Manual MRM3-2 GB
Woodward
TD_MRM3-2_09.08_GB_Rev.New
9
Figure 3.3: Measuring of earth current with core-type CT (IE)
With the combination of phase and earth current measuring, CTs to be connected according to
Figure 3.2. and Figure 3.3.
3.1.1 Analog Inputs
The analog input signals of the phase currents I
L1
(B3 - B4), I
L2
(B5 - B6), I
L3
(B7 - B8) and the earth
current I
E
(B1 - B2) are fed to the protection device via separate input CTs.
The current measuring quantities are galvanic decoupled, analogously filtered, and then fed to the
analog/digital converter.
3.1.2 Output Relays
The MRM3-2 has 5 output relays. Two of these relays with two change-over contacts and three re-
lays with one change-over contact each are used for signaling. The protective functions can be
freely allocated except of those for the self-supervision relay.
•
Relay 1: C1, D1, E1 and C2, D2, E2
•
Relay 2: C3, D3, E3 and C4, D4, E4
•
Relay 3: C5, D5, E5
•
Relay 4: C6, D6, E6
•
Relay 5: Self-supervision C7, D7, E7
All relays are operating according to the n. o. principle with the exception of the self-supervision re-
lay, which operates acc. to the n. c. principle.
