A bus bar connection device comprising: - a first bushing having a first connection surface that is an end of an internal stem conductor stuck out of a nose of the first bushing; - a second bushing having a second connection surface that is an end of an internal stem conductor stuck out of a nose of the second bushing; - a connection element to electrically connect the first connection surface with the second connection surface, - the first bushing having the same axis as the second bushing when the bus bar connection device is in connected position, - the first connection surface of the first bushing being placed opposite to the second connection surface of the second bushing when the bus bar connection device is in connected position; and - a tube-like insulation adapter surrounding the nose of the first bushing, the nose of the second bushing, and the connection element as one when the bus bar connection device is in connected position, wherein the connection element includes a combination of a cup-like socket conductor and a bar-like plug conductor, the plug conductor being fitted into the socket conductor, the fitting interface being conjugate sliding contact, and wherein the adapter 20 has a cylindrical conductive layer on its inner side and an encircling channel that is a broader-radius portion near the middle of a cavity of the adapter, and a rim that is an edge of a bank of the encircling channel inside the adapter at the conductive layer, an inner diameter of the adapter being the smallest at the rim, wherein the outer diameter of the socket conductor is larger than the inner diameter of the rim, and wherein the encircling channel has an inner diameter larger than the outer diameter of the socket conductor, characterized in that the bank, which is perpendicular to the axis of the adapter, is configured to be pushed by the edge of the socket conductor, when the socket conductor is fixed to the first connecting surface of the first bushing which is inserted into the adapter, so that the bushing is not pulled out of from the adapter. - a first bushing having a first connection surface that is an end of an internal stem conductor stuck out of a nose of the first bushing; - a second bushing having a second connection surface that is an end of an internal stem conductor stuck out of a nose of the second bushing; - a connection element to electrically connect the first connection surface with the second connection surface, - the first bushing having the same axis as the second bushing when the bus bar connection device is in connected position, - the first connection surface of the first bushing being placed opposite to the second connection surface of the second bushing when the bus bar connection device is in connected position; and - a tube-like insulation adapter surrounding the nose of the first bushing, the nose of the second bushing, and the connection element as one when the bus bar connection device is in connected position, wherein the connection element includes a combination of a cup-like socket conductor and a bar-like plug conductor, the plug conductor being fitted into the socket conductor, the fitting interface being conjugate sliding contact, and wherein the adapter 20 has a cylindrical conductive layer on its inner side and an encircling channel that is a broader-radius portion near the middle of a cavity of the adapter, and a rim that is an edge of a bank of the encircling channel inside the adapter at the conductive layer, an inner diameter of the adapter being the smallest at the rim, wherein the outer diameter of the socket conductor is larger than the inner diameter of the rim, and wherein the encircling channel has an inner diameter larger than the outer diameter of the socket conductor, characterized in that the bank, which is perpendicular to the axis of the adapter, is configured to be pushed by the edge of the socket conductor, when the socket conductor is fixed to the first connecting surface of the first bushing which is inserted into the adapter, so that the bushing is not pulled out of from the adapter.