The protection of the insulation monitoring device is necessary to protect the device from short circuits, in particular at the end of the equipment useful life. Without a suitable protection, a fire could be produced which should damage seriously the switchboard.For these reasons, in accordance with the IEC 60364 reference standard, the switchboard manufacturer cannot ignore the duty of protection.
It is also true that the insulation monitoring device cannot be accidentally disconnected for several reasons:
- QSO Switchboards are equipped with a locked door. Only qualified and authorized personnel are expected to open it.
- The E 91hN/32 fuse holder that protects the insulation monitoring device has no disconnecting performance under load, and therefore, in order to open the handle it is necessary to operate on the circuit upstream, disconnecting this way the operating theatre from the supply.
- The E 91hN/32 fuse holder is sealed, and it may only be opened intentionally.