Micom P634 - Connection; Connecting Measuring and Auxiliary Circuits

5.6 Connection
The P634 Transformer Differential Protection Device must be connected in
accordance with the terminal connection diagram as indicated on the type
identification label. The relevant terminal connection diagrams that apply to the
P634 are to be found either in the supporting documents supplied with the
device, or in Section 5.7, (p. 5-22).
In general copper conductors with a cross section of 2.5 mm² (US: AWG12) are
sufficient to connect a system current transformer to a current input on the P634.
To reduce CT knee-point voltage requirements, it may be necessary to install
shorter copper conductors with a greater cross section between the system
current transformers and the current inputs on the P634. Copper conductors
having a cross section of 1.5 mm² (US: AWG14) are adequate to connect binary
signal inputs, the output relays and the power supply input.
All connections run into the system must always have a defined potential.
Connections that are pre-wired but not used should preferably be grounded when
binary inputs and output relays are isolated. When binary inputs and output
relays are connected to common potential, the pre-wired but unused connections
should be connected to the common potential of the grouped connections.
5.6.1 Connecting Measuring and Auxiliary Circuits
5.6.1.1 Power Supply
Before connecting the auxiliary voltage V
A
for the P634 power supply, it must be
ensured that the nominal value of the auxiliary device voltage corresponds with
the nominal value of the auxiliary system voltage.
5.6.1.2 Current-Measuring Inputs
When connecting the system transformers, it must be ensured that the
secondary nominal currents of the system and the device correspond.
WARNING
The secondary circuit of live system current transformers must not be
opened! If the secondary circuit of a live CT is opened, there is the danger
that the resulting voltages will endanger personnel and damage the
insulation.
WARNING
For pin-terminal connection devices, the terminal block for system current
transformer connection is not a shorting block! Therefore always short-circuit
the system current transformers before loosening the threaded terminals.
5.6.1.3 Connecting the Measuring Circuits
The system current transformers must be connected in accordance with the
standard schematic diagram shown in Fig. 5-9, (p. 5-14). It is essential that the
grounding configuration shown in the diagram be followed. If the CT or VT
5 Installation and Connection
P634
P634/EN M/R-42-A // P634‑311‑653 5-13