ABB MDAR, Инструкция по эксплуатации

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I.L. 40-385.5
6-1
6.1 DISTANCE MEASUREMENT
PRINCIPLE
MDAR (REL-300) consists of 3 step dis-
tance zones and one optional pilot distance
zone. Each zone consists of four variable
mho distance units, three ØG-units and one
ØØ-unit.
6.1.1 ØG fault detection
ØG fault detection is accomplished by three quadra-
ture polarized phase units, ØA, ØB and ØC. Equa-
tions (1) and (2) are for operating and reference
quantity, respectively. The unit will produce output
when the operating quantity leads the reference
quantity.
V
XG
- [I
X
+ K
o
(I
o
)] Z
CG
(1)
and (V
Q
) (2)
where V
XG
= V
AG
, V
BG
, or V
CG
I
X
= I
A
, I
B
or I
C
I
o
= (I
A
+ I
B
+ I
C
)/3
Z
CG
= PLTG, Z1G, Z2G and Z3G ground
distance reach settings in terms of
Z
1L
/PANG secondary ohms for ØG
faults.
Z
1L
, Z
oL
= Positive and zero sequence line
impedances in relay ohms.
PANG, GANG= Angles in degrees of Z
1L
and Z
oL
.
K
o
= Zero sequence current compensat-
ing factor
ZR = Ratio of zero to positive sequence
line impedance in absolute value.
V
Q
= quadrature phase voltages, i.e., V
CB
,
V
AC
and V
BA
for ØA, ØB and ØC
units, respectively.
It should be noted that the unit may lose its direction-
ality if [I
X
+ K
o
(I
o
)] Z
CG
product is higher than the
phase voltage V
XG
. Correction of this problem is to
supervise the distance unit with FDOG unit.
6.1.2 3Ø fault detection
3Ø fault protection is accomplished by the logic of
any operation of one of the three ØG-units (ØA, ØB
an ØC), plus
the 3ØF output signal from the faulted phase selector
unit.
However, for 3Ø fault condition, the equations for the
computation of distance unit reach will be (3) and (4)
instead of (1) and (2):
V
XG
- I
X
Z
C
P (3)
and (V
Q
) (4)
where V
XG
= V
AG
, V
BG
, or V
CG
I
X
= I
A
, I
B
or I
C
Z
CP
= PLTP, Z1P, Z2P and Z3P zone reach
settings in terms of Z1L/PANG sec-
ondary ohms for multi-phase faults.
V
Q
= quadrature phase voltages i.e., V
CB
,
V
AC
and V
BA
for ØA, ØB and ØC
units, respectively. Use pre-fault volt-
age for V
Q
when all 3 faulted volt-
ages are:
below 1.0 volt RMS for Z1P unit,
below 7.0 volt RMS for Z2P, Z3P
and PLTP units.
6.1.3 ØØ fault detection
The ØØ-unit responds to all ØØ and ØØG faults, and
some ØG faults. Equations (5) and (6) are for operat-
ing and reference quantity, respectively. It will pro-
duce output when the operating quantity leads the
reference quantity.
(V
AB
- I
AB
Z
CP
) (5)
and (V
CB
- I
CB
Z
CP
) (6)
6.1.4 Characteristics
Figure 8 — ØØ/ØØG faults
=
Z
0L
Z
1L
–
Z
1L
( )
-----------------------
Z
oL
Z
1L
-------- 1 –
 
 
=
= (ZR GANG PANG 1‘) –
∠
Section 6. OPERATING PRINCIPLES OF SENSING UNITS