The Fla 15/97 outdoor load-disconnectors with arc quenching vacuum chambers represent a series of advantages for the customers, not only by its state-of-the-art performances but also its environmental friendliness. In its design the products as such exhibit a link with the Fla 15/60 load-disconnectors which have successfully been proven in operation and which are manufactured on the basis of design documents originating from the German company Driescher. The external inlets and the operating principle of this switching device remains unchanged. Since many years the Fla 15/60 load-disconnectors are well known due to their high level of operation reliability and operation safety. Currently there are more than 30 000 pieces of Fla 15/60 load-disconnectors in operation.
The load-disconnectors comply with the following standards: IEC 694, IEC 129, IEC 265. Supporting insulators used with this load-disconnectors meet the pollution requirements as specified by class III.
The simple and rugged design of Fla load-disconnectors was tested in various climatic conditions with excellent results.
The steel, welded base frame of the switching device is made of open steel profiles, the form of which is very adequate for hot galvanisation. This kind of surface treatment provides for a corrosion free surface of the frame and makes easy the inspection of the surface. Hot galvanised coating is deposited also on load-disconnector shafts, seated in bronze bearings, and on all other steel parts including the accessories. All current carrying parts are manufactured of silver coated electrolytical copper and as a bulk they form a loop-free path for the current flow.
The cross sections of current carrying parts are dimensioned adequately. The pressure exerted by contact pressure springs, made of stainless steel, are one of the prerequisites for a defect-free switching process, even after many years of operation in severest operating conditions and in areas where icing can be encountered.
The load-disconnectors are delivered with supports made of cycloaliphatic resin.
The load-disconnectors can be completed with built-in earthing switches mounted on that side where a fixed or movable support is installed. When using the earthing switches the operating drive mechanism must be of double or triple design, with a rugged mechanical interlocking system that prevents an incorrect handling with the system. In such a case the number of draw bars and rocking bearings is to be increased adequately.
Load-disconnectors and the earthing switches are operated by external manual or motor operated drive mechanisms.
The load-disconnectors sometimes are equipped with additional encapsulated contacts (protection degree IP 44), mounted directly to the frame. These contacts serve for a remote indication of both the ON and OFF operating state of the disconnector.
The load-disconnectors feature a high margin of short-circuit withstand capacity, both for the load-disconnectors and for the built-in earthing switches.
The design and the quality of materials used in this load-disconnector provide for low operation and maintenance costs.

Advantages

• possibility of replacing the minimum oil arc quenching chambers with vacuum chambers
• higher life expectancy
• very low burn-off of the contacts
• compatibility between the old and the new arc quenching chambers
• higher performances

The switching occurs in tight and encapsulated vacuum quenching chambers which easily can be installed as a replacement for the old minimum oil chambers (filled with Shall Diala D or the Shell Fluid 4600 oil, the disposal of the latter of which can use biological processes).

Withstand voltages of Fla 15/97 load disconnectors

When in ON position the vacuum arc quenching chamber, together with the switching mechanism installed in a case made of insulating material, is connected in parallel to the current carrying path. This path has been designed for the through-flow of rated current values. When switching the load-disconnector OFF the main contacts first disconnect and in this way the whole current is redirected to the branch in parallel. In this branch we can find the vacuum chamber and additional switching device connected in series with the chamber. This circuit mechanically is designed as a fork with switching rollers which are shaped in form of a half dish. As soon as the main contacts have separated to an appropriate distance the contacts inside the vacuum chamber disconnect and the resulting arc gets cut during the first pass of the current through zero. Subsequently, the rocking insulator moves and a distance between the load-disconnector contacts now is clearly visible. The life expectancy of the vacuum chamber and the quick breaking mechanism is 5000 cycles, at minimum. All components installed in the current carrying path are silver coated. All metallic parts of the quick breaking mechanism are made of stainless steel.

Compatibility between the old and the new chambers

The Fla 15/60 load-disconnectors, which already were built-in into the frame can additionally be equipped with vacuum arc quenching chambers by using adapters (Cu busbars). The figure shows a retrofitted Fla 15/60 load-disconnector which now becomes the Fla 15/97 type.
Note: With some of the load-disconnector types also the control and contacting arms on movable supports have to be replaced.

Three-pole outdoor load-disconnector Fla 15/97 for mounting on wooden and concrete pole

1) hexagonal head screw, washer and spring washer

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