Benning ST 755+ - Page 72

9.1 Requirements for tests and measurements
Testing
5284 / 08/2023 enBENNING ST 755+ / ST 760+72
Current measurements
• The test sample is secured and placed onto an insulated surface.
• The measuring circuit is closed. Otherwise, no current is measured and the test result will
be incorrectly displayed as being positive.
• Please observe inductive and capacitive circuits.
• If accessible conductive components of different potentials are arranged in such a way that
they all can be touched with one hand, the sum of their contact currents has to be regarded
as the measured value.
• When used in an ITpower supply network, leakage current measurement is only possible
using the alternative leakage current measuring method.
• For information devices and components carrying SELV/ PELV, testing of the contact
current may be dispensed with if damage to the test sample might occur as a result of the
measurement.
• Direct/differential current measuring method:
– If the insulating resistance cannot or should not be measured, the protective conductor
current or contact current must be measured using the direct current measuring method
or differential current measuring method.
– Measurement with both polarities (L<->N; N<->L)
– For the direct and differential current measuring method, the test socket is supplied with
mains voltage.
• Alternative leakage current measuring method:
– The alternative leakage current measuring method is only valid if there are no mains
voltage-dependent switching devices in the test sample.
– The test sample has passed the insulating resistance test [}page80].
– Test with mains equivalent voltage (230V-AC).
– The test sample has passed the protective conductor resistance test [}page79].
– Test samples with capacitor circuits can cause higher leakage currents. Please check
whether the measured leakage current values comply with the applicable limits.
Resistance measurements
• Insulating resistance:
– For information devices and components carrying SELV, testing of the insulating
resistance may be dispensed with if damage to the test sample might occur as a result
of the measurement.
– In case of test samples which are connected to each other via fastenings or are
galvanically isolated from each other or have a common protective conductor: Please
test each component individually.
– Test samples with electrically operated switching elements might, if necessary, prevent
the testing voltage from being applied to all accessible conductive and active
components. Please test such test samples at mains voltage and being particularly
careful.
– Test samples with magnetic, thermal or optical switching elements might prevent the
testing voltage from being applied to all accessible conductive and active components.
Please test such test samples with the contact of the switching element being closed.
– If for test samples with heating elements and a power of P>3.5kW the value falls
below the limit, the test sample still shall be considered to be in proper condition as long
as the limit for the protective conductor current is not exceeded.