ABB RELION REX640 Engineering Manual page 7

Safety information
Dangerous voltages can occur on the connectors, even though the
auxiliary voltage has been disconnected.
Non-observance can result in death, personal injury or substantial
property damage.
Only a competent electrician is allowed to carry out the electrical
installation.
National and local electrical safety regulations must always be
followed.
The frame of the protection relay has to be carefully earthed.
The protection relay contains components which are sensitive to
electrostatic discharge. Unnecessary touching of electronic
components must therefore be avoided.
Whenever changes are made in the protection relay, measures should
be taken to avoid inadvertent tripping.