HT instruments SIRIUS89N User Manual
Page 118
SIRIUS89N
EN - 116
phase with voltage and a leakage current phase shifted by 180° with respect to the
voltage. The highest time is to be considered as significant result.
The test at ½I
∆n
SHALL NEVER cause the RCD tripping.
NOTE:
•
Before effecting the test at the RCD rated current the instrument carries out a test
at ½I
∆n
to measure the contact voltage and the overall earth resistance; if during
this test the RCD trips the indication l
"rcd" is displayed. During this test the RCD
may trip for three possible reasons:
a) The RCD tripping current is lower than ½I
∆n
.
b) An earth plate is already present on the installation which added to the earth
generated by the instrument causes the RCD tripping.
c) There is no earth installation.
•
If during measurement of contact voltage the voltage detected is higher than the
safety value (50V or 25V) the test is interrupted; proceeding with the test under
such conditions would mean to keep the contact voltage applied to all the metal
masses connected to the earth for a too long time resulting to be dangerous.
•
Among the test results of the RCD tripping time also the earth resistance value R
a
is
displayed in
Ω, this value for the TN and IT systems is not to be considered while
for the TT systems it is merely indicative.
16.6. Test of RCD Tripping Time (Rcd, Rcd/Dc)
PURPOSE OF THE TEST
Check the real tripping time of the general RCDs (it does not apply to the selective
RCDs).
INSTALLATION PARTS TO BE CHECKED
When facing RCDs with tripping current to be selected it is useful to effect this test
to check the real RCD tripping current. For RCDs with fixed differential current this
test can be effected to detect any leakage of the installation users.
In case the earth installation is not available effect the test connecting one
instrument ‘s terminal on a conductor downstream the RCD and one terminal on the
other conductor upstream the RCD itself.
ALLOWABLE VALUES
The tripping current shall range from ½I
∆n
to I
∆n
.
NOTE:
•
Make reference to the notes of the previous chapter.
•
To check whether significant leakage currents are present on the installation operate
as follows:
a) After deactivating all the loads effect the tripping current measurement and take
note of the value.
b) Activate the loads and effect a new measurement of the tripping current; if the
RCD trips with a lower current, the installation leakage is the difference between
the two tripping currents. If during the test "rcd" is displayed the installation
leakage current added to the current for contact voltage measurement (½I
∆
n
)
causes the RCD tripping.