GE 889 - Page 519

CHAPTER 4: SETPOINTS FLEXLOGIC
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–389
HYSTERESIS
Range: 0.1 to 50.0% in steps of 0.1%
Default: 3.0%
This setting defines the pickup – drop out relation of the element by specifying the width
of the hysteresis loop as a percentage of the pickup value as shown above in the
Direction, Pickup, and Hysteresis setpoints figure.
RATE OF CHANGE TIME UNIT (dt)
Range: millisecond, second, minute
Default: milliseconds
This setting specifies the time base dt when programming the FlexElement as a rate of
change element.
The setting is applicable only if the Operating Mode is set to “Delta”.
RATE OF CHANGE TIME
Range: 40 to 65535 in steps of 1
Default: 40
This setting specifies the duration of the time interval for the rate of change mode of
operation.
The setting is applicable only if the Operating Mode is set to “Delta”.
EXAMPLES
13.8 kV power system:
• Phase VT Connection: Wye
• Phase VT Secondary: 66.4 V
• Phase VT Ratio: 120:1 (phase to neutral primary voltage = 120*66.4 = 7968 V)
• Aux VT Connection: Vab
• Aux VT Secondary: 115 V
• Aux VT Ratio: 120:1(phase-phase primary voltage = 13800V)
• Phase CTs Primary: 2000 A
• Ground CT Primary: 500 A
• Frequency: 60Hz
Detecting voltage difference:
Phase Angle DegBASE = 360 deg
Harmonic Content H
BASE
= 100% of nominal
THD THD
BASE
= 100%
Frequency f
BASE
= nominal frequency as entered under the SYSTEM
SETUP menu
Volt/Hz BASE = 1.00
RTDs BASE = 1.00°C
I
2
t (arcing Amps) BASE = 2000 kA
2
*cycle
Impedance Z
BASE
= PhaseVTSecondary / PhaseCTSecondary, where
PhaseVTSecondary and PhaseCTSecondary are the
secondary nominal voltage and the secondary nominal
current of voltage and current bank to calculate the
impedance.
PhaseVTSecondary is specified in the setting under
Setpoints > System > Voltage Sensing, and
PhaseCTSecondary is determined by the order code.
Measured or calculated analog
value related to:
Base Unit