Type “A” Bushings
The Type “All bushings introduced in 1924 have been modified many times, but all designs have in common the use of a single-piece porcelain which extends through the apparatus and provides the major insulation of the bushing.
Type “All detachable cable conductor bushings manufactured prior to 1941 used a mounting support flange bolted to a clamping ring which, in turn, is cemented to the porcelain. In some older modifications of this construction, the support flange is cemented directly to the porcelain.
From 1941 to 1952 a modification of the detachable-cable bushing eliminated the support flange by gasketing the ground-porcelain surface of the bushing against the apparatus housing.
In 1952 a more modern design, having a detachable cable conductor, was made by using a three- section mounting clamp and washer. This same design is also built with a solid conductor.
The majority of Type “A” bushings in service use no liquid filler. However, some designs, particularly high current ratings, have been manufactured with No. 10-C oil in the bushing, or with provisions for self-filling the bushing with oil from the transformer to improve radio-influence- voltage characteristics.
Type “B” Bushings
ngs were in active Production from 1916 to 1930, and continued in limited
d terminal cap providing a weather-tight structure The Type “B” bushi
application to 1945. The Type “B” bushings are compound-filled bushings but are characterized by a flexible cable conductor, rather than a rigid core. The bushing consists of a one-piece porcelain assembled with clamping rings, a support flange an
around the upper portion of a flexible, varnished-cambric-insulated cable conductor. The space between the porcelain and the insulated conductor is filled with a pliant insulation compound. A typical bushing of this design is shown.
These bushings were also furnished as double conductor (Type BD) and as triple conductor (Type BE).
Type “F” Bushings
Type “F” bushings were in use from 1948 to approximately 1955 on G. E. power, distribution and instrument transformers, and oil circuit breakers, in voltage ratings from 92 to 330 kV. They were furnished in 69-kV ratings for special application.
To provide a voltage supply for potential devices, ome Type “F” bushings rated 92 kV and above were built with a capacitance tap. All oil-circuit-breaker bushings, 115 kV and above are provided with a capacitance tap.
The Type “F” bushing design is a completely sealed, oil-filled construction with Herkolite insulating cylinders and concentric oil ducts around a central metal tube or rod.
s
Type “L” Bushings
Types “L,” “LI” and “LM” bushings were manufactured from 1932 to 1951. They were used on power, distribution and instrument transformers, and oil circuit breakers in ratings of 15 to 73 kV inclusive.
The Type “L” bushings consists of one-piece porcelain assembled to provide a liquid-tight structure around the upper portion of the core. The core is Herkolite insulation wound on a central metallic tube or rod. The space between the core and the porcelain is oil filled.
plications in the range of 15 to 69
e porcelain and Herkolite is oil-filled and completely sealed.
Type “LC” Bushings
Type “LC” bushings have been in production since 1951 for ap kV.
The Type “LC” bushing core consists of resin-impregnated Herkolite insulation, wound on a central metallic tube or rod. The upper porcelain is center-clamped; the space between th
8 to 1948 and were used on power, akers rated 92 to 230 kV. For special own to 34.5 kV. The bushin s are of the open-type construction
ht opper
To provide a voltage supply for potential devices some Type “OF” bushings rated 73 kV and above were built with a capacitance tap.
Type “OF” Bushings
Type “OF” and “OFI” bushings were manufactured from 19 distribution and instrument transformers, and oil circuit bre applications they were also used d
1 g with glass expansion chambers for observing the oil level.
The Type “OF” bushing consists of two or more porcelains structure around the series of spaced, concentric, Herkolite in tube or rod.
assembled so as to provide an oil-tig sulating cylinders and a central c
Type “S” Bushings∗ (Rigid Core)
Types “S”, “SI”, and “SM” bushings were manufactured from 1916 to approximately 1932 for
of the core is enclosed by porcelain, the space between the porcelain and core being filled with a solid insulating compound.
transformers and oil circuit breakers in ratings from 15 to 73 kV.
The general construction of the Type “S” bushing embodies a rigid core, consisting of a metal tube or rod covered with Herkolite insulation. The upper part
Figure 10-8 General Electric Type S Bushings
∗ Type “S” (Forms F, DF and EF) is flexible cable bushings and has been redesignated as Types “B”, “BD” and
“BE”. Description of these bushings is listed under Type “B” bushings. Type “S” bushings with no form letter have been redesignated Type “A”. Description is listed under Type “A” bushings.
Type “U” Bushings
Type “U” bushings are designed for applications between ution and instrument ers, and on oil circuit breakers. They are of the
d type.
e fundamental principle of design of the Type “U” bushing is the proper combination of volta
equalizers and oil-impregnated paper on a cen tube or 23 and 700 kV on power, distrib
transform
completely sealed oil-fille Th
ge stress tral metal
rod.
Production of these bushings in the 69 through 138 kV ratings has included both magnetic liquid level gages and transparent glass expansion chambers. To provide a voltage supply for potential devices all Type “U” bushings, 92 kV and above, are built with a capacitance
Figure 10-9 General Electric Type U Bushings
tap, which can also be used for power factor tests. All Type “U” bushings below 92 kV are provided with a power factor test tap to facilitate field-testing.