Technical service for the entire service life of your transformer!


Transformers are subject to a natural ageing process. For this reason, they require scheduled testing and checking. This cycle interval is mainly dependent on the location and operating conditions, as even an issue such as significant dirt can endanger operational reliability.


We offer needs-based solutions here:


Inspection and cleaning of transformers


Cast resin insulation testing

Testing and measurement of insulation resistance of MV transformers incl. measurement protocol

Monitoring of insulating oil as per DIN EN 60422
Standard testing of all transformers, converters and switching devices filled with mineral oil up to 72.5 kV

Test items:
  • Colour and appearance (ISO 2049)
  • Breakdown voltage (IEC 60156)
  • Water content (IEC 60814)
  • Neutralisation value (IEC 62021-1)
  • Dielectric loss factor (IEC 60247)


Insulating oil preparation/drying in oil transformers

Preparation of oil to a breakdown strength of at least 60 kV at 2.5 mm electrode separation using mobile preparation equipment

Sealing work

High voltage and low voltage bushings, cover seals, Buchholz screw connections, viewing glasses, off-circuit tap changers etc.

Retrofitting work

Buchholz protector relay, hermetic protection block, pressure switch, thermometer, air dehumidifier, vibration damper

Conversion work

Conversion to touch-proof plug-in bushings (MV side) and protection against touching (NV side)

Elektrotechnische Werke Fritz Driescher & Söhne GmbH · Driescherstr. 3 · 85368 Moosburg · GERMANY · · Phone: +49 8761 681-0 · Fax: +49 8761 681-137
Driescher GmbH Eisleben · Hallesche Str. 94 · 06295 Lutherstadt Eisleben · GERMANY · · Phone: +49 3475 7255-0 · Fax: +49 3475 7255-109