Abb Technology Ltd

Abb Schweiz Ag

Abb Technology Ag

Hitachi Energy Ltd

Abb Power Grids Switzerland Ag

Gunnar Andersson

Tommy Larsson

Bengt-Olof Stenestam

Jim Andersson

Pontus Sundqvist

A method for determining the relative humidity of an insulating liquid filled electric apparatus including a container containing insulating liquid and gas, a communication unit providing communication between the gas of the container and gas of an external environment, and providing dehydration of gas passing through the communication unit, wherein the method includes: continuously measuring and storing the relative humidity of the gas in the container, calculating an average value of the relative humidity in the gas based on the stored humidity measurements during a certain time period, and determining the relative humidity of the insulating liquid based on the average value of the relative humidity in the gas and a relationship between the relative humidity of the gas and the relative humidity of the insulating liquid at equilibrium.

Method and device for determining the relative humidity of an insulating liquid filled electric apparatus

A universal control and diagnostic system for a transformer that may be retrofit with existing control and tap-changer equipment, the system providing for remote monitoring and control of the equipment and for measuring various criteria associated with the tap-changer to substantially minimize damage to the equipment during a maneuver and for substantially avoiding carbonization of a connected contact.

Control system for a transformer or reactor

A method and means for diagnosing transformer tap changers is provided. Pressure is monitored in an insulating liquid of a tap changer for a period of time in which switching of the tap changer is carried through. Switching-related information is extracted from the pressure diagram. Quantities from pressure peaks are related to specific arcings of the switching sequence. Early error detection is achieved, whereby transformed failures may be avoided. Repeated measurements may be followed by trend evaluation. If a trend indicating tap changer problems is detected, an alarm signal is triggered. The transformer may be switched off if the pressure exceeds a predetermined emergency value. Information of the base pressure in the tap changer may be extracted and converting it to level of insulating liquid.

Tap changer monitoring

A method and apparatus for condition diagnosing of a tap changer immersed in a cooling fluid, controlling and regulating an inductive power device, such as a transformer or reactor. The diagnosing method compares and evaluates expected heat exchanges between the tap changer and ambient air and the inductive power device, an expected amount of heat generated by the tap changer during operation, together with an actual temperature of the fluid. From the actual temperature, expected heat exchanges and expected generated heat, the heat balance in the system may be obtained and is used for disgnosing the operation conditions of the tap changer. The results from the condition diagnosing may be used as indicators that can alarm operators or may be sent as a data signal to remote and/or portable display means, such as a computer.

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Nyhammar, Sweden

Gunnar Andersson