The residual current transformer should be installed in a place that is easy to access and keep away from strong magnetic fields. There is no problem with the installation of the transformer. The transformer can be hung directly on the cable or fixed in the distribution box.
The residual current transformer installation and the upper or lower end of the switch breaker do not affect the monitoring of the protected line. However, in order to facilitate maintenance in the future, it is better to install at the lower port of the switch. It is not necessary to power off the upper switch during power failure maintenance, and only need to disconnect the switch at this level.