5
High Voltage Instrument Transformers | CA/UT/KA
User Manual
ELECTRICAL CONNECTIONS/
Primary connections
The most common connector materials are copper and
aluminum. They can have a tin or silver coating with so as to
prevent galvanic pair corrosion and improve their contact.
Do not bring aluminum into contact with copper-based
materials unless special precautions are taken.
Material Finish Cleaning
Copper
Copper/Brass
We recommend cleaning the contact surfaces with
a soft cloth (avoid brushing with a metal brush)
Aluminum
Aluminum
Bare
We recommended vigorously brushing the contact
surfaces with a soft metal brush (preferably
stainless steel) or sandpaper, until you see the
characteristic shine of the clean metal
Copper/Brass
Only impregnate the contact surfaces to be used with contact
grease, keeping the others clean. Remove excess grease to
avoid contamination.
Tightening must be carried out using a torque wrench, as shown
on the diagram plates and in Annex II.
Change of primary ratio (if applicable). In current transformers
(CA) and combined (KA), depending on the model, the change
of primary ratio can be done in one or both primary terminals.
The position and torque of the links is indicated on the diagram
plates next to the terminal (Fig. 7) or under the protective cover
(Fig. 8). Before commissioning the transformer, check and make
sure that the primary connection is in the ratio corresponding to
the operating current.
Secondary connections
The secondary winding(s) must be connected to earth through
one of its terminals, preferably in the secondary terminal box
itself.
In case of secondary with intermediate taps, the common
terminal must be grounded.
Check that the secondary connections are correctly tightened
and the contact surfaces are clean.
The screws of the lower cable gland cover, the block cover
and the terminals must be tightened to the torque specifi ed in
Annex II.
In the terminal box there is a terminal block where the secondary
wires are connected.
The disposition of the terminals is indicated on the secondary
marking plate on the inside of the box cover.
A faulty contact or a bad connection can lead to rapid transformer deterioration
Current transformer (CA)
and current secondaries
of the combined
transformer (KA)
Any secondary that is not loaded must be short-circuited and grounded
The voltage between open circuit secondary terminals can reach dangerous values
and can even destroy the device
Voltage transformer (UT)
and voltage secondaries
of the combined
transformer (KA)
Any secondary that is not loaded must be left open and grounded at a single point
The current in a short-circuited secondary can reach dangerous values and can even
destroy the device
Avoid excessive torque, as the connector may su er damage such as cracks which may expand in the future and
cause it to break
An inadequate torque may cause improper contact and cause the terminals to heat up during operation
CAUTION
Do not use the secondary terminal block as a step
To make or check the primary connections, a lifting platform or a ladder should be used,
maintaining the necessary safety conditions for work at height. In no case may the
terminal block be used as support
Check the correct external wiring.
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