Efficient Variable Creation in SCADA: Structured Tags & Excel Import

ByHANI_AUTOMATION HANI

Key Takeaway: Managing hundreds of tags in a SCADA project can be tedious. Using structured variables and Excel import not only saves time but also reduces errors. This article explains how to create structured tags efficiently and import them into your SCADA application.

Why Structured Variables Matter in SCADA

In any industrial automation project, you often deal with multiple identical devices—motors, valves, sensors. Defining each tag individually is not only time-consuming but also prone to inconsistency. Structured variables solve this by grouping related data into a single template, much like a blueprint. Once the template is defined, you can create as many instances as needed, each inheriting the same structure but representing a different physical device.

Think of a template as a cookie cutter and instances as the cookies. The cutter defines the shape; each cookie is a concrete realization. In SCADA, a template might include tags like RunFeedback, RemoteFeedback, StartOutput, FrequencyFeedback, and FrequencyOutput. For three motors, you create three instances—Motor1, Motor2, Motor3—all based on the same template.

Example Template: MotorTemplate

  • RunFeedback – Boolean
  • RemoteFeedback – Boolean
  • StartOutput – Boolean
  • FrequencyFeedback – Real
  • FrequencyOutput – Real

Using Excel to Create and Import Tags

Most SCADA packages provide an Excel template for bulk tag creation. Typically, the workbook contains multiple sheets: one for basic tags, one for templates, and one for structured variable instances. While the basic tag sheet is straightforward, the real power lies in the template and instance sheets.

The template sheet defines the structure—name, data type, and member tags. The instance sheet then references the template and assigns a unique name to each instance. Finally, the basic tag sheet lists all the flattened tags that the SCADA system actually uses, often with a naming convention like InstanceName.MemberTag.

Sheet Purpose Example Content
Template Defines the structure of a reusable tag group MotorTemplate: RunFeedback (bool), Frequency (real), etc.
Structure Variable Creates instances based on a template Motor1 (MotorTemplate), Motor2 (MotorTemplate)
Basic Variable Lists all individual tags used in the project Motor1.RunFeedback, Motor1.Frequency, Motor2.RunFeedback, etc.

After filling out the Excel sheets, you save the file and use the SCADA software’s import function (often a “DB Import” button) to bring all tags into the project. This method is far more efficient than creating each tag manually, especially for large systems.

Challenges with Traditional Excel Import

Despite the convenience, the standard Excel import process has its quirks. The template file is often password-protected (though the password can be obtained from the vendor). More importantly, the format does not always follow a logical template-instance hierarchy. You must fill in the basic variable sheet with fully qualified tag names, which can be error-prone when dealing with hundreds of instances.

Ideally, you should only need to define the template and the instances, and the software would automatically generate the basic tags. Some advanced SCADA systems, like Siemens WinCC, support a more intuitive import where you simply list templates and instances, and the system resolves the rest. Unfortunately, many domestic SCADA packages still require the full flat list.

Pro Tip:

To streamline the process, consider using a script or a third-party tool that converts a simple template-instance table into the required Excel format. This can save hours of manual work and reduce mistakes.

A Better Way: Template-Instance Import

The most logical approach is to provide just two pieces of information: the template definition and the list of instances. For example:

Templates:

MotorTemplate: RunFeedback(bool), RemoteFeedback(bool), StartOutput(bool), FrequencyFeedback(real), FrequencyOutput(real)

Instances:

Motor1 (MotorTemplate)
Motor2 (MotorTemplate)
Motor3 (MotorTemplate)

This method is not only cleaner but also mirrors the actual engineering thought process. It’s surprising that many SCADA tools still don’t support this natively, forcing engineers to rely on workarounds or external utilities.

Practical Tips for Efficient Tag Management

  • Plan your tag structure early. Identify repetitive device types and create templates before starting the project.
  • Use consistent naming conventions. For instance, “DeviceType_Number.MemberName” makes it easy to understand and troubleshoot.
  • Leverage Excel formulas. If you must fill the basic variable sheet, use formulas to concatenate instance names and member names automatically.
  • Validate before import. Double-check data types and addresses to avoid runtime errors.
  • Explore third-party tools. Some utilities can convert a simple template-instance list into the required SCADA import format, saving significant time.

Common Pitfall: Forgetting to update the basic variable sheet after changing a template. Always re-export and re-import to keep everything synchronized.

Conclusion

Efficient variable creation is a cornerstone of productive SCADA engineering. While the built-in Excel import is a step up from manual entry, it often falls short in terms of user-friendliness. By understanding structured variables and employing smart workarounds, you can drastically cut down development time and improve project quality. As automation systems grow more complex, mastering these techniques becomes essential for every controls engineer.

Remember, the goal is not just to get the tags into the system, but to do so in a way that is maintainable and scalable. Whether you’re working with a small HMI or a large distributed control system, investing time in a solid tag management strategy pays off throughout the project lifecycle.

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