ABB Modures LZ92-1 User Manual

3. DETERMINING THE SETTINGS
All important settings on the distance relays LZ91, LZ92 and I,Z92-1 are thumb-
wheel switches. The corresponding setting formulas are printed on the frontplate
(see Figures 9.3 to 9.8).
In each case the setting in the correct dimensions is obtained by inserting the
number indicated on the thumbwheel switches in the formula and working it out.
The settings themselves (e.g. impedance of the under impedance starting uni ts)
are printed in italics.
Settings which are normally only made once during commissioning are miniature
switches located on the PCB's. Information relating to these settings is marked
on the frontplate of the KI91, KZ91 respectively KZ91-l behind the hinged flap
of the equipment rack (Figures 9. 3 to 9. 8) . A symbol shows on which PCB the
particular functional switch is to be found. The PCB's in the units KI91, KZ91
respectively KZ91-1 are numbered from left to right seen from the front and as
marked on the frontplate. (There is no PCB 3 in KI91.) Further information on
this can be found in Section 3.9.
3.1 Selecting the operating mode
3.1.1 Distance relay LZ91
A choice can be made between two operating modes using miniature switch 1 on
PCB 1 of unit KI91 (Fig. 9.21):
Mode A
Mode L
for solidly grounded systems, i.e. earth faults have to be tripped.
for ungrounded or impedance grounded systems, but only with
acyclical phase-preference for cross-country faults.
3.1.2 Distance relay LZ92
As with the distance relay LZ91, a choice can be made between the modes A and
L using miniature switch 1 on PCB 1 of unit KZ91. In this case, however,
mode 1::::, also permits cyclical (LO in the code) as well as acyclical (Ll in the
code) phase-preference for cross-country faults. This change is made by appro-
priately positioning soldered link LB7 on PCB 1 (see Fig. 9.22).
Standard phase-preferences are R before T before S (acyclically) respectively
R before T, T before S, S before T (cyclically).
3.1.3 Distance relay LZ92-l
In solidly grounded systems in which it is essential that earth faults be
tripped mode j;- should be set.
In ungrounded or impedance grounded systems the same phase-preference must be
set as is used in the rest of the system.
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ABB Modures LZ92-1 Specifications

General

Brand	ABB
Model	Modures LZ92-1
Category	Relays
Language	English