This part of IEC 60034 which is an international standard provides a common basis for measuring techniques and instruments; the arrangement of test circuits; normalization and testing procedures; noise reduction; the documentation of test results; the interpretation of test results. with respect to partial discharge off-line measurements on the winding insulation of rotating electrical machines. The measurement methods described in this international standard are applicable to stator windings of machines with and without conductive slot coating and to the stator windings of machines made with form wound and random wound windings. In special cases like high voltage rotor field windings, this document is applicable as well. The measurement methods are applicable when testing with alternating sinusoidal voltages from 0.1 Hz up to 400 Hz. Interpretation guidelines are given in this standard and are applicable only if all the following requirements are fulfilled: Measurements performed with power frequency of 50 or 60 Hz, or when testing with power supply within a frequency range of 45 Hz to 65 Hz. Form wound windings and winding components such as bars and coils Winding with conductive slot coating. This is usually valid for machines with voltage rating of 6 kV and higher. For machines without conductive slot coating and testing at frequencies differing significantly from power frequencies, the interpretation guidelines are not applicable. The testing procedures for off-line PD-measurements of this standard can be used for assessing the uniform quality of manufacturing or/and the trending of converter driven machines as well. NOTE Testing of low voltage machines with so called Typ I - insulation systems is defined in IEC 60034-18-41. Testing procedures for qualification of converter driven high voltage machines with so called Typ II insulation systems are dealt with in IEC 60034-18-42 (in addition to the optional electric tests described there).