SEL-487E Data Sheet Schweitzer Engineering Laboratories, Inc.
6
all modes of transformer operation. The single V/Hz element
in the relay can be assigned to either set of three-phase
voltage inputs.
Distance Elements
The SEL-487E protects transformers and transmission
lines with as many as four zones of phase distance and
ground distance elements with either mho or quadrilateral
characteristics. You can set all four zones independently
in the forward or reverse direction. The distance elements
are secured with load-encroachment logic, which prevents
operation of the phase distance elements under high load
conditions; line harmonic-blocking logic, which prevents
element operation when a transformer in the protection
zone is being energized or experiencing an overexcitation
condition; and CCVT transient detection, which blocks
the distance elements when there is transient on the system
with CCVTs that may cause the distance element to over-
reach. All mho elements use positive-sequence memory
polarization that expands the operating characteristic in
proportion to the source impedance. This provides depend-
able and secure operation for close-in faults. The quadri-
lateral phase and ground distance elements provide improved
fault and arc resistance coverage, including application
on short lines.
Out-of-Step Detection
The SEL-487E supports out-of-step detection by using
timers and blinders that are set outside any of the distance
elements. A power swing is declared when an impedance
locus travels through the blinders slower than a preset
time. This logic blocks the distance elements in case of a
stable power swing.
Adaptive Time-Overcurrent
Elements (51S)
The relay supports 20 adaptive time-overcurrent elements
with selectable operate quantity and programmable time-
delay and pickup levels. Choose from the ten time-
overcurrent curves shown in Table 1 (five IEC and
five U.S.). Each torque-controlled time-overcurrent ele-
ment has two reset characteristics. One choice resets the
elements if current drops below pickup for one cycle
while the other choice emulates the reset characteristic of
an electromechanical induction disk relay.
The adaptive time-overcurrent elements in the SEL-487E
allow the selection of a wide variety of current sources as
operate quantities to the element. Select the time-overcurrent
element operate quantity from any one of the following
current sources:
➤ Filtered phase currents: IAmFM, IBmFM, ICmFM
➤ Maximum filtered phase current: IMAXmF
➤ Combined filtered phase currents (any two
terminals): IAmmFM, IBmmFM, ICmmFM
Figure 5 Volts/Hertz Curve Diagrams
Time (seconds)
Volts/Hertz (%)
24U101 (110,33)
24U109 (150,22)
24U116 (200,14)
Volts/Hertz (%)
Time (seconds)
33
24U101 (110,33)
24U102 (150,22)
24U103 (200,14)
24U104 (120,30)
24U107 (130,27)
Figure 6 Mho Characteristics
Table 1 Supported Time-Overcurrent Curves
U.S. Curves IEC Curves
U1 (moderately inverse) C1 (standard inverse)
U2 (inverse) C2 (very inverse)
U3 (very inverse) C3 (extremely inverse)
U4 (extremely inverse) C4 (long-time inverse)
U5 (short-time inverse) C5 (short-time inverse)
Expanded
Characteristic
Steady State
Characteristic
Relay Reach
Z
R
Z
S
X
R
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