System for recording physical variables of at least one component of a tap-changing transformer and for monitoring the at least one component of the tap-changing transformer, comprising: at least one sensor (7 1, 7 2,..., 7 N) for recording the physical variables of the at least one component of the tap-changing transformer and having a computer which is communicatively connected to a measuring device which is communicatively connected to the at least one sensor (7 1, 7 2,..., 7 N) for the purpose of receiving the physical variables of the at least one component of the tap-changing transformer, wherein the system has the following features: • a receiving area which is designed to receive the physical variables collected in the measuring device as a function of the time of the at least one sensor (7 1, 7 2,..., 7 N); • a data processing area which filters the physical variables as a function of the time of the at least one component of the tap-changing transformer and uses the filtered signals to create a high-resolution envelope curve representing a signal level of the physical variable of the at least one component; and • a data analysis area which determines a first limit value curve and a second limit value curve, the position of which can be changed in the direction of an ordinate, wherein the values of the first limit value curve represent a limit value, • wherein the first limit value curve and the second limit value curve are updated on the basis of envelope curves for subsequently measured physical variables using the first limit value curve and the second limit value curve for previously measured physical variables, wherein the values of the first limit value curve represent a limit value, and • wherein, in order to determine the first and second limit value curves, o an envelope curve obtained by means of data reduction is generated from the high-resolution envelope curve, o the envelope curve is determined using a multiplicity of supporting points which are determined on the basis of the high-resolution envelope curve, o the envelope curve is spread by setting a function at each supporting point, characterized in that o the function which is set at each supporting point of the envelope curve is an asymmetrical function which is open at the bottom, in particular a parabola which is open at the bottom and is narrower on the left than on the right. • a receiving area which is designed to receive the physical variables collected in the measuring device as a function of the time of the at least one sensor (7 1, 7 2,..., 7 N); • a data processing area which filters the physical variables as a function of the time of the at least one component of the tap-changing transformer and uses the filtered signals to create a high-resolution envelope curve representing a signal level of the physical variable of the at least one component; and • a data analysis area which determines a first limit value curve and a second limit value curve, the position of which can be changed in the direction of an ordinate, wherein the values of the first limit value curve represent a limit value, • wherein the first limit value curve and the second limit value curve are updated on the basis of envelope curves for subsequently measured physical variables using the first limit value curve and the second limit value curve for previously measured physical variables, wherein the values of the first limit value curve represent a limit value, and • wherein, in order to determine the first and second limit value curves, o an envelope curve obtained by means of data reduction is generated from the high-resolution envelope curve, o the envelope curve is determined using a multiplicity of supporting points which are determined on the basis of the high-resolution envelope curve, o the envelope curve is spread by setting a function at each supporting point, characterized in that o the function which is set at each supporting point of the envelope curve is an asymmetrical function which is open at the bottom, in particular a parabola which is open at the bottom and is narrower on the left than on the right. o an envelope curve obtained by means of data reduction is generated from the high-resolution envelope curve, o the envelope curve is determined using a multiplicity of supporting points which are determined on the basis of the high-resolution envelope curve, o the envelope curve is spread by setting a function at each supporting point, characterized in that o the function which is set at each supporting point of the envelope curve is an asymmetrical function which is open at the bottom, in particular a parabola which is open at the bottom and is narrower on the left than on the right.