Measurement for Grid power quality

Some regulations or specific contracts require energy providers to keep voltage characteristics at any supply terminal within specified limits. These specifications cover limits or values related to voltage, frequency, rapid voltage changes, harmonics, interharmonics, unbalance, dips, swells, interruptions, flicker, ….

Measurements are typically made on the energy provider side (to check delivered energy complies to the contract) and on the consumer side (to check received energy complies with the contract) with Power Quality Instruments class A according to IEC 61000-4-30.

The main standards (see table 2 of IEC TR 63213) are specified below:

Fig. S7 – Standards for Grid power quality assessment

Application assessment standards or rules	Method standards	Usual product standards
EN 50160 Voltage characteristics of electricity supplied by public electricity networks	IEC 61000-4-30^[a]^[b] class A Testing and measuring techniques – Power quality measurement methods	Power Quality Instruments (PQI)^[c] IEC 62586-1 Power Quality Instruments (PQI) + IEC 62586-2^[a] Functional tests and uncertainty requirements
IEC/TS 62749 Assessment of Power Quality – Characteristics of electricity supplied by public electricity networks

^ ¹ ² Compliance with IEC 62586-2 means compliance with IEC 61000-4-30
^ IEC 61000-4-30 provides the following definitions:
Class A: this class is used where precise measurements are necessary, for example, for contractual applications that may require resolving disputes, verifying compliance with standards, etc. Any measurements of a parameter carried out with two different instruments complying with the requirements of Class A, when measuring the same signals, will produce matching results within the specified uncertainty for that parameter.
Class S: this class is used for statistical applications such as surveys or power quality assessment, possibly with a limited subset of parameters. Although it uses equivalent intervals of measurement as Class A, the Class S processing requirements are much lower. Some surveys may assess power quality parameters of several measurement sites on a network; other surveys assess power quality parameters at a single site over a period of time, or at locations within a building or even within a single large piece of equipment.
^ Usually, energy providers are checking the power quality they deliver to users with a PQI-A, and energy users are checking the power quality they receive from energy providers with a PQI-A.