Patent ID: 9128477
Filing Date: 2015-09-08
Classification: G01R,G05B

Abstract:
1. A device for diagnosing the status of an electrical apparatus having a sealed fluid based insulating system, the device comprising: at least one input for receiving measurements of a current running through the device and measurements of an actual apparatus fluid pressure; at least one surrounding temperature sensor for receiving surrounding temperature measurements, the at least one surrounding temperature sensor being connected to the at least one input; a transformer; a sealed bushing attached to the transformer, the sealed bushing including a sealed chamber comprising a first liquid insulating medium, a second gas insulating medium, an insulation, an electrical conductor, and a pressure sensor in the sealed chamber and in contact with the first liquid insulating medium; and a diagnosing unit, the diagnosing unit configured to perform diagnosis of the sealed bushing, wherein the diagnosing unit comprises: means for measuring current within the electrical conductor, means for determining a pressure of the first insulating medium based upon the current within the electrical conductor, means for determining a pressure of the second insulating medium based on the current within the electrical conductor, means for combining the pressure of the first insulating medium and the second insulating medium to determine a corresponding theoretical apparatus fluid pressure, means for receiving actual apparatus fluid pressure from the at least one input unit, means for comparing the actual apparatus fluid pressure with the theoretical apparatus fluid pressure, and means for diagnosing the status of the apparatus based on the comparison, wherein the theoretical fluid pressure is determined based on a model of the change in fluid pressure in relation to apparatus temperature.