NOVA AND NOVA PRO
Measurements
39
Notes:
Displayed result:
Z ...............
Fault loop impedance,
I
SC.....................
Prospective fault current,
❑
The measurement of fault loop impedance using trip-lock function does not normally
trip an RCD. However, if the trip limit may be exceeded as a result of leakage current
flowing through the PE protective conductor or a capacitive connection between L
and PE conductors.
❑
The specified accuracy of the test parameter is valid only if the mains voltage is
stable during the measurement otherwise the symbol of NOISE DURING
MEASUREMENT will be displayed
.
5.5.
Z LINE Line impedance and prospective short-circuit current
The line impedance is a measurement of the impedance of the current loop when a short-
circuit to the neutral conductor occurs (conductive connection between phase conductor
and neutral conductor in single-phase system or between two phase conductors in three-
phase system). A high test current is used to perform the line impedance measurement.
Prospective short circuit current is calculated as follows:
Where:
𝐼
𝑃𝐹𝐶
=
𝑈
𝑁
×
𝑠𝑐𝑎𝑙𝑖𝑛𝑔
𝑓𝑎𝑐𝑡𝑜𝑟
𝑍
𝐿−𝑁
(
𝐿
)
Nominal input voltage U
N
Voltage range
115V
(93 V
U
L-PE
134 V)
230V
(185 V
U
L-PE
266 V)
400V
(321V
U
L-PE
485 V)
How to perform line impedance measurement
