Avo do such a meter (LT7), I would think most manufacturers would have a meter to do this.
As to why, Well you need one to Measure Ze (Earth fault loop impedance, external to the installation)& Zs* (Earth fault loop impedance of the cct under test)
These Values are needed when filling in Certificates on work completed. And also more importantly to verify if the cct is in a good condition (Zs low enough) so that under a fault the protective device will operate in the required time.
* this value can be derived from calculation as well as measurement Zs=Ze + (R1+R2)
