Scatter Correction And Pre-Arcing Time Evaluation For Cb Closing - Hitachi Relion 650 Series Technical Manual

1MRK 511 557-UEN Rev. A
The healthiness of electrical feedback signals (CB current or load voltage) are evaluated inside
ACBMSCBR function. From a healthy load voltage signal, ACBMSCBR evaluates the zero crossings
by comparing the polarity of consecutive samples. If two consecutive samples have opposite polarity,
a zero crossing must be located between them. This is shown in
crossings ZC1 and ZC2 have been detected. Using linear interpolation, the time stamp of a zero-
crossing point is calculated between the two samples of opposite polarity.
IEC19000764 V1 EN-US
Figure 120: Interpolation of zero-crossings from adjacent samples
If "Load voltage" or "None" is selected either in FeedbackSigC or FeedbackSigO and both source
voltage and load voltage are considered healthy, the phase shift between the two signals is
calculated from the time stamps of the zero crossings and provided on the UPHSFTLX output.
12.18.7.4

Scatter correction and pre-arcing time evaluation for CB closing

As suggested by CIGRE WG 13.07, the controlled energizing angles can be optimized based on the
position of the angle on the gap voltage across breaker contacts. The value of the gap voltage can
vary based on the load configuration. For example, in case of a star grounded load without stored
energy, the magnitude of the gap voltage is equal to the connected source voltage whereas in case
of ungrounded load, the total gap voltage across the first two simultaneous closing phases together
is equal to the phase-phase voltage.
Conceptually, every breaker closes onto the gap voltage. To optimize the controlled switching
performance in the system, the function statistically optimizes the switching angle considering the
breaker characteristics.
It is generally assumed that the mechanical switching times and the dynamic dielectric withstand
properties of a circuit breaker, as a mechanical device, are not perfectly constant but normally
distributed around the mean value. The breaker data comes with a specification of ±3σ scatter value
and a mean value of μ. The scatter value of ±3σ defines the maximum (99.7%) deviation from the
mean value that can be expected under realistic conditions.
For mechanical closing time of the CB, the mean value is obtained from the input INPPRICLLX and
its scatter from the setting ScatterMechCl. Thus, the final mechanical operating time for any specific
closing operation is expected to lie between the limits: (INPPRICLLX – ScatterMechCl) and
(INPPRICLLX + ScatterMechCl).
Similarly, for the rate of decrease of dielectric strength (RDDS) of the CB, the mean value is obtained
from the setting RDDS and the scatter from ScatterRDDS. Thus, the final RDDS for any specific
closing operation is expected to lie between the limits:
RDDS
min
IECEQUATION19049 V2 EN-US
and
Technical Manual
ZC ZC ZC ZC
1 1 2 2
Half cycle
time
IEC19000764-1-en.vsdx
 
ScatterRDDS
 
RDDS 1
100
© 2021 Hitachi Energy. All rights reserved.
Figure 120 where two zero
GUID-C3EF9951-C3B8-4C0F-8B19-BC136DC0DB2B v2
Section 12
Monitoring
277