LumaSMART
®
User Manual
Installation of Probes and Accessories
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3.
Ensure the probe tip is not crushed and that the probe cable does not exhibit an overly sharp bend radius
as it emerges from the coil.
Caution:
Probes are usually installed during the phase assembly. The main concern is to keep the
probes from being damaged during the remainder of the manufacturing process. If the probes are
installed during phase assembly, it could be many weeks before the transformer is completed and in
testing—probes must be protected during this time. A method frequently used to protect probes is
to place unused portions in a well-marked cotton bag and tie it on top of the winding.
To install probe tip directly in contact with the winding conductor:
1.
Determine the exact spot on the winding conductor (hottest spot) to locate the probe tip (as determined
by the transformer manufacturer) — usually, for shell form transformers, on the top of the outside turn of
the coil for easier access.
2.
Lay the probe on top of the winding conductor, in direct contact with the metal, with the probe tip at the
exact spot where the temperature is to be measured. Place the sensor so that a portion of it is on the
conductor so that it cannot be crushed by an adjacent winding if there is a sudden change in current
causing an abrupt contraction of the coils.
3.
Hold the probe tip on the conductor while wrapping the crepe tape (insulating paper) onto the conductor,
as normally as possible. After the probe exits the crepe tape, route it along the conductor in such a way as
to minimize damage to the probe.
4.
Cover the probe tip a minimum of 38 mm (1.5 in) with crepe tape. Cover the black tip plus a minimum of
the 6.5 mm (0.25 in) white PFA Teflon wrapper portion.
5.
Ensure the fiber optic probe is not crushed or pinched when the next coils are laid on top of the coil on
which the probe is wrapped.
6.
Test the probes during each major step— phase assembly, core stacking, tanking, and fitting— by
connecting to a LumaSMART controller. This raises awareness of protecting the fiber optic probes during
each step.
(The LumaSense 812 Portable Monitor can be used for this process (Refer to Section 2.3.3
for more information. Also refer to Section 4.5
Testing the Probe Signal Strength
.)
7.
Be sure to test the final probe assembly, inside the transformer and its final connection to the tank wall
penetrators (installed at the transformer wall), just prior to adding oil into the transformer. Ensure all
probes are properly functioning. This is the last opportunity to correct problems inside the transformer.
Ensure that the probes are securely and tightly connected to the tank wall penetrators.
Note:
If all probes are properly functioning during Step 7, any problems that arise later will most
likely be caused by equipment located outside the transformer wall and can be easily corrected.
3.4.4
Alternate Probe Tip Installation Methods
Nylon or fiberboard tubing can be used as a guide through which the fiber optic probes can later be inserted. This
technique allows the sensor to be inserted after the transformer is assembled.
Although certain manufacturers have successfully used this method, there are potential problems with this
approach:
•
If the tubing is crimped, the sensor cannot be inserted all the way to the proper location;
•
If the exact lengths are not known in advance, the sensing tip may not extend to the specific temperature
measurement point;
•
If the lengths are known, the fiber thermal expansion coefficient and tubing are different and can lead to
movement of the sensor tip as the transformer heats.
