232
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUPED PROTECTION ELEMENTS
CHAPTER 7: PROTECTION
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
The terms in the above equations are defined as follows.
•
T
operate
represents the operate time in seconds.
•
TDM represents the multiplier setting.
•
I
represents the input current.
•
I
pickup
represents the pickup current setting value.
•
T
reset
represents 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 the programming of 41 recloser
curves. Refer to the
FlexCurves
settings section for additional details on the recloser
curves.
Phase time overcurrent
The phase time overcurrent element can provide a desired time delay operating
characteristic versus the applied current or be used as a simple definite time element. The
phase current input quantities may 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. For example, if
the element reset characteristic is set to instantaneous and the element is blocked, the
time accumulator will be cleared immediately.
The phase time overcurrent pickup can be dynamically reduced by a voltage restraint
feature. This is accomplished via the multipliers corresponding to the phase-to-phase
voltages of the voltage restraint characteristic curve. The pickup level is calculated as
multiplier value times the programmed pickup. If the voltage restraint feature is disabled,
the pickup level always remains at the set value.
Figure 197: Phase time overcurrent voltage restraint characteristic
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