Unsa ang mga Prueba Ang Kinahanglan Pasabotan Ug Maayo nga Transformer sa Kasinatian?

Kamusta sa tanan, ako si Oliver, ug nagsilbi nako sa pagpangita sa current transformer (CT) tungod sa 8 ka tuig.

Gikan sa pagtumong sa mga equipment sa pagsulay sa lugar hangtod sa pagdumala sa kompletong inspeksyon team, nakakita nako kung paano ang libo ka outdoor CTs nga nagdaog sa buhat series sa mga sulay — sama sa pagdaog sa military training camp — bago sila mahimong gamiton.

Ang ilang adlaw, mogutan nako ang usa ka kasinatian:

“Oliver, ang aming factory nagbuhat og bag-ong batch sa outdoor CTs. Naghunahuna mi sa inspeksyon, pero dili kami sigurado unsa ang kinahanglan nga mga sulay. Mahimo ka ba mosulti?”

Ania ang praktikal nga pangutana! Karon, gusto nako ishare sa inyo:

Unsa ang mga kinahanglan nga sulay aron mabuhat ang qualified outdoor current transformer bago maapprove para sa paggamit?

Walay fancy technical terms — basi lang talk batas sa akong 8 ka tuig nga eksperyensya sa lab ug field. Let's break it down!

1. Unsa ang Unang Butang: Asa Man Gikan Ang Mga Sulay?

Ayaw ninyo lingid ang size — bisan ang CT magpakita kaayo og liit, importante gyud ang iyang papel sa power system protection ug metering.

Ang iyang accuracy direkta ang naapektuhan:

• Kon ang mga protective relays trip correctly o dili;

• Kon ang energy billing fair ug accurate;

• Kon ang mga operators adunay clear picture sa real-time status sa grid.

Busa ang tanan nga mga sulay wala gibuhat aron mas daghan ang problema — gibuhat sila aron sigurado nga ang tanan nga CTs makadula sa harsh environments — ulan, init, high voltage, extreme temperatures — ug padayon reliable sa dugang ka tuig.

2. Sulay 1: Visual & Structural Inspection — Ang "First Impression" Check

Mukhang simple, apan importante kaayo kini nga step!

Nag-check mi:

• Adunay deformation, rust, o crack ang housing?

• Intact ug clearly labeled ang mga terminals?

• Aged o improperly installed ang sealing gasket?

• Complete ug accurate ang nameplate?

Mukhang minor, apan ang pag-overlook niini mahimong moadto sa serious issues later — sama sa water ingress, short circuits, o explosion.

3. Sulay 2: Insulation Resistance Test — Makapugos Ba Ni Ini?

Kini usa sa pinaka basic nga electrical tests.

Namihasa mi:

• Primary winding vs. secondary winding;

• Primary winding vs. ground;

• Secondary windings among each other;

• Secondary winding vs. ground.

Gamit ang 2500V megohmmeter, ang insulation resistance dapat wala mobaba sa 1000 MΩ.

Kon mobati kini, walay lisod — balik sa factory.

4. Sulay 3: Power Frequency Withstand Voltage Test — Pila Ka Pressure Ma-take Ni Ini?

Kini sama sa ultimate stress test!

Sa short, gi-apply nami og much higher AC voltage kontra normal operation levels (for example, 95 kV for 1 minute on a 35 kV CT) aron masulay kung ang CT can withstand without breakdown.

Kini nga sulay nag-check:

• Kon reliable ang main insulation design;

• Kon adunay manufacturing defects;

• Kon likely to occur ang internal discharges.

Kon mobati kini, serious safety risk na — repair is a must.

5. Sulay 4: Ratio and Polarity Test — Accurate Ba Ang Data?

Kini usa ka core functional test.

Ratio Test

Nag-verify mi kon ang actual transformation ratio matches the nameplate. For example, kon 400/5 ang iyang says pero 420/5 ang iyang measures, off ang imong metering — which affects billing.

Polarity Test

Nag-confirm mi sa relative direction between primary and secondary windings. A reversed polarity can cause differential protection to malfunction, which is a big deal.

Even if everything else passes, if this part fails — the CT is still not usable.

6. Sulay 5: Error Test — Pila Ka Accurate Ni Ini?

Kini ang final exam para sa metering-grade CTs.

Namihasa mi:

• Ratio error;

• Phase angle error;

Then compare the results with national standards or contract specifications to see if they fall within acceptable limits.

For example, a 0.2S class CT must have a ratio error within ±0.2% and a phase angle error within ±10 minutes of arc — otherwise, it can't be used for trade settlement.

This test usually requires a standard CT and an error tester, so it’s high-precision work — no room for mistakes.

7. Sulay 6: Excitation Characteristic Test — How Well Does It Handle Fault Conditions?

Kini espesyalmente importante para sa protection-grade CTs.

By applying voltage to the secondary side and recording the current curve, we assess whether the core saturation characteristics meet design requirements.

In short:

• If the excitation characteristic is too soft, the CT may saturate early during faults, causing protection failure;

• If it’s too stiff, the excitation current might be too high, affecting stability.

So this is a key test for protection-class CTs.

8. Sulay 7: Sealing & Moisture Resistance Test — Can It Survive Outdoors?

Since it’s an outdoor CT, it has to face rain, humidity, and temperature changes.

We perform:

• Water spray test: simulate heavy rain and check waterproof performance;

• Sealing check: inspect flanges and cable entries for potential water ingress;

• Temperature-humidity cycling: simulate extreme weather conditions to test long-term sealing.

If the seal isn’t tight, over time moisture builds up inside, oxidation happens, insulation drops — and trouble begins.

9. Sulay 8: Mechanical Strength Test — Is It Tough Enough?

Don’t think of a CT as just electronics — it also needs to survive transport, installation, wind, snow, and vibration.

We do:

• Vibration test: simulate transport and operational vibrations;

• Impact test: simulate accidental bumps or wind pressure;

• Thermal shock test: see if materials crack under rapid temperature changes.

Especially for composite-insulated CTs, this test is crucial.

10. Final Thoughts

As someone who’s spent 8 years in CT testing, here’s what I’ve learned:

“A qualified outdoor CT doesn’t just roll off the production line — it must go through layers of inspections and rigorous testing.”

From visual checks to withstand voltage, from ratio and polarity to error analysis, from sealing to mechanical strength — every step matters.

If you're a manufacturer, don’t skip any test just to save time. If you're a buyer, never buy CTs without complete test reports.

After all, power system safety is no joke — a small CT carries a big responsibility.

If you ever run into problems during testing or want to know more about real-world CT testing practices, feel free to reach out. I’d love to share more hands-on experience and tips.

Here’s hoping every outdoor current transformer runs safely and accurately, guarding the grid day and night!

— Oliver