Application – 2
2–9
21 Phase Distance
The phase distance function (21) is designed for
system phase fault backup protection and is
implemented as a two-zone mho characteristic.
Three separate distance elements are used to detect
AB, BC, and CA fault types. The ranges and
increments are shown in Table 2-1. The diameter,
offset, system impedance angle (relay characteristic
angle), and definite time delay need to be selected
for each zone for coordination with the system
relaying in the specific application.
When the generator is connected to the system
through a delta/wye transformer, proper voltages
and currents (equivalent to the high side of the
transformer) must be used in order for the relay to
see correct impedances for system faults. By
enabling the Delta-Y Transform feature (see Section
2.1, Configuration, Relay System Setup), the relay
can internally consider the 30° phase shift through
the delta/wye transformer, saving auxiliary VTs.
Impedance calculations for various VT connections
are shown in Table 2-2. All impedance settings are
secondary relay quantities and can be derived from
the following formula:
Z
SEC
= Z
PRI
x (R
C
÷ R
V
)
where Z
SEC
= secondary reflected impedance, Z
PRI
=
primary impedance, R
C
= current transformer ratio,
and R
V
= voltage transformer ratio.
The minimum current sensitivity depends on the
programmed reach (diameter and offset). If the
current is below the minimum sensitivity current,
the impedance calculated will saturate, and not be
accurate. This will not cause any relay misoperation.
N
O
I
T
C
N
U
F
E
G
N
A
R
T
N
I
O
P
T
E
S
T
N
E
M
E
R
C
N
I
)
1
2
(
e
c
n
a
t
s
i
D
e
s
a
h
P
2
#
,
1
#
r
e
t
e
m
a
i
D
e
l
c
r
i
C
0
.
0
0
1
o
t
1
.
0
Ω
0
.
0
0
5
o
t
5
.
0
(
Ω
)
1
.
0
Ω
2
#
,
1
#
t
e
s
f
f
O
0
.
0
0
1
o
t
0
.
0
0
1
-
Ω
0
.
0
0
5
o
t
0
.
0
0
5
-
(
Ω
)
1
.
0
Ω
2
#
,
1
#
e
l
g
n
A
e
c
n
a
d
e
p
m
I
0
o
0
9
o
t
o
1
o
2
#
,
1
#
y
a
l
e
D
e
m
i
T
s
e
l
c
y
C
0
6
1
8
o
t
1
e
l
c
y
C
1
Table 2-1
Phase Distance (21) Setpoint Ranges
Direct-Connected
Delta/Wye Transformer Connected
AB Fault
BC Fault
CA Fault
L-L or L-G to L-L
VT Connection
L-G
VT Connection
L-G
V
AB
I
a
I
b
V
BC
I
b
I
c
V
CA
I
c
I
a
V
A
V
B
I
a
I
b
V
B
V
C
I
b
I
c
V
C
V
A
I
c
I
a
V
BC
V
AB
( 3 ) I
b
V
B
V
0
I
b
V
AB
V
CA
( 3 ) I
a
V
A
V
0
I
a
V
CA
V
BC
( 3 ) I
c
V
C
V
0
I
c
L-L or L-G to L-L
Table 2-2
Impedance Calculation
Содержание M-3425
Страница 1: ...Instruction Book M 3425 Generator Protection ...
Страница 14: ... 13 M 3425 Generator Protection Relay Figure 1 External Connections ...
Страница 33: ...x M 3425 Instruction Book This Page Left Intentionally Blank ...
Страница 89: ...M 3425 Instruction Book 2 52 This Page Left Intentionally Blank ...
Страница 125: ...1 3 A B C M 3425 Instruction Book 4 26 This Page Left Intentionally Blank ...
Страница 187: ...M 3425 Instruction Book 6 50 This Page Left Intentionally Blank ...
Страница 207: ...M 3425 Instruction Book C 4 This Page Left Intentionally Blank ...
Страница 209: ...D 2 M 3425 Instruction Book Figure D 1 Volts Hz 24 Inverse Curve Family 1 Inverse Square ...
Страница 210: ...Inverse Time Curves Appendix D D 3 Figure D 2 Volts Hz 24 Inverse Family Curve 2 ...
Страница 211: ...D 4 M 3425 Instruction Book Figure D 3 Volts Hz 24IT Inverse Curve Family 3 ...
Страница 212: ...Inverse Time Curves Appendix D D 5 Figure D 4 Volts Hz 24IT Inverse Curve Family 4 ...
Страница 215: ...D 8 M 3425 Instruction Book Figure D 5 Definite Time Overcurrent Curve ...
Страница 216: ...Inverse Time Curves Appendix D D 9 Figure D 6 Inverse Time Overcurrent Curve ...
Страница 217: ...D 10 M 3425 Instruction Book Figure D 7 Very Inverse Time Overcurrent Curve ...
Страница 218: ...Inverse Time Curves Appendix D D 11 Figure D 8 Extremely Inverse Time Overcurrent Curve ...
Страница 223: ...D 16 M 3425 Instruction Book This Page Intentionally Left Blank ...