FIELD OF THE INVENTION:
The invention relates to the development of a novel bushing head assembly (36
KV 12500 A) at the LV side of a power transformer for connection through copper
cable in replacement of earlier practice of sectional copper flat bars, providing
more degree of freedom and flexibility in connection for high rating transformer.
BACKGROUND AND PRIOR ART:
Currently, in the majority of generator transformers 21/420 kV class, bushing head
assembly is designed for flat copper bar connection. This increased number of
joints between terminal gear assembly and bushing head assembly. Due to rigidity
of copper bar, it has been observed that connection between bushing head &
terminal gear was not proper which results in transformer turret heating problem.
In the transformer under consideration, high current low voltage terminal
connection is shifted from copper bar to copper cable terminal connection.
Earlier type bushing head assembly is of variable length. Length of bushing head
assembly is totally dependent on terminal gear design. As a result earlier type
bushing head assembly could not be standardized. But due to development of this

arrangement bushing head assembly can now be standardized and can be
supplied in short interval of time.
OBJECTS OF THE INVENTION:
The object of the invention is to improve connection of the bushing of power
transfer on the way to increase flexibility and degree of freedom.
Further object of the invention is to reduce heating effect of turret.
Still another object of the invention is to increase productivity by way of reducing
time of connection.
Also the objection is focused at standardization of bushing design.
SUMMARY OF THE INVENTION:
In present invention, transformer turret heating is one of the major problems
faced by the customer. To comply to the customer requirement of reduced turret
heating and subsequent losses in transformer, this unique bushing head assembly
has been developed in respect of new terminal gear assembly.

This development has been used in new design generator transformer (200 MVA,
21/400 KV class) with respect to terminal gear (cable type) & connection to
terminal gear (cable type).
After implementation of such development current flow has been smooth,
productivity has increased and turret heating problem has been reduced due to
improved cable type connection.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1: Shows the drawing of bushing head assembly & crimping terminal.
Figure 2: Shows the connection diagram of conventional type bushing head
assembly & terminal gear assembly suitable for 200 MVA 21/400 KV
Terminals gear. In this diagram bushing head assembly is connected
with flat copper bar terminal gear.
Figure 3: Shows the connection diagram of novel type bushing head assembly
& terminal gear assembly suitable for 200 MVA 21/400 kV Terminals
gear. In this diagram bushing head assembly is connected with
copper cable terminal gear.

Figure 4: Shows the side view of conventional terminal gear (copper bar type)
connection with bushing head assembly.
The drawing also shows how meticulously the connection has been done
maintaining the required clearances from earth parts (turret body).
Figure 5: Shows the side views of novel terminal gear (copper cable type)
connection with bushing head assembly.
The drawing also shows how meticulously the connection has been done
maintaining the required clearances from earth parts (turret body).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT:
This patent is being filed for developing a bushing head assembly part of LV
bushing 36 KV 12500 ampere bushing of 200 MVA, 21/420 KV generator
transformer. Development has been done in this transformer to improve
connection, reduce heating in LV Turret & to increase productivity with respect to
termination of bushing head assembly length with the use of unique bushing head.
In case of copper bar type connection of terminal gear with bushing head
assembly, the connection is not proper due to rigidity of copper bar. This results in
reduced contact surface area and resultant increase in current density at contact

spots. These contact spots are region of high temperature and results in heating
and losses.
In conventional design copper flat sectional bars are selected based on the current
on the LV side, which is generally high in addition to other parameters i.e. current
density, current gradient and basic insulation level.
In respect of present invention the length of bushing head assembly is fixed
whereas in conventional design, length of bushing head is variable due to variation
of current rating and sizes of copper flat bars.
The basic problem for connection with copper bars (12) lies in its shape, size and
hardness as the same involves several steps as cutting to sizes, drilling holes,
bending, locking through locking arrangement (13) and connection to bushing
head assembly (14).
The new bushing head assembly (10) is on the contrary is a simple configuration
as shown in Fig.1, wherein the low voltage terminal gear with copper cable (15) is
connected through sleeve arrangement (17) and tightly held by the cleat
arrangement (16). The method results flexibility between connection points and
increased productivity.

The new bushing head assembly (10) is used for a generator transformer with
cable type terminal gear assembly (15). In the present development, cable type
terminal gear (15) with the use of crimping terminal (11) into bushing head
assembly (10) has been envisaged which is suitable for low voltage high current
bushing head assembly.
Thus changing of copper bar to copper cable in higher rating job, automatically
changes the connection and configuration of bushing head assembly.

WE CLAIM
1. A bushing head assembly (10), characterized by a standard size & shape for
connecting low voltage copper cable terminal gear (15) of variable sizes for
power transformer.
2. A bushing head assembly (10) as claimed in claim 1, configured to connect
crimping terminal (11) for flexible cable.
3. A bushing head assembly (10) as claimed in claim 1, wherein cleat
arrangement (16) is disposed to hold the cables in a fixed position.
4. A bushing head assembly (10) as claimed in claim 1, wherein sleeve
arrangement (17) is configured to provide better alignment of cables in
respective positions, insulation and assembly.
5. A method to connect low voltage power cable terminal gear (15) of variable
sizes in the standard bushing head assembly (10) of a power transformer
through necessary crimping terminal (11), sleeve arrangement (17), and cleat
arrangement (16).