Satec expertmeter EM720 Operation Manual page 214

Appendix E EN50160 Evaluation and Recording
214
Signaling voltages are not evaluated if the supply voltage
crosses a voltage tolerance limit (±15% Un).
Target Values
The voltage levels given by the EN50160 in Figure 1 of Clause
2.13 are taken from the so-called "Meister-curve" which
defines the maximum permissible ripple control voltages in
LV networks.
Compliance with the EN50160 requires that the 3-second
mean of signal voltages shall be less or equal to the specified
limits for 99% of a day.
EM720 Power Quality and Revenue Meter