Woodward highprotec MRI4, User Manual

Page: 48 / 727

Installation and Connection
Current Transformers (CT)
Check the installation direction.
It is imperative that the secondary sides of measuring transformers be
grounded.
The current measuring inputs may exclusively be connected to current
measuring transformers (with galvanic separation).
CT secondary circuits must always to be low burdened or short-circuited during
operation.
For current and voltage sensing function external wired and appropriate current
and voltage transformer shall be used, based on the required input
measurement ratings. Those devices provide the necessary insulation
functionality.
All current measuring inputs can be provided with 1 A or 5 A nominal. Make
sure that the wiring is correct.
Sensitive Ground Current Measurement
The proper use of sensitive current measuring inputs is the measurement of small currents like they could occur in
isolated and high resistance grounded networks.
Due to the sensitiveness of these measuring inputs don´t use them for the measurement of ground short circuit
currents like they occur in solidly earthed networks.
If a sensitive measuring input should be used for the measurement of ground short circuit currents, it has to be
ensured, that the measuring currents are transformed by a matching transformer according to the technical data of
the protective device.
48 MRI4 DOK-HB-MRI4-2E