SCADA Tutorial Part 3 - How to Evaluate 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. A 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.

Although you need sensors, control relays and a communications network to make a complete SCADA system, it’s your choice of a master station and RTUs that really determine the quality of your SCADA system.

Sensors and control relays are essentially commodity items. Yes, some sensors are better than others, but a glance at a spec sheet will tell you everything you need to know to choose between them.

An IP LAN/WAN is the easiest kind of network to work with, and if you don’t yet have LAN capability throughout all your facilities, transitioning to LAN is probably one of your long-term goals. But you don’t have to move to LAN immediately or all at once to get the benefits of SCADA. The right SCADA system will support both your legacy network and LAN, enabling you to make a graceful, gradual transition.

Your SCADA RTUs need to communicate with all your on-site 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.

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 longterm 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, geodiverse 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.