Method and device for testing a tap changer of a transformer

Apparatus for testing a complete tap changer of a multi-phase transformer having a winding comprising a plurality of taps between which the tap changer can be switched, wherein a separate tap changer is present for each phase of the multi-phase transformer and each separate tap changer is designed to change a transmission ratio of the transformer, wherein the apparatus comprises:

• a test signal generation device, a measuring device and a control device,
• wherein the apparatus is designed to supply a respective test signal for each phase of the multi-phase transformer to the winding of the multi-phase transformer assigned to the respective phase and to the tap changer by means of the test signal generation device and the control device,
• wherein the apparatus is designed to repeatedly actuate the tap changer to cause the tap changer to switch between each of the plurality of taps in order to change the transmission ratio with each actuation and test completely the tap changer,
• wherein the apparatus is designed to determine a curve of an electrical measurement variable of the multi-stage transformer by means of the measuring device over time respectively during each switch of the tap changer between each of the plurality of taps depending on the test signal,
• wherein the control device is designed to filter the curves in order to prevent selected curves from the switching between selected taps of the plurality of taps from being output, and
• wherein the control device is designed to output the filtered curves representing complete testing of the tap changer.