Abstract: The present invention relates to a method and a monitoring system, for monitoring a vacuum on-load tap changer. The tap changer includes a housing with insulating fluid, a diverter switch inside of the housing and including at least one movable contact and at least two vacuum interrupters, and at least one pressure sensor which measures the pressure in the housing. The method, which is performed by a processing circuitry in the system, includes determining a pressure signature, including two succeeding peaks within a time interval, continuously measuring the pressure, detecting when the measured pressure shows the pressure signature, determining, based on the measured pressure within the pressure signature, the time between the first rise in pressure and the second drop, and setting the determined time to represent the switch time of the diverter switch.

Abstract: The present invention relates to a method and a monitoring system, for monitoring a vacuum on-load tap changer. The tap changer includes a housing with insulating fluid, a diverter switch inside of the housing and including at least one movable contact and at least two vacuum interrupters, and at least one pressure sensor which measures the pressure in the housing. The method, which is performed by a processing circuitry in the system, includes determining a pressure signature, including two succeeding peaks within a time interval, continuously measuring the pressure, detecting when the measured pressure shows the pressure signature, determining, based on the measured pressure within the pressure signature, the time between the first rise in pressure and the second drop, and setting the determined time to represent the switch time of the diverter switch.

Abstract: The present disclosure relates to a method of monitoring switching by an on-load tap changer (OLTC) 1 from a first contact 3a to a second contact 3b of a transformer winding 2. The method includes measuring a voltage of the transformer. The method also includes measuring a temperature of the OLTC. The method also includes, based on the measured voltage and temperature, determining whether the switching from the first contact to the second contact has been successful.

Abstract: The present disclosure relates to a method of monitoring switching by an on-load tap changer (OLTC) 1 from a first contact 3a to a second contact 3b of a transformer winding 2. The method includes measuring a voltage of the transformer. The method also includes measuring a temperature of the OLTC. The method also includes, based on the measured voltage and temperature, determining whether the switching from the first contact to the second contact has been successful.

Abstract: A method and a device for diagnosing the status of an electrical apparatus having a sealed fluid based insulating system. The device includes at least one input for receiving measurements of a current running through the apparatus and measurements of an actual apparatus fluid pressure as well as a diagnosing unit. The diagnosing unit determines a corresponding theoretical apparatus fluid pressure based on the measured current, compares the actual apparatus fluid pressure with the theoretical apparatus fluid pressure and diagnoses the status of the apparatus based on the comparison.

Abstract: 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.

Abstract: A method and a device for diagnosing the status of an electrical apparatus having a sealed fluid based insulating system. The device includes at least one input for receiving measurements of a current running through the apparatus and measurements of an actual apparatus fluid pressure as well as a diagnosing unit. The diagnosing unit determines a corresponding theoretical apparatus fluid pressure based on the measured current, compares the actual apparatus fluid pressure with the theoretical apparatus fluid pressure and diagnoses the status of the apparatus based on the comparison.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: The present invention discloses a method and apparatus (5) for condition diagnosing of an inductive power device (1), such as a transformer or reactor, having power windings (2) immersed in a fluid (3) being cooled by cooling devices (4). The diagnosing method basically compares and evaluates expected heat flows into and out from the inductive power device (1) system together with an actual and a previous heat content of such a system. From the heat flows the heat balance in the system may be obtained and is used for diagnosing the operation conditions of the inductive power device (1). The results from the condition diagnosing may be used as indicators (70) that can alarm operators, may be sent as a data signal (80) to remote and/or portable display means (85), such as a computer, or may be used as input data to control or simulation systems.

Abstract: 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 then extracted from the pressure diagram. The method, preferably used for single-phase tap changers, comprises the step of relating quantities from pressure peaks to specific arcings of the switching sequence. Early error detection is achieved, whereby transformed failures may be avoided. Repeated measurements ae followed by trend evaluation. If a trend indicating tap changer problems is detected, an alarm signal is triggered. The invention may include switching off the transformer if the pressure exceeds a predetermined emergency value as well as extracting information of the base pressure in the tap changer and converting it to level of insulating liquid.

Abstract: The present invention discloses a method and apparatus (5) for condition diagnosing of an inductive power device (1), such as a transformer or reactor, having power windings (2) immersed in a fluid (3) being cooled by cooling devices (4). The diagnosing method basically compares and evaluates expected heat flows into and out from the inductive power device (1) system together with an actual and a previous heat content of such a system. From the heat flows the heat balance in the system may be obtained and is used for diagnosing the operation conditions of the inductive power device (1). The results from the condition diagnosing may be used as indicators (70) that can alarm operators, may be sent as a data signal (80) to remote and/or portable display means (85), such as a computer, or may be used as input data to control or simulation systems.

Abstract: The present invention discloses a method and apparatus (4) for condition diagnosing of a tap changer (1) immersed in a cooling fluid (3), controlling and regulating an inductive power device (5), such as a transformer or reactor. The diagnosing method basically compares and evaluates expected heat exchanges between the tap changer (1) and ambient air and the inductive power device (5), an expected amount of heat generated by the tap changer (1) during operation, together with an actual temperature of the fluid (3). 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 (1). The results from the condition diagnosing may be used as indicators (70) that can alarm operators or may be sent as a data signal (78) to remote and/or portable display means (79), such as a computer.

Abstract: The invention relates to a condenser body for field control in transformer bushings and the connection of the body to the conductor of a transformer winding for transformers used in HVDC converter plants. The condenser body is arranged as a solid of revolution with concentrically laid condenser layers. It is formed from one end with an outwardly-directed straight frustum of a cone and from the other end with an inwardly-directed straight frustum of a cone.