Drop-out fuse cutout

  • THC
  • RW8/PRWG1
  • RW5/HRW5
  • "KB/KU/KS"
  • RN1/RN3
  • THD

Quality Construction
Efficient Current Transfer
The cutout has an all copper single piece current path with Silver-plated contacts. Terminals are tin-plated brass for use with copper or aluminum conductor.
Galvanized steel hooks are standard on all cutouts, for use with a portable tool. The hooks are mounted under the top contact and serve as a guide for the fuse holder when closing at an off centre angle.
Top Contact
The top contact is designed such that it provides a smooth self aligning action during closing; the top contact is formed from highly conductive copper and is silver-plated, which provides a continuous current path from dome nut to PG clamp.
The contact is designed to maintain firm and constant pressure with the fuse holder contact surface until fault interruption is accomplished. Backing the top contact is the Loadbreak bracket, which prevents over-racking. Used in conjunction with a load break tool of the correct rating, the cutout can be opened under load.
The hinge on the cutouts employs a large pivot area for the fuse holder's trunnion and is manufactured from brass for its strength and superior electrical properties. The hinge contacts are of a highly conductive copper alloy and silver-plated to ensure an efficient current transfer from the trunnion casting.
Insulator (Silicone)
The advantages of HTV silicone are numerous, namely,
1. Silicone is the only housing materials that are able to transfer their intrinsic hydrophobic behavior to pollution layers. Therefore, leakage currents are suppressed and the risk of flashover is reduced. Moreover, composite insulators with silicone housings do not require cleaning. Some other polymers such as EPDM or some special Cycloaliphatics are also hydrophobic but not able to coat the pollution layers deposited on the housing surface.
2. High tensile strength to weight ratio.
3. Improved performance in highly polluted areas.
4. An unattractive target for vandals and very resistant to projectile damage.
5. Flexibility, providing better seismic capabilities and preventing cascade failure of post units.
6. High resistance to UV degradation.
7. High resistance to thermal extremes (-35oC to +50oC)
Insulator (Porcelain)
These insulators of sky-glazed grey porcelain, with leakage distances range from 230mm720mm, with BIL ratings of 110kV-170kV.
Tin plated copper alloy parallel groove type terminals are standard on all cutouts. They can accommodate aluminum or copper conductor. The parallel groove terminal is designed to accommodate two different size conductors, as is the case when arrestors are being used. Eyebolt and Lug mount options are also available.

Fuse Holder
The solid cap on the single vent fuse holder is made of silverplated brass, which provides efficient current transfer.
An integral ring is provided in the top tube casting for opening and closing the fuse holder using conventional disconnect tools from the ground, from a bucket truck or from a cherry picker.
The toggle type trunnion casting is of silver-plated brass for efficient current transfer to the lower hinge contacts. Cams on the trunnion ensure high-pressure current path to the lower contacts. The pivot bosses are cast full round for smooth rotational operation in the hinge but prevent the trunnion from disengaging when closing the fuse tube. The spring operated link ejector assists with clearing low-level fault currents. A groove in the centre of the link ejector guides the fuse tail directly from the fuse tube to the attachment nut. Radii on the link ejector minimise the bending stress on the fuse tail to prevent strands breaking.
The link is pinned to the trunnion with a brass pin to provide resistance to corrosive elements and assure smooth pivotal action. An interlocking device between link and bottom tube casting prevents excessive tension on the fuse link during closure, which could cause link breakage during closure.
The link employs an impact effect to ensure toggle action of the trunnion during low fault and overload interruptions. Dropout action is assured. The link provides sufficient surface area to facilitate re-fusing by a linesman wearing gloves.
Fuse Tube
The inside diameter of the fuse tube increases the internal pressure, giving superior and reliable expulsion action. During frequently encountered intermediate fault ranges, this diameter also permits higher TRV, (Transient Recovery Voltage), values to be tolerated. The liner is constructed of an arc quenching material. The tube is manufactured from fiberglass, which permits a smaller bore and provides higher burst strength.
It is protected from the weather and environment by an ultra violet resistant coating.
All mounting brackets are manufactured from steel to international standards and are hot dip galvanized. Stainless steel options are available on request.
Higher interrupt capacities
By using a copper arc-shortening rod attached to the dome nut inside the top of the fuse tube, lowering the fuse link, higher interrupt ratings are obtainable. It is necessary to use fuse links with removable button heads when using an arc-shortening rod.
Creepage distance
Cutouts are available for use under various pollution conditions.
Units are available in 245mm to 870mm, other creepage
distance are available on request.
Extra Corrosion protection
All cutouts are available with components made from stainless steel and plated copper alloy, to offer greater corrosion resistance for severely aggressive environments where corrosion can become a major factor.

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