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.2 Power Quality

Electrical power quality is the measurement and analysis of the voltage delivered to customers. These parameters (voltage amplitude, fl icker, harmonics, unbalance) describe the voltage waveform and offer very important information about the effi ciency of the electrical installation being analysed.A poor electrical supply may affect electrical installations in very different ways and cause signifi cant problems in the installation and connected electrical equipmentThere are currently a series of International standards that defi ne not only minimum levels of electrical power quality but also how to measure these parameters.
Power Quality Industrial analyzers

Events

These are voltage variations which affect the effective value of the half cycle of the voltage wave. According to this value, compared as a percentage to the declared nominal voltage at the point of measurement, events are classifi ed in the following way: ••• Interruptions: Voltage event where the effective value is below 10 % (or 1 % according to criteria used) of the declared nominal voltage. Dips/ Sags: Events with values between 90 % and 10 % (or 1 % according to criteria used) of UDINDips/sags are drops in voltage caused by the variation of the system’s impedance due to protective devices operating and usually last between 10 ms and 1 min. Overvoltages :A phenomenon where the voltage increases above 110 % of the declared voltage (107 % according to criteria used). These are classifi ed as temporary (when the duration is relatively long) or transient (when the duration is a few milliseconds). DipsInterruptions Overvoltage

IEC 61000-4-30

This Standard describes the measurement method which must be used in equipment measuring the quality of electrical supply. This Standard provides two classes of equipment:Class A equipment. For contractual applications, resolving disputes or to be used as a reference.Class B equipment. For obtaining data for internal use where a high degree of accuracy is not required.It is vital that electrical power quality equipment measures in accordance with this Standard including (specifying the class), as it ensures the correct accumulation of results. ••

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