The Measuring Instruments (Active Electrical Energy Meters) Regulations 2006 (revoked)

Permissible effect of disturbances — Electromagnetic environment U.K.

16.—(1) Under rated operating conditions and in the presence of a disturbance, the performance requirements shall be as set out below.

(2) Where the relevant instrument is intended to be used in a specified permanent continuous electromagnetic field the permitted performance during the radiated electromagnetic field-amplitude modulated test shall be within MPE.

(3) General

(a) As relevant instruments are directly connected to the mains supply and as mains current is also one of the measurands, a special electromagnetic environment is used for electricity meters.

(b) The relevant instrument shall comply with the electromagnetic environment E2 and the additional requirements in sub-paragraphs (4) and (5) below.

(c) The electromagnetic environment and permissible effects reflect the situation that there are disturbances of long duration which shall not affect the accuracy beyond the critical change values and transient disturbances, which may cause a temporary degradation or loss of function or performance but from which the relevant instrument shall recover and shall not affect the accuracy beyond the critical change values.

(d) When there is a foreseeable high risk due to lightning or where overhead supply networks are predominant, the metrological characteristics of the relevant instrument shall be protected.

(4) Effect of disturbances of long duration

Table 4

Critical change values for disturbances of long duration

1 In the case of electromechanical relevant instruments, no critical change values are defined for harmonic contents in the current circuits and for DC and harmonics in the current circuit.
Disturbance	Critical change values in percent for relevant instruments of class
	A	B	C
Reversed phase sequence	1.5	1.5	0.3
Voltage unbalance (only applicable to polyphase relevant instruments)	4	2	1
Harmonic contents in the current circuit1	1	0.8	0.5
DC and harmonics in the current circuit1	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

(5) Permissible effect of transient electromagnetic phenomena

(a) The effect of an electromagnetic disturbance on a relevant instrument shall be such that during and immediately after a disturbance any output intended for testing the accuracy of the relevant instrument does not produce pulses or signals corresponding to an energy of more than the critical change value; and in reasonable time after the disturbance the relevant instrument shall—

(i) recover to operate within the MPE limits;

(ii) have all measurement functions safeguarded;

(iii) allow recovery of all measurement data present prior to the disturbance; and

(iv) not indicate a change in the registered energy of more than the critical change value.

(b) The critical change value in kWh is m · U_n · I_max · 10-⁶ (m being the number of measuring elements of the relevant instrument, U_n in Volts and I_max in Amps).

(c) For overcurrent the critical change value is 1.5 %.