Introduction

FN18 is a general purpose, three-pole, load break switch that offers switchgear owners and assemblers the advantages of an advanced interrupting technology and proven, dependable performance in a compact design. The switch is available to switchgear assemblers as a building block for metal-enclosed and pad-mounted switchgear applications in ratings from 12 upto 24kV. The standard FN18 switch includes a heavy-duty steel frame with stand-off insulators, a unique puffer-type arc extinguishing system, an operating mechanism and current-carrying components, including blade-type interrupters with cast hinges and jaw connectors. Optional accessories and features include a variety of operating handles, a motor operator, auxiliary switches, a shunt trip device, fuse bases, mechanical fuse tripping, grounding switches, mechanical door interlocking and key interlocking.

Main Product Features

FN18 switch disconnectors are based on a modular principle, which gives it a wide range of functionality. With a unique design that extinguishes electric arcs and enables
high switching capacity, they represent an attractive solution as a key breaking element for applications in enclosed switchgear and transformer compact substations. In combination with current limiting fuses, FN18-F fuse switch disconnectors ensure control over the full range of overload and short-circuit currents.

The basic unit consists of a frame with insulators and current carrying parts. Two different types of operating mechanisms, snap action mechanism type K or stored spring energy mechanism type A, can be mounted on the frame. Fuse bases with or without fuse tripping mechanism, and an earthing switch type , suitable for both direct mounting and free standing components, complete the basic equipment of a switch disconnector. These modules can be easily configured according
to customer expectations. Accessories, such as shunt trip, under-voltage release, auxiliary
switches, motor operation and various systems for manual operation can easily be added.

Technical Specification

Basic Desigins

• FN18 load break switch

standard feature consists of chassis, insulators and current
carrying parts with the following pole distance:
– 12 kV – pole distance 150 mm, 170 mm and 210 mm
– 17.5 kV – pole distance 170 mm and 210 mm
– 24 kV – pole distance 170 mm*, 235 mm and 275 mm
– 36/40.5 kV – pole distance 360 mm
* – with insulating barriers
Rated currents are:
– 400, 630 and 1250 A up to 24 kV
– 630/800/1000 A for 36/40.5 kV

• FN18 load break switch with fuse

Is delivered with the same pole distances as the standard feature.
Fuse base type F is delivered for installation on both the opening and pivot sides, with or without automatic tripping.
A fuse base with six insulators can also be delivered separately with some form of signal indication when a fuse blows or for installation on the pivot side of the switch

• Mechanisms

Type A with two springs
The opening spring is always charged before the switch can be closed by means of a closing spring. This means the opening spring is always charged in a closed switch, which in turn can be
tripped immediately by hand, electrically or by a fuse-link striker system.

Type K with one spring
Closing or opening the switch is performed by charging the springpast the dead centre.

A and K mechanisms may cooperate with motor drives.

• Earthing Switch

D type earthing switch

This type of earthing switch is equipped with a quick spring mechanism. It can be mounted on the pivot side of the switch
disconnector or on the fuse base when the latter is on the pivot
side of the switch.

DB type earthing switch

Designed to be an independent assembly for both sides of the
disconnector.

Overall and installation dimensions