HT instruments SIRIUS87 - Manual (Page 74)

SIRIUS 87
EN - 72
ALLOWABLE VALUES
The guidelines do not give any indication on the maximum resistance values which cannot
be overcome, in order to be able to declare the positive outcome of the continuity test.
The guidelines IEC/EN61557-1 simply requires that the instrument in use warns the
operator if the test was not carried out with a
current of at least 0.2 A and an open
circuit voltage ranging from 4 V to 24 V.
The resistance values can be calculated according to the sections and lengths of the
conductors under test, anyway if the instrument detects values of some ohm the test can
be considered as passed.
11.2. INSULATION RESISTANCE MEASUREMENT
Purpose of the test is to heck that the insulation resistance of the installation complies with
the requirements of standards.
NOTE: This test is to be effected on an open circuit with any load disconnected.
INSTALLATION PARTS TO BE CHECKED
a) Between each active conductor and the earth (the neutral conductor is considered an
active conductor except in the case of TN-C systems where it is considered part of the
earth (PEN). During this measurement all active conductors can be connected to each
other, in case the measurement result does not fall within the standard limits the test is
to be repeated for each single conductor.
b) Among active conductors. The standards recommends to check the insulation among
the active conductors when this is possible (ATTENTION).
ALLOWABLE VALUES
The values of test voltage and minimum insulation resistance are reported in the following
table (CEI 64-8/6 Tab. 61A):
Rated circuit voltage (V) Test voltage (V) Insulation resistance (M )
SELV and PELV* 250
0.250
Up to 500 V included, except for the
above circuits.
500
1.000
Over 500 V 1000
1.000
* In the new standards the terms SELV and PELV replace the old definitions "safety low
voltage" or "functional".
Test voltage values and relative limit values for the most common kinds of test.