Functions
2.7 Monitoring Function
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009
134
Figure 2-46
Current symmetry monitoring
Broken Conductor
A broken wire of the protected line or in the current transformer secondary circuit can be detected if a minimum
current
PoleOpenCurrent
flows via the line. If the minimum phase current is below this limit while the other
phase currents are above this limit, an interruption of this conductor may be assumed. If current asymmetry
occurs (see margin heading „Current symmetry“), the device issues the indication
„Fail Conductor“
(No. 195).
Voltage Symmetry
In healthy network operation it can be expected that the voltages are nearly balanced. The monitoring of the
measured values in the device checks this balance. The smallest phase voltage is compared to the largest.
Non-symmetry is detected when
|U
min
| / | U
max
| <
BAL. FACTOR U
as long as | U
max
| >
BALANCE U-LIMIT
U
max
is the largest of the three phase-to-phase voltages and U
min
the smallest. The symmetry factor
BAL.
FACTOR U
(address
2903
) represents the allowable asymmetry of the voltages while the limit value
BALANCE
U-LIMIT
(address
2902
) is the lower limit of the operating range of this monitoring (see Figure 2-47). The
dropout ratio is about 97%.
After a settable time, this malfunction is signaled as
„Fail U balance“
(no. 167).
Summary of Contents for Siprotec 7VK61
Page 8: ...Preface SIPROTEC 7VK61 Manual C53000 G1176 C159 3 Release date 05 2009 8 ...
Page 14: ...Contents SIPROTEC 7VK61 Manual C53000 G1176 C159 3 Release date 05 2009 14 ...
Page 316: ...Literature SIPROTEC 7VK61 Manual C53000 G1176 C159 3 Release date 05 2009 316 ...
Page 328: ...Glossary SIPROTEC 7VK61 Manual C53000 G1176 C159 3 Release date 05 2009 328 ...
