Hitachi Relion 650 Series Technical Manual page 67

1MRK 511 557-UEN Rev. A
IEC17000175 V2 EN-US
Figure 27:
Inductive loads, upon interruption of current, create high-frequency Transient Recovery Voltages
(TRV). Similar to the case of de-energization of capacitive loads, the circuit breaker should have
gained sufficient dielectric strength to avoid re-ignitions after current interruption.
IEC17000176 V2 EN-US
Figure 28:
Generally, targeting high arcing time for interrupting inductive current can increase the current
chopping, thus creating higher TRV. Conversely, targeting low arcing time can help in reducing the
TRV but the circuit breaker might not gain sufficient dielectric strength to withstand the TRV after
initial interruption. The minimum arcing time for re-ignition free interruption of a circuit breaker can be
deduced from inductive switching type tests for the specific circuit. By default, PWC600 applies a
compromise strategy of opening the primary contacts in the middle between the minimum arcing time
defined for the specific circuit breaker model and the nominal half cycle length of power frequency.
This algorithm is implemented in Switchsync Setting Tool (SST) and described in more detail in the
User Manual.
In case of a transformer, the charging current is usually so small that a modern circuit-breaker will
extinguish it by chopping within a very short time, usually not exceeding a millisecond. Thus, the
instant of contact separation will essentially coincide with the interruption instant.
Figure 29
no energy is stored in the reactor prior to energization, the source voltage wave shown in the figure
will appear across the circuit breaker contacts until the circuit breaker closes electrically. If a
command is given at any random instant t
electrically at t
point on wave D
circumstances, it is recommended to optimize the switching targets based on the design and
connection configuration of connected load that need to be switched. A point-on-wave controller such
as PWC600 analyzes the reference voltage signal and identifies a favorable switching target (D
Technical Manual
t t
open int
Current_L1 Vtrv_L1
Capacitive load de-energization
Reactor de-energization
shows an ideal circuit breaker closing on a grounded single phase reactive load. Assuming
and mechanically after the circuit breaker operating time T
rsi
at which this switching happens might create undesirable transients. In such
rsi
© 2021 Hitachi Energy. All rights reserved.
Contact_Gap_Dielectric_Strength_L1
to the circuit breaker, the circuit breaker will close
rsc
Controlled Switching and Monitoring
Time(ms)
Vsource_L1
IEC17000175‐2‐en.vsdx
. However, the random
CB
Section 7
, at
osi
61