A transformer, particularly a medium frequency transformer, comprising: a transformer core having a first core leg having a first longitudinal axis and second core leg having a second longitudinal axis; a first low voltlage, LV, winding arranged around the first core leg, the first LV winding extending along a first length in the direction of the first longitudinal axis; a first high voltage, HV, winding arranged around the first LV winding, the first HV winding extending along a second length in the direction of the first longitudinal axis, wherein the second length is shorter than the first length; a second LV winding arranged around the second core leg, the second LV winding extending along a third length in the direction of the second longitudinal axis; a second HV winding arranged around the second LV winding, the second HV winding extending along a fourth length in the direction of the second longitudinal axis, wherein the fourth length is shorter than the third length; wherein the first HV winding is provided with a first HV connector and a second HV connector of the transformer, each extending substantially perpendicular away from the first longitudinal axis, and wherein the second HV winding is provided with a third HV connector and a fourth HV connector of the transformer, each extending substantially perpendicular away from the second longitudinal axis, characterised in that the transformer further comprises a first field grader having two plate elements between which an end of the first HV connector is arranged, a second field grader having two plate elements between which an end of the third HV connector is arranged, and a third field grader having two plate elements between which an end of the second HV connector and an end of the fourth HV connector are arranged. a transformer core having a first core leg having a first longitudinal axis and second core leg having a second longitudinal axis; a first low voltlage, LV, winding arranged around the first core leg, the first LV winding extending along a first length in the direction of the first longitudinal axis; a first high voltage, HV, winding arranged around the first LV winding, the first HV winding extending along a second length in the direction of the first longitudinal axis, wherein the second length is shorter than the first length; a second LV winding arranged around the second core leg, the second LV winding extending along a third length in the direction of the second longitudinal axis; a second HV winding arranged around the second LV winding, the second HV winding extending along a fourth length in the direction of the second longitudinal axis, wherein the fourth length is shorter than the third length; wherein the first HV winding is provided with a first HV connector and a second HV connector of the transformer, each extending substantially perpendicular away from the first longitudinal axis, and wherein the second HV winding is provided with a third HV connector and a fourth HV connector of the transformer, each extending substantially perpendicular away from the second longitudinal axis, characterised in that the transformer further comprises a first field grader having two plate elements between which an end of the first HV connector is arranged, a second field grader having two plate elements between which an end of the third HV connector is arranged, and a third field grader having two plate elements between which an end of the second HV connector and an end of the fourth HV connector are arranged.