Gas-in-oil analyses can provide indications of thermal or electrical abnormalities in the active component. Furan analyses support the assessment of the aging of cellulose-based insulating materials. We do not evaluate the results in isolation, but rather in conjunction with comparative values, operating history, load, and other tests. Only this comprehensive view allows for a reliable recommendation regarding monitoring, maintenance, or overhaul.

Oil regeneration can be beneficial if the insulating oil's properties can be improved and there is no further damage to the transformer that would preclude it. However, it does not replace repairs to the windings, active components, bushings, or sealing systems. Therefore, we examine the oil condition, analyze the results, check the moisture content, assess the age of the oil, and determine the suspected cause of the damage. This assessment determines whether conditioning, regeneration, replacement, or a more extensive overhaul is necessary.

Depending on the findings, on-site services can include testing, oil treatment, sealing work, replacement of bushings, and certain overhauls. A factory overhaul is required if extensive disassembly, rewinding, vacuum drying, or work on the active component under controlled workshop conditions is necessary. We determine the appropriate course of action based on the damage pattern, transportability, safety requirements, and the necessary testing equipment.

The scope of testing depends on the design, the extent of the repair, and agreed-upon VDE, IEC, or customer specifications. Depending on the order, we test, for example, insulation and winding resistances, gear ratios, oil condition, or partial discharge behavior. The results are compared with defined criteria and existing reference values. This creates a verifiable acceptance certificate for the work performed.

We compare the condition of the active components, windings, insulation, tank, bushings, and switching components with the repair costs, failure risk, and expected remaining service life. Delivery time, replacement availability, and the transformer's importance to operations are equally important. Repair is worthwhile if the structural integrity is sound and the result is economically viable.

Partial discharge measurement can be useful if local electrical activity is suspected in or on the insulation, or if a defined condition or acceptance test is required. The measurement setup, interference level, and operating condition influence the results. We therefore evaluate the results in conjunction with the design, history, and other electrical or oil-related tests.