Creepage distances of functional insulation shall be not less than those specified in Table 18. However, if the working voltage is periodic and has a frequency that exceeds 30 kHz, the creepage distances shall also be determined from Table 2 of IEC 60664-4. These values shall be used instead if they exceed the values in Table 18.The creepage distances may be reduced if the appliance complies with Clause 19 with the functional insulation short-circuited.Table 18 – Minimum creepage distances for functional insulationCompliance is checked by measurement.