MI 2792 PowerQ4 Plus
Theory and internal operation
120
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
a retained voltage between 85 % and 90 % of
U
Nom
can occur very frequently as a result
of the switching of loads in network users’ installations.
5.2.4 Short interruptions of the supply voltage
Under normal operating conditions the annual occurrence of short interruptions of the
supply voltage ranges from up to a few tens to up to several hundreds. The duration of
approximately 70 % of the short interruptions may be less than one second.
5.2.5 Long interruptions of the supply voltage
Under normal operating conditions the annual frequency of accidental voltage
interruptions longer than three minutes may be less than 10 or up to 50 depending on
the area.
5.2.6 Supply voltage unbalance
Under normal operating conditions, during each period of one week, 95 % of the 10 min
mean RMS values of the negative phase sequence component (fundamental) of the
supply voltage shall be within the range 0 % to 2 % of the positive phase sequence
component (fundamental). In some areas with partly single phase or two-phase
connected network users’ installations, unbalances up to about 3 % at three-phase
supply terminals occur.
5.2.7 THD voltage and harmonics
Under normal operating conditions, during each period of one week, 95 % of the 10 min
mean values of each individual harmonic voltage shall be less or equal to the value
given in table bellow.
Moreover, THD
U
values of the supply voltage (including all harmonics up to the order
40) shall be less than or equal to 8 %.
Table 5.6: Values of individual harmonic voltages at the supply
Odd harmonics
Not Multiples of 3
Multiples of 3
Even harmonics
Order h Relative
voltage (U
N
)
Order h
Relative
voltage (U
N
)
Order h Relative
voltage (U
N
)
5
6,0 %
3
5,0 %
2
2,0 %
7
5,0 %
9
1,5 %
4
1,0 %
11
3,5 %
15
0,5 %
6..24
0,5 %
13
3,0 %
21
0,5 %
17 2,0
%
