Siemens GM-SG

Electrical
Connections
Transformer
Bus
Joints
-
Insulation
The
typical
transformer
to
switchgear
bus
joint
shown
in
Figure
24
is
different
from
other bus
joints
in
the
switchgear
main bus
.
In
the
transformer
bus
joints
,
there is
a
transition
from
the
fully
insulated
switchgear
system
to
the
transformer
,
where the
spacing
between conductors
is
usually large enough
so
that
the conductors
need
not
be
insulated
.
The
use
of flexible
connectors
in
this
area
insures
correct
alignment
of
the
switchgear
conductors
to
the
transformer
conductors
.
If
the installed clearance
(
phase
-
to
-
phase
or
phase
-
to
-
ground
)
is
less
than
6
"
(
152
mm
)
for
8.25
kV
and
15
kV
switchgear
(
3.5
"
(
89
mm
)
for
5
kV
switchgear
)
,
the
joint
must
be insulated
.
Refer
to
Figure
24
,
and insulate bus
joint
connections
as
outlined under
"
Bus
Joint Insulation
-
Taping
"
.
Bus
Joint Insulation
-
Taping
Insulation boots
are
normally
provided
for
repetitive
or
standard bus
joint
conditions
.
Where boots
are
not
provided
,
the
bus
joints
must
be
carefully
taped
to
the
required
insulation level
as
described below
.
See
Figure
26
,
which
depicts taped
joints
associated
with
a
cable
lug mounting
arrangement
for
multiple
cables
.
(
Note
:
When the cables
associated
with
Figure
26
have been
installed
,
the
cable
terminations
and
exposed
bus
must
also be insulated
)
.
1
.
Inspect
bolted
joints
to
insure
they
are
correctly
assembled
;
bolt heads
in
proper
direction and
hardware has been
torqued
to
proper
value
.
All
surfaces
must
be
free of
dust
,
dirt
or
other
foreign
material
.
2
.
Apply
a
mastic
pad
over
nuts
and
a
second
pad
over
the bolt
heads
.
Use
either
small
(
15
-
171
-
988
-
001
:
3.25
"
x
4.50
"
(
83
mm
x
114
mm
)
or
large
(
15
-
171
-
988
-
002
:
4.50
"
x
6.50
”
(
114
mm
x
164
mm
))
size
pad
most
suitable
for
joint
involved
.
Remove
backing
and
press
adhesive side down
and
mold
in
place
covering
all
sharp
projections
.
Cover
hardware and
sharp
edges
of
bus
bar
if
any
will
be
against
the
tape
.
3
.
Apply
half
-
lapped
layers
of
4
”
(
102
mm
)
wide
tape
(
15
-
171
-
987
-
002
)
or
1
"
(
25
mm
)
wide
tape
(
15
-
171
-
987
-
001
)
over
the
joint
.
Each
layer
should
overlap
the bus bar insulation
by
at
least
1
-
1
/
2
"
(
38
mm
)
.
Stretching
of
tape
10
%
to
15
%
in
problem
areas
may
help
in
eliminating
voids and wrinkles
.
For
5
kV
class
equipment
,
use
two
half
-
lapped
layers
of
tape
over
mastic
pads
.
For
8.25
kV
and
15
kV
class
equipment
,
use
three
half
-
lapped
layers
of
tape
over
the mastic
pads
.
Avoid excessive
pressure
on
the
completed
bus
joint
insulation
.
If
bus
joints
are on
standoff
insulators
,
apply
tape
per
the
above
procedures
except
the
half
-
lapped
tape
should
overlap
the insulator
by
at
least
2
"
(
51
mm
)
.
1.50
"
(
38
mm
)
min
.
overlap
Bus
Insulation
1
"
or
4
"
Tape
(
1
/
2
Lapped
)
8.25
&
15
kV
-
3
layers
4.76
kV
-
2
layers
Mastic Pad
Note
1
Note
1
1.50
"
(
38
mm
)
min
.
overlap
8.25
&
15
kV
4
"
(
102
mm
)
7
"
(
178
mm
)
4.76
kV
*
4.76
kV
2
"
(
51
mm
)
Build
up
equal
to
insulation
thickness
18
"
(
457
mm
)
8
^
58
15
kV
2
"
(
51
mm
)
4
"
(
102
mm
)
T
\
^
Note
1
Note
1
I
-
-
-
"
Ground
sensing
CT
Note
1
:
Dimensions
are
for reference
only
.
Size
and
location
of
stress
cone as
recommended
by
cable
manufacturer
Ground
lead
to
shielding
at stress
cone
must
pass
thru
CT
as
shown
for
proper
relay
operation
.
Figure
25
.
Primary
Cable
Termination and Insulation
Minimum clearance
over
insulation
phase
to
phase
(
A
)
and
phase
to
ground
(
B
)
shall
not
be less than
:
4.76
kV
-
1.75
"
(
45
mm
)
8.25
kV
&
15
kV
-
3.25
"
(
83
mm
)
Uninsulated
Transformer
Connection
Mastic Pad
Insulated
Switchgear
1
"
or
4
"
tape
(
1
/
2
lapped
)
4.76
kV
-
2
layers
8.25
kV
&
15
kV
-
3
layers
Q
Flexible
/
Connector
Insulated Phase Ends
Bus
r
-
i
/
m
B
1 1 1
Bus
Insulation
1
"
or
4
"
Tape
(
1
/
2
Lapped
8.25
&
15
kV
-
3
layers
4.76
kV
-
2
layers
I I
A
"
A
' '
B
D
B
Bus
Insulation
1.5
"
(
38
mm
)
min
.
overlap
Mastic
Pad
1.50
"
(
38
mm
)
min
.
Overlap
-
Rear
View
(
Bottom
Cable
)
Side
View
(
Top
Cable
)
D
=
6.00
"
(
152
mm
)
min
.
for
8.25
kV
&
15
kV
D
=
3.50
"
(
89
mm
)
min
.
for
4.76
kV
Figure
26
.
Typical
Cable
Terminal
Mounting
and Insulation
Figure
24
.
Taped
Joint Insulation
-
Switchgear
Bus
to
Transformer
Throat
29
Courtesy of NationalSwitchgear.com