Schweitzer Engineering Laboratories, Inc. SEL-487E Data Sheet
5
TiDL
The SEL-487E-5 TiDL receives and automatically syn-
chronizes data streams from connected and commis-
sioned SEL-TMU devices. The TiDL technology does
not require an external time source for local relay protec-
tion functions.
Protection Features
Differential Element
In the SEL-487E, the phase differential elements employ
operate (IOPn, where n = A, B, C) and restraint (IRTn)
quantities that the relay calculates from the selected wind-
ing input currents. Figure 4 shows the characteristic of
the filtered differential element as a straight line through
the origin of the form:
IOPA (IRTA) = SLPc • IRTA
For operating quantities (IOPA) exceeding the threshold
level O87P and falling in the operate region of Figure 4,
the filtered differential element issues an output. There
are two slope settings, namely Slope 1 (SLP1) and Slope 2
(SLP2). Slope 1 is effective during normal operating
conditions, and Slope 2 is effective when the fault detec-
tion logic detects an external fault condition. In general,
the relay uses filtered and unfiltered (instantaneous) ana-
log quantities in two separate algorithms to form the dif-
ferential element. The adaptive differential element responds
to most internal fault conditions in less than one and a
half cycles.
The differential element includes one harmonic blocking
and one harmonic restraint element; select either one or
both of them. The combination of harmonic blocking and
restraint elements provides optimum operating speed and
security during inrush conditions. Waveshape-based
inrush detection addresses inrush conditions that contain
low second- and fourth-harmonic content. Fast subcycle
external fault detection supervision adds security during
external faults with CT saturation. The harmonic block-
ing element includes common or independent second-
and fourth-harmonic blocking and independent fifth-
harmonic blocking.
Negative-Sequence Differential
Element
Turn-to-turn internal faults on transformer windings may
not cause enough additional current flow at the transformer
bushing CTs to assert a phase-current differential element,
but left undetected can be very destructive to the trans-
former. When turn-to-turn faults occur, the autotransformer
effect on the shorted section of winding causes a very large
current flow relative to the shorted windings but small
compared to the remainder of the unaffected winding. To
detect these destructive internal faults, the SEL-487E uses a
sensitive negative-sequence current differential element.
This element detects the phase-current unbalance caused
by internal fault by using a single-slope characteristic. Using
negative-sequence restraint, the differential element is not
affected by fluctuating negative-sequence quantities on
the power system and is able to detect turn-to-turn short cir-
cuit conditions in as little as two percent of the total trans-
former winding. External fault detection logic from the
phase-differential element is used to block the negative-
sequence differential element, keeping it secure during
external faults and inrush conditions when CT saturation
may occur.
V/Hz Elements
The SEL-487E provides comprehensive V/Hz protection
(24). The SEL-487E maintains frequency tracking from
40.0 to 65.0 Hz when voltage inputs are provided to the
relay. Two independent V/Hz curves with definite and
custom 20-point curve characteristics can be selected using
programmable logic. Use the two independent V/Hz curves
for loaded versus unloaded transformer protection, allow-
ing maximum sensitivity to overexcitation conditions during
Figure 3 SEL TiDL System
T-Protocol
Figure 4 Adaptive Slope Differential Characteristics
IOPA (IRTA)
Operating Region
SLP2
087P
SLP1
Restraining Region
IRTA
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