Directive 2014/32/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of measuring instruments (recast) (Text with EEA relevance) (c. 32)

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ANNEX V U.K.

SPECIFIC REQUIREMENTS U.K.

4. Permissible effect of disturbances U.K.

4.1. General U.K.

As electrical energy meters 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.

The meter shall comply with the electromagnetic environment E2 and the additional requirements in points 4.2 and 4.3.

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 meter shall recover and shall not affect the accuracy beyond the critical change values.

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

4.2. Effect of disturbances of long duration U.K.

Table 3

a 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.
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 circuitsa	1	0,8	0,5
DC and harmonics in the current circuita	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

4.3. Permissible effect of transient electromagnetic phenomena U.K.

4.3.1. The effect of an electromagnetic disturbance on an electrical energy meter shall be such that during and immediately after a disturbance: U.K.

• any output intended for testing the accuracy of the meter 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 meter shall:

• recover to operate within the MPE limits, and

• have all measurement functions safeguarded, and

• allow recovery of all measurement data present prior to the disturbance, and

• not indicate a change in the registered energy of more than the critical change value.

The critical change value in kWh is

(m being the number of measuring elements of the meter, U_n in Volts and I_max in Amps).

4.3.2. For overcurrent the critical change value is 1,5 %. U.K.