HPS EnduraCoil 1.2 KV Manual De Instrucciones página 16

Field Service (continued)
DANGER
Failure to de-energize and ground the transformer
before opening the enclosure and/or working
on the transformer will result in serious personal
injury or death.
Electrical equipment should be installed, operated,
serviced, and maintained, only by qualified
personnel.
Installation, Operation, and Maintenance Guide - Cast Resin Transformers
6. High Core Loss
Causes are high input voltage and/or lower frequency.
 gap in the core due to shifting during shipment or
handling.
7. Burned Insulation or Insulation Failure
With evidence of burned insulation, check for the following:
 continuous overload condition
 excessive harmonics
 overheating due to lack of ventilation
 lightening surge
 switching or line disturbance
 broken leads or arresters
 damaged terminals or terminal boards
 shorted turns or mechanical damage
 contamination (insulation failure)
If transformer cores show evidence of overheating and
discoloration, insulation near the core may also appear
discolored. Very high core temperatures are caused by:
 high input voltage
 lower frequency or saturation of the core due to
voltage harmonics.
8. Ferroresonance
Significant over voltages may occur on transformers due to
the phenomena of ferroresonance. Ferroresonance is caused
by both the use of single pole switching with ungrounded
primaries and capacitor switching restrike.
The transient voltages generated are well in excess of the
transformer's inherent ability to withstand over voltage.
Transformers are designed to operate at 6% over voltage at
rated load, and 10% over voltage at no load.
In order to reduce the risk and help protect the transformer,
the user may want to consider that transformers operating at
60 kV BIL or higher, have metal oxide arrestors installed at the
entry point to the transformer on all phases. This applies to
either the primary or secondary, if either are rated 60 kV BIL
or higher. Ferroresonance may cause significant damage to
electrical equipment, particularly transformers and protection is
recommended.
9. High Exciting Current
Can be caused by:
 high input voltage
 low frequency
 shorted turns
 gaps in the core due to shifting during shipment or
handling.
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