![Schweitzer Engineering Laboratories SEL-421-4 Instruction Manual Download Page 245](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-421-4/sel-421-4_instruction-manual_1216726245.webp)
5.85
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Functions
Quadrilateral Phase-Distance Elements
Quadrilateral Phase-Distance Elements
NOTE:
The SEL-421-4 provides fast
and secure tripping, but does not have
high-speed distance elements. Typical
detection time for the SEL-421-4 is
1.5 cycles.
The SEL-421-5 has two groups of quadrilateral phase-distance elements: high-
speed elements and conventional elements. There are five zones (Zone 1 through
Zone 5) of conventional elements, and three zones of high-speed elements
(Zone 1 through Zone 3). Reach settings for the Zone 1 through Zone 3 elements
are the same for the two groups. For example, setting XP1 = 4
sets the Zone 1
reactance reach for both high-speed elements and conventional elements to
4 Ohms secondary.
Notice that setting XP
x
(
x
= 1–5 or
x
= 1–3) is an impedance (not reactance) set-
ting. You can set the impedance and resistive (RP
x
) reach for each zone inde-
pendently.
NOTE:
It is recommended to enable
the phase mho elements in
conjunction with the phase
quadrilateral elements to provide
detection for phase-to-phase faults
during SPO conditions.
The SEL-421 also has five independent zones of mho phase-distance protection
(see
Mho Phase-Distance Elements on page 5.80
for more information).
Although the mho and quadrilateral phase elements are independent, you can
enable both at the same time. To this end, the outputs from the mho and quadrilat-
eral phase elements are ORed to a single protection output (see
,
).
For both the high-speed and conventional quadrilateral phase-distance elements,
Zone 1 and Zone 2 distance elements operate in the forward direction only. You
can set Zone 3 for the high-speed elements and Zone 3 through Zone 5 for the
conventional elements to operate in either forward or reverse directions.
summarizes the zone directional settings for the high-speed and con-
ventional elements.
The impedance reach for each zone of quadrilateral phase-distance protection lies
on the line positive-sequence impedance angle (Z1ANG) rather than on the ordi-
nate (reactance) of the impedance plane. When setting the reactance reach of the
relay, do not convert the line impedance to a reactance. Enter the impedance
value at the line angle in the same way you would enter the impedance value
when setting a mho element. For example, if the line impedance is Z = 2 +j15
(15.13
82.4°
) secondary, enter the following settings for an 85 percent
Zone 1 reach:
Z1ANG = 82.4°
XP1 = 12.86
(15.13 • 0.85)
shows the first three zones of the quadrilateral phase characteristic.
Notice that the right blinders are parallel to the line impedance, and not parallel
to the reactance axis. There is no setting for –RP, the left blinder; this value is
fixed at the negative value of the lowest forward looking resistive RP
n
setting
(
n
= 1–5). For example, if RP1 is set to RP1 = 3.8
, and if RP1 is the minimum
of RP1 through RP5, then the left blinder setting becomes –3.8
. Zones set to
OFF (XP
n
= OFF), reverse looking zones (DIR
n
= R) and zones not included in
the E21XP setting are excluded from the calculations to determine the minimum
RP value in the forward direction.
NOTE:
If the relay is using a remote
data acquisition system, such as TiDL,
the operating times will be delayed by
1.5 ms. Use caution when setting the
relay coordination times to account
for this added delay.
Table 5.53
High-Speed and Conventional Element Directional Setting Summary
Zones
High-Speed Elements
Conventional Elements
Zone 1
Forward only
Forward only
Zone 2
Forward only
Forward only
Zone 3
Forward/Reverse
Forward/Reverse
Zone 4
NA
Forward/Reverse
Zone 5
NA
Forward/Reverse
NOTE:
The resistive reach of the
quadrilateral phase-distance element
setting RP
n
is reduced to RPP
n
based
on the ratio of I2/I1 using the
following equation if 32QE is not
asserted:
RPPn
0.25
I2
I1
-----
0.75
•
+
RP
n
•
=
Summary of Contents for SEL-421-4
Page 6: ...This page intentionally left blank ...
Page 14: ...This page intentionally left blank ...
Page 30: ...This page intentionally left blank ...
Page 104: ...This page intentionally left blank ...
Page 128: ...This page intentionally left blank ...
Page 536: ...This page intentionally left blank ...
Page 584: ...This page intentionally left blank ...
Page 616: ...This page intentionally left blank ...
Page 696: ...This page intentionally left blank ...
Page 750: ...This page intentionally left blank ...
Page 755: ...Instruction Manual PM400 01 NB SEL 400 Series Relays Instruction Manual 20171006 ...
Page 776: ...This page intentionally left blank ...
Page 932: ...This page intentionally left blank ...
Page 976: ...This page intentionally left blank ...
Page 1024: ...This page intentionally left blank ...
Page 1038: ...This page intentionally left blank ...
Page 1064: ...This page intentionally left blank ...
Page 1128: ...This page intentionally left blank ...
Page 1206: ...This page intentionally left blank ...
Page 1316: ...This page intentionally left blank ...
Page 1350: ...This page intentionally left blank ...
Page 1464: ...This page intentionally left blank ...
Page 1468: ...This page intentionally left blank ...
Page 1492: ...This page intentionally left blank ...
Page 1518: ...This page intentionally left blank ...