GE OSKF User manual

© GE Grid Solutions
INSTRUCTION MANUAL - 19201
CURRENT TRANSFORMER
TYPE OSKF

Instruction Manual
© GE Grid Solutions 2
GE Grid Solutions
Av. Noss Senhor d Pied de, 1021
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Instruction Manual
© GE Grid Solutions 3
W rning!
Any person involved ith transport, installation, energizing, operation and maintenance of Current
Transformer (CT) type OSKF must read these instructions prior to any action related to these
current transformers.
These CT are built under strict conditions hich guarantee the Highest Quality achievement. In
order to keep this high quality during CT’s lifespan, it is utmost important that the instructions in
this Manual be thoroughly read and complied ith.
THESE CURRENT TRANSFORMERS CAN NOT BE STORED IN A HORIZONTAL POSITION FOR
MORE THAN FOUR MONTHS. IF THE TIME OF TRANSPORTION AND STORAGE EXCEEDS THIS
PERIOD, IT IS MANDATORY TO UNPACK AND PUT THE TRANSFORMER INTO A VERTICAL
POSITION, FIXING ITS BASE TO THE GROUND AND REMOVING THE BELLOWS BLOCKING
SYSTEM (SEE ITEM 4.0).
Preliminary Remarks
During reception of the CT, 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........................................................................... 6
2.2. Secondary circuit .............................................................................................................. 6
2.3. Paper-oil insulation ........................................................................................................... 6
2.4. Cast aluminum tank .......................................................................................................... 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............................................................................................................................. 9
4. BELLOWS BLOCKING SYSTEM AND ASSEMBLY IN THE STRUCTURE............................. 9
4.1. Bellows blocking system ................................................................................................... 9
4.2. Assembly in the structure................................................................................................ 10
5. CONTACT SURFACES PREPARATION............................................................................... 10
6. CONNECTIONS .................................................................................................................... 10
6.1. Primary Terminals........................................................................................................... 10
6.2. Primary bar type (if applicable) ....................................................................................... 11
6.3. Double / Triple Reconnection Primary type (if applicable) ............................................... 11
6.4. Grounding....................................................................................................................... 11
6.5. Secondary terminals ....................................................................................................... 11
6.6. Terminal marking ............................................................................................................ 11
7. OIL LEVEL INDICATOR ........................................................................................................ 11
8. INSPECTION BEFORE FIRST ENERGIZING ....................................................................... 12
9. MAINTAINENCE AFTER ENERGIZING ................................................................................ 12
10. PROPER DISPOSAL OF TRANSFORMERS COMPONENTS AFTER LIFESPAN ............ 14

Instruction Manual
© GE Grid Solutions 5
1. GENERAL DRAWING
Description and characteristics of the OSKF Current Transformers. For more details, see set of
dra ings.
1. Top Cover
2. Oil Level Indicator (metallic bello s)
3. Lifting eyes
4. Primary terminals: aluminum or copper
5. Cast aluminum
6. Porcelain insulator
7. Terminal box and cover
8. Fixation Base
General Drawing of OSKF

Instruction Manual
© GE Grid Solutions 6
2. DESIGN AND CONSTRUCTION
2.1. Inverted construction nd
prim ry circuit
The active part of the OSKF current
transformer is located above the
porcelain 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,
allo ing high level performance, relating
to electrodynamics and thermal effects,
in a presence of short-circuit currents.
The primary bar (simple or multiple
ratios) ith magnetic circuits are
centered to assure a distributed
magnetic flo in uniform ay to avoid
local saturation. This arrangement
allo s also better accuracy in transient
conditions.
2.2. Second ry circuit
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
ith gaps.
OSKF may have metering and protection
cores ith different loads and different
accuracy classes. Secondary turns are
evenly ound around the circumference
of the ring-shaped cores. Changing ratio
is available by means of taps on the
secondary or primary side.
All secondary indings are enclosed in
an aluminum box hich protects them
against high frequency disturbances
hile acting as a lo voltage shielding
electrode. This aluminum box is
extended up to the base by an aluminum
tube hich contains all secondary leads.
The cross section of the earth
connections is designed to support
defect currents.
The bottom of the hermetic and
atertight secondary terminal box is
closed by a fitted plate, ith or ithout
cable gland depending on customer
requirements.
2.3. P per-oil insul tion
Insulation bet een primary and
secondary circuits is made by multiple
layers of insulating papers impregnated
ith mineral oil.
To protect the oil from the environment,
the CT head is closed by a metallic
bello s. Due to its ave shape
construction, the bello s adapts to the
changes in oil volume ithout producing
any increase or decrease in internal
pressure. This bello s resists aging and
corrosion.

Instruction Manual
© GE Grid Solutions 7
2.4. C st luminum t nk
The active part is housed in a cast
aluminum tank hich supports the
insulator.
2.5. Extern l met llic p rts
The external metallic parts do not
require maintenance and they are
protected against corrosion effects.
3. TRANSPORT, RECEPTION,
UNPACKING AND STORAGE
3.1. Tr nsport tion
The CT shall be transported in horizontal
position (in vertical position if the CT
height does not exceed the transport
limit) in an appropriated packing. For
overseas shipment, the CT is packed in
ooden crates designed according to SEI
(cat. 4) specification. The crates can be
stacked, but no more than one crate
stacked over.
3.2. Reception
Whether the shipment is of
manufacturer’s or customer’s
responsibility, the customer inspector or
the service agent must check the
follo ing on receipt of delivery:
If the crates sho any signs of impact,
blo s 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
ritten 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 for arding 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 ithin eight
days after receipt of the material.
3.3.Unp cking
Material required for unpacking and
lifting the transformer up to vertical
position:
Qty Description
1 Crane, munck or hoist
1 S ing-bar of 0.7 to 0.9m of length
ith 2 holes
1 Lifting eyes for M10 threaded hole
4 Shackles of 18mm (3/4”) diameter
1 Graphite grease MOLYKOTE type
P37 or equivalent.
2 Slings of 1.5m of length (to see
capacity belo )
C p city
10 000 N for OSKF 72, 123 and 145 KV
30 000 N for OSKF 170kV up to 550kV

Instruction Manual
© GE Grid Solutions 8
Unpacking the transformer shall be
made ith caution:
1) Remove the smaller extremities;
2) Remove the upper cover;
3) Remove the larger extremities.
NEVER lift tr nsformer by its prim ry
termin l. Lift it by the lifting eyes on the
tr nsformer top. See pictures to proceed:
To lift the transformer ith crane or
munck, follo the marks on the ooden
crate, once they indicate the right
position for the slings (nylon belts
reinforced) and avoids blo s and
vibrations.
Follo the instructions sho n in the
dra ing belo for lifting the CT. All
cables or slings shall be kept in vertical
position during the lifting. It is
recommended to lift the transformer
slo ly.
A = 120 mm
These ood blocks should be
fixed on the support. The plank
height shall allo having a
distance of 500mm bet een
the support and transformer’s
feet hen CT is in horizontal
position.
During handling,
the cables must
be kept in vertical
position.
Support
Synthetic foam cushion to absorb
impact
During handling, the
cables must be kept
in vertical position

Instruction Manual
© GE Grid Solutions 9
3.4. Stor ge
The units can be stored:
No more than four months after
the CT left the factory
In the horizontal position;
On a smooth surface;
Minimum and maximum
ambient temperature as per
CT specification.
More than four months after the
CT left the factory
On a smooth surface;
Unpacked;
Put in vertical position;
Remove the bello s blocking
device as described in item 4.
NOTE: The units stored outside in
vertical position must be scre ed 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 bello s 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 bello s to
protect it against contact ith the top
cover.
In order to remove the blocking system,
place the current transformer in vertical
position on a flat surface.
Remove the bello s blocking device,
follo ing the procedure belo :
1) Mark the position of the top cover
ith respect to the head of the
transformer ith a vertical line
(using a marker, chalk or pencil);
2) Scre the lifting eye M10 (if
applicable);
3) Remove the scre s that fix the top
cover;
4) Remove the bello s blocking device
and the protection film;
5) Confirm by visual check that the
bello device is in good condition:
a) Geometry: Top of the bello is
horizontal (i.e. not tilted due to
possible deformation of the
bello s convolutions). No
distortion and/or asymmetry of
the bello s (i.e. convolutions are
evenly displaced around the
circumference of the bello s)
b) Surface: no damage or
deformation such as dents
and/or buckling in the bello
TO AVOID DAMAGE TO THE BELLOWS
DEVICE, NEVER SUPPORT ANY MATERIAL
ON THE BELLOWS.

Instruction Manual
© GE Grid Solutions 10
6) Reinstall the Top Cover ith care
lining up the vertical marker line ith
the head of the transformer to
ensure that original fixing position is
maintained. Confirm that the
bello s is free for internal
movement and in a vertical position.
The green oil level marker shall be
clearly visible through the indo .
7) Tighten the fixing scre s. The
threads shall be lubricated ith
grease << MOLYKOTE P37>> or
equivalent. The scre s shall be
tightened to a maximum torque of
7N.m for scre M6 and 16N.m for
scre M8.
8) Remove the lifting eye M10 (if
applicable)
4.2. Assembly in the structure
The transformer shall be set up in
vertical position.
It is very important that the surface on
hich the CT ill 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
scre s.
Remove the lo er 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 ith sandpaper 150
grain in order to eliminate the oxidation
layer. Scrub the contact surfaces ith a
metallic brush (diameter of the thread
0.3mm) and impregnate ith grease of
the type “PENETROX” or equivalent. All
the surfaces must be completely covered
ith grease.
For silver or tinned contacts, only clean
(do not use sandpaper) and polish the
side of the aluminum. Cleaning silver or
tinned surfaces ith sandpaper could
cause damage to the protection layer.
6. CONNECTIONS
6.1. Prim ry Termin ls
Connect the high voltage cable, or tube,
to the primary terminals ith
appropriate connectors so that they
assure a good contact.
Lifting eye M10
Top Cover
Cushions of
synthetic
foam
Protection
film
Bello
Fix scre

Instruction Manual
© GE Grid Solutions 11
6.2. Prim ry b r type (if pplic ble)
Primary bar is al ays supplied
completely assembled ith the delivered
CT. Clean the primary terminal as
explained in “CONTACT SURFACES
PREPATION”
6.3. Double / Triple Reconnection
Prim ry type (if pplic ble)
The current ratio of the OSKF can be
single ith only one single bar, double or
triple primary ratio. Double or triple
primary ratio can be easily changed by
the user follo ing the instruction of the
approved set of dra ing. This changing
ratio is made by means of reconnection
bars located in the top tank, closer to
primary terminals. See set of dra ing to
kno ho the reconnection bars need to
be positioned in order to have the
required ratio.
6.4. Grounding
The transformer fixation base has one or
t o plates that should be linked to the
substation ground system through the
grounding connector supplied ith the
equipment.
6.5. Second ry termin ls
Connect protection and/or measure
instruments to the secondary terminals
as sho n on the nameplate. See the
tightening torque in dra ings of the
project
A point of e ch second ry termin l
must be connected to the ground in
order to fix the potenti l.
Second ry termin ls not used must
be short-circuited nd grounded.
6.6. Termin l m rking
Primary and secondary terminal marking
are done according to the specified
standard. See set of dra ing.
Primary and secondary connection
scheme are sho n on schematic plates,
fixed on the CT.
7. OIL LEVEL INDICATOR
The position of the oil indicator can be
verified through the rectangular indo
of the top cover.
The plate of the indicator is divided in
three areas. Central area sho s the
green strip and higher and lo er areas
are sho n ith a red strip. In normal
conditions, the indicator sho s 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.

Instruction Manual
© GE Grid Solutions 12
8. INSPECTION BEFORE FIRST
ENERGIZING
After putting the CT in vertic l
position, it is necess ry to w it t
le st 48 hours before putting it in
oper tion.
Verify termin ls connections to
ssure the correct tightening torque.
Verify if there re no open-circuited
second ry termin ls. If so, they must
be short-circuited nd e rthed.
Verify if one point of e ch second ry
termin l is connected to ground.
Verify the ground connections of
tr nsformer fix tion b se.
Verify the correct position of the
prim ry termin l (tr nsformer with
reconnection prim ry b rs). See set
of dr wing.
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
scre s and bello s could have a small
quantity of oil. This shall not be
considered as an oil leakage provided
the bello s are positioned ithin the
green strip area.
It is not necess ry to remove oil
s mples for n lysis. The CT is
hermetic lly se led
If required, small quantity of oil can be
taken. Al ays verify oil level indicator
before take oil samples.
Never complete oil volume without
prior form l uthoriz tion of GE.
Import nt rem rk:
During commissioning, it is
recommended to register the values
acquired for each of the performed tests
in order to compare ith future
measurements during the CT lifetime.
The measurements taken in the factory
are important as so the measurements
during commissioning of each CT. The
comparison bet een test results
measured at the field allo s follo ing
the evolution of each parameter.
9. MAINTAINENCE AFTER ENERGIZING
After installation and energizing, the CTs
shall not require any further
intervention. Ho ever, it is suggested
performing visual inspections during the
first eeks of service in order to:
Verify the position of oil level
indicator. CTs in the same circuits
shall have similar oil levels. If the
indicator is significantly belo or
above the green level, in
comparison ith other CTs, it is
recommended checking the
presence of any of leaking. If
leaking is found, remove the CT
from operation and inform GE;
Verify if there is no oil leakage near
the fixation base and secondary
terminal box;

Instruction Manual
© GE Grid Solutions 13
With an infrared imaging device,
check if the primary terminal
connections are not overheating.
Compare ith other CTs from the
same circuit.
After one year of operation, it is advised
a detailed inspection of tightening
torques and oil leakage and thereafter
t ice per year according to the
substation maintenance contract.
If possible, GE suggests disconnecting
the CT and to perform the follo ing
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 bello s and verify if there is
any signal of oil leakage near the
fixation of the bello s and / or if the
bello s is in good condition.
Tests
It is recommended after the first fe
hours of operation and henever there
is a change in the CT primary current (in
the bar connection), performing the
measurement of the primary terminal
temperature ith a proper temperature
measuring instrument.
It is advised to perform the follo ing
tests before putting the CT in operation
and thereafter at four year intervals
depending on availability of the CT:
1) Ratio (TTR);
2) Polarity (Polarity meter);
3) Saturation Voltage (ac voltage
source, Voltmeter and Ammeter);
4) Ohm Resistance (Wheatstone
bridge);
5) Insulation Resistance ith any
megohmmeter;
6) Tan δ of the HV insulation (Double
M4100, Omicron CPC100 or any
equivalent).
Import nt rem rk:
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

Instruction Manual
© GE Grid Solutions 14
10.PROPER DISPOSAL OF
TRANSFORMERS COMPONENTS
AFTER LIFESPAN
The instrument transformers are mainly
composed of the follo ing components,
hich after transformer’s lifespans
require a properly disposal in order to
prevent environmental contamination.
Components Recommended
Dispos l
Metallic materials Metal recycling
company
Resin and materials
saturated ith resin
Oil disposing
company properly
licensed to perform
such
activity
Oil (PCB-free) –
classified as Class I
hazardous residue
Oil disposing
company properly
licensed to perform
such activity
Material
contaminated ith
oil
Co-processing or
incineration at a
company properly
licensed
Porcelain insulator Industrial landfill
properly licensed
Other materials Industrial landfill
properly licensed
The disposal of oil and components
contaminated ith oil directly into the soil
or ater is prohibited.
For further information or clarifications,
contact GE environment department: +55
35 36297112.