HT instruments MACROTEST G3 - Manual (Page 91)

MACROTESTG3 - COMBIG3
EN - 90
12.3. CHECKING CIRCUIT SEPARATION
Definitions
A SELV system is a zero-category system or safety extra low voltage system
characterized by power supply from an independent (e.g. batteries, small generator set) or
safety source (e.g. safety transformer), protective separation from other electrical systems
(double or reinforced insulation or earthed metal screen) and absence of earthed points
(insulated from the earth).
A PELV system is a zero-category system or protective extra low voltage system
characterized by power supply from an independent (e.g. batteries, small generator set) or
safety source (e.g. safety transformer), protective separation from other electrical systems
(double or reinforced insulation or earthed metal screen) and, unlike SELV systems,
presence of earthed points (not insulated from the earth).
A system with Electrical Separation is a system characterized by a power supply from an
insulation transformer or independent source with equivalent characteristics (e.g. motor
generator set), protective separation from other electrical systems (insulation no lower
than that of the insulation transformer), protective separation to earth (insulation no lower
than that of the insulation transformer).
Purpose of the test
The test, to be performed if protection is obtained through separation must check that the
insulation resistance measured as described below (according to the type of separation)
complies with the limits reported in the table relating to insulation measurements.
Parts of the system to be checked
 SELV System (Safety Extra Low Voltage):
 Measure the resistance between the active parts of the circuit being tested
(separated) and the active parts of the other circuits.
 Measure the resistance between the active parts of the circuit to be tested
(separated) and the earth.
 PELV System (Protective Extra Low Voltage):
 Measure the resistance between the active parts of the circuit being tested
(separated) and the active parts of the other circuits.
Electrical separation:
 Measure the resistance between the active parts of the circuit being tested
(separated) and the active parts of the other circuits.
 Measure the resistance between the active parts of the circuit to be tested
(separated) and the earth.
Allowable values
The test has a positive result when the insulation resistance shows values higher or equal
to those indicated in Table 3.