Insulating oil in Siemens voltage regulators

02/01/2004 - Volume I - Issue I

The purpose of this report is to highlight the importance of verifying the integrity and dielectric strength of insulating oil, following the storage of voltage regulators. Prior to energizing a regulator that has been stored, it is imperative to verify the acceptable condition of the insulating oil. If during storage a gasket seal or a pipe threaded seal has been compromised, there is the possibility that moisture can be drawn into the tank as a result of natural temperature changes. Sufficient amounts of the insulating oil can affect the integrity and dielectric strength of the insulating oil which could cause a catastrophic failure of the regulator. Such failure could result in serious personal injury including death.


As to the free-breathing voltage regulators (advertised as unidirectional breathers) manufactured by Allis-Chalmers, Siemens-Allis, Inc., and Siemens Power Transmission & Distribution, Inc., these regulators were typically shipped from the factory with caps to "seal" the breather pipes. The corresponding operator's manuals instruct the user to replace the caps with manufacturer supplied with manufacturer supplied screens, except when the regulator is being transported. Accordingly, use of breather caps during storage is not the manufacturer's recommended use for the caps. Incorrect use of the caps could lead to an incomplete seal of the breather pipes. Ambient temperature swings occurring during storage could create a vacuum within the tank, possibly causing condensation to be drawn into the regulator tank. Corresponding potential deterioration of the oil integrity could result in catastrophic failure of the regulator upon subsequent energization. In sum, we highlight the importance of proper storage of voltage regulators. Furthermore, we stress the importance of verifying the integrity of insulating oil prior to energization.