SCADA and Web-Based Monitoring

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The following content is from a recent thread on SolarPro’s technical discussion forum. It is a response to a QA article published in the August/September 2014 issue of SolarPro. Visit to join the conversation.

Original post from john.ciempa: Many of the questions raised in the “SCADA Versus Web-Based Monitoring” article are good to ask while evaluating your monitoring and control provider. However, many of the generalizations were not well explored or explained. Supervisory control and data acquisition (SCADA) is a growing trend in the ever-evolving and fast-moving PV industry. Many monitoring providers are working with utilities, EPCs and owner/operators to define and meet changing needs and to continue to set the bar for industry standards in reporting and monitoring. Below are comments from Draker’s ( applications engineering team related to generalizations made in the article. These comments are organized based on the themes explored in the original publication.

Differences between SCADA and web-based monitoring. As the article highlights, the traditional difference between SCADA and cloud-based monitoring DAS systems relates to the supervisory control capabilities (often remote via the Internet) of multiple devices on a project site. However, this scenario is quickly changing, since many monitoring providers have evolved and offer supervisory control as part of their product offering. In fact, of the 64 web-monitoring DAS companies interviewed for the Greentech Media report, “Global PV Monitoring: Technologies, Markets and Leading Players, 2014–2018,” 40 offer SCADA solutions. Many of the companies, including Draker, incorporate and deploy industry-proven products from companies like Schweitzer Engineering Laboratories to meet supervisory control requirements as part of their product offering.

The author stated: “Commercial plant operation requires such a high level of reliability that a firmware-based device—such as a programmable logic controller (PLC) or a similar type of smart relay—is necessary for plant control.” The statement implies that web-based monitoring solutions are not as reliable. This is inaccurate: most PV DAS providers, including Draker, utilize highly reliable firmware-based devices for standard data collection and deploy PLCs for sites requiring the more robust operational functionality of a full SCADA solution.

The article describes web-based monitoring solutions as license based.  This is true; however, the article does not do a good job of communicating the details on how a SCADA solution handles communication, data storage, maintenance, and other associated factors and costs. An article exploring and describing these differences, and the specific pros and cons of different solutions, would be worthwhile.

The article also points to custom software functionality as a differentiator and to some degree an advantage. However, we could argue that customization is really a disadvantage, since traditional SCADA providers require software engineering to build out site-specific analysis tools, which adds tremendous cost during SCADA system development and requires ongoing in-house software engineering support to maintain.

Many web-based monitoring providers customize the software when customer requirements go beyond the standard feature sets. In addition, many providers offer portfolio management and O&M and asset management, including performance assessments, alarming, reporting (financial and technical), troubleshooting and service ticketing. Additionally, as providers develop customer-requested new analysis tools or enhanced feature sets, they deploy that functionality to all sites and to all customers within the web-based monitoring platform. This financially benefits site owners, operators and developers, as it eliminates the need to have an in-house software engineering team build such functionality.

A final difference outlined in the article relates to portfolio management solutions, which are more widely enabled with a web-based monitoring solution and not as easily enabled in a traditional SCADA solution. Traditional SCADA integration may require significant development efforts and costs beyond the individual plant SCADA deployment to achieve true portfolio management across multiple sites in different utility regions.

Choosing the right platform. The article asserts that project size should dictate the decision to choose traditional SCADA versus web-monitoring solutions. Size is quickly becoming a poor indicator for the type and extent of SCADA required for a project. Many small projects are now increasingly finding that utilities require supervisory control. At Draker, we have seen sites as small as 30 kW that need some form of control functionality. It is important to understand the requirements for these projects so that the client and developer can choose a cost-effective solution. In many cases, it would be more cost effective for these projects to use the supervisory control integrated into a web-based monitoring solution than to deploy a traditional SCADA solution.

Does the utility (or ISO) have control requirements? This is essentially the only distinction between SCADA and DAS. In addition to understanding whether control is required, defining the type and extent of control as well as the security requirements are equally critical when choosing an appropriate solution. It is also common to have a DAS system for the owner and a separate SCADA for the utility. Many utilities provide their own interface and just need secure access to the DAS. To comply with security issues while reducing overall costs with shared hardware, utilizing the owner’s preferred web-based monitoring provider to deploy SCADA as part of the full solution is often the best overall choice.

What is the makeup of the client’s labor force? Understanding the client’s labor force is important, both at the time of system deployment and also for future maintenance. Ease of use, customer support and training, and portfolio uniformity are often important factors when selecting a DAS system with or without control.

Where does the hardware reside? Both SCADA and web-based monitoring solutions include on-site hardware, and both can provide cloud-based backup as well as backup power and complex redundant systems on any utility-scale site.

Is the provider financially viable? Whether you are choosing a SCADA or DAS function set, viability is always important when choosing project partners. Draker is one of the oldest web-based monitoring providers in North America, with more than 1.5 GW of solar PV systems under management. Many web-based solution providers, including Draker, have put together third-party–assured business continuity solutions for their customers that protect customer data and access to the software in the cloud.

Who will manage O&M? It is important to consider who will manage the O&M today and over the lifetime of the project. Ease of use, adoption of industry standard functions and a strong customer support team are all important factors to consider. Maturing O&M trends in the PV industry will require more-open DAS platforms that continually changing O&M teams can easily transfer and access.

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