NOVA AND NOVA PRO
Measurements
25
5.3.6.
Contact voltage
Leakage current flowing to the PE terminal causes a voltage drop across earth resistance,
which is called contact voltage (Uc). This voltage is present on all accessible parts connected to
the PE terminal and should be lower than the safety limit voltage.
The parameter contact voltage is measured without tripping-out the RCD. R
L
is a fault loop
resistance and is calculated as follows:
R
=
U
C
L
I
Δ
N
Displayed contact voltage relates to the rated nominal differential current of the RCD and is
multiplied by a safety factor. See the table 5.1 for detailed contact voltage calculation
.
RCD type
Contact voltage Uc
G
G
Uc
1.05
I
Δ
N
S
S
Uc
1.05
2
I
Δ
N
G
G
Uc
1.05
2
I
Δ
N
S
S
Uc
1.05
2
2
I
Δ
N
Table 5-1
: Relationship between Uc and I
Δ
N
How to perform contact voltage measurement
Step 1
Select the
RCD
function with the FCT key and select the
Uc
mode with the
▲▼ and
◀▶navigation
keys. The following menu will be displayed:
Figure 5-12: Contact voltage measurement menu
Step 2
Set the following measuring parameters and limit values:
•
I
ΔN
: Nominal residual current,
•
Type
: RCD type,
•
Limit:
Limit contact voltage.
