4. The liquid level inside the tank must be checked (see
Insulating Liquid Maintenance section of this manual).
On transformers equipped with a liquid level gauge,
the liquid level may be read directly from the gauge.
On transformers that are not gauge equipped, the tank
liquid level must be determined by removing the liquid
level plug (see Figure 2). At 25 °C liquid temperature,
the liquid level should be at the bottom edge of the
liquid level plug hole.
If the tank temperature is greater than ambient air tem-
perature, the transformer tank must be vented to zero
pressure before the liquid level plug is removed. Failure
to do so may cause hot oil to be sprayed from the plug
hole and may result in severe personal injury.
5. Special procedures must be followed when
energizing a transformer in ambient temperatures
below -20°C. Contact your Eaton representative for
further instructions. Failure to follow special start-
up procedures may cause premature failure of the
transformer and its components. Also, note warning
and caution statements in Switches and Protective
Devices section of this manual for further precautions
when operating under-oil loadbreak accessories in
insulating liquid temperatures below 0°C.
Pre-service inspection (interior)
Pre-service interior inspection may not be required if
exterior inspection reveals no evidence of damage.
If interior inspection is required, the transformer must be
opened by removing the manhole/handhole or tank cover.
See the Tank Cover Removal and Installation section of
this manual.
Pre-service interior inspections should be restricted to
noting defects or damage that may prevent proper operation
of the transformer.
Inspect for:
1. Moisture on underside of the tank cover or man-hole
cover.
2. Loose, shifted, or damaged parts (bushings, fuse
holders, etc.).
3. Broken or loose connections.
4. Contaminated insulating liquid (sediment or foreign
objects on the tank bottom, dirt or air bubbles
suspended in the liquid).
Internal damage
If concealed internal damage is suspected, it may be
necessary to lower the insulting liquid level to complete the
inspection. Refer to the Insulating Liquid Maintenance
section of this manual.
Contaminated insulating liquid
If moisture is found inside the tank, or there is evidence
that the insulating liquid may be otherwise contaminated, a
liquid sample should be taken for analysis. Samples should
be drawn from the bottom of the tank. For instruction on
sampling the insulating liquid please see the Insulating
Liquid Maintenance section of this manual.
If moisture is present in the liquid, the transformer must
be dried out. Contact your Eaton representative for special
instructions on dry-out or other decontamination processes.
CAUTION
Elevated Pressure. Can cause severe personal injury.
Do not remove liquid level plug (see Figure 2) before
venting transformer to zero pressure. Pull ring on
pressure relief valve to relieve pressure.
Figure 2. Liquid level plug.
WARNING
Fire Hazard. Energizing transformer in ambient
temperatures below -20 °C can result in fire and cause
severe personal injury or death. Contact your Eaton
representative for further instructions on energizing
transformer in ambient temperatures below -20 °C.
CAUTION
Before opening the transformer tank for Pre-Service
Inspection, read the Insulating Liquid Maintenance
section in this manual. This section explains safety
precautions that should be taken and gives instructions
on how to prevent insulating liquid contamination.
3Three-phase pad-mounted compartmental type installation and maintenance instructions MN202001EN August 2015
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