GE KOTEF-72 User manual

© GE Grid Solutions
INSTRUCTION MANUAL - 19401
72.5kV COMBINED TRANSFORMER
TYPE KOTEF-72

Instruction Manual
© GE Grid Solutions 2
GE Grid Solutions
Av. Nossa Senhora da Piedade, 1021
37504-358 Itajubá - MG – Brasil
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Owner revision Date Prepared Approved

Instruction Manual
© GE Grid Solutions 3
Warning!
Any person involved with transport, installation, energizing, operation and maintenance of 72kV
Combined Transformer type KOTEF72 must read these instructions prior to any action related
to these current transformers.
These Combined Transformer are built under strict conditions which guarantee the Highest
Quality achievement. In order to keep this high quality during Combined transformers lifespan,
it is utmost important that the instructions in this Manual be thoroughly read and complied
with.
THESE COMBINED TRANSFORMERS CAN NOT BE STORED IN A HORIZONTAL POSITION.
Preliminary Remarks
During reception of the Combined Unit, it is important to check unpacking attentively in order to
control the condition of the transportation crate and the transformer itself. Any irregularities
shall be recorded on the transport delivery note and a formal communication shall be sent to
the responsible person immediately.
The supplied insulator can be made of porcelain, therefore, sudden movements that could cause
damage due to cracks shall be avoided.

Instruction Manual
© GE Grid Solutions 4
INDEX
1. GENERAL DRAWING ............................................................................................................. 5
2. DESIGN AND CONSTRUCTION ............................................................................................. 6
2.1. Inverted construction and primary circuit for CT part ......................................................... 6
2.2. Secondary circuit for the CT part ...................................................................................... 6
2.3. Paper-oil insulation ........................................................................................................... 6
2.4. Cast aluminum tanks ........................................................................................................ 7
2.5. External metallic parts ....................................................................................................... 7
3. TRANSPORT, RECEPTION, UNPACKING AND STORAGE .................................................. 7
3.1. Transportation................................................................................................................... 7
3.2. Reception ......................................................................................................................... 7
3.3. Unpacking ................................................................................................................................. 7
3.4. Storage ............................................................................................................................. 8
4. BELLOWS BLOCKING SYSTEM AND ASSEMBLY IN THE STRUCTURE ............................. 8
4.1. Bellows blocking system ................................................................................................... 8
4.2. Assembly in the structure .................................................................................................. 9
5. CONTACT SURFACES PREPARATION ................................................................................. 9
6. CONNECTIONS .................................................................................................................... 10
6.1. Primary Terminals ........................................................................................................... 10
6.2. Primary bar type (if applicable) ....................................................................................... 10
6.3. Two bar or Four bar Reconnection Primary type (if applicable) ....................................... 10
6.4. Grounding ....................................................................................................................... 10
6.5. Secondary terminals ....................................................................................................... 10
6.6. Terminal marking ............................................................................................................ 11
7. OIL LEVEL INDICATOR ........................................................................................................ 11
8. INSPECTION BEFORE FIRST ENERGIZING ....................................................................... 11
9. MAINTAINENCE AFTER ENERGIZING ................................................................................ 12
10. PROPER DISPOSAL OF TRANSFORMERS COMPONENTS AFTER LIFESPAN ................ 13

Instruction Manual
© GE Grid Solutions 5
1. GENERAL DRAWING
Description and characteristics of the KOTEF72 Combined Transformers. For more details, see
set of drawings.
1. Top Cover
2. Oil Level Indicator (metallic bellows)
3. Lifting eyes (4x)
4. Primary terminals: aluminum or tinned copper alloy
5. Cast aluminum tanks (upper-CT and bottom-VT)
6. Insulator: Porcelain or Composite
7. Secondary terminal box
General Drawing of KOTEF72

Instruction Manual
© GE Grid Solutions 6
2. DESIGN AND CONSTRUCTION
2.1. Inverted construction and
primary circuit for CT part
The active part of the CT current
transformer part is located above the
insulator. The advantages of this
construction concern the primary
circuit conception. The primary circuit is
short, rigid and straight, minimizing
heating. In addition, it bears
electrodynamics forces more easily,
allowing high level performance,
relating to electrodynamics and thermal
effects, in a presence of short-circuit
currents. The primary bar (simple or
multiple ratios) with magnetic circuits
are centered to assure a distributed
magnetic flow in uniform way to avoid
local saturation. This arrangement
allows also better accuracy in transient
conditions.
2.2. Secondary circuit for the CT part
The ring-shaped magnetic circuits are
manufactured either from very high
permeability grain oriented steel or
from nickel alloy. In order to achieve a
satisfactory transient behavior,
protection cores can also be provided
with gaps.
CT part of the KOTEF72 may have
metering and protection cores with
different loads and different accuracy
classes. Secondary turns are evenly
wound around the circumference of the
ring-shaped cores. Changing ratio is
available by means of taps on the
secondary or primary side.
All secondary windings are enclosed in
an aluminum box which protects them
against high frequency disturbances
while acting as a low voltage shielding
electrode. This aluminum box is
extended up to the base by an
aluminum tube which contains all
secondary leads. The cross section of
the earth connections is designed to
support defect currents.
The bottom of the hermetic and
watertight secondary terminal box is
closed by a fitted plate, with or without
cable gland depending on customer
requirements.
2.3. Paper-oil insulation
Insulation between primary and
secondary circuits is made by multiple
layers of insulating papers impregnated
with mineral oil.
To protect the oil from the environment,
the KOTEF72 head is closed by a
metallic bellows. Due to its wave shape
construction, the bellows adapts to the
changes in oil volume without
producing any increase or decrease in
internal pressure. This bellows resists
aging and corrosion.

Instruction Manual
© GE Grid Solutions 7
2.4. Cast aluminum tanks
The active parts, CT and VT, are housed
in a cast aluminum tank.
2.5. External metallic parts
The external metallic parts do not
require maintenance and they are
naturally protected against corrosion
effects.
3. TRANSPORT, RECEPTION,
UNPACKING AND STORAGE
3.1. Transportation
The KOTEF72 shall be transported in in
vertical position in an appropriated
packing. Wooden crates are designed to
withstand paved or unpaved roads.
The crates cannot be stacked.
3.2. Reception
Whether the shipment is of
manufacturer or customer
responsibility, the customer inspector
or the service agent must check the
following on receipt of delivery:
If the crates show any signs of impact,
blows or fractures, or if the
transformers have any sign of damage
or oil leakage, the customer inspector
or the service agent in charge of receipt
shall make a written remark on
shipment documents. The receipt
control, mainly for the porcelain
insulators and the secondary terminal
box, shall be done in the presence of the
forwarding agent, if possible. The
remarks regarding the condition of the
goods shall clearly state details of the
damages found at the time of reception.
In case of damages, the customer
inspector in charge of receipt shall
notify GE and the insurance
representative. All contact information
is indicated on shipment insurance
documents. This declaration shall be
made within eight days after receipt of
the material.
3.3.Unpacking
Material required for unpacking and
lifting the transformer up to vertical
position:
Qt
y
D
escription
1
Crane, munck or hoist
1
Swing
-
bar of 0
.
7 to 0
.
9m of length
with 2 holes
1
Graphite grease MOLYKOTE type
P37 or equivalent.
3
Slings of
2
.
0
m of length (
capacity
10000N / 1000 kg)
Unpacking the transformer shall be
made with caution:
1) Remove the smaller extremities;
2) Remove the upper cover;
3) Remove the larger extremities.
NEVER lift a KOTEF72 combined
transformer by its primary terminal. Lift
it by the lifting eyes on the transformer
top. See pictures to proceed:

Instruction Manual
© GE Grid Solutions 8
To lift the transformer with crane or
munck, follow the marks on the wooden
crate, once they indicate the right
position for the slings (nylon belts
reinforced) and avoids blows and
vibrations.
Follow the instructions shown in the
drawing below for lifting the CT. All
cables or slings shall be kept in vertical
position during the lifting. It is
recommended to lift the transformer
slowly.
3.4. Storage
The transformer shall be stored in
vertical position on a flat and stable
surface, keeping a reasonable distance
from any kind of traffic (people or
vehicle).4.
NOTE: The units stored outside in
vertical position must be screwed on to
the ground, even if the storage is
foreseen for a short period of time.
4. BELLOWS BLOCKING SYSTEM AND
ASSEMBLY IN THE STRUCTURE
4.1. Bellows blocking system
For transportation purposes, the
metallic bellows device is blocked
(secured from movement) using
cushions of synthetic foam slightly
compressed by the top cover. A
protection of plastic film is also put in
place on the periphery of the bellows to
protect it against contact with the top
cover.
In order to remove the blocking system,
place the current transformer in vertical
position on a flat surface.
Remove the bellows blocking device,
following the procedure below:
1) Mark the position of the top cover
with respect to the head of the
transformer with a vertical line
(using a marker, chalk or pencil);
2) Remove the screws that fix the top
cover;
3) Remove the bellows blocking device
and the protection film;
4) Confirm by visual check that the

Instruction Manual
© GE Grid Solutions 9
bellow device is in good condition:
a) Geometry: Top of the bellow is
horizontal (i.e. not tilted due to
possible deformation of the
bellows convolutions). No
distortion and/or asymmetry of
the bellows (i.e. convolutions are
evenly displaced around the
circumference of the bellows)
b) Surface: no damage or
deformation such as dents
and/or buckling in the bellow
TO AVOID DAMAGE TO THE BELLOWS
DEVICE, NEVER SUPPORT ANY
MATERIAL ON THE BELLOWS.
5) Reinstall the Top Cover with care
lining up the vertical marker line
with the head of the transformer to
ensure that original fixing position is
maintained. Confirm that the
bellows is free for internal
movement and in a vertical position.
The green oil level marker shall be
clearly visible through the window.
6) Tighten the fixing screws. The
threads shall be lubricated with
grease << MOLYKOTE P37>> or
equivalent. The screws shall be
tightened to a maximum torque of
7N.m for screw M6 and 16N.m for
screw M8.
4.2. Assembly in the structure
The combined transformer shall be set
up in vertical position.
It is very important that the surface on
which the Combined Transformer will
be set up is flat (tolerance for no more
than 1mm).
Verify if the four feet are supported on
the structure. If not, it is necessary to
insert a shim before putting the fixation
screws.
Remove the lower lid of black plastic, if
applicable, from secondary terminal
box. It is only used for transport. It
cannot be used as tube guide.
5. CONTACT SURFACES PREPARATION
It is recommended to clean all
aluminum contact surfaces with
sandpaper 150 grain in order to
eliminate the oxidation layer. Scrub the
contact surfaces with a metallic brush
(diameter of the thread 0.3mm) and
impregnate with grease of the type
“PENETROX” or equivalent. All the
Top Cover
Cushions of
synthetic
foam
Protection
film
Bellow
Fix screw

Instruction Manual
© GE Grid Solutions 10
surfaces must be completely covered
with grease.
For silver or tinned contacts, only clean
(do not use sandpaper) and polish the
side of the aluminum. Cleaning silver or
tinned surfaces with sandpaper could
cause damage to the protection layer.
6. CONNECTIONS
6.1. Primary Terminals
Connect the high voltage cable, or tube,
to the primary terminals with
appropriate connectors so that they
assure a good contact.
6.2. Primary bar type (if applicable)
Primary bar is always supplied
completely assembled with the
delivered CT. Clean the primary
terminal as explained in “CONTACT
SURFACES PREPATION”
6.3. Two bar or Four bar
Reconnection Primary type (if
applicable)
The current ratio of the Combined
Transformer can be single with only one
single bar, double or triple primary ratio.
Double or triple primary ratio can be
easily changed by the user following the
instruction of the approved set of
drawing. This changing ratio is made by
means of reconnection bars located in
the top tank, closer to primary
terminals. See set of drawing to know
how the reconnection bars need to be
positioned in order to have the required
ratio.
Example of HV recconection
6.4. Grounding
The Combined Transformer bottom
tank (VT part) has one grounding pad
that should be linked to the substation
ground system through an appropriate
grounding connector.
6.5. Secondary terminals
Connect protection and/or measure
instruments to the secondary terminals
as shown on the nameplate. See the
tightening torque in the drawings of the
project
A point of each secondary terminal
must be connected to the ground in
order to fix the potential.

Instruction Manual
© GE Grid Solutions 11
CT terminals: Secondary terminals not
used must be short-circuited and
grounded. NEVER leave the secondary
terminals of a current transformer in
open circuit.
VT terminals: Secondary terminals not
used shall stay in open circuit. NEVER
short circuit or earth more than one
point of each secondary terminals of a
voltage transformer
6.6. Terminal marking
Primary and secondary terminal
marking are done according to the
specified standard. See set of drawing.
Primary and secondary connection
scheme are shown on schematic plates,
fixed on the Combined Unit.
7. OIL LEVEL INDICATOR
The position of the oil indicator can be
verified through the rectangular
window of the top cover.
The plate of the indicator is divided in
three areas. Central area shows the
green strip and higher and lower areas
are shown with a red strip. In normal
conditions, the indicator shows the
green strip of the indicator.
In case of oil level indicator is in either
of the red areas, the transformer must
be removed from operation and GE
informed immediately.
8. INSPECTION BEFORE FIRST
ENERGIZING
Verify terminals connections to assure
the correct tightening torque.
Verify if there are no open-circuited
secondary terminals for the CT and
shorted terminals for the VT.
Verify if one point of each secondary
terminal is connected to ground.
Verify the ground connections of the
ground pad.
Verify the correct position of the
primary terminal (transformer with
reconnection primary bars). See set of
drawing.
Verify that the oil level indicator is in
the green strip area.
Whilst all care is taken in the factory
during oil filling, the surface near of
screws and bellows could have a small
quantity of oil. This shall not be
considered as an oil leakage provided
the bellows are positioned within the
green strip area.
It is not necessary to remove oil
samples for analysis. The Combined
Transformer OSKF72 is hermetically
sealed

Instruction Manual
© GE Grid Solutions 12
If required, small quantity of oil can be
taken. Always verify oil level indicator
before take oil samples.
Never complete oil volume without
prior formal authorization of GE.
Important remark:
During commissioning, it is
recommended to register the values
acquired for each of the performed
tests in order to compare with future
measurements during the Combined
Transformer lifetime. The
measurements taken in the factory are
important as so the measurements
during commissioning of each
Combined Transformer. The
comparison between test results
measured at the field allows following
the evolution of each parameter.
9. MAINTAINENCE AFTER ENERGIZING
After installation and energizing, the
OSKF72 shall not require any further
intervention. However, it is suggested
performing visual inspections during
the first weeks of service in order to:
 Verify the position of oil level
indicator. KOTEF72 in the same
circuits shall have similar oil
levels. If the indicator is
significantly below or above the
green level, in comparison with
other KOTEF72, it is
recommended checking the
presence of any of leaking. If
leaking is found, remove the
OSKF72 from operation and
inform GE;
 Verify if there is no oil leakage;
 With an infrared imaging device,
check if the primary terminal
connections are not overheating.
Compare with other KOTEF72
from the same circuit.
After one year of operation, it is advised
a detailed inspection of tightening
torques and oil leakage and thereafter
twice per year according to the
substation maintenance contract.
If possible, GE suggests disconnecting
the KOTEF72 and to perform the
following examinations:
1) Insulator: Depending on the
pollution level, it is necessary to
clean the porcelain;
2) Metallic components: check for
corrosion;
3) Tightening torque of primary and
secondary connections. Any
adjustments shall be carried out as
described in the item “Primary
Terminals” of this document;
4) Secondary terminal box: If
necessary clean inside the terminal
box.
5) Verify oil level indicator and if there
is any signal of oil leakage;
6) Remove the top cover to have
access to the bellows and verify if
there is any signal of oil leakage
near the fixation of the bellows and
/ or if the bellows is in good
condition.

Instruction Manual
© GE Grid Solutions 13
Tests
It is recommended after the first few
hours of operation and whenever there
is a change in the KOTEF72 primary
current (in the bar connection),
performing the measurement of the
primary terminal temperature with a
proper temperature measuring
instrument.
It is advised to perform the following
tests before putting the KOTEF72 in
operation and thereafter at four year
intervals depending on availability of
the KOTEF72:
1) Ratio (TTR);
2) Polarity (Polarity meter);
3) Saturation Voltage for CT (ac
voltage source, Voltmeter and
Ammeter);
4) Ohm Resistance (Wheatstone
bridge);
5) Insulation Resistance with any
megohmmeter;
6) Tan δ of the HV insulation (Double
M4100, Omicron CPC100 or any
equivalent).
Important remark:
During commissioning and tests, it is
recommended recording the results
acquired in the tests abovementioned.
In case of doubts, please contact the
technical assistance support of GE: +55
35 3629 7042 or 7038 or 7000
10. PROPER DISPOSAL OF
TRANSFORMERS COMPONENTS
AFTER LIFESPAN
The instrument transformers are mainly
composed of the following components,
which after transformer’s lifespans
require a properly disposal in order to
prevent environmental contamination.
Components
Recommended
Disposal
Metallic materials
Metal recycling
company
Resin and materials
saturated with resin
Oil
disposing
company properly
licensed to perform
such
activity
Oil (PCB
-
fr
ee)
–
classified as Class I
hazardous residue
Oil
disposing
company properly
licensed to perform
such activity
Material
contaminated with
oil
Co
-
processing or
incineration at a
company properly
licensed
Porcelain insulator
Industrial landfill
properly l
icensed
Other materials
Industrial landfill
properly licensed
The disposal of oil and components
contaminated with oil directly into the soil
or water is prohibited.
For further information or clarifications,
contact GE environment department: +55
35 36297112.