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Another major application is the long-term power quality monitoring. This can be used to
confirm a compliance to the standard power supply quality norms. The function provides
a voltage unbalance level which corresponds to the 95
th
percentile of the ten minutes'
average values of voltage unbalance recorded over a period of up to one week. It means
that for 95 percent of time during the observation period the voltage unbalance was less
than or equal to the calculated percentile. An alarm can be obtained if this value exceeds
the value that can be set.
The function uses five different methods for calculating voltage unbalance.
•
Negative-sequence voltage magnitude
•
Zero-sequence voltage magnitude
•
Ratio of negative-sequence to positive-sequence voltage magnitude
•
Ratio of zero-sequence to positive-sequence voltage magnitude
•
Ratio of maximum phase voltage magnitude deviation from the mean voltage
magnitude to the mean of phase voltage magnitude.
Usually, the ratio of the negative-sequence voltage magnitude to the positive-sequence
voltage magnitude is selected for monitoring the voltage unbalance. However, other
methods may also be used if required.
10.4.6
Signals
Table 938:
PQVUB Input signals
Name
Type
Default
Description
V_A
SIGNAL
0
Phase A voltage
V_B
SIGNAL
0
Phase B voltage
V_C
SIGNAL
0
Phase C voltage
V
1
SIGNAL
0
Positive phase sequence voltage
V
2
SIGNAL
0
Negative phase sequence voltage
V
0
SIGNAL
0
Zero sequence voltage
BLOCK
BOOLEAN
0=False
Block all outputs except measured values
Table 939:
PQVUB Output signals
Name
Type
Description
MN_UNB_AL
BOOLEAN
Alarm active when 3 sec voltage unbalance exceeds the
limit
PCT_UNB_AL
BOOLEAN
Alarm active when percentile unbalance exceeds the
limit
OBS_PR_ACT
BOOLEAN
Observation period is active
1MAC059074-MB A
Section 10
Power quality measurement functions
615 series ANSI
1069
Technical Manual
Содержание Relion 615 series
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