Cé acu na tástáil atá le déanamh ar an ngnathchóiméadaithe voltaí?

Practical Experience Sharing from an Electrical Engineer in the Field
By Oliver, 8 Years in the Electrical Industry

Seo, is mise Oliver agus táim ag obair sa tionscal leictreach le 8 bliain.

Ó mhaolúcháin ar stiúir substations go maolaíocht agus anailís faillí ar iomlán na gcórais leictreacha, is é an seónadaithe voltáil (VT / PT) an chuid is minicí raimh i mo chuid oibre.

Le linn deireanach, d'fhiafraigh cara óg orm:

“Cé acu na trialacha atá le déanamh ar sheónadaithe voltáil? Agus conas a bhfios do dhéanann tú má tá fadhb ann?”

Ceist iontach! Go minic, níl ach roinnt oibrithe réitigh ina gcoinne aon rud ach an ceangal nó an voltás — ach chun tuiscint a bheith ar stád sláinte PT, is gá sé ráithe trialaí gairmiúla.

Inniu, roinnt eolais praiticiúla a roinnt leat — bunaithe ar mo chuid taithí ar an láthair — cén ttrialacha a dhéantar go hiondúil ar sheónadaithe voltáil, cén fáth is tábhachtach iad, agus conas iad a dhéanamh.

Gan teicnisleoireacht chumhachtach, gan caighdeáin gan teorainn — ach eolas úsáideach a úsáideann tú i do shaol.

1. Cén fáth Triail a Dhéanamh?

Cé go mbeadh seónadaithe voltáil cosúil le simplí, tá trí ról tábhachtach acu: tomhas, mearachtaí, agus cosaint.

Má tharla rud, d’fhéadfadh sé a bheith mar thoradh:

• Léitheanna míchruinn;

• Mis-operation nó fadhb cosaint;

• Foilseacháin voltás ar fud an chórais.

Sin an fáth go bhfuil triail rialta chosúil le full check-up do do PT. Cabhróidh sé le fadhbáil luath agus meascáin móra a shárú.

2. An Cúig Trial is Coitianta ar Sheónadaithe Voltáil

Bunaithe ar mo chuid taithí 8 bliana, seo na cúig trial is coitianta agus is tábhachtach:

Trial 1: Trial Résistance Insulation

Aim: Chun insulation idir windings agus idir windings agus talamh a sheiceáil.

Is é seo ceann de na trialacha is bunúsacha agus is tábhachtacha.

Insulation míchruinn féadfadh a bheith mar thoradh ar sheiceáil sín, short circuits, nó fiú explosions.

Conas é a dhéanamh:

• Úsáid 2500V megohmmeter ó primary go secondary agus go dtí an talamh;

• Úsáid 1000V megohmmeter ó secondary go dtí an talamh;

• Tomhas insulation resistance idir primary agus secondary, primary go dtí an talamh, agus secondary go dtí an talamh;

• Comhlíon le dáta stairiúil — drops suntasach cuireann in iúl gur gá tuilleadh scrúdú.

Mo chomhord:

• Caithfidh é a dhéanamh ar instaláid nua;

• Cuid den maolaíocht bhliantúil;

• Triail chomh maith tar éis mothúchán, lightning strikes, nó tripping events.

Trial 2: Trial Ratio

Aim: Deimhníodh gur comhthéacs an raíocht réadúil leis an luach nameplate chun tomhas agus cosaint cruinn a chinntiú.

Mar shampla, PT rated ag 10kV/100V ní mór a bheith ag output within tolerance; ar a laghad, d'fhéadfadh relays cosaint a dhéanamh mis-operation.

Conas é a dhéanamh:

• Cuir a known low voltage (e.g., 100V–400V) ar an taobh primary;

• Tomhas an secondary voltage agus ríomh an ratio réadúil;

• Comhlíon leis an nameplate — acceptable error is usually ±2%.

Mo thaithí:

• D'fhéadfadh mismatch a léiriú inter-turn shorting;

• Ar ábhar amháin, is é a bhí ina cheangal míchruinn, mar shampla reversed polarity;

• Re-test always after terminal changes or repairs.

Trial 3: Trial Caracteristic Excitation (Volt-Ampere Curve)

Aim: Aimsiú an core is saturated nó an tsean nó mothúchán a bheith ann.

Is é seo an trial is tábhachtach do electromagnetic VTs, go háirithe i gcórais a bhfuil suíomh ferroresonance.

Conas é a dhéanamh:

• Cuir AC voltage ar an secondary winding;

• Cuir isteach an voltage go gradamach agus record current values;

• Plot the U-I curve and observe the knee point.

Key interpretation:

• A normal curve will show a clear knee point;

• A smooth, non-kinked curve suggests core saturation;

• A steep initial slope may indicate moisture damage.

Real case: I once found abnormal excitation characteristics on a PT — turned out it had water ingress due to poor sealing. After drying, it returned to normal.

Trial 4: Trial DC Resistance

Aim: Chun broken strands, turn-to-turn shorts, nó poor connections in the windings a sheiceáil.

DC resistance testing helps uncover hidden defects inside the windings.

Conas é a dhéanamh:

• Úsáid a DC resistance tester;

• Tomhas an resistance of both primary and secondary windings;

• Compare results with factory values or previous measurements — deviation should not exceed ±2%.

Important notes:

• Temperature affects results — best to compare under similar conditions;

• On large PTs, allow time for discharge before testing to avoid residual charge errors.

Trial 5: Dielectric Loss Factor (tanδ) Trial

Aim: Assess the aging or moisture condition of insulation materials.

This advanced test is often used for high-voltage VTs, especially capacitive voltage transformers (CVTs).

Conas é a dhéanamh:

• Úsáid a tanδ tester;

• Apply a set voltage and measure the dielectric loss factor;

• Typically acceptable value is tanδ ≤ 2% (varies by device).

Common issues:

• High values suggest insulation degradation or moisture;

• If standard isn't met, consider drying or replacement.

3. Additional Auxiliary Testing Methods

In addition to the five main tests, these supplementary methods are also useful:

Infrared Thermal Imaging

• Detect overheating at connection points;

• Identify hotspots early;

• Especially useful for monitoring operating equipment.

Partial Discharge Detection

• Detect weak internal discharges;

• An effective early warning for insulation degradation;

• Recommended for high-voltage PTs in critical applications.

Wiring Inspection + Polarity Test

• Ensure correct wiring and consistent polarity;

• Prevent metering inaccuracies or protection misoperations.

4. My Final Suggestions

As someone with 8 years of field experience, I want to remind all professionals:

“Don’t wait until the voltage transformer fails before thinking about testing.”

Performing regular comprehensive checks every year not only ensures stable system operation but also greatly extends the life of your equipment.

Here are my recommendations for different roles:

For Maintenance Personnel:

• Learn to use basic instruments (megohmmeters, multimeters, ratio testers);

• Understand each test procedure and standard;

• Record test data regularly and build comparison records.

For Technical Staff:

• Master advanced tests like excitation curves and tanδ;

• Combine infrared and partial discharge detection to improve diagnostics;

• Understand the PT’s role in the system to avoid blind operations.

For Managers or Procurement Teams:

• Clarify testing requirements during equipment selection;

• Request complete factory test reports from suppliers;

• Establish lifecycle management and schedule regular inspections.

5. Closing Thoughts

Voltage transformers may seem small, but they play a crucial role in the entire power system.

They’re not just about stepping down voltage — they’re the eyes of the system, the ears of protection, and the heart of metering.

After 8 years in the electrical field, I often say:

“Details determine success or failure, and testing ensures safety.”

If you ever encounter abnormal PT behavior, unusual test results, or don’t know how to diagnose a problem, feel free to reach out — I’m happy to share more hands-on experience and solutions.

May every voltage transformer run stably and safely, safeguarding the accuracy and reliability of our power grid!

— Oliver