AS IEC 60990:2018 pdf free.Methods of measurement of touch current and protective conductor current.
4.2 Test transformer
The use of a test transformer for isolation is optional. For maximum safety, a test transformer for isolation (T2 in Figure 2, T in Figure 6 to Figure 14) shall be used and the main protective earthing terminal of the EQUIPMENT under test (EUT) earthed. Any capacitive leakage in the transformer shall then be taken into account. As an alternative to earthing the EUT, the test transformer secondary and the EUT shall be left floating (not earthed), in which case the capacitive leakage in the test transformer need not be taken into account.
If transformer T is not used, the EUT shall be mounted on an insulating stand and appropriate safety precautions taken, in view of the possibility of the body of the EUT being at hazardous voltage.
4.3 Earthed neutral conductor
EQUIPMENT intended for connection to a TT or TN power distribution system shall be tested
with minimum voltage between neutral and earth.
NOTE Descriptions of various power distribution systems are given in Annex I.
The protective conductor and the earthed neutral conductor for the EUT should have a voltage difference of less than 1 % of line-to-line voltage (see example in Figure 1).
A local transformer, see 4.2, will achieve this requirement.
Alternatively, if the voltage difference is 1 % or more, the following are examples of methods which, in some cases, will avoid measurement errors due to this voltage:
— connecting the terminal B electrode of the measuring instrument network to the neutral terminal of the EUT instead of the protective earthing conductor (see 6.1.2) of the supply;
— connecting the earthing terminal of the EUT to the neutral conductor, instead of the protective earthing conductor, of the supply.
5.1.2 Perception and startle-reaction The network of Figure 4 shall be used for low level electric shock limits. This circuit is to be applied where the a.c. limit value in the product standard is up to 2 mA r.m.s. or 2,8 mA peak.
5.1.3 Letgo-immobilization The network of Figure 5 shall be used for higher level electric shock limits. This circuit is to be applied where the a.c. limit value in the product standard is more than 2 mA r.m.s. or 2,8 mA peak.AS IEC 60990 pdf download.