GE 750 Instruction Manual page 33

CHAPTER 1: GETTING STARTED
1.4.2 S2 System Setpoints
750 FEEDER MANAGEMENT RELAY – INSTRUCTION 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.
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
setpoints page:
SENSING
"600 A"
PHASE CT PRIMARY:
Since the example does not contemplate a ground CT, the setpoints for
and can be left unchanged. For additional information refer to Current
SENSTV GND CT
Sensing on page 5–22.
For voltage transformers, make the following changes in the
setpoints page:
SENSING
APPLICATION EXAMPLE
S2 SYSTEM SETUP  CURRENT
GND CT PRIMARY
S2 SYSTEM SETUP  BUS VT
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