Outdoor load disconnectors, produced in accordance with the Driescher company´s documentation, used for several years on high-voltage long-distance lines, have proven their high reliability and safety of operation. Load disconnectors are intended particularly for terminal branchings in radial arrangement.
Load disconnectors satisfy standards IEC 129, IEC 694 and IEC 265. Using insulators satisfy the third grade of contmination area according.
Simple load disconnectors of a sturdy structure proved themselves in an excellent way under very different climatic conditions.
The foundation welded frame is made of open steel profiles which guarantee perfect surface protection from corrosion caused by heat zinc coating that can be controlled on all places. The shafts of the load disconnectors mounted in bronze bearings as well as all other steel components are protected by heat zinc coating, too.
Switching takes place in a tightly closed extinguishing chamber, filled either with Shell Diala D transformer oil or biologically degradable Shell Fluid 4600 transformer oil.
With regard to this fact, Fla 15/60 load disconnectors meet the extreme environmental requirements.
The biological degradation ability of the Shell Fluid 4600 oil was tested and is guaranted by the Deutsche Shell AG company. Measurements were carried out in accordance with the international methodics CEC-L-33-A.93.
In order to ensure a safe and reliable disconnection of electric path the DRIBO Flb 15/60 load disconnectors are equipped with arc quenching horns.
All current conduction components are made of silver plated electrolytical copper and constitute a loopless current conduction path.
The cross-section of the conductors on the current conduction path is sufficiently dimensioned. Appropriate contact pressures of the stainless steel springs ensure optimum prerequisites for faultless switching even after several years of the load disconnector operation under extreme operating conditions as well as under load.
The load disconnectors are delivered with such made of a cyclo-aliphatic resin or porcelain bearings.
The load disconnectors can be provided with earthing switches located on the side either of the fixed or of the pendulum bearing, possibly on both sides. The use of earthing switches requires a double or triple drive with a sturdy blocking mechanism preventing incorrect handling. The number of pull rods and pendulum bearings is correspondingly increased.
Control of the load disconnectors and earthing switches is ensured by means of hand, possibly motor outdoor drives.
The load disconnectors can be provided with encased auxiliary switches (IP 44 protection) installed directly on the frame of the device ensuring thus reliable switching-on and switching-off signalling.
The values of the short-circuit resistance are kept so as to ensure an adequately large reserve. These values apply both for the disconnectors and built-in earthing switches.
The construction of the load disconnectors and the quality of the materials being used ensure low cost operating conditions and maintenance.
Under normal operating conditions it is not necessary for the load disconnectors to undergo a preventive maintenance during the period of ten years.

Withstand voltages of Fla 15/60 and DRIBO Flb 15/60 load disconnectors

Tried and tested oil extinguishing chambers, parallelly connected to the main circuit, are provided with a quick-action switching mechanism.The extinguishing chambers are of an adequately sturdy structure ensuring that their tightness remains undamaged even under extreme service conditions. Each extinguishing chamber is filled with a quantity of about 0,5 l of Shell Diala D or Shell Fluid 4600 oil.

The above drawings show the current flow during switching in switching-on position, intermediate position and switched-off position of the disconnector. The contact arm mounted on the pendulum bearing is provided, on its end, with two rollers (2) their concave sides being inwards oriented. The extinguishing chamber (1) is controlled by the stainless-steel forked contact (3). When controlling the switch, the fork is positively entrained by the roller both during switching-on and switching-off. The snap-action mechanism connected with the said fork acts on the contact system inside the chamber and closes or opens immediately the contacts of the extinguishing chamber independently on the speed of the hand control. When switching-off, first of all the main contacts and only after having achieved the safety switching-off distance the contact system inside the extinguishing chamber is opened by the snap-action mechanism.Parallel connection of the switching chambers to the main circuit.

Sectional view of the extinguishing chamber

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