5 Theory and internal operation
91
5.2
EN 50160 Standard Overview
EN 50160 standard define, describes and specifies the main characteristics of the
voltage at a network user’s supply terminals in public low voltage and medium voltage
distribution networks under normal operating conditions. This standard describes the
limits or values within which the voltage characteristics can be expected to remain over
the whole of the public distribution network and do not describe the average situation
usually experienced by an individual network user. An overview of EN 50160 limits are
presented on table bellow.
Table 5.5: EN 50160 standard overview
Supply voltage
phenomenon
Acceptable
limits
Meas.
Interval
Monitoring
Period
Acceptance
Percentage
Power frequency
49.5 ÷ 50.5 Hz
47.0 ÷ 52.0 Hz
10 s
1 Week
99,5%
100%
230V ± 10%
95%
Supply voltage variations,
U
Nom
230V +10%
-15%
10 min
1 Week
100%
Flicker severity Plt
Plt
≤
1
2 h
1 Week
95%
Voltage Dips (
≤
1min)
10 to 1000 times
(under 85% of
U
Nom
)
10 ms
1 Year
100%
Short Interruptions
(
≤
3min)
10 ÷ 100 times
(under 1% of U
Nom
)
10 ms
1 Year
100%
Accidental long interruptions
(> 3min)
10 ÷ 50 times
(under 1% of U
Nom
)
10 ms
1 Year
100%
Voltage unbalance u-
0 ÷ 2 %,
occasionally 3%
10 min
1 Week
95%
Total harm. distortion, THD
U
8%
10 min
1 Week
95%
Harmonic Voltages, Uh
n
See Table 5.6
10 min
1 Week
95%
5.2.1 Power frequency
The nominal frequency of the supply voltage shall be 50 Hz, for systems with
synchronous connection to an interconnected system. Under normal operating
conditions the mean value of the fundamental frequency measured over 10 s shall be
within a range of:
50 Hz ± 1 % (49,5 Hz... 50,5 Hz) during 99,5 % of a year;
50 Hz + 4 % / - 6 % (i.e. 47 Hz... 52 Hz) during 100 % of the time.
5.2.2 Supply voltage variations
Under normal operating conditions, during each period of one week 95 % of the 10 min
mean U
Rms
values of the supply voltage shall be within the range of
U
Nom
± 10 %, and all
U
Rms
values of the supply voltage shall be within the range of
U
Nom
+ 10 % / - 15 %.
5.2.3 Voltage dips (Indicative values)
Under normal operating conditions the expected number of voltage dips in a year may
be from up to a few tens to up to one thousand. The majority of voltage dips have
duration less than 1 s and a retained voltage greater than 40 %. However, voltage dips
with greater depth and duration can occur infrequently. In some areas voltage dips with
