ABB Relion REG670, Technical Manual

Page: 281 / 1298

7.7.6 Monitored data
Table 120: LEXPDIS Monitored data
Name Type Values (Range) Unit Description
XOHM REAL - Ohm Reactance in Primary
Ohms
XPERCENT REAL - % Reactance in percent of
Zbase
ROHM REAL - Ohm Resistance in Primary
Ohms
RPERCENT REAL - % Resistance in percent of
Zbase
7.7.7 Operation principle
The Loss of excitation (LEXPDIS) protection in the IED measures the apparent
impedance seen out from the generator.The measurement loop of apparent impedance
can be chosen as the positive sequence loop or any one of the three phase-to-phase
loops depending on the available current and voltage signals. It is recommended to use
positive sequence quantities for function operation.
Measured mode Measured apparent impedance
Z
posseq
posseq
posseq
U
I
=
EQUATION1771 V1 EN
(Equation 49)
Z
L1L2
1 2
1 2
L L
L L
U U
I I
-
=
-
EQUATION1772 V1 EN
(Equation 50)
Z
L2L3 2 3
2 3
L L
L L
U U
I I
-
=
-
EQUATION1773 V1 EN
(Equation 51)
Z
L3L1 3 1
3 1
L L
L L
U U
I I
-
=
-
EQUATION1774 V1 EN
(Equation 52)
There are three characteristics in LEXPDIS protection as shown in figure 120 .
Naimly:
1MRK502052-UEN B
Section 7
Impedance protection
275
Technical manual