GE D90 Plus - Page 245

CHAPTER 7: PROTECTION GROUPED PROTECTION ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 235
FlexCurves
FlexCurves are described in the FlexCurves section later in this chapter. The curve shapes
for FlexCurve are derived from the formulae:
Eq. 18
Eq. 19
where
• T
operate
= operate time (in seconds)
• TDM = multiplier setting
• I = input current
• I
pickup
= pickup current setting
• T
reset
= reset time in seconds (assuming the energy capacity is 100% and the reset
mode is “Timed”)
Definite time curve
The Definite Time curve shape operates as soon as the pickup level is exceeded for a
specified period of time. The base definite time curve delay is in seconds. The curve
multiplier of 0.00 to 600.00 makes this delay adjustable from instantaneous to 600.00
seconds in steps of 10 ms. The definite time curve shapes are defined as follows:
Eq. 20
Eq. 21
where
• T
operate
= operate time (in seconds)
• TDM = multiplier setting
• I = input current
• I
pickup
=pickup current setting
• T
reset
= reset time in seconds (assuming the energy capacity is 100% and the reset
mode is “Timed”)
Recloser curves
The D90
Plus
uses the FlexCurve feature to facilitate programming of 41 recloser curves. See
the FlexCurves settings section earlier in this chapter for details.
Phase time overcurrent
The phase time overcurrent element can provide a specified time-delay operating
characteristic versus the applied current or be used as a simple definite time element. The
phase current input quantities can be programmed as fundamental phasor magnitude or
total waveform RMS magnitude as required by the application.
Two methods of resetting operation are available: “Timed” and “Instantaneous.” When the
element is blocked, the time accumulator resets according to the reset characteristic. For
example, if the element reset characteristic is set to “Instantaneous” and the element is
blocked, the time accumulator clears immediately.
The Phase TOC1 Pickup setting can be dynamically reduced by a voltage restraint feature
(when enabled). This is accomplished via the multipliers (Mvr) corresponding to the phase-
to-phase voltages of the voltage restraint characteristic curve (see figure); the pickup level
is calculated as Mvr times the Phase TOC1 Pickup setting. If the voltage restraint feature is
disabled, the pickup level always remains at the setting value.
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