To facilitate inspection or the like by locking an electric wire inserted from an electric wire introduction port of a easing body on an opening part side, providing a removable terminal block terminal, and arranging a clearance between the easing inside wall and the terminal.

In setting of a current/voltage converter 21, an electric wire 29 is passed through an electric wire introduction port 26, an opening part 24 in a casing body 22 is opened so that a terminal block terminal 27 and a measurement unit 23 are connected together via the electric wire 32, and the terminal 27 is inserted through the opening part 24 so as to be positioned in a mounting position of the easing body 22. As a notch 36 is arranged in the terminal 27, a clearance is generated between the casing body 22 inside wall and the terminal 27, so that the electric wire 29 can be avoided. Then, the terminal 27 is fixed to the casing body 22 by means of a bolt 31, while the electric wire 29 is fixed to a terminal block 28, and the opening part 24 is closed by means of a lid body 25. For cleaning/inspection, the opening part 24 is opened, the bolt 31 is removed, and the terminal 27 is pulled out with the electric wire 29 left installed in the terminal block 28. The terminal 27 can be pulled out easily through the notch 36.