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High Voltage Instrument Transformers | CA/UT/KA
User Manual
Grounding
The ground terminal of the transformer must be properly
connected to the ground network by a connection capable of
carrying the network’s fault current. Check that the connection
is tightened correctly and that the contact surfaces are clean.
The low voltage (neutral) terminal of the voltage primary
winding must always be grounded when the transformer is in
service (not applicable for CA). This terminal can be located
inside the secondary terminal box on the side of the box or on
the outside of the tank (Fig. 9.)
The tangent delta measurement tap(if it has one) must always
be grounded when the transformer is in service.
If it needs to be removed, the following steps must be followed
to reconnect it (only applicable for CA series):
› Check the thread conditions. If necessary, clean them and
apply contact grease.
› Tighten the connection screws on the block and the base
correctly, per the tightening torque specifi ed in Annex II.
› Ground connection is tested with a multimeter connected
between the link and the CT base. Measurement should be
done at the lowest scale and the result must be below 0.3 ohm
(Fig. 10).
Always follow the Arteche Manual for instructions on transport,
storage, handling and installation.
ARTECHE instrument transformers do not require maintenance.
There are no moving parts and no components susceptible to
wear and tear, so no active maintenance is required.
However, some companies perform some monitoring operations
on instrument transformers as part of a general substation
maintenance program. These maintenance programs are not
intended to extend the life of the units, as the measures have no
impact on the state of the insulation or the performance of the
units. These programs serve to know the state of the isolation, so
that the user can make decisions based on the results obtained,
as well as detect situations that may be causing damage to the
unit.
We at Arteche, as manufacturers, do not establish any specifi c
measures, since the decision depends on:
› the resources available to each user,
› the location of the instrument transformer (can be a position
which is more or less critical),
› the environmental and electrical conditions that the unit must
withstand at each specifi c point,
› the history of the unit,
› the specifi c types or the problematic units,
› etc.
The following inspection points are only a suggestion in case
they are within the user’s maintenance policy.
1. Physical inspection:
a. Mechanical: Look for signs of impact, damage or loose
parts.
b. Electrical: Check the correct state of the electrical
connections.
c. Oil: Look for oil leaks and check the oil level.
2. Dielectric tests:
d. Electrical tests to evaluate the insulation of the equipment.
For the test procedure, see Annex III.
3. Oil tests:
e. Tests performed on oil samples. The oil tests analyze the
state of the insulating liquid and show the properties
of the system in general. The transformer oil contains
information on the status of the device. Therefore,
analysis of used oil can provide early indications of paper
deterioration, overheating points and electrical faults.
This data can be useful as a guide for corrective actions
which should be applied for the transformer. When taking
oil samples, follow Arteche’s user manual on oil sampling.
As a general rule, the transformer should be fi lled with
the same amount of oil as extracted. If this is not possible,
please contact with Arteche.
4. Thermographic testing:
f. Use of thermographic cameras.
INSPECTION AND MONITORING
DANGER
ELECTRIC SHOCK AND/OR INJURY
› Everything should only be carried out by personnel qualifi ed in the maintenance and verifi cation
of the equipment
› Do not touch live parts
DANGER
The transformer must be fi rmly grounded. A faulty or non-existent connection may cause damage,
even destroying the device
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