Socket electrical connector and plug electrical connector

The invention relates to a socket electrical connector and a plug electrical connector. The socket electrical connector is provided with an insulator, a holding cavity sunk from the insulator, a first and a second clapper that are extended into the holding cavity and located at different heights, a first and a second terminal arranged on the first and the second clapper respectively, and additional power source terminals arranged at two sides of the second clapper. The holding cavity comprises a first and a second holding cavity with different sizes that are communicated with each other and hold the first and the second clapper. The plug electrical connector comprises a first and a second space used for butt jointing the first and the second clapper. The second space is provided with plug additional power source terminals. The plug electrical connector can be fully plug-connected into the socket electrical connector, the second holding cavity of the socket electrical connector can be used for plug-connecting