SCADA Interview Questions: SCADA stands for Supervisory Control and Data Acquisition. This article provides PLC SCADA interview questions and answers.
SCADA is a type of software application and hardware control that defines the way data and real-time processing is controlled. You mostly find SCADA in every industries such as power plants and oil and refining businesses.
You can also find SCADA rules in telecommunications and transportation industries. If you plan to go for an interview in this job field, here are some questions you might be asked in your interview.
SCADA (supervisory control and data acquisition) is a system, operates with coded signals over communication channels so as to provide control of remote equipment (using typically one communication channel per remote station).
Acronym for supervisory control and data acquisition, a computer system for gathering and analyzing real time data. SCADA systems are used to monitor and control a plant or equipment in industries such as telecommunications, water and waste control, energy, oil and gas refining and transportation.
A SCADA system gathers information, such as where a leak on a pipeline has occurred, transfers the information back to a central site, alerting the home station that the leak has occurred, carrying out necessary analysis and control, such as determining if the leak is critical, and displaying the information in a logical and organized fashion.
SCADA systems can be relatively simple, such as one that monitors environmental conditions of a small office building, or incredibly complex, such as a system that monitors all the activity in a power plant or the activity of a municipal water system or other plants.
Programmable Logic Controller or PLC is a computing system used to control electromechanical processes.
SCADA stands for Supervisory Control and Data Acquisition. It is a type of industrial control system that is used to monitor and control facilities and infrastructure in industries.
Acronym for supervisory control and data acquisition, a computer system for gathering and analyzing real time data.
SCADA systems are used to monitor and control a plant or equipment in industries such as telecommunications, water and waste control, energy, oil and gas refining and transportation.
Supervisory control is a general term for control of many individual controllers or control loops, whether by a human or an automatic control system, although almost every real system is a combination of both.
SCADA machines have several different forms. You can have field level devices such as sensors.
You can have remote terminal units (RTUs), a main controller or “master station,” or you can have a simple computer system interface that displays data for the user.
Some of the reasons or advantages why SCADA systems are implemented are:
SCADA is a methodology that defines performance and protection of data for the plant or communication center.
It helps improve productivity for employees and helps the economy save energy.
A remote terminal unit operates at 110V/240V.
A programmable logic controller (PLC) is much cheaper and more flexible with programming.
PLCs have been replacing RTUs because they are also easier to troubleshoot and have more sophisticated controls than RTUs.
An HMI (human machine interface) is the system that connects to a SCADA database that displays data for the user.
The HMI allows the operator to review diagnostic data and trending graphs.
DDE is the acronym for dynamic data exchange.
DDE provides a communication protocol that allows devices to send and receive communication signals. This protocol was developed by Microsoft.
SCADA allows users to create object-oriented graphs, they can offer trending graphs to review data in real-time.
SCADA also deals with big data, so you can develop a database system that displays trends over a number of years. This allows the business quick access to important data that can be used for future growth and enhancements.
SCADA systems gather data and send them to a central machine that processes the data. The SCADA software is used to manage the data and display it to the user.
SCADA also logs information about who runs reports and the data that is used.
SCADA has an alarm or alert system that interfaces with personnel to send them a warning when a system is not working properly.
The historian is the name given to the software service that collects events and logs them into the database for future use.
Yes
Most are included.
Yes
Yes
Changes take place immediately as there is no compiling. If there are redundant servers all changes are automatically sent to the Standby servers.
Exchange of data with other applications and systems is done with Ethernet, Modbus, OPC, ODBC (SQL), or through an API.
The OPC interface supports OPC-DA (Real-time Data Access), OPC-HAD (Historical Data Access), and OPC-AE (Alarms and Events).
The system supports being a Modbus or DNP3 Slave so other systems can connect and access real-time data.
This is accomplished by configuring a virtual device which only the points required for the other system are mapped.
Any ODBC compliant (SQL) database.
Data integrity & system control is maintained through server mirrored redundancy.
The system supports triple mirrored server redundancy.
No, the redundancy is mirrored. Mirrored redundancy means that no programming or extra database configuration is required to make the redundancy work.
All functions are available from the standby or redundant server.
If a server fails, then automatically connect to the standby server as soon as the client detects that Main server has failed, transparent to the user.
All server functions are mirrored to the redundant server. The system provides for Data backups to Local or Storage on a network client with backup device (like large hard drive or tape).
No, the transfer is transparent to the users and all functions are as normal.
No, only the server acting as Main will communicate to the IO.
The servers are mirrored and all functions are transferred transparently to the users or functions ongoing.
If redundant LANs are installed the transfer is transparent to the system.
Yes
The system has only one configuration database and any change made are automatically propagated to all servers and clients. Nothing else is required.
Yes assuming that the users on the other clients have permissions to see the display page.
The system has an Export function which allows saving the database to any media.
Import the backup file or database.
The system uses a objects/addresses for defining IO devices. Define the object, and configure the individual parameters in the IO window.
This can be used as a template object so it can be reused in the system.
Yes and the polling configuration is easily controlled by adjusting the communications parameters of the device.
Yes the system maintains all the last values of every point in the system with a timestamp.
As many groups and-or individual as is needed, no limit.
The security level can be defined down to the database point level.
The system primary input is through the pointing device. A screen keyboard can be implemented for function not on an external keyboard.
True Color
The 3D effects are done with shading and sizing techniques like most artists do.
Objects can be made into templates from which instances are created. Each instance contains all database entries.
Typically only addressing and selection of the physical IO device are necessary.
Yes, but it is recommended to copy/paste the original object into the library and modify it as a new object; thereby, keeping the original library.
The changes will take affect immediately to all other instances of object or template in the system.
Yes
Yes
Yes
Yes
The AutoCAD, DXF, and all other graphics formats supported by the particular vendor software can be imported or copied and pasted into the drawing builder.
The use of undo function is used to reestablish deletions. It also support layers so graphics objects can be put on separate layers to prevent accidental changes.
Use a snap to grid or align the object with the alignment tool.
Special effects are done with colors, lines, shading etc.
Special color tags may be created. When these are referred to for colors, changing the tag color will change all instances that use that color.
Objects with common attributes can be selected, and the changes will apply to all in the selected group.
Alarms are reported and are always visible on any page through the alarm banner which is normally at the bottom of the page.
There is an Alarm Management system within the system that provides for alarm redirection, sorting, filtering, filed editing, etc.
Custom alarm lists can be embedded on any page that is filtered for that specific page. For instance, you only what to see the alarms that pertain to a specific substation or breaker.
No but we can also configure as per requirement.
Yes. This is true even on cluster servers.
Yes
Yes
The system provides for as many alarm groups as desired or individual & group.
Alarms can be prioritized by severity, time, device, etc.
Yes and alarms can be sent out to groups or individuals via Email, pager, and/or text messages to cell phones.
Any database object may be configured to be placed in the Historian and trended.
Any point in the system can also be viewed using a feature called Current Trending which allows operators to select a point to view the current trend of a point without it being configured in the Historian.
All trending is accessed through the Historian using standard menus items.
Data can be viewed in a list or graphically without custom configuration. If needed, custom trend pages can be configured in the system.
The Historical database or Historian is a SQL accessible database. This allows SQL queries to access the data and display it on screens.
There are also standard tools to extract the data so no SQL knowledge is required to extract data.
For instance, display the Maximum and Average can be internal to a mimic or external to a mimic (a trend page to itself).
Historical data is stored in weekly files on all the servers. The files can be archived or restored at anytime without shutting down the system.
All data, reports, configuration, and events etc. are stored in the one Historical database.
The data is actually stored in weekly/monthly/yearly files and the system is configurable as to how many days are keep online.
The system has a inbuilt Reports Runtime engine embedded that provides for reports from any historian parameter.
Reports function is required to generate a new report design then move the report template into the Historian for general reporting; display, print, email, etc any report.
Pull up a report template and select the parameters to report, click generate report, and the report data appears.
Communication with devices, plant floor, and other devices is done by the selected media:
RS-485 to devices converted to Ethernet, modbus, OPC, direct Ethernet, cable, fiber, radio, or any usable media.
Currently the fastest method of communication to devices and the plant floor is via some media using Ethernet.
The system provides a data quality parameter with most protocols and devices.
Using managed switches and proper cabling performance is keep with growth. For example, limiting the RS-485 devices to 5 or 6 units per 485 LAN connected to the Ethernet.
The system uses the IEC61131-3 (logic engine) programming.
Most customers use the “function block programming” to write the functions desired that are not already in the system or they use Visual Basic Script (VBS), but VBS requires programming code knowledge.
Yes
Yes
Yes the system is event driven. Can we activate other Windows applications Yes, in fact, we launch other manufacturer’s software to do many device specific functions like waveform capture and harmonics.
Author : By Dr. Jay Park
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Sir please can you tell me for scada security engg what they will ask in interview
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Please how can I download the software to learn