
14
Technical guide VUC
|
1ZSC000562-AAX en, Rev. 1
MVI
MC
RVI
TR
RC
BPC
x
v
MVI
MC
RVI
TR
RC
BPC
x
v
MVI
MC
RVI
TR
RC
BPC
x
v
MVI
MC
RVI
TR
RC
BPC
x
v
Switching sequence, VUCL
By using an auxiliary contact system (MC, RC) in combination
with the vacuum interrupters (MVI, RVI) only two vacuum
interrupters are required per phase.
The switching sequence is that for an assymetrical pennant
cycle always going with the main contact first (called diverter
switch with one transition resistor #1 in IEC 60214-1,
2003-02). Fig. 16 shows the current path during normal
operation, from x to the neutral point (could also be to the
next phase). When commuting the load from x to v, the first
part of the operation sequence is to open the bypass contact
(BPC), Figs. 17 and 18. Next is to open the main vacuum
interrupter (MVI) and hence let the current flow through the
Fig. 16.
Fig. 17.
Fig. 18.
Fig. 19.
transition resistor (TR), Fig. 19. The main contact (MC) is then
rotated (Figs. 20 and 21) in order to connect to v. The main
vacuum interrupter then closes, leading to an associated
circulating current driven by the difference in voltage potential,
Fig. 22. The load current now goes from v to the neutral point.
The voltage is now changed one step. The bypass contact
is then connected to v (Figs. 23 and 24). The load current
is now via the normal path from v to the neutral point. In
Fig. 25, the transition resistor is disconnected when opening
the resistor vacuum interrupter (RVI). The resistor contact
(RC) is then rotated (Fig. 26) and makes to the v-side. Finally,
the sequence is completed and next service position is fully
reached when the resistor vacuum interrupter is closed, see
Fig. 27.