While operating DC railways with running rails as return conductor, various ground resistances generate voltages that might be dangerous for humans or buildings. One of the measures to protect humans from impermissible contact voltages is the temporary short-circuiting of the various grounding systems according to DIN EN 50122-1.

This measurement device monitors the potentials of the connected grounds and evaluates the occurring voltages (referring to technical specifications). The voltage between the two earths respectively return conductor that are to be monitored is continuously measured.

By exceeding the threshold setting a switching command is given via a potential-free changeover for the activation of further devices such as an earth short circuiting device or isolation switch.

Available from Witt are three products for this purpose:

EPM 80

EPM 100