Unsaon ang pag-handle sa mga kasuloban sa transformer?
Mga karaniwang pagkakamali sa transformer ug ang ilang paagi sa pag-handle.
1. Overheating sa Transformer
Ang overheating mao ang labi ka masamyo alang sa mga transformer. Ang daghang mga pagkawasay sa insulasyon sa mga transformer gikan sa overheating. Ang pagtaas sa temperatura nagbawas sa dielectric strength ug mechanical strength sa mga materyales sa insulasyon. Ang IEC 354, Loading Guide for Transformers, nag-ingon nga kapag ang pinaka mainit nga temperatura sa usa ka transformer makadako og 140°C, ang mga bula mahimong mag-ugmad sa langis. Kini nga mga bula mahimong mabawasan ang performance sa insulasyon o makahimo og flashover, resulta mao ang pagkawasay sa transformer.
Ang overheating labi ka nakaimpluwensya sa lifespan sa mga transformer. Sumala sa 6°C rule sa transformer, sa temperature range gikan 80–140°C, para sa kada 6°C na pagtaas sa temperatura, ang rate sa pagkawasay sa effective service life sa insulasyon sa transformer nag-doble. Ang national standard GB1094 usab nag-spesifyha nga ang average winding temperature rise limit alang sa oil-immersed transformers mao ang 65K, ang top oil temperature rise mao ang 55K, ug ang core ug tank mao ang 80K.
Ang overheating sa transformer kasagaran ipailustrar isip abnormal nga pagtaas sa temperature sa langis. Ang posible nga pangunahon nga mga dahon ania (1) overload sa transformer; (2) pagkawasay sa cooling system (o incomplete engagement sa cooling system); (3) internal fault sa transformer; (4) dili tama nga indication gikan sa temperature measuring device.
Kapag natukod ang abnormal nga pagtaas sa temperature sa langis sa transformer, ang gibanggit nga posible nga mga dahon dapat ibersyonan usa ka adlaw-adlaw aron makab-ot ug tama nga paghunahuna. Ang key inspection ug handling points mao kini:
(1) Kon ang operational instruments nagpakita nga ang transformer overloaded, ug ang temperature gauges sa three phases sa single-phase transformer bank nagpakita og halos parehas nga readings (kon posible ang deviation sa pipila ka grados), ug ang transformer ug cooling system nag-operate normal, ang pagtaas sa temperature kasagaran gikan sa overload. Sa kasong ini, palihog pahibalo sa upper-level dispatching department ug imong rekomenda ang pag-transfer sa load aron makurangan ang magnitude ug duration sa overload.
(2) Kon ang pagtaas sa temperature gikan sa incomplete engagement sa cooling system, ang sistema dapat i-activate immediate. Kon ang cooling system naka-failed, ang dahon dapat ma-identify ug i-address immediate. Kon ang fault dili maka-resolve immediate, ang temperature ug load sa transformer kinahanglan strict monitoring, ang continuous report sa dispatching department ug production management, ang reduction sa load sa transformer, ug ang operation sa transformer sumala sa corresponding load value matching the cooling capacity sa current cooling condition.
(3) Kon ang remote temperature measurement device naghatag og high-temperature alarm signal kon ang indicated value labi ka taas, pero ang local thermometer nagpakita og normal nga readings ug wala pay uban pang signs sa transformer fault, ang alarm kasagaran false signal gikan sa fault sa remote temperature measurement circuit. Ang kasagaran nga faults mahimo mapabilin sa appropriate time.
(4) Kon sa three-phase transformer bank, ang oil temperature sa usa ka phase makadako labi ka taas kaysa sa iyang historical oil temperature sa sama nga load ug cooling conditions, ug ang cooling system ug thermometer normal, ang overheating kasagaran gikan sa internal fault sa transformer. Palihog immediate notify sa professional personnel aron makuha ang oil sample para sa chromatographic analysis aron mas identify ang fault. Kon ang chromatographic analysis nagpakita og internal fault, o kon ang oil temperature continue nagtaas sa unchanged load ug cooling conditions, ang transformer dapat i-take out of service sumala sa on-site regulations.
2. Pagkawasay sa Cooling System
Ang cooling system makatabang sa pag-disipate sa heat gikan sa windings ug core pinaagi sa transformer oil. Ang tanang 500kV main transformers gamiton ang forced oil circulation with forced air cooling. Kon ang cooling system nag-operate normal o dili, kasagaran critical condition alang sa normal operation sa transformer. Ang pagkawasay sa cooling equipment kasagaran nga common fault sa transformer. Kapag ang cooling equipment naka-failed, ang operating temperature sa transformer makadako rapid, ug ang insulation life loss makadako sharp.
Sa panahon sa pagkawasay sa cooling equipment, ang operators kinahanglan strict monitoring sa temperature ug load sa transformer, ang continuous report sa dispatching department ug operation supervisors. Kon ang load sa transformer exceed ang specified limit sa faulty cooling conditions, ang request sa load reduction dapat sumala sa on-site regulations.
Dapat mosugyot nga sa panahon sa pagtaas sa oil temperature, ang core ug windings mas taas ang pag-init kaysa sa langis. Ang oil temperature mao ang labi ka slight nga pagtaas, pero ang core ug winding temperatures mahimong labi ka taas. Kasagaran kon ang oil pumps naka-failed, ang relative temperature rise sa windings versus oil far exceeds ang normal value sa nameplate. Ang oil temperature mao ang labi ka slight nga pagtaas o wala pay notable, pero ang core ug winding temperatures mahimong far exceed ang allowable limits.
Sa higayon, sa gradual nga pagtaas sa oil temperature, ang core ug winding temperatures continue nagtaas sa even higher values, maintaining a certain temperature rise over oil sa given load ug cooling conditions. Konsekwentemente, sa panahon sa pagkawasay sa cooling equipment, dili ra ang oil ug winding temperatures ang dapat observed, apan ang allowable operating capacity ug time sa transformer sa cooling system outage, sumala sa manufacturer ug on-site regulations, kinahanglan followed. Ang uban pang operational changes usab dapat monitored aron comprehensive assessment sa operating condition sa transformer.
Para sa pag-check sa pagkawasay sa cooling equipment, determine ang scope sa outage (individual fan or oil pump stopped, entire group stopped, single-phase or three-phase stopped), refer sa cooling system control circuit diagram aron locate ang fault point, ug minimize ang downtime sa cooling equipment.
Kon ang individual fan or oil pump naka-failed pero ang uban normal nga operate, ang posible nga mga dahon ania:
One phase sa three-phase power supply sa fan or oil pump open-circuited (fuse blown, poor contact, or broken wire), causing increased motor current, thermal relay operation or power cutoff, or motor burnout;
Bearing or mechanical failure sa fan or oil pump;
Fault sa corresponding control relay, contactor, or other components sa fan or oil pump control circuit, o circuit break (e.g., loose terminal, poor contact);
Thermal relay setting too low, causing false operation.
Kon ang cause mokontra sa power supply or circuit fault, ang broken wire dapat quick repair, fuse replacement, ug power ug circuit restoration. Kon ang control relay damaged, dapat replace sa spare. Kon ang fan or oil pump damaged, immediate maintenance request.
Kon ang group (or several) fans or oil pumps stop simultaneously, ang likely cause mao ang power supply fault sa group, blown fuse, thermal relay operation, o damaged control relay. Ang standby fan or oil pump dapat immediately engage, then restore ang fault.
Kon ang tanang fans or oil pumps sa main transformer stop, kinahanglan due sa failure sa main power supply sa one or all three phases sa cooling system. Sa kasong ini, check kon ang standby power supply automatically engaged. Kon dili, manually engage ang standby power supply quick, identify ang fault cause, ug eliminate it.
Sa panahon sa handling sa power supply faults ug restoration sa power, pay attention sa following:
Sa panahon sa replacement sa fuses, first open ang circuit power ug load-side switch or isolator. Sa live fuse replacement, kon ang second phase installed, ang three-phase motor receive two-phase power, generating a large current that may blow ang newly installed fuse.
Use fuses with specifications ug capacity matching sa design.
Sa panahon sa restoration sa power ug restarting sa cooling equipment, start in steps or groups as much as possible aron avoid simultaneous startup sa tanang fans ug oil pumps, which may cause current surge ug blow fuses again.
After three-phase power restored, kon ang fans or oil pumps still dili start, mao ang possible kay ang thermal relay dili reset. Reset ang thermal relay. Kon wala pay fault sa cooling equipment, dapat restart normal.
3. Abnormal Oil Level
Abnormal transformer oil level includes abnormal main tank oil level and abnormal on-load tap changer (OLTC) oil level. 500kV transformers generally use oil reservoirs with diaphragms or bladders, with pointer-type oil level gauges indicating the oil level. The oil level of both can be observed via the gauge.
If transformer oil level is low, the cause should be investigated. If low oil level is due to low ambient temperature or light load causing oil temperature drop to the minimum oil level line, oil should be added promptly. If oil level drops due to serious oil leakage, measures should be taken immediately to stop the leak and add oil.
High transformer oil level may be caused by:
excessive oil filling, with oil level rising with temperature during high ambient temperature or high load;
cooling system failure;
internal transformer fault.
When oil level is too high, check the load and oil temperature, confirm cooling system normality, verify all valve positions are correct, and check for any signs of internal faults. If oil level is excessively high or oil overflows, and no other faults are present, a small amount of transformer oil may be drained appropriately.
High oil level in the OLTC oil reservoir, besides oil temperature, may also be caused by overheating of electrical joints or other reasons causing seal failure in the OLTC compartment, allowing insulating oil from the main tank to leak into the OLTC compartment, causing abnormal rise in OLTC oil level. When OLTC oil level rises abnormally and continuously, even overflowing from the OLTC oil reservoir breather, immediately report to the dispatching department, have professionals conduct testing and analysis, request taking the faulty transformer out of service for maintenance.
500kV transformers generally use oil reservoirs with diaphragms or bladders and pointer-type oil level gauges, which indicate oil level based on the position of the diaphragm or bladder bottom. The following conditions may cause inaccurate pointer indication:
Gas accumulated under the diaphragm or bladder causes it to float above the actual oil level, resulting in higher oil level indication;
Breather blockage prevents air from entering when oil level drops, causing higher oil level indication;
Rupture of the bladder or diaphragm allows oil to enter the space above, possibly causing lower oil level indication.
These three situations may lead to incorrect oil level indication, requiring operators to carefully observe and analyze during normal operation.
4. Light Gas Relay Operation
When the light gas relay operates, it indicates abnormal transformer operation and should be inspected and handled immediately. Methods are as follows:
(1) Inspect the transformer’s appearance, sound, temperature, oil level, and load. If severe oil leakage is found and oil level is below the 0 mark on the gauge, possibly below the gas relay level that triggers alarm signals, the transformer should be immediately taken out of service and the leak repaired promptly.
If abnormal temperature rise or unusual operating sound is detected, there may be an internal fault. Transformer abnormal noise comes in two types: one caused by mechanical vibration, the other by partial discharge. A listening rod (or flashlight) can be used—press one end firmly against the casing and listen with the ear at the other end—to determine if noise originates from internal components (mechanical vibration or partial discharge). Discharge noise usually has a rhythmic pattern similar to corona noise on high-voltage bushings. If suspicious internal discharge noise is detected, immediately perform oil chromatographic analysis and intensify monitoring.
(2) Extract gas sample for analysis. Usually, on-site qualitative judgment is combined with laboratory quantitative analysis.
For gas sampling, use a syringe of appropriate volume. Remove the needle and attach a short piece of plastic or oil-resistant rubber tubing. Before sampling, fill the syringe and tubing with transformer oil to expel air, then push the plunger fully to expel the oil. Connect the tubing to the gas relay’s vent valve (ensure airtight connection). Open the gas relay vent valve and slowly pull back the syringe plunger to draw gas into the syringe.
Bring a flame near the syringe needle and slowly push the plunger to release the gas, observing whether the gas is flammable. Simultaneously, send the gas to the lab for gas composition analysis for accurate judgment.
If the gas is found flammable or chromatographic analysis confirms an internal fault, the transformer should be immediately taken out of service.
If the gas is colorless, odorless, and non-flammable, and chromatographic analysis identifies it as air, the gas relay alarm may be a false alarm due to secondary circuit fault. The circuit should be inspected and repaired promptly.
During gas sampling, use a colorless transparent syringe for easy observation of gas color. The procedure must be conducted under strict supervision, maintaining safe distance from live parts.
5. Transformer Tripping
When a transformer trips automatically, a comprehensive inspection should be conducted immediately to identify the cause before taking action. Specific inspection items include:
(1) Based on protective relay signals, fault recorder, and other monitoring device displays or printouts, determine which protection operated.
(2) Check load, oil level, oil temperature, oil color, and whether there is oil spraying, smoking, bushing flashover or rupture, pressure relief valve operation, or other obvious fault signs before tripping, and whether gas is present in the gas relay.
(3) Analyze the fault recorder waveform.
(4) Understand system conditions: whether short-circuit faults occurred inside or outside the protection zone, whether system operations or switching overvoltages occurred, or inrush current during closing.
If inspection shows the automatic trip was not caused by a transformer fault, the transformer may be re-energized after external faults are cleared.
If any of the following conditions are found, internal transformer fault should be suspected. The cause must be identified, the fault eliminated, and electrical tests, chromatographic analysis, and other targeted tests must confirm the fault is resolved before re-energizing:
(1) Gas extracted from the gas relay is confirmed flammable by analysis; (2) Obvious internal fault signs in the transformer, such as tank deformation, abnormal oil level, severe oil spraying; (3) Obvious flashover marks or damage, breakage on transformer bushings; (4) Two or more protective relays (differential, gas, pressure) operated.
6. Abnormal Noise
(1) If the noise is loud and noisy, it may be due to transformer core issues. For example, loose clamps or core-tightening bolts. Instrument readings are generally normal, and oil color, temperature, and level show no significant change. In this case, stop transformer operation and conduct inspection.
(2) If the noise contains a boiling water sound or "gurgling" bubble sound, it may indicate a serious winding fault causing nearby parts to overheat and vaporize oil. Poor contact in the tap changer causing local overheating or winding turn-to-turn short circuit can both produce this sound. Immediately stop transformer operation and perform maintenance.
(3) If the noise contains loud, irregular explosion-like sounds, it may indicate insulation breakdown in the transformer body. Stop operation and perform maintenance.
(4) If the noise contains a "zizi" discharge sound, it may be due to surface partial discharge on the transformer body or bushings. If it is a bushing issue, corona glow or small blue/purple sparks may be visible in poor weather or at night. Clean the bushing surface and apply silicone oil or silicone grease. Stop the transformer, and check whether core grounding and clearances between live parts and ground meet requirements.
(5) If the noise contains continuous, rhythmic knocking or rubbing sounds, it may be due to mechanical contact caused by vibration of certain components, or abnormal noise caused by electrostatic discharge.
7. Oil Spraying and Explosion
Oil spraying and explosion occur when internal fault short-circuit currents and high-temperature arcs rapidly age the transformer oil, and the protective relay fails to cut off power in time, allowing the fault to persist and internal tank pressure to continuously increase. High-pressure oil and gas then spray out from the explosion-proof pipe or other weak points of the tank, causing an accident.
(1) Insulation damage: Local overheating such as turn-to-turn short circuits damages insulation; transformer water ingress causes insulation moisture and damage; overvoltage such as lightning strikes damages insulation—these are basic factors leading to internal short circuits.
(2) Wire breakage causing arcing: Poor welding of winding conductors or loose lead connections may cause wire breakage under high current surge. High-temperature arcs at the break point vaporize oil, increasing internal pressure.
(3) Tap changer failure: In distribution transformers, the high-voltage winding tap section is connected via the tap changer. The tap changer contacts are in series in the high-voltage winding circuit and carry load and short-circuit currents. If the moving and stationary contacts overheat, spark, or arc, the tap section winding may short circuit.
8. Emergency Shutdown of Transformer
A running transformer should be immediately stopped if any of the following conditions are observed:
(1) Abnormal or significantly increased internal noise; (2) Severe damage and discharge on bushings; (3) Smoke, fire, or oil spraying from the transformer; (4) The transformer has a fault, but the protection device fails to operate or operates incorrectly; (5) Fire or explosion nearby poses a serious threat to the transformer.
In case of transformer fire, immediately disconnect the power, stop fans and oil pumps, summon fire personnel immediately, and activate fire extinguishing equipment. If the fire is caused by insulating oil overflowing and burning on the top cover, open the lower drain valve to release oil to an appropriate level to stop overflow, preventing oil level from dropping below the cover and causing internal fire. If the fire is due to an internal fault, oil must not be drained, to prevent air from entering and forming an explosive mixture that could cause a severe explosion.
In summary, when a transformer fault occurs, accurate judgment and proper handling are essential—preventing fault escalation while avoiding unnecessary shutdowns. This requires improved diagnostic capability and accumulated operational experience to correctly identify and promptly handle transformer faults, preventing accident expansion.
Factors causing abnormal transformer noise are numerous, and fault locations vary. Only by continuously accumulating experience can accurate judgments be made.
