System; Current Sensing - GE Multilin 850 Instruction Manual

CHAPTER 4: SETPOINTS

System

Current Sensing

850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 4-15: System Display Hierarchy
The Current Sensing menu provides the setup menu for the Current Transformers (CTs)
connected to the 850 terminals. The setup of the three-phase CTs, the Ground CT, and the
Sensitive Ground CT requires a selection of primary CT ratings. The secondary CT ratings
are selected in the 850 Order code. The CT inputs are grouped in banks of four currents on
the 850 – three inputs for phase currents A, B, and C, and one input for ground current. The
basic AC card has two AC banks, definable at the time of ordering the relay with either one
bank currents and one bank voltages.
The 850 Feeder Protection System has 9 AC inputs, 8 of which reside on the card inserted
in slot J, and one on the card inserted in slot K.
The 8 AC inputs from the card inserted in slot J are as follow:
• four AC input currents, i.e. 3 CTs for phase currents and 1 CT for the ground or residual
connection current
• four AC input voltages, i.e. 3 VTs for phase voltages and 1 VT for the auxiliary voltage
The single AC input from the card inserted in slot K is used to connect to the sensitive
ground CT for measuring small currents which cannot be correctly measured by a
standard type of current input.
The Current sensing selection for the 850 is organized in a menu as shown:
Path:
Setpoints > System > Current Sensing > CT Bank 1-J1
CT BANK NAME
Range: up to 13 alphanumeric characters
Default: CT Bank 1-J1
SYSTEM
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