Hitachi Relion 650 Series Technical Manual page 286

Section 12
Monitoring
Gap voltage
RDDS
1
0

IEC20000101 V2 EN-US
Figure 123: Pre-arcing time and scatter correction during gap voltage zero closing
The value of PPREARCLX (in milliseconds) is calculated as.
IECEQUATION20100 V2 EN-US
Closing at gap voltage peak
The objective of considering breaker scatter for gap voltage peak application is to maximize the pre-
striking voltage.
Aiming for current making precisely at gap voltage peak may actually result in fairly low pre-strike
voltage.
above) is lower than the maximum system voltage gradient.
the breaker when the maximum RDDS (as defined above) is greater/equal the maximum system
voltage gradient.
IEC19000912 V2 EN-US
Figure 124: Voltage peak closing with low-RDDS circuit breaker : (a) Closing target at gap
280
2

T
T
6
1
Figure 124(a) displays the behavior of the breaker when the maximum RDDS (as defined
Angle
(a)
Nominal dielectric strength with slope
RDDS
Mechanically scattered dielectric strength
Electrically scattered dielectric strength
with slope RDDS
max
Electrically scattered dielectric strength
with slope RDDS
min
voltage peak. (b) Shifted closing target for maximum pre-strike voltage.
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0 = Gap voltage zero
1 = Electrical target making instant
2 = Mechanical target closing instant
 
PPREARCLX= T
2
1
 
T
SCATTERLX = 1
6
Figure
(b)
Earliest probable pre-strike instant
Latest probable pre-strike instant
Nominal prestrike instant
1MRK 511 557-UEN Rev. A
1 = Pre-arcing time
0 = Scatter correction
GUID-5C077764-B3AB-4FFC-A59F-5ABBC7B44C12 v2
125(a) displays the behavior of
Angle
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