Monitoring your transformer is key to safe and efficient operation. But it can be an involved task. Part of the difficulty is that routine inspections often occur while the transformer is under load. This exposes workers to potential arc flash risks, calling for special PPE. Inspection windows provide a way to monitor without having to open the transformer cabinet. This helps workers more easily comply with electrical safety requirements. It also may remove the requirement for certain PPE during routine inspections.

What are inspection windows?

Inspection windows are an electrical maintenance safety device. They provide a convenient and safe way to monitor the internals of the transformer cabinet. Namely, the gauges and bushings.

Types of inspection windows

Inspection windows come in a few different styles. In this article, we’ll cover the different versions and installation considerations for each.

Infrared (IR) windows

An infrared (IR) inspection window allows light energy to pass between the inside and outside of the cabinet. This is key for measuring the temperature of the transformer’s bushings and other components inside the cabinet. These windows are commonly made of crystal, not glass. It is important to consider the placement of the IR window. It should be located where a heat gun can easily point at the bushings. The gun will give you an accurate temperature reading of each bushing. And, you don’t even have to open the cabinet.

IR windows also work with thermal imaging cameras. A thermal imaging device gives you an overall picture of heating around the tank and bushings. It also gives some information about the unit’s overall operating temperature. This can help identify unusual hotspots. Hotspots at the bushings can be caused by loose or faulty connections. Finding and correcting such issues early prevents catastrophic failures later on.

Viewing windows

Unlike the infrared option, viewing windows allow visual inspections only. Providing visual checks inside the cabinet. Viewing windows are typically glass instead of crystal. Some viewing windows are made of more durable materials, especially for industrial applications where broken glass would pose a significant risk.

Without opening the cabinet, you can check the fluid level, temperature, and pressure gauges. You can also inspect the bushings and cable terminations. But, you won’t be able to take a heat reading through the glass.

Should you get both?

IR windows provide both thermal and visual monitoring options. For this reason, they are an ideal choice. But, if you don’t need thermal monitoring, viewing windows work great. Viewing windows may also cost less. They are the perfect choice for monitoring the open and closed positions of mechanically operated switches.

Installing IR & Viewing Windows

We can install a viewing or IR window on any transformer you order. We’re happy to add this feature to new-built or reconditioned units on request.

If you’ve already got a transformer on-site, you can still install viewing and IR windows. It’s a fairly straightforward process.

A shop technician installing an IR window on a padmount transformer

Where to put an IR window

If you’re installing an IR window, make sure it’s placed so you can easily take temperature readings of the bushings.

You can strategically place the IR window so that you can see the gauges through it, too. If so, you won’t need a separate viewing window to check gauges.

Where to put a viewing window

If you’re installing a viewing window, make sure it’s placed so you can effectively see what you need to monitor visually. Place the window where you can read the pressure vacuum, liquid level, and/or temperature gauges.

Conclusion

Reach out if you’ve got any questions about viewing and IR windows. If you’re ordering a transformer and would like these installed, fill out the form below.

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