To provide an emergency connection circuit which can speedily, easily and safely constitute an emergency connection circuit by a preliminary transformer when a transformer connected between a bus bar and a plurality of branch lines breaks down, and to provide a connection device used for the emergency connection circuit.

Connection to sides of branch lines 72, 76 and 80 in the preliminary transformer 106 is performed by connecting the connection device 14 to an input terminal 118 after a preliminary branch line breaker 86 is detached from a preliminary branch line 84. The connection device 14 has a truck which can move on rails of the preliminary branch line breaker 86 and a relay electrode terminal which is arranged in the truck and in which one end is connected to a connection terminal of a cable 110 connected to the preliminary transformer 106 and other end is connected to the input terminal 118 of the preliminary branch line breaker 86. Thus, the emergency connection circuit by the preliminary transformer can speedily, easily and safely be constituted. An electric isolation distance between a connection point of the preliminary breaker with a branch line side and the other high pressure unit can sufficiently be secured.