1. Chem oil test of transformer and other oils

is used to monitor the functional capabilities of transformers and other equipment and to optimize the maintenance plan, which ensures the life span of the transformer.

Testing includes:

• Physicochemical and dielectric analysis of oil,
• Estimation of operating condition, degradation degree of oil and inhibitor content
• Estimation of humidity of paper-oil insulating system
• Recommendations for oil maintenance or other tests and activities

An oil sample may be taken during normal operation using a clean, dry 1 l bottle. For an accredited analysis, the sampling must be carried out by an individual who is competent to take samples and is accredited according to ISO/IEC 17025. For additional information on sampling please contact us at tel. +386 1 474-3661.

Determination of 9 dissolved gases in transformer oil is used to monitor and diagnose incipient faults in power and instrument transformers in operation, but also in new transformers during factory testing. With systematic checks once a year we can detect incipient faults within the transformer even before they lead to serious faults or trip the Buchholz relay.

Testing includes:

• Analysis of the gases dissolved in transformer oil (hydrogen, methane, ethane, ethylene, acetylene, CO, CO2, oxygen, nitrogen),
• Diagnosis of the condition of the transformer; detection of thermal and electrical faults at an early stage and assessment of the reason a Buchholz relay is tripped or the transformer is shut down,
• Estimation of transformer operating reliability
• Recommendations for further testing, maintenance activities or activities on faulty transformer

An oil sample may be taken during normal operation using a gas-tight 250 ml syringe. In exceptional situations it is also possible to use a dry 1 l bottle. For an accredited analysis, the sampling must be carried out by an individual who is competent to take samples and is accredited according to ISO/IEC 17025. For additional information on sampling please contact us at tel. +386 1 474-3661.

Determination of furanic compounds in transformer oil is used to monitor and diagnose incipient thermal faults, cooling system faults, damage to the paper insulation, and the rate of ageing of the paper insulation in power and instrument transformers in operation, but also in new transformers during factory tests. With systematic checks once a year we can detect incipient faults within the transformer even before they lead to serious faults, trip the Buchholz relay, or noticeably shorten the life span.

Testing includes:

• Analysis of 5 furanic compounds dissolved in the transformer oil,
• Diagnosis of the condition of the transformer; detection of paper damages or thermal incipient faults at an early stage and assessment of the reason a Buchholz relay is tripped or the transformer is shut down,
• Estimation of the degree of degradation or ageing of paper insulation and the operational reliability of the transformer
• Recommendations for further testing and maintenance activities or activities on faulty transformer.

An oil sample may be taken during normal operation using a gas-tight 250 ml syringe. In exceptional situations it is also possible to use a dry 1 l bottle. For an accredited analysis, the sampling must be carried out by an individual who is competent to take samples and is accredited according to ISO/IEC 17025. For additional information on sampling please contact us at tel. +386 1 474-3661.

HPLC testing is carried out on the same sample as DGA testing.


4. COMBINED TESTING (DGA+HPLC+partial Chem oil test) of instrument transformers

On the basis of the results of combined testing, we assess the condition of the instrument transformer with regard to both the ageing and moisture content of the insulation system and also possible electrical and thermal incipient faults (the possibility of explosion), and the quality of the insulating oil and paper insulation. Based on these results we can determine potential reductions in reliable and safe operation or the need to take the transformer out of service. Combined testing can be carried out using only a small amount of sample oil, which we sample using a gas-tight 250 ml syringe when the transformer is not in operation, ideally as soon as possible after it is shut down. For an accredited analysis, the sampling must be carried out by an individual who is competent to take samples and is accredited according to ISO/IEC 17025. For additional information on sampling please contact us at tel. +386 1 474-3661.


5. DP TESTING Degree of polymerization of paper insulation

Analysis of the degree of polymerization of the paper insulation is not a routine test used to monitor a transformer in operation because it is necessary to take a sample of the paper insulation, which requires at least partially opening the transformer. DP analysis of the paper insulation allows us to assess its mechanical (tensile) strength, which is a critical property used to determine the safe operation of the transformer, particularly upon short-circuit or other mechanical stresses.
The analysis gives information on the condition of the paper insulation at the sampling site, so we usually choose a site for testing (such as the exit point of the lead from the windings) where a lower level of polymerization and, therefore, weaker paper can be expected. This test is carried out when the results of the HPLC testing indicate that the paper insulation is already somewhat degraded or damaged.

Data on the degree of polymerization is absolutely required when preparing a diagnosis of the remaining life span of the transformer, or when planning any kind of transformer revitalization or maintenance activities.

The transformer servicer carries out the sampling. There must be an agreement regarding the sampling site and sampling method. For additional information on sampling please contact us at tel. +386 1 474-3661.

6. Analysis of the presence or absence of PCBs (polychlorinated biphenyls) in oil with the Quick-screen method or gas chromatography

Oil contaminated with PCBs is rated a special waste because it is poisonous and ecologically hazardous, so it is obligatory to perform an analysis of the presence of PCBs in oil before it is disposed of or before performing extensive work on the transformer. In compliance with the Slovenian legislation in force, each apparatus with more than 5 liters of oil must have a document (a manufacturer's declaration or the oil testing report) showing the absence of PCBs in the device's oil.