Manifestations and corrective measures for transformer errors

Manifestations and corrective measures for transformer errors

1. Table of diagnostics, causes and solutions to fix the dry transformer  error

Signal The cause of the error Solution
Low insulation resistance. The coil is damp. Clean with dry air and ventilation.
Aging Clean, contact to manufacturer.
The protective device automatically jumps when the power is turned on The coil is shorted Contact to manufacturer
The regulator is not correct or the primary is not connected properly Check the pressure regulator position and wiring the primary winding. 
The fuse burned or incorrect type Replace the fuse.
Choose the right load current
Protective relays. The time/current setting is incorrect Check load current /time setting
Wrong secondary voltage The primary voltage is missing Check the installation process again. Contact the electric company
The pressure regulator is not properly positioned or the clamp or ECU (engine control unit) is loose Return the pressure regulator to the correct position. Tighten ecu, clamp. 
Coil break Contact the manufacturer.
Unbalanced secondary voltage Ecu, the clamp is loose in one phase.  Check power supply line, review the installation process and contact the utility power company.
The fuse has broken one phase Replace the fuse
Coil is breaked Contact the manufacturer
Low voltage installation part. Low voltage asymmetric load.  Review the low voltage installation process.
Loss of a primary phase Contact the utility power company
Transformer activates false during operation Activation and warning are set up incorrectly.  The thermometer is not correct Review settings and test Thermometer.
Pt100 (Resistance Temperature Detectors) sensor error on measuring temperature or thermistor Check sensor and thermistor
Broken fuse Replace the fuse
Contact the manufacturer
The time on the relay has been incorrect Check the setting time
Overcurrent relay jump or high-voltage fuse fire during the operation Secondary-party is short-circuit Eliminate the cause of the problem
The insulating material is punctured Contact to manufacturer
Relay jump wrongly while operating Transformer error Contact to manufacturer
Broken current transformer that supplies power to the relay Check current transformer
The temperature was abnormally high ventilation is not enough Check the ventilation, add fans if needed
Transformer overload
Reduce the load or replace higher capacity transformers
Heat at the core Clean the core and tighten it
 The cable is hot Check the electric cable load current. Check cable layout and cable diameter again.
High Earthing voltage
Loss of single-phase earth conductor Check earth conductor
Transformer sound  Excessive supply current.
Loose terminal (COSSE), ecu or accessories.
Replace ecu, terminal (COSSE) or tighten.
  Pour sound from walls or obstructions. Install soundproof panels. Install the transformer not parallel to the wall. Install the anti-vibration base under the transformer.
  The power supply frequency is low. Contact the electric utility company
Fuming Broken insulation Contact the manufacturer. Apply transformer fire-fighting manuals

2. Table of diagnostics, causes and solutions to fix errors in oil transformers

Signal The cause of the error Solution
Low insulation resistance Ground fault, lack of oil. Contact to manufacturer
The secondary voltage is not stable  Lack of primary voltage Review the installation process and contact the electrical company
Pressure regulator has been displaced or ecu, terminal is incorrect or loose Review the position of the pressure regulator and wiring
The coil is broken Contact to manufacturer
Secondary voltage is asymmetric  Single-phase fuse is fired Replace the fuse
Ecu and terminal are loose in one phase Review wiring. Review construction and installation process and contact the electricity company
Coil break Contact to manufacturer
Low-voltage installations make secondary voltages asymmetric Check for low voltage installation
There is no primary single-phase power Contact the electric utility company
The overcurrent relay is activated  Problem inside the transformer Contact the manufacturer
Error of current transformer for relay Check current variables
Fake activation during operation Wrong warning and triggering setting. Defective thermometer Check settings again. Check the heat meter.
PT100 sensor error in oil transformer or thermistor temperature measurement Check sensor and thermistor
The relay time is set incorrectly Reset the relay setting time
Short circuit of secondary controller Check to eliminate the cause of the problem
Temperature is abnormal on the thermometer during operation Connector and terminal of transformer are hot Clean the surface of the terminal, ecu and tighten.
Cable is hot The cable is smaller than the standard. Replace the cable
The coil temperature gauge, the top oil layer temperature meter emit a warning or cause a jump. Insufficient heat dissipation. High ambient temperature Check the radiator again. Install a fan if necessary
Overload Transformer Reduce the load or install a higher power transformer
Oil temperature is too high Reduce load
water temperature is too high Reduce load
Poor circulation of oil, water or air Check oil, water and air circulation again.
Excessive ground voltage Loss of single-phase earth conductor Check  earth conductor
Transformer sound Cable voltage is higher than specified level. Loose core. Reduce the supply voltage or change the voltage regulator position. Tighten the core.
Rebound sound from a wall or barrier Install the sound suppression plate. Place the transformer in a direction not parallel to the wall. Use vibration-damping rubber under the transformer.
Low frequency Contact the power company
Relay jump fail during operation Short inside transformer Contact to manufacturer
Short current transformer for the relay Testing current transformer again
Transformer temperature is high Oil level is low Open the oil level check valve
Oil pump protection Check the oil pump and protect the oil pump
Buchholz-gas relay alarm The gas is hot Reduce Transformer load. If the released gas is flammable, sample the gas using a dissolved gas analyzer. Report the transformer separation and contact the manufacturer.
The released gas is colorless and odorless If the released gas is not flammable.
Reduce the load to continue operating and strengthen monitoring.
Relay jump Arc to analyze the poles Gas analysis using DGA gas analyzer. Contact the manufacturer.
Oil level is low Add more oil and fix the leak.
Soldered only when the transformer is filled with oil or inert gas (nitrogen).
The oil indicator indicates that the oil level is too high or too low Oil level is incorrect Adjust the oil level.
Seal leaks.
The transformer should only be soldered when it is full of oil or inert gas (nitrogen).
The relay indicates incorrect oil pressure.  Deviation Oil/water pressure is less than 0.03 bar Reduce water pressure, check valve, clean water circulation / cool.
Report a leak Leaks in cooling. Repair/replace cooling.
The protective pressure relay is high, the pressure regulator under load (OLTC) warns Pressure increases in the pressurized elements under load Check and repair the switching switch of the pressure regulator
The pressure regulator under the load slipped from the rungs Switching operation is not performed well (stop at the intermediate position of the step changer) Check the pressure regulator, interlock and actuator
Pressure relief device jumps The pressure in the transformer increases dramatically Analyse gas and contact to manufacturer
Gas leak warning Pull the gas out Analyze gas and contact to the manufacturer

3. Conclusion
Above, MBT gave some manifestations, causes, and ways to overcome some basic errors during the electrical transformer operation. Hopefully, the above knowledge will help our customers and partners to have the most overview, the most effective way to handle errors in the transformer.
To limit the problem of minor errors; To modify the maintenance process, and make transformers stable and long-term operation, individuals and businesses with demand for transformers should learn and choose a transformer company with a high reputation in the market.  


Transformer is the key product of Hanoi Electric Transformer Manufacture Joint Stock Company (MBT). Our company is proud to be a manufacturer and supplier of top quality transformers, electrical cabinets - power stations in Vietnam.  With more than 20 years of experience in research and production, together with highly qualified staff, modern equipment, and technology, the market has highly appreciated MBT company products and services.
With the business motto: "Quality nurture reliability", customers who come to MBT will always receive products with high quality, reasonable prices, fast delivery time and good warranty service. 
Contact now +84 913 006 538 for free consultation support and receive the most preferential transformer quotation.   

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