PTAP-AFH927

Technical Guide34.5 kV, 150 kV BIL

Type DO-III, Oil Immersed Drawout

ABB

Expulsion Fuse Holder

General Description

The ABB “DO-III” fuse holder is a draw out load breakexpulsion fuse holder designed for use with pad-mountedtransformers filled with transformer oil or other approved fluid.It is designed to protect the distribution system in the eventof an internal transformer fault, secondary fault, or severeoverload when used with properly coordinated series fuses.Following industry safety practices, the “DO-III” fuse holdercan be used to break load.

Features & Advantages

Oil ContainmentThe “DO-III” fuse holder’s housing has been redesigned toimprove safety and minimize environmental concerns. Itfeatures a vent hole located within the gas space of padmounted transformers. This vent hole reduces the risk of oilspillage resulting from line personnel inadvertently removingthe puller assembly without first venting the transformer. Theredesigned housing also incorporates an optional check valveas another method to reduce the risk of injury or cleanupcaused by excessive oil spillage. There are two methods forapplying the check valve. First, it can be used in conjunctionwith the vent hole to limit the amount of spillage produced ifthe oil level rises above the vent hole. Secondly, the checkvalve can serve as the sole protection by sealing the venthole. In this configuration the amount of oil released isdependent on the speed at which the puller assembly iswithdrawn. As shown in Figure 1, the check valve actuatesas the puller assembly is withdrawn and seals the transformer.

InterchangeableThe “DO-III” fuse holder is generally interchangeable withcompetitive designs. The housing, fuse cartridge, and pullerare individually interchangeable with competitive counterparts.

Tapered FlangeThe “DO-III” fuse holder’s designed housing incorporates a7° tapered flange. The tapered gasket seat holds the tankgasket in place during installation and retains the gasket inservice.

High Impact Strength Operating HandleThe operating handle is constructed of a special impactresistant, glass reinforced polymer to prevent breakage duringhot stick operations and accidental dropping on hard surfaces.

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Positive Latching HandleThe handle is designed with sufficient clearance between thehandle clamp and the lip of the outer tube in order to providesmoother operation and to ensure positive latching for greatersafety .

Hot Oil Resistant HousingThe “DO-III” fuse holder’s outer tube is constructed of a hightemperature, high dielectric strength, arc resistant, glassreinforced, polyester material. This material has proven itselfover many years of use in these types of distributiontransformer applications.

Large Contact SurfaceThe “DO-III” fuse holder has a large contact surface area tominimize heating of the contacts and provide positive contactalignment.

InstallationThe “DO-III” fuse holder is inserted through the transformertank wall. The mounting nut should be tightened between100 and 120 in-lbs (11.3 to 13.6 N-m). The assembly mustbe used in series with a current limiting fuse or isolation link.Connect the high voltage bushing lead to either the isolationlink or the current limiting fuse, and attach the link or fuse tothe lower contact in accordance with supplier’srecommendations. Next, connect the transformer’s primarywinding to the upper contact. Refer to Figure 2 for illustrationof proper connections. Remove puller assembly and installfuse element in accordance with supplier’s recommendations.

Design Tests

The ABB Type “DO-III” fuse holder successfully passed abattery of tests including:• Dielectric tests• Load switching tests• Fault interruption tests• Mechanical strength tests• Seal integrity tests• Contact temperature rise tests

Production Tests

In addition to the design testing, the following routineproduction tests are done on an audit basis to ensurecompliance to requirements:

• Dimension check on critical dimensions.• Insertion force test to verify contact pressure.• Visual inspection to verify molding and assembly process.

Figure 1: Fuse cartridge withdrawn closing check valve.

ABB 3

Figure 2: Illustration of DO-III fuse holder connections

ABBABB Inc.1128 S. Cavalier DriveAlamo, TN 38001, USATelephone: 731-696-5561Fax: 731-696-5362www.abb.com

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Type DO-III Drip Tray DrawoutExpulsion Fuse Holder Drip TrayPTAP-AFH927

Technical Information

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General Description

The ABB drip tray is designed for application on side wallmounted, draw out fuse holder assemblies. It prevents thetransformer insulating fluid from dripping onto the moldedrubber primary terminators and cables as the expulsion fuseis extracted from the transformer. The purpose of the driptray is to protect these rubber encapsulated components,which may not be compatible with certain transformer insu-lating fluids, by capturing the insulating fluid released as thepuller assembly is extracted.

Features and Advantages

DurabilityThe ABB drip tray incorporates a unique latch design whichprevents the transverse and cantilever loads applied duringhook stick fuse insertion and extraction from detaching it. Itis virtually impossible to inadvertantly dislodge the drip tray.The tray remains attached with 25 pound weight attachedto its lip.

InterchangeabilityThe ABB drip tray can be applied to all draw out fuseholders currently avilable.

Ordering Information

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