IG-168-EN version 05; 17/04/2020
26
Commissioning
General instructions
transforma
.dis: Distribution transformers immersed
in dielectric liquid up to 3150 kVA
6.1.2. Natural ester transformers
Natural esters have higher freezing points than those
of mineral oil. The liquid could therefore freeze during
prolonged exposure to temperatures below -10°C.
In these cases,
Ormazabal
recommends the following
actions to ensure correct commissioning:
1.
Temp ≥ -10°C, same considerations as mentioned in
point 6.1.1.
2.
Temp ≤ -10 °C or recently reached, there are two
options:
a.
Maintain under vacuum, without load, for at least
12 hours in order to heat the ester and decrease
its viscosity. Then carry out the same operations as
mentioned in point 6.1.1.
b.
Move the transformer indoors for at least 24 h, to
allow the ester to heat up and decrease its viscosity.
Then carry out the same operations as mentioned
in point 6.1.1.
It may not be possible to determine the exact temperature
reached when storing or transporting the transformer, or
the ester may still be at a temperature below -10 °C while
the outside temperature is higher, due to the thermal
inertia of the ester. In order to guarantee the integrity of the
transformer,
Ormazabal
therefore recommends following
one of the two previous options before handling the off-
load tap changer when the outside temperature is below
-5°C.
Risk of death caused by electric shock and of
irreversible damage to the transformer or to the
electrical installation.
•
Carefully follow the instructions in section “7.1.
Access for maintenance operations” before handling
the facility.
• Do not operate the tap changer with electrical power
applied to the transformer.
Summary of Contents for velatia transforma.dis
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