ABB Modures LZ91 - Page 17

It is always possible to set the magnitude and phase-angle in the case of the
input transformer unit according to HESG 440 754 (see Section 3.12).
The k factor only bears an influence on the distance measuring system.
0
3.4 Impedance settings of the various zones
3.4.1 Determining the reaches of the distance zones
In order to calculate the settings the fault impedances and the phase-angles
of the sections of line to be protected must be known.
Z3
=
0, BS (a+ k · b2 l .
i----- Z2 = 0, 85 (a + k · b1 l
-
-
b2
-
Z1
=0,85·0
-
I
-
~·-- Zus = 1,2
I
b1
·a
I
A
-
a
-
b
-
B
(
Fig. 3.9 - Reaches of the various distance zones
a, b
2
us
zone impedances
infeed factor which takes into account an intermediate
infeed and the consequential apparent increase in the
impedance by the relay
corresponding line impedances
overreach zone impedance Zus = 1.5 z
1
15