What are the applications of GIS voltage transformers in digital substations?

Hey everyone, I’m Echo, and I’ve been working with voltage transformers (VTs) for 12 years.

From learning how to wire and do error tests under my mentor’s watchful eye, to now participating in all kinds of smart substation projects — I’ve seen the power industry evolve from traditional systems to fully digital ones. Especially in recent years, more and more 220 kV GIS systems are adopting electronic voltage transformers (EVTs), slowly replacing the old-school electromagnetic types.

A few days ago, a friend asked me:

“Echo, they keep saying digital substations are the future — so what role do electronic voltage transformers really play? Are they reliable?”

Great question! So today, I want to talk about:

What advantages do electronic voltage transformers bring to 220 kV GIS and digital substations — and what should we pay attention to during real-world applications?

No fancy jargon — just plain talk based on my 12 years of hands-on experience. Let’s dive in!

1. What Is an Electronic Voltage Transformer?

Simply put, an Electronic Voltage Transformer (EVT) is a new type of device that uses electronic technology to measure high-voltage signals.

Unlike traditional electromagnetic VTs, which rely on cores and windings to sense voltage, EVTs use resistive or capacitive voltage dividers, or even optical principles, to capture voltage signals. Then, built-in electronics convert the analog signal into a digital output.

2. Why Do Digital Substations Need It?
2.1 It Speaks “Digital” Natively — Perfect for Smart Systems

Traditional VTs output analog signals, which still need to be converted into digital before they can be used by protection relays or monitoring systems. But EVTs output digital data directly, cutting out the middle step. This improves both data accuracy and transmission speed.

Think of it like switching from a landline phone to a video call app — clearer, faster, and easier to manage.

2.2 No Saturation, No Fear of Harmonics

Traditional VTs can easily go into magnetic saturation during faults or harmonic-rich conditions, causing measurement errors or even false trips. But since EVTs have no iron core, they don’t suffer from saturation at all — making them ideal for complex environments with frequent harmonics or fault currents.

2.3 Compact Design — Perfect Fit for GIS

GIS systems are all about saving space. Since EVTs don’t have bulky cores and windings, they’re much smaller and lighter than traditional VTs. That makes them a great match for tight GIS installations.

3. Real-World Use in 220 kV GIS Systems

In the past few years, our company has worked on several 220 kV digital substation projects, and almost all of them used electronic voltage transformers. Paired with merging units (MUs) and intelligent terminals, the system performance has been pretty solid.

Here’s one example: We once worked on a city substation where space was extremely limited, but high-precision metering and fast protection response were required. We chose a capacitive EVT with a fiber-optic interface. Not only did it save space, but it also achieved millisecond-level data response, and the protection actions were super responsive.

4. Things to Watch Out for in Real Applications

Even though EVTs have many advantages, there are still some points to keep in mind during actual use:

4.1 Sensitive to Power Supply and Temperature

Since EVTs contain electronic components, they’re sensitive to temperature changes and power stability. In areas with extreme temperature swings or high humidity, it's better to choose models with heating and dehumidification functions.

4.2 Merging Unit (MU) Reliability Matters

EVTs usually work together with merging units. If the MU fails, the whole system goes down. That’s why in most of our projects, we use dual-redundant MUs to ensure system reliability.

4.3 Calibration Needs Special Tools

Traditional error testers may not work well with EVTs because they output digital signals. You’ll need specialized digital calibration tools, such as digital standard sources or network analyzers.

5. Final Thoughts

As someone who’s spent over a decade in this field, here’s my take:

“Electronic voltage transformers aren’t some futuristic tech — they’re already here, and they’re getting more mature every day.”

Especially in the context of digital substations and smart grids, their advantages are clear. As long as you select the right model, install it properly, and maintain it regularly, EVTs can definitely handle measurement and protection tasks in 220 kV GIS systems.

If you're working on digital substation projects or just curious about electronic voltage transformers, feel free to reach out. I’d love to share more hands-on experience and practical tips.

Here’s hoping every electronic voltage transformer runs smoothly and safely, helping build smarter, more efficient substations!

— Echo