International Electrotechnical Commission

Assessment of power quality – Characteristics of electricity supplied by public networks - Edition 1.0
 N TS 62749

Annotation

This Technical Specification specifies the expected characteristics of electricity at the SUPPLY TERMINALS of public low, medium and high voltage, 50 Hz or 60 Hz, networks.

NOTE 1 The boundaries between the various voltage levels may be different for different countries/regions. In the context of this TS, the following terms for system voltage are used:

- low voltage (LV) refers to UN ? 1 kV;

- medium voltage (MV) refers to 1 kV < UN ? 35 kV;

- high voltage (HV) refers to 35 kV < UN ? 230 kV;

NOTE 2 Because of existing network structures, in some countries/regions, the boundary between medium and high voltage can be different.

Most of the recommendations for power quality at the SUPPLY TERMINALS are expressed as POWER QUALITY INDICES that describe the manner in which the characteristics of electricity vary. Such variations may appear random in time, with reference to any specific supply terminal, and random in location, with reference to any given instant of time. As such, the POWER QUALITY INDICES are based on the occurrence of the applicable electromagnetic phenomena:

- continuous phenomena, i.e. deviations from the nominal value that occur continuously over time. Such phenomena occur mainly due to load pattern, changes of load, non-linear loads or distributed generation, and

- discontinuous phenomena or events, i.e. sudden and significant deviations from normal or desired wave shape which typically occur due to unpredictable events (e.g. faults) or external causes (e.g. weather conditions).