# The Measuring Instruments Regulations 2016, Paragraph 4.2: Effect of disturbances of long duration


Table 3
Critical change values for disturbances of long duration
Disturbance
Critical change values in percent for meters of class
A
B
C
Reversed phase sequence
1.5
1.5
0.3
Voltage unbalance (only applicable to polyphase meters)
4
2
1
Harmonic contents in the current circuits
1
0.8
0.5
DC and harmonics in the current circuit
6
3
1.5
Fast transient bursts
6
4
2
Magnetic fields; HF (radiated RF) electromagnetic field; Conducted disturbances introduced by radio-frequency fields; and Oscillatory waves immunity
3
2
1
In the case of electromechanical electricity meters, no critical change values are defined for harmonic contents in the current circuits and for DC and harmonics in the current circuit.

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Source: https://www.legislation.gov.uk/uksi/2016/1153/schedule/1E/paragraph/4.2 (the official version)
Page: https://openlegislation.uk/measuring-instruments-regulations-2016/schedule-1E/paragraph-4.2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.