Unsa ang mga butang sa pagkawasak sa mga ferromagnetic voltage transformers sa mga new energy power stations?

Gikan sa Felix, 15 Ka Tuig sa Industriya sa Elektrisidad

Kamusta tanan, ako mao si Felix, ug nagsilbi na ko sa industriya sa elektrisidad samtang 15 ka tuig.

Gikan sa pag-uli sa tradisyonal nga substation commissioning ug maintenance hangtod karon nga nag-manage sa operasyon sa sistema sa elektrisidad para sa daghang photovoltaic ug wind power projects, usa sa labi kahimtang nga mga aparato nga gipangandoy nako mao ang Electromagnetic Voltage Transformer (PT).

Adunay panahon, ang usa ka shift operator sa usa ka new energy plant nagtanong nako:

“Adunay electromagnetic voltage transformer nga dili mapugos ang pag-init, makapalit og dili normal nga ingon, ug adunay mga panahon nga mogawas sa protection malfunctions. Ania ang nag-yari?”

Kini usa ka labi kahimtang nga problema, lalo na sa new energy plants. Isip usa ka key measurement ug protection component, bisan tubtob ang PT mag-fail, mahimo kini mokaon sa dili eksakto nga metering hangtod sa full tripping o mas sayop pa, ang damage sa equipment.

Karon, gusto nako mopangutana:

Ania ang mga labi kahimtang nga mga kasagaran nga mga kasalaan sa electromagnetic voltage transformers? Asa ang nag-yari? Ug pila ang atong pangutana?

Wala kompleks nga termino — basi real-life situations nga nakakita nako samtang 15 ka tuig. Tan-awon nato unsa ang labi kahimtang nga mga kasalaan sa kini nga "old friend."

1. Ania ang Electromagnetic Voltage Transformer?

Pangutan-ona nato ang basic function.

Ang electromagnetic voltage transformer, o giingon usab VT o PT, mao ang essentially a step-down transformer nga nag-convert sa high voltage ngadto sa standard low voltage (usual 100V o 110V), nga gigamit sa measuring instruments ug relay protection systems.

Ang iyang structure mao ang labi simple: ang primary winding adunay daghan nga turns ug thin wire, konektado sa high-voltage side; ang secondary winding adunay gamay nga turns ug thick wire, konektado sa control circuit.

Apan, tungod sa kini nga structural characteristic, madaling maapektuhan kini sa operating conditions, load changes, ug resonance phenomena.

2. Kasagaran nga Mga Kasalaan ug Root Cause Analysis

Batasan sa akong 15 ka tuig sa field experience, ang labi kahimtang nga mga tipo sa mga kasalaan mao ang:

Kasalaan 1: Abnormal Heating o Masayop Pa Smoke/Burning

Kini usa sa labi dangerous nga issues — mahimo kini mokaon sa insulation degradation o masayop pa fire.

Possible Causes:

• Secondary short circuit o overload (e.g., multiple protection devices connected in parallel without checking capacity);

• Core saturation (especially during ferroresonance);

• Insulation aging o moisture ingress;

• Loose terminals causing high contact resistance ug localized heating.

Real Case:

Adunay panahon, nakita nako ang PT nga overheating badly sa PV step-up station — infrared thermography showed temperatures over 120°C. Sa disassembly, natukod nato ang secondary winding insulation burned through. Ang cause mao ang open circuit condition caused by a disconnected secondary breaker while still connected to a high-impedance meter.

Tips:

• Never allow the PT secondary to run open-circuited — although not as dangerous as CTs, it can still cause voltage distortion and measurement errors;

• Use infrared thermography regularly to check terminal and enclosure temperatures;

• If abnormal heating is detected, shut down immediately for inspection.

Kasalaan 2: Ferroresonance Causing Voltage Fluctuations

Kini usa sa labi overlooked pero dangerous nga problems sa new energy plants.

Symptoms:

• Unbalanced three-phase voltage;

• Voltage fluctuating up and down with buzzing noise;

• Protection misoperations or false trips;

• Sometimes even false ground signals appear.

Root Cause:

• In ungrounded or arc suppression coil grounded systems, when line-to-ground capacitance combines with PT excitation inductance under certain conditions, ferroresonance can occur;

• It often gets triggered during breaker switching, sudden loss of voltage, or single-phase grounding.

Real Case:

Sa usa ka wind farm, every time the main transformer was energized, ang PT emitted a humming noise, ug bus voltage fluctuated wildly, even triggering the standby auto-switch incorrectly. After investigation, it turned out to be caused by ferroresonance. Installing a damping resistor in the open delta solved the problem.

Prevention Suggestions:

• Install anti-resonance devices (such as open-delta resistors or microprocessor-based suppressors);

• Use anti-resonant type PTs (like JDZXW series);

• Optimize operation mode to avoid long-term non-full-phase operation;

• During outage maintenance, perform magnetizing curve tests to assess core saturation tendency.

Kasalaan 3: Low or No Secondary Voltage Output

Kini nga mga issues labi kahimtang affect metering ug protection logic, ug sometimes mistaken for other device failures.

Possible Causes:

• Primary fuse blown (often after lightning strikes or overvoltage events);

• Secondary fuse blown or air switch tripped;

• Incorrect polarity or ratio setting;

• Inter-turn short circuits in internal windings;

• Oxidized or loose terminal connections.

Real Case:
In one PV station, SCADA showed abnormally low bus voltage. On-site inspection revealed that the PT primary fuse had blown. Replacing it restored normal operation. Further analysis showed it was caused by a voltage surge from nearby lightning.

Troubleshooting Steps:

• Check fuses and breakers first;

• Measure primary and secondary voltages for consistency;

• Verify wiring and polarity;

• Perform ratio test and insulation resistance test if necessary.

Kasalaan 4: Internal Discharge or Insulation Breakdown

Kini usually occurs in humid or heavily polluted environments, especially in coastal or high-altitude areas.

Symptoms:

• Smell of burning or visible discharge marks on housing;

• Crackling sounds during operation;

• Reduced insulation resistance;

• In severe cases, explosion or tripping occurs.

Possible Causes:

• Moisture ingress causing insulation deterioration;

• Surface dirt or dust buildup reducing creepage distance;

• Long-term overloading or harmonic effects;

• Manufacturing defects or transport damage.

Real Case:

A PT installed near the coast repeatedly tripped during the rainy season. Inspection revealed clear signs of internal discharge — the root cause was poor sealing allowing moisture to enter.

Countermeasures:

• Increase protection rating (IP54 or higher);

• Install dehumidifiers or space heaters;

• Regular cleaning and drying;

• Conduct insulation and partial discharge tests before commissioning.

Kasalaan 5: Human Error or Wiring Mistakes

Human error remains a major cause of many incidents.

Common Mistakes Include:

• Switching isolators under secondary load;

• Reversed polarity causing incorrect metering or protection misjudgment;

• Accidental removal of grounding wires leading to floating potentials;

• Performing live work without proper safety measures.

Real Case:

A new technician replaced a PT secondary fuse without disconnecting the power, causing a short circuit — the fuse holder burned out and nearly caused injury.

Key Takeaways:

• Strengthen training and standardize procedures;

• Clearly label wiring to prevent mistakes;

• Enforce lockout/tagout procedures to eliminate live work;

• Ensure one-point grounding of all PT secondary circuits.

3. My Suggestions and Field Experience Summary

As a 15-year veteran in the electrical field, I always say:

“Though small, the electromagnetic voltage transformer plays a critical role in measurement, metering, and protection.”

It may not be as noticeable as a circuit breaker or as large as a transformer, but once it fails, it can trigger a chain reaction.

So here are my recommendations:

For Daily Operation & Maintenance:

Regular inspections — listen for unusual sounds, smell for burning, and measure temperature;

• Check fuses, breakers, and grounding integrity;

• Record operational data and compare with historical trends;

• Increase inspection frequency before and after thunderstorm seasons.

For Fault Diagnosis:

• Prioritize checks on secondary circuits and fuses;

• Use multimeters to verify voltage levels;

• Conduct insulation resistance, ratio, and magnetizing characteristic tests when needed;

• Take immediate action to suppress resonance if suspected.

For Equipment Selection:

• Consider environmental factors (humidity, altitude, salt fog);

• Prefer anti-resonant PTs;

• Choose appropriate rated capacity to avoid long-term overloading;

• Leave room for redundancy to support future expansion.

4. Final Thoughts

Although structurally simple, electromagnetic voltage transformers play a vital role in new energy power plants.

They act like the "eyes" of the power system, telling us exactly how "high" the voltage is.

After 15 years in the field, I firmly believe:

“Details determine success or failure. Safety comes above everything.”

If you're dealing with tricky PT issues on site, feel free to reach out — I'm happy to share more hands-on experiences and troubleshooting methods.

May every PT operate stably, keeping our grid safe and intelligent!

— Felix