Critical infrastructure

SCADA Interview Questions

SCADA (supervisory control and data acquisition) 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 certain 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.

1. Q: What are some different levels of SCADA machines and systems?
   

   A: 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.

Q: Why do companies use SCADA?

A: 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.

Q: What voltage does an RTU operate with?

A: A remote terminal unit operates at 110V/240V.

Q: Why would a company want to use a PLC over an RTU?

A: 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.

Q: What is an HMI?

A: 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.

Q: What is DDE?

A: 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, so if the shop is a Microsoft shop, you will probably need to know some things about DDE and how devices communicate.

Q: What are some advantages of SCADA over other protocols?

A: 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.

Q: How does SCADA handle data?

A: 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.

Q: How does SCADA handle issues?

A: SCADA has an alarm or alert system that interfaces with personnel to send them a warning when a system is not working properly.

Q: What is the “Historian” in SCADA?

A: The historian is the name given to the software service that collects events and logs them into the database for future use.

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