The present invention relates to a power source coupling for connecting two power coupling parts (5, 6): a first power coupling part (5) which is mounted on a first component (1) so as to be longitudinally displaceable and has a first connecting plate (16) with one or more first power coupling elements (18), and a second power coupling part (6) which is mounted on a second component (4) so as to be displaceably mounted between a first and a second position. The second power coupling part (6) has a second connecting plate (17) with one or more second power coupling elements (19) which are able to cooperate with the first power coupling elements (18) when the first power coupling part (5) is in the first position. A protective element (51) is provided on the first power coupling part (5) so as to be adjustable in position, and which in the first position of the power coupling part (5) covers the first power coupling elements (18) when the second power coupling part (6) is not attached, and in the second position of the power coupling part (5) is in an open position.