SCADA: A Tool for Managerial Excellence

Supervisory Control And Data Acquisition (SCADA) is a automation tool which is being used in manufacturing industry for accurate, timely and quality production. The other role of SCADA is to make available real time data related to production for technical and managerial analysis. Today, in this competitive era, Managers have to be more equipped with such tools for increasing the production efficiency. This paper will discuss about architecture and working of SCADA and will explore various applications of it.

INTRODUCTION: The manufacturing industries are facing a very tough competition in regards of production efficiency. Production efficiency refers to managing the quality and accuracy with proper speed. It’s a big challenge for any manager to manage resources that is from inventory .

TYPES OF SCADA
1. D+R+N (Development +Run + Networking)
2. R+N (Run +Networking)
3. Factory focus

FEATURES OF SCADA
1. Dynamic process Graphic (Mimics)
2. Alarm summery
3. Alarm history
4. Real time trend
5. Historical time trend
6. Reports
7. Security (Application Security)
8. Data base connectivity
9. Device connectivity
10. Scripts
11. Recipe management

MANUFACTURE OF SCADA
Modicon (Telemecanique) Visual look
Allen Bradly : RS View
Siemens: win cc
Gefanc:
KPIT : ASTRA
Intelution : Aspic
Wonderware : Intouch


2. WHAT DOES SCADA MEAN?
SCADA stands for Supervisory Control And Data Acquisition. As the name indicates, it is not a full control system, but rather focuses on the supervisory level. As such, it is a purely software package that is positioned on top of hardware to which it is interfaced, in general via Programmable Logic Controllers (PLCs), or other commercial hardware modules. SCADA systems are used in industrial processes: e.g. steel making, power generation (conventional and nuclear) and distribution, chemistry. Now a days they are also being used in some experimental facilities such as nuclear fusion.

3. ARCHITECTURE
HARDWARE ARCHITECTURE: One distinguishes two basic layers in a SCADA system: the "client layer" which caters for the man machine interaction and the "data server layer" which handles most of the process data control activities. The data servers communicate with devices in the field through process controllers. Process controllers, e.g. PLCs, are connected to the data servers either directly or via networks or fieldbuses that are proprietary (e.g. Siemens H1), or non-proprietary (e.g. Profibus). Data servers are connected to each other and to client stations via an Ethernet LAN. The data servers and client stations are NT platforms but for many products the client stations may also be W95 machines.

SOFTWARE ARCHITECTURE: The products are multi-tasking and are based upon a real-time database (RTDB) located in one or more servers. Servers are responsible for data acquisition and handling (e.g. polling controllers, alarm checking, calculations, logging and archiving) on a set of parameters, typically those they are connected to. However, it is possible to have dedicated servers for particular tasks, e.g. historian, datalogger, alarm handler. Fig. 2 shows a SCADA architecture that is generic for the products that were evaluated.

COMMUNICATIONS
INTERNAL COMMUNICATION: Server-client and server-server communication is in general on a publish-subscribe and event-driven basis and uses a TCP/IP protocol, i.e., a client application subscribes to a parameter which is owned by a particular server application and only changes to that parameter are then communicated to the client application.

ACCESS TO DEVICES: The data servers poll the controllers at a user defined polling rate. The polling rate may be different for different parameters. The controllers pass the requested parameters to the data servers. Time stamping of the process parameters is typically performed in the controllers and this time-stamp is taken over by the data server. If the controller and communication protocol used support unsolicited data transfer then the products will support this too. The products provide communication drivers for most of the common PLCs and widely used field-buses, e.g., Modbus. Both Profibus and Worldfip are supported but CANbus often not [3]. Some of the drivers are based on third party products (e.g., Applicom cards) and therefore have additional cost associated with them. A single data server can support multiple communications protocols: it can generally support as many such protocols as it has slots for interface cards. The effort required to develop new drivers is typically in the range of 2-6 weeks depending on the complexity and similarity with existing drivers, and a driver development toolkit is provided for this.

INTERFACING: Application Interfaces / Openness
The provision of OPC client functionality for SCADA to access devices in an open and standard manner is developing. There still seems to be a lack of devices/controllers, which provide OPC server software, but this improves rapidly as most of the producers of controllers are actively involved in the development of this standardThe products also provide
An Open Data Base Connectivity (ODBC) interface to the data in the archive/logs, but not to the configuration database,
An ASCII import/export facility for configuration data,
A library of APIs supporting C, C++, and Visual Basic (VB) to access data in the
RTDB, logs and archive. The API often does not provide access to the product's
internal features such as alarm handling, reporting, trending, etc.
The PC products provide support for the Microsoft standards such as Dynamic Data Exchange (DDE) which allows e.g. to visualise data dynamically in an EXCEL
spreadsheet, Dynamic Link Library (DLL) and Object Linking and Embedding (OLE).

DATABASE: The configuration data are stored in a database that is logically centralised but physically distributed and that is generally of a proprietary format. System (RDBMS) at a slower rate either directly or via an ODBC interface.

SCALABILITY: Scalability is understood as the possibility to extend the SCADA based control system by adding more process variables, more specialised servers (e.g. for alarm handling) or more clients. The products achieve scalability by having multiple data servers connected to multiple controllers. Each data server has its own configuration database and RTDB and is responsible for the handling of a sub-set of the process variables (acquisition, alarm handling, archiving).

REDUNDANCY: The products often have built in software redundancy at a server level, which is normally transparent to the user. Many of the products also provide more complete redundancy solutions if required.

4. FUNCTIONALITY
4.1 ACCESS CONTROL: Users are allocated to groups, which have defined read/write access privileges to the process parameters in the system and often also to specific product functionality.

4.2 MMI
The products support multiple screens, which can contain combinations of synoptic diagrams and text. They also support the concept of a "generic" graphical object with links to process variables. These objects can be "dragged and dropped" from a library and included into a synoptic diagram. Most of the SCADA products that were evaluated decompose the process in "atomic" parameters (e.g. a power supply current, its maximum value, its on/off status, etc.) to which a Tag-name is associated. The Tag-names used to link graphical objects to devices can be edited as required. The products include a library of standard graphical symbols many of which would however not be applicable to the type of applications encountered in the experimental physics community. Standard windows editing facilities are provided: zooming, re-sizing, and scrolling.  On-line configuration and customization of the MMI is possible for users with the appropriate privileges. Links can be created between display pages to navigate from one view to another.

4.3 TRENDING: The products all provide trending facilities and one can summarise the common
capabilities as follows:
The parameters to be trended in a specific chart can be predefined or defined online
A chart may contain more than 8 trended parameters or pens and an unlimited
number of charts can be displayed (restricted only by the readability)
Real-time and historical trending are possible, although generally not in the same chart
Historical trending is possible for any archived parameter
Zooming and scrolling functions are provided
Parameter values at the cursor position can be displayed
The trending feature is either provided as a separate module or as a graphical object (ActiveX), which can then be embedded into a synoptic display. XY and other statistical analysis plots are generally not provided.
4.4 ALARM HANDLING: Alarm handling is based on limit and status checking and performed in the data servers. More complicated expressions (using arithmetic or logical expressions) can be developed by creating derived parameters on which status or limit checking is then performed. The alarms are logically handled centrally, i.e., the information only exists in one place and all users see the same status (e.g., the acknowledgement), and multiple alarm priority levels (in general many more than 3 such levels) are supported. It is generally possible to group alarms and to handle these as an entity (typically filtering on group or acknowledgement of all alarms in a group). Furthermore, it is possible to suppress alarms either individually or as a complete group. The filtering of alarms seen on the alarm page or when viewing the alarm log is also possible at least on priority, time and group. However, relationships between alarms cannot generally be defined in a straightforward manner. E-mails can be generated or predefined actions automatically executed in response to alarm conditions.

4.5 LOGGING/ARCHIVING: The terms logging and archiving are often used to describe the same facility. However, logging can be thought of as medium-term storage of data on disk, whereas archiving is long-term storage of data either on disk or on another permanent storage medium. Logging is typically performed on a cyclic basis, i.e., once a certain file size, time period or number of points is reached the data is overwritten. Logging of data can be performed at a set frequency, or only initiated if the value changes or when a specific predefined event occurs. Logged data can be transferred to an archive once the log is full. The logged data is time-stamped and can be filtered when viewed by a user. The logging of user actions is in general performed together with either a user ID or station ID. There is often also a VCR facility to play back archived data.

4.6 REPORT GENERATION: One can produce reports using SQL type queries to the archive, RTDB or logs. Although it is sometimes possible to embed EXCEL charts in the report, a "cut and paste" capability is in general not provided. Facilities exist to be able to automatically generate, print and archive reports.

4.7 AUTOMATION: The majority of the products allow actions to be automatically triggered by events. A scripting language provided by the SCADA products allows these actions to be defined. In general, one can load a particular display, send an Email, run a user defined application or script and write to the RTDB. The concept of recipes is supported, whereby a particular system configuration can be saved to a file and then re-loaded at a later date. Sequencing is also supported whereby, as the name indicates, it is possible to execute a more complex sequence of actions on one or more devices. Sequences may also react to external events. Some of the products do support an expert system but none has the concept of a Finite State Machine (FSM).

5. APPLICATION DEVELOPMENT
5.1 CONFIGURATION: The development of the applications is typically done in two stages. First the process parameters and associated information (e.g. relating to alarm conditions) are defined through some sort of parameter definition template and then the graphics, including trending and alarm displays are developed, and linked where appropriate to the process parameters. The products also provide an ASCII Export/Import facility for the configuration data (parameter definitions), which enables large numbers of parameters to be configured in a more efficient manner using an external editor such as Excel and then importing the data into the configuration database. However, many of the PC tools now have a Windows Explorer type development studio. The developer then works with a number of folders, which each contains a different aspect of the configuration, including the graphics.The facilities provided by the products for configuring very large numbers of parameters are not very strong. However, this has not really been an issue so far for most of the products to-date, as large applications are typically about 50K I/O points and database population from within an ASCII editor such as Excel is still a workable option. On-line modifications to the configuration database and the graphics is generally possible with the appropriate level of privileges.

5.2 DEVELOPMENT TOOLS: The following development tools are provided as standard:
a graphics editor, with standard drawing facilities including freehand, lines,
squares circles, etc. It is possible to import pictures in many formats as well as
using predefined symbols including e.g. trending charts, etc. A library of generic
symbols is provided that can be linked dynamically to variables and animated as
they change. It is also possible to create links between views so as to ease
navigation at run-time.
a data base configuration tool (usually through parameter templates). It is in
general possible to export data in ASCII files so as to be edited through an ASCII
editor or Excel.
a scripting language
an Application Program Interface (API) supporting C, C++, VB
a Driver Development Toolkit to develop drivers for hardware that is not
supported by the SCADA product.

5.3 OBJECT HANDLING: The products in general have the concept of graphical object classes, which support inheritance. In addition, some of the products have the concept of an object within the configuration database. In general the products do not handle objects, but rather handle individual parameters, e.g., alarms are defined for parameters, logging is performed on parameters, and control actions are performed on parameters. The support of objects is therefore fairly superficial.

6. EVOLUTION: SCADA vendors release one major version and one to two additional minor versions once per year. These products evolve thus very rapidly so as to take advantage of new market opportunities, to meet new requirements of their customers and to take advantage of new technologies. As was already mentioned, most of the SCADA products that were evaluated decompose
the process in "atomic" parameters to which a Tag-name is associated. This is impractical in the case of very large processes when very large sets of Tags need to be configured. As the industrial applications are increasing in size, new SCADA versions are now being designed to handle devices and even entire systems as full entities (classes) that encapsulate all their specific attributes and functionality. In addition, they will also support multi-team development. As far as new technologies are concerned, the SCADA products are now adopting:
Web technology, ActiveX, Java, etc.
OPC as a means for communicating internally between the client and server
modules. It should thus be possible to connect OPC compliant third party modules to that SCADA product.

7. ENGINEERING: Whilst one should rightly anticipate significant development and maintenance savings by adopting a SCADA product for the implementation of a control system, it does not mean a "no effort" operation. The need for proper engineering can not be sufficiently emphasised to reduce development effort and to reach a system that complies with the requirements, that is economical in development and maintenance and that is reliable and robust. Examples of engineering activities specific to the use of a SCADA system are the definition of:
A library of objects (PLC, device, subsystem) complete with standard object behaviour (script, sequences), graphical interface and associated scripts for animation.
Templates for different types of "panels", e.g. alarms,
Instructions on how to control e.g. a device ...,
A mechanism to prevent conflicting controls (if not provided with the SCADA),
Alarm levels, behaviour to be adopted in case of specific alarms.


8. APPLICATION: Control systems are used at all levels of manufacturing and industrial processing. A manufacturing plant that employs robotic arms will have a control system to direct robotic arms and conveyor belts on the shop floor. It may use that same system for packaging the finished product and tracking inventory. It may also use a control system to monitor its distribution network. A chemical company will use control systems to monitor tank levels and to ensure that ingredients are mixed in the proper proportions. A Las Vegas casino will use control systems to direct the spray from water fountains in coordination with the lights and music. Control systems are also used in the drilling and refining of oil and natural gas. They are used in the distribution of water and electricity by utility companies, and in the collection of wastewater and sewage. Virtually every sector of the economy employs control systems at all levels. The term "supervisory control and data acquisition" (SCADA), however, is generally accepted to mean the systems that control the distribution of critical infrastructure public utilities (water, sewer, electricity, and oil and gas). SCADA systems are still to come into widespread infrastructural use in India. In this country they are being used primarily for automation in industrial production, and to some extent for specialized process control.

9. POTENTIAL BENEFITS OF SCADA: The benefits one can expect from adopting a SCADA system for the control of experimental physics facilities can be summarised as follows:

A rich functionality and extensive development facilities. The amount of effort
invested in SCADA product amounts to 50 to 100 p-years!
The amount of specific development that needs to be performed by the end-user is limited, especially with suitable engineering.
Reliability and robustness. These systems are used for mission critical industrial processes where reliability and performance are paramount. In addition, specific development is performed within a well-established framework that enhances reliability and robustness.
Technical support and maintenance by the vendor.

For large collaborations, as for the CERN LHC experiments, using a SCADA system for their controls ensures a common framework not only for the development of the specific applications but also for operating the detectors. Operators experience the same "look and feel" whatever part of the experiment they control. However, this aspect also depends to a significant extent on proper engineering.

SCADA AS TOOL FOR MANAGERIAL EFFECTIVENESS: The biggest challenge for any manager would be to optimize the resources and achieve the maximum output from them. To take this challenge, along with his interpersonal skills, he has to be very accurate in decision making and controlling of resources. For these purposes he must have the accurate and timely information. The most crucial aspect in decision making is accurate and timely information.  In manufacturing industries it’s very difficult to get the accurate and on time information, because of many reasons such as the size of plant, large number of machines with large variety and every machine may have hundreds of parameters. Solution to this is SCADA systems, as SCADA systems are Supervisory Control And Data Acquisition systems, designed for collecting the accurate information from every machine for all the parameters and properly control them as per the system.   

A SCADA application has two elements:
1. 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. 2. 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.
SCADA is used around the world to control all kinds of industrial processes — SCADA can help you increase efficiency, lower costs and increase the profitability of your operations.


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 more fast-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?