How to shorten the oiling time for 110 kV voltage transformers?

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

From tagging along with my mentor doing insulation tests to now leading teams handling all kinds of high-voltage equipment issues — I’ve done a lot of oil refilling in my time. Especially when it comes to 110 kV voltage transformers, oil refill is a key part of daily maintenance. But let’s be honest — it's also one of the biggest time-wasters.

A few days ago, a colleague messaged me:

“Echo, every time we refill oil in our 110 kV VTs, it takes two or three hours. It’s so slow. Any way to speed this up?”

That’s such a real question! So today, I want to share with you:

How can we effectively reduce the oil refill time for 110 kV voltage transformers? Are there any practical tips or tricks?

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

1. First Things First: Why Does Oil Refill Take So Long?

A lot of people think oil refill is just hooking up a hose and opening a valve. But in reality, there are several factors that can really slow things down:

• Poor oil flow due to air blockage;

• Incomplete vacuum, making it hard for oil to enter;

• Outdated methods relying only on gravity feed;

• Safety checks slowing everything down mid-process.

All these make the whole job feel slow and inefficient.

So if you want to speed things up, you have to start by improving both your process and tools.

2. Key Steps + Time-Saving Tips

Tip #1: Do Vacuum Pre-Treatment — Don’t Wait Until the Oil Arrives to Start Pumping!

A lot of folks drain the old oil first, then start vacuuming, and finally refill — which easily takes over two hours.

Here’s what I suggest instead:

Pump the vacuum ahead of time, including the entire oil system — hoses, valves, even the VT itself.

Once the new oil arrives, you just open the valve and pump it right in — no more waiting around.

Pro Tip: Use a vacuum-assisted oil filling machine — it can fill while pumping vacuum at the same time, cutting time in half!

Tip #2: Upgrade Your Equipment — Stop Using Manual Pumps!

Manual oil filling isn’t just tiring — it also tends to introduce bubbles and air into the system.

Nowadays, there are electric vacuum oil filling machines that offer several advantages:

• Built-in vacuum pump — vacuum and fill at the same time;

• High flow rate — you can finish filling in minutes;

• Comes with oil filtration — helps clean impurities as you go.

Yes, they cost more upfront, but in the long run, they save time, effort, and headaches. Totally worth it!

Tip #3: Optimize Oil Path Design — Don’t Let Air Slow You Down!

Sometimes it’s not the oil that’s slow — it’s the trapped air causing blockages.

What I always do:

• Make sure the air vent valve is open before starting;

• Try to fill from the bottom, letting air escape from the top — creates smooth flow;

• If there are multiple ports, use the lower one first.

This helps the oil flow smoothly without bubbles or clogs — and that means faster refills.

Tip #4: Test Oil Quality Beforehand — Don’t Find Out Too Late!

Nothing’s worse than nearly finishing the refill, only to find out the oil doesn’t meet standards — like low dielectric strength or high moisture content. Then you have to drain it all and start over.

To avoid this mess:

Test the oil quality before refilling, including:

• Breakdown voltage;

• Moisture content;

• Color and odor check.

If the oil passes, then proceed. This avoids costly rework later.

Tip #5: Standardize the Process & Team Up — Don’t Be the Only One Doing All the Work!

Oil refilling shouldn’t be a solo mission. The best results come from clear分工 and teamwork:

• One person monitors pressure and oil level;

• One handles the valve and oil machine;

• One records data and takes photos for documentation;

• One stays ready for emergency support.

With a clear plan and good coordination, the job gets done fast — and safely.

3. Final Thoughts

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

“Oil refilling isn’t about brute force — it’s about smart technique. A pro can finish in 10 minutes; an amateur might struggle for hours.”

If you're still using outdated methods, it’s time to upgrade your tools and processes.

Remember these key points:

• Vacuum in advance;

• Use efficient oil filling equipment;

• Optimize oil path design;

• Test oil before filling;

• Have a solid team and clear workflow.

These will not only save you time, but also reduce the risk of equipment failure.

If you ever run into issues during oil refilling — like pressure won’t build up, too many bubbles, or oil won’t fill completely — feel free to reach out. I’d love to share more hands-on experience and practical advice.

Here’s hoping every voltage transformer runs safely, steadily, and efficiently — guarding the power grid like a true silent hero!

— Echo