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 (L1) 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 (L2) in the direction of the first longitudinal axis , wherein the second length (L2) is shorter than the first length (L1); a second LV winding arranged around the second core leg , the second LV winding extending along a third length (L3) 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 (L4) in the direction of the second longitudinal axis , wherein the fourth length (L4) is shorter than the third length (L3); 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 (L1) 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 (L2) in the direction of the first longitudinal axis , wherein the second length (L2) is shorter than the first length (L1); a second LV winding arranged around the second core leg , the second LV winding extending along a third length (L3) 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 (L4) in the direction of the second longitudinal axis , wherein the fourth length (L4) is shorter than the third length (L3); 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. <EOS>