Ano ang mga dahilan ng mababang insulation sa low-voltage side ng isang dry-type transformer?
Kamusta lahat, ako si Felix, at nagsasagawa ng pag-aayos ng mga kaputanan sa electrical equipment nang halos 15 taon na.
Sa loob ng mga taong ito, nakapaglakbay ako sa iba't ibang pabrika, substations, at distribution rooms sa buong bansa, nagtroubleshoot at nagrepair ng iba't ibang uri ng electrical equipment. Ang dry-type transformers ay isa sa pinaka-karaniwang mga device na kinakatawan namin.
Ngayon, isang kaibigan ang naghingi sa akin:
“Ano ang ibig sabihin kung ang low-voltage side ng isang dry-type transformer ay may mababang insulation resistance?”
Magandang tanong — lalo na para sa maintenance personnel. Kaya, ipaliwanag ko ito sa simple terms, batay sa mga real-life cases na in-handling ko sa loob ng mga taon.
1. Ano ang Ibig Sabihin ng "Low Insulation on the Low-Voltage Side"?
Simulan natin sa isang maikling overview:
Ang dry-type transformer ay isang air-cooled, oil-free, insulated transformer na karaniwang ginagamit sa mga gusali, malls, ospital, data centers — mga lugar kung saan mahalaga ang fire safety.
Ang kanyang low-voltage side ay karaniwang lumalabas ng 400V o 230V at direktang nagbibigay ng power sa mga loads.
Kapag sinabi natin "low insulation on the low-voltage side", ibig sabihin nito na ang insulation resistance sa pagitan ng low-voltage winding at ground (core o enclosure) ay mas mababa kaysa normal — nangangahulugan na ang insulation performance ay nabawasan.
Sa madaling salita: ang dating fully non-conductive barrier ay ngayon ay nagpapayag ng maliit na leakage currents na lumipas. Ito ay maaaring magresulta sa tripping, arcing, o kahit short circuits!
2. Common Causes (All From Real Cases I’ve Fixed)
Batay sa aking field experience, ang pangunahing dahilan ng mababang insulation sa low-voltage side ng dry-type transformers ay nasa sumusunod na kategorya:
2.1 Moisture / Condensation
Ito ang pinaka-karaniwang dahilan, lalo na sa mga mainit na lugar tulad ng Timog Tsina o coastal regions, o sa mga bagong installed na transformers na hindi pa ganap na nadry out.
Halimbawa: Noong nakaraang taon, nacheck ko ang isang bagong dry-type transformer sa isang pabrika sa Xiamen. Ang insulation sa low-voltage side ay lamang ang ilang puluhang megaohms — way below standard (dapat ≥500MΩ). Kapag binuksan namin ang cabinet, may condensation sa loob! Naglabas pala ang unit ng moisture sa panahon ng transport at dahil sa mataas na humidity.
Solutions:
Check for water ingress;
Gumamit ng heat gun o infrared lamp upang idry out;
I-send back sa factory para sa vacuum drying kung kinakailangan;
Install a dehumidifier o space heater bilang prevention.
2.2 Dust or Foreign Material Buildup
Ang dry-type transformers ay umiiral sa air para sa cooling, kaya maraming silang vents — na gumagawa rin sila ng prone sa dust accumulation sa paglipas ng panahon.
Ang dust ay maaaring conductive — lalo na ang metal dust o salt particles — at kapag pinagsama sa moisture, ito ay maaaring malaking bawasan ang insulation levels.
Isang beses akong nakita ang puting crystalline deposits sa low-voltage terminals ng isang transformer sa isang chemical plant. It was caused by corrosive gases, and the insulation was clearly compromised.
Solutions:
Regularly clean, lalo na sa paligid ng terminals at windings;
Install filters sa dusty environments;
Gumamit ng specialized insulating cleaners — never wash with water;
Check for clogged ventilation openings.
2.3 Winding Aging or Partial Discharge Damage
Ang mga winding sa dry-type transformers ay karaniwang encapsulated sa epoxy resin — matatag, pero hindi indestructible.
Ang long-term operation under high temperatures, overloads, o harmonic conditions ay maaaring mag-resulta sa degradation, crack, o carbonization ng insulation layer, na nagiging sanhi ng partial discharge at eventually reduced insulation.
Isang beses, nirepair ko ang isang dry-type transformer na nasa serbisyo na ng 8 taon. Ang kanyang low-voltage insulation ay bumaba mula 1000MΩ hanggang 20MΩ. Sa inspection, nakita namin ang clear signs of carbonization sa surface ng winding.
Solutions:
Check operating temperature records for long-term overheating;
Measure partial discharge levels (if possible);
Replace damaged windings or the entire unit;
Improve ventilation, reduce load, and avoid frequent overloads.
2.4 Loose or Oxidized Terminal Connections
Ang loose terminal connections ay maaaring magresulta sa localized heating, na pagkatapos ay nakakaapekto sa surrounding insulation materials.
Halimbawa, isang beses akong nagtrabaho sa isang dry-type transformer na konektado sa isang UPS system. Ang low-voltage insulation ay bigla na lang bumaba sa ibaba ng 100MΩ. Inspection revealed a loose copper busbar bolt — ang contact area ay burned at even smoked before.
Solutions:
Regularly tighten all terminal connections;
Use a torque wrench according to specifications;
Check for oxidation, discoloration, or burn marks;
Polish or replace heavily oxidized terminals.
2.5 Poor Enclosure or Grounding
Ang enclosure at core ng isang dry-type transformer ay dapat na maayos na grounded. Kung ang grounding ay mahina, ito ay maaaring lumikha ng floating voltages, na nagiging sanhi ng maliwang insulation readings.
Isang beses, sa panahon ng commissioning check sa isang bagong site, nakita kong ang low-voltage insulation ay lamang ang ilang daang kiloohms. Nakita namin na ang ground wire ay nasira ng mga construction workers, na nagresulta sa energized core — falsely indicating low insulation.
Solutions:
Check for broken or loose ground wires;
Test ground resistance (should be ≤4Ω);
Ensure the core is well connected to the enclosure;
Avoid misdiagnosis due to grounding issues.
2.6 Measurement Errors / Improper Testing Methods
Sometimes, the problem isn't with the equipment itself, but how the test was conducted.
Examples include:
Using a 500V megohmmeter instead of a 2500V one;
Not disconnecting secondary cables or other connected devices;
Failing to discharge before testing, causing residual charge interference;
Ending the test too early before the reading stabilizes.
I’ve made this mistake before — almost condemned a perfectly good transformer.
Solutions:
Use the correct megohmmeter (2500V for dry-type transformers);
Disconnect all external wiring;
Discharge for at least 1 minute before testing;
Record R15 and R60 values, calculate absorption ratio (R60/R15 ≥ 1.3);
Consider dielectric loss tests for further confirmation.
3. How to Test and Diagnose
Here's the step-by-step process I use for diagnosis:
4. Repair Suggestions & Preventive Measures
Repair Suggestions:
If moisture is the issue, drying may restore insulation;
If dust or debris is the cause, cleaning often restores performance;
If windings are aged or damaged, send for factory repair or replacement;
If terminal connections are the problem, tighten or replace them;
All operations must be done with power off, lockout-tagout applied!
Preventive Measures:
Regular inspections (quarterly), using infrared thermography to detect hotspots;
Periodic cleaning (annually), paying attention to hidden corners;
Install dehumidification systems (especially in humid areas);
Monitor load to avoid long-term overloading;
Consider online monitoring systems (for high-end users);
Keep detailed equipment records and track changes over time.
5. Final Thoughts
Ang mababang insulation resistance sa low-voltage side ng isang dry-type transformer ay maaaring teknikal, pero sa karamihan ng kaso, ito ay maaaring matukoy at ma-resolve gamit ang basic tools at procedures.
Bilang isang tao na nagsasagawa ng electrical equipment repair nang 15 taon, gusto kong i-emphasize:
“Insulation doesn’t fail suddenly — it deteriorates slowly over time.”
With regular checks and timely maintenance, most problems can be caught early and prevented from becoming serious.
If you're dealing with a similar issue on-site and aren't sure how to proceed, feel free to reach out — we can work through it together and find the best solution.
Remember this key message:
“Prevention is better than cure — catch it early, fix it early.”
Stay safe, keep the lights on!
— Felix
