67
The characteristics of loop measurements with 3 wires, with ( ) or without tripping (
) are
the same as those of earth measurements in a live condition, with or without tripping, respectively:
see § 4.2.5.1.
Characteristics of calculation of short-circuit current I
K
:
Display range
400 A
4000 A
40 kA
Resolution
0,1 A
1 A
10 A
Accuracy
Resistances, impedances:
Accuracy values indicated for earth measurements in a live condition (see
§ 4.2.5)
Short-circuit current:
Accuracy of impe accuracy of measurement of voltage U
mes
, if it is
used
Calculation formula
I
K
= U
REF
/ Z
LOOP
(or Z
LINE
)
4.3.5.2
INFLUENCING QUANTITIES
Same as for earth measurements in a live condition (cf. § 4.2.5.2))
4.3.6 WARNINGS
OR
ERROR
REPORTS
(ZLOOP
LOOP
MEASUREMENTS)
Preliminary remark:
The complete list of coded errors is given in § 7.
Same as for earth measurements in a live condition, except for the rod and the current probe
measurement, which do not apply to loop measurements: see § 4.2.6.
4.4 2-WIRE LOOP MEASUREMENT (
Z LINE)
4.4.1 DESCRIPTION OF THE FUNCTION
This function measures the line impedance between conductors "L" and "N" of the power network.
This measurement can also be used to calculate short-circuit currents, in order to size fuses and
circuit breakers.
It is possible to check the impedance between conductors "L" and "PE" or between two "L"
conductors, but the measuring cables must systematically be connected to terminals "L" and "N" of
the measuring instrument.
4.4.2 PREPARATION FOR THE MEASUREMENT (CONNECTION)
→
If necessary, in "SET-UP" mode:
-
set the threshold voltage U
L
(see § 3.2),
-
set the alarm threshold Z
L
or R
L
(see § 4.3.2),
-
choose the value of U
REF
to be used to calculate short-circuit currents (see § 4.3.2),
→
Set the switch to ZLINE,
→
Connect the line power plug (or 2 separate cables) to the installation to be tested.
Summary of Contents for C.A 6454
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