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I.L. 40-385.1B
FAULT LED flashes. It flashes once per second if
only the LAST FAULT contains targets. It will flash
twice per second if two or more fault records are con-
tained. These records can be deleted by applying a
rated voltage to the Ext. Reset Terminals (TB5/5 and
TB5/6), or through a remote communication inter-
face. By pressing the Reset pushbutton, the LED will
be reset to the Metering mode and the fault informa-
tion will still be retained.
The activation of fault data storage is controlled by
the selection of TRIP/Z2TR/Z2Z3 in the FDAT func-
tion, where:
TRIP ---start to store fault data only if trip action oc-
curs.
Z2TR ---start to store fault data if Zone 2 units pick
up or any trip action occurs.
Z2Z3 ---start to store fault data if Zone 2 or Zone 3
units pick up or any trip action occurs.
3.4.17 Out-of-Step Block (OSB) Logic
The Out-of-Step Blocking (OSB) logic (power swing
block supervision) in MDAR is a double blinder
scheme. It contains two blinder units, providing 4
blinder lines. The nature of the logic (shown in Figure
3-18a) is that the outer blinder 21BO must operate
50ms or more ahead of the inner blinder 21BI, in or-
der for an OSB condition to be identified. The OSB
signal is a negated input to the AND-131 (Z1P),
AND-147 (Z2P), AND-160 (Z3P), and AND-176
(PLTP) for supervising the 3-phase distance trip. In
addition to controlling the OSB logic, the blinder
units also may be used to supervise distance relay
tripping. Phase distance unit tripping cannot take
place unless 21BI operates. This prevents operation
of the distance relay on load. The OSB signal is also
applied to the reclosing logic for initiating RB.
The following quantities are used for the blinder
sensing:
Blinder
Line
Polarizing
Left
-j(V XG + I X R C (PANG–90
Right
j(V XG - I X R C (PANG–90
where VXG
=
Phase to ground voltage, V A G or
V BG
3-8
Operating
°
°
) I X (PANG–90
)
°
°
)
I X (PANG–90
)
I
=
Phase current in
X
R
=
Setting of the unit (R
C
inner blinder (21BI), RU for outer
blinder (21BO).
PANG =
The positive sequence line imped-
ance angle.
Operation occurs if the operating voltage leads the
polarizing voltage. The characteristics are as shown
in Figure 3-18b.
Both inner and outer blinders are included in phases
A and B for OSB detection on the SPT application.
Blinder reaches are determined by the setting of RT
and RU, respectively.
3.4.17.1 Security Logic for Subsequent Out-of-
Step (OS) Condition
Model power system tests, when using a motor-gen-
erator-set, show that the Zone 1 impedance unit may
overreach or respond to a reversed fault. This was
attributable to motor-generator set instability follow-
ing delayed clearing on an external fault. The Zone
1 relay, in all cases, identified the fault location and
type correctly and responded much later to the
swing condition.
Logic was added utilizing the inner blinder and Zone
1 sensing sequence, plus a 50 ms timing action (as
shown in Figure 3-18a), AND-131A, AND-131B,
AND-131C and OR-122A, to differentiate between a
fault and a subsequent out-of-step condition. This
logic will not affect normal Zone 1 trip time, nor will it
affect normal out-of-step blocking.
3.4.18 Optional Single-Pole-Trip (SPT) Logic and
Outputs
The logic for Single-Pole-Trip operation provides the
following functions (see Figure 3-20):
• Single-pole-trip (SPT) and single-pole reclosing
initiate (RI1) on single-phase-to ground faults.
• Three-pole-trip (3PT) with three-pole-reclosing
initiate (RI2) on all multi-phase faults.
• Three-pole-trip with or without three-pole reclos-
ing initiate on all faults if the functional display trip-
mode selector "TTYP" is not set on the SPR or
SR3R position.
• Three-pole-trip and reclosing block (RB) on un-
successful reclosing.
φ
φ
A or
B
or R
). RT for
T
U
(5/92)
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