Neutral Protection Settings; S2 System Setpoints - GE Multilin 750 Quick Reference Manual

Neutral protection settings

1. Time Overcurrent 1 (function 51N1):
• Curve shape = Moderately Inverse
• Pickup = 120 A
• Multiplier = 10
2. Instantaneous Overcurrent 1 (function 50N1):
• Pickup = 120 A
• Phases required = Any two
• Delay = 0 seconds
3. Instantaneous Overcurrent 2 (function 50N2):
• Pickup = 2000 A
• Phases required = Any two
• Delay = 0 seconds
The above data will be used to configure the relay protection. In this example, the relay will
be used for Phase and Neutral Overcurrent protection only; that is, functions 51P1, 50P1,
50P2, 51N1, 50N1, and 50N2.
In this manual, Neutral Overcurrent is to the residual current, calculated from the currents
measured at the phase CT inputs: terminals G7-H7 for phase A, G8-H8 for phase B and G9-
H9 for phase C. Since it is a calculated value, it cannot be used to generate oscillography.
Ground Overcurrent refers to the current measured at terminals G10-H10, or at terminals
G3-H3 for Sensitive Ground Overcurrent, when the relay is fitted to measure sensitive
ground current.
You should now be familiar with maneuvering through and editing setpoints. As such, we
will now limit our discussion to just the values that must be programmed, in order to meet
the requirements of the example application. Any setpoints not explicitly mentioned should
be left at the factory default value.

S2 System setpoints

The S2 setpoints page contains setpoints for entering the characteristics of the equipment
on the feeder electrical system. In our example, these characteristics are specified under
the Power System Data and Instrument Transformer Data headings in the previous sub-
section. From this information and the resulting calculations, program the page S2
setpoints as indicated.
For current transformers, make the following change in the
SENSING setpoints page:
PHASE CT PRIMARY
Since the example does not contemplate a ground CT, the setpoints for
and SENSTV GND CT
of the 750/760 instruction manual.
For voltage transformers, make the following changes in the
SENSING setpoints page:
VT CONNECTION
NOMINAL VT SECONDARY
750/760 Quick Reference Guide
: "600 A"
can be left unchanged. For additional information refer to Chapter 5
TYPE: "Delta"
VOLTAGE: "115.0 V"
Application example
S2 SYSTEM SETUP
GND CT
S2 SYSTEM SETUP
CURRENT
PRIMARY,
BUS VT
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