A method for monitoring transformer bushings, comprising: recording time series comprising information from a first bushing sensor, a second bushing sensor, a third bushing sensor, and a fourth bushing sensor, wherein the first bushing sensor and the second bushing sensor are connected to a common first phase of a high voltage source, and the third bushing sensor and the fourth bushing sensor are connected to a common second phase of the high voltage source; generating a first time series comprising information from the first bushing sensor and the second bushing sensor during a predetermined time interval; generating a second time series, substantially simultaneously with the first time series, comprising information from the third bushing sensor and the fourth bushing sensor during the predetermined time interval; characterized in that the method further comprises: generating a correlation model for the first time series and the second time series; measuring a first signal corresponding to a measurement of the first time series; measuring a second signal corresponding to a measurement of the second time series; determining a difference between the measured first signal or the measured second signal, and an estimated first signal or an estimated second signal being estimated by means of the correlation model and the measured second or first signal; generating a signal indicative of a bushing problem if it is determined that the determined difference is larger than a predetermined threshold value. recording time series comprising information from a first bushing sensor, a second bushing sensor, a third bushing sensor, and a fourth bushing sensor, wherein the first bushing sensor and the second bushing sensor are connected to a common first phase of a high voltage source, and the third bushing sensor and the fourth bushing sensor are connected to a common second phase of the high voltage source; generating a first time series comprising information from the first bushing sensor and the second bushing sensor during a predetermined time interval; generating a second time series, substantially simultaneously with the first time series, comprising information from the third bushing sensor and the fourth bushing sensor during the predetermined time interval; characterized in that the method further comprises: generating a correlation model for the first time series and the second time series; measuring a first signal corresponding to a measurement of the first time series; measuring a second signal corresponding to a measurement of the second time series; determining a difference between the measured first signal or the measured second signal, and an estimated first signal or an estimated second signal being estimated by means of the correlation model and the measured second or first signal; generating a signal indicative of a bushing problem if it is determined that the determined difference is larger than a predetermined threshold value. generating a correlation model for the first time series and the second time series; measuring a first signal corresponding to a measurement of the first time series; measuring a second signal corresponding to a measurement of the second time series; determining a difference between the measured first signal or the measured second signal, and an estimated first signal or an estimated second signal being estimated by means of the correlation model and the measured second or first signal; generating a signal indicative of a bushing problem if it is determined that the determined difference is larger than a predetermined threshold value.