through the controls programmed into your RTU’s.
• Real-time time and date Stamping- What value will your reports give you without accurate time and date information? To make the most out of your alarm logging, find an RTU that provides for accurate date/time stamping of COS alarms.
• Watchdog timer- You need to ensure that the RTU restarts after a power failure. Watchdog timers give you the assurance that your equipment is back online after power is restored.

What to Look For in a SCADA Master
Your SCADA master is the core of your SCADA monitoring system. You need the most advanced master that cab provide you will all of the important features your business absolutely must have in a monitoring system. When looking for a SCADA master, make sure your choice has the following features:

• Derived Control functions- An advanced SCADA will allow you to issue derived controls (automated responses) to specific combinations of sensor inputs. The right SCADA solution will make it easy for you to program these automatic system responses, and it will also give you the freedom to design the exact response you need. These control functions are not present in all SCADA systems, and could be the difference between keeping your network online and losing revenues during a primary power outage or other preventable problem.
• Automatic pager and email alarm notification- You can’t physically monitor your SCADA master screen ever minute of the day. If there is a problem at one of your sites, an advanced SCADA master will automatically send a page or email directly to on-call technicians. Your technicians will receive specific details about the location of the problem, drastically reducing repair times and expense, and protecting precious revenue-generating uptime.
• Robust data presentation options- Your SCADA master should display alarms in a language you can understand. It should also give you a complete description of every alarm, and how you can correct the problem.
• Nuisance alarm filtering- Nuisance alarms can cause your staff to be more careless about responding to alarms by distracting them from truly critical COS events. After many instances of dealing with nuisance alarms, your technicians may stop responding - even to dangerous critical alarms. Look for a SCADA master that provides for nuisance alarm filtering to prevent your technicians from being desensitized to important network events.
• Expansion options- Your SCADA system is not a short-term investment. You need a system that will last your company for at least 10 to 15 years. To maximize your equipment investment, find a SCADA master that will support the growth of your network along with your monitoring needs. This includes the capability to include other protocols and equipment as they are introduced into your operation.
• Backup master support- Advanced SCADA systems support several backup masters, located at different sites. If your main SCADA master fails, a backup master at a different site can resume the master functions, without interrupting your monitoring. Because your SCADA system protects against costly downtime, you must be absolutely certain that you SCADA system is able to withstand natural disasters and other major threats.
• Support for a variety of protocols and devices- Early SCADA systems were designed to support devices from a single vendor. These types of system aren’t effective, as vendors sometimes drop support for their products, or simple close their doors. Advanced SCADA systems support a variety of open-source protocols (a few even exceed 25 supported protocols) to prevent your system becoming obsolete, even if your vendor goes out of business.

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