
10
Technical guide VUC
|
1ZSC000562-AAX en, Rev. 1
L (m)
3
2
1
VUCG.N/C
650 kV
short
VUCG.N/III
650 kV
VUCL.N/III
650 kV
VUCL.N/F
650 kV
VUCG.N/F
650 kV
Design differences across the VUC range of on-load tap-
changers
The VUC range of tap-changers consists of two diverter
switches and three tap selectors.
The diverter switches are VUCG and VUCL. Both have arc
quenching in vacuum interrupters. In VUCG the load current
goes continuously through the vacuum interrupters, while
VUCL has a by-pass contact for the load current when not
operating.
The maximum rated through current for VUCG and VUCL is
the same for all types of connection (N, T, E, B).
Diverter switch housing and top section
The top section forms the flange that is used for mounting to
the transformer cover, and for carrying the gear box for the
operating shafts. The top section includes a connection for
the conservator pipe, draining and sampling connections, an
earthing terminal, the supervisory device, and the cover with
its gasket. The top section is available in two designs, one for
cover mounting and one for pre-mounting (yoke-mounting) on
the transformer’s active part.
The diverter switch housings have high quality seals that
guarantee vacuum and overpressure-proof performance
under all service conditions. In case of material ageing after
extremely long service the seals can be re-tightened from the
inside of the housing.
The bottoms and heads of the cylinders are made of cast
aluminum.
The drive shafts and bevel gears are placed beside the
diverter switch cylinders, thereby providing easy access to the
diverter switches.
The bottom section has locating holes for the diverter switch,
bearings, brackets for the tap selector mounting and the
current terminal for the diverter switch. There is also a drain
valve in the bottom which should only be opened during the
drying process of the transformer.
The top and bottom sections are fixed to a cylinder of glass
fiber reinforced epoxi. The bushings through the cylinder
wall are sealed by O-ring gaskets with elastic pressure. Each
ready-made unit is tested under vacuum and the outside is
exposed to helium and checked for leaks with the use of a
helium gas detector.
Fig. 5. On-load tap-changers type VUC, size comparison.