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Eliminates need
to physically remove power bus
The Lapp-Doble test terminal functions as an electrical switch
permanently connected in series between the power bus and
the equipment to be tested, so it eliminates the need to physically
remove the power bus during testing. In the closed position,
the Lapp-Doble test terminal permits electrical
Lapp-Doble test terminal on the entrance
bushing of a power transformer
power to be transferred from the power bus to the equipment.
When you wish to test the equipment, you first de-energize
the power bus. Then you back off the two captive bolts at
the top of the Lapp-Doble test terminal and loosen the other
bolts to let the terminal’s copper blades swing out in an
open position.
With the bus grounded, the equipment is now isolated from
the power bus and you may perform standard Doble or other
dielectric tests. During testing, the equipment is energized
by the high voltage cable from the Doble test set, and the
center casting of the terminal is connected to the test set’s
“guard” so any stray leakage current is bypassed and returned
to the test set without being measured.
Loosening and tightening the bolts on the test terminal
and connecting the terminal to the test set takes only a matter
of minutes. What’s more, depending on the equipment you’re
testing and its location, testing can often be accomplished
without a boom or bucket truck, or extra personnel.
Extended
service life, significant savings, and more
Extended service
life without a risk of equipment failure
If you extend the service life of existing substation equipment
without performing periodic field dielectric tests, you face
the risk that the equipment will fail electrically, resulting
in expensive downtime, lost revenue, and costly repair and
replacement. On the other hand, if you perform periodic field
dielectric tests to ensure that your equipment doesn’t fail
but you haven’t installed Lapp-Doble test terminals, your
testing costs can be significant.
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Because Lapp-Doble test terminals make it so easy to test
the dielectric strength of your substation equipment, they
let you extend the equipment’s service life without these
added risks and testing costs.
Significant savings
By eliminating the need to physically disconnect the equipment
being tested from the power bus, Lapp-Doble test terminals
significantly reduce labor costs and boom and bucket truck
time. The text, table, and graph on the next page can help
you determine the savings you can expect when you install
Lapp-Doble test terminals at your utility.
Lapp-Doble test terminal on a current transformer
Reduced risk of equipment damage during bus removal
Because the Lapp-Doble test terminal makes it possible to
isolate virtually any substation equipment from its power
bus without physically removing the power bus, it eliminates
the risk of equipment damage that’s otherwise associated with
testing.
Improved safety for maintenance personnel
The Lapp-Doble test terminal improves safety by minimizing
boom and bucket truck crews’ time.
Lapp-Doble test terminal on a lightning
arrester
Reduced downtime; maximized on-line time
Because the Lapp-Doble test terminal facilitates field dielectric
testing compared with testing that requires removal of the
power bus, it reduces equipment downtime and maximizes equipment
on-line time delivering valuable electrical power.
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Ease of use
The Lapp-Doble test terminal is easy to use. Bolts are captively
affixed to the terminal so they won’t become lost or be dropped
during the testing procedure. And the terminal is designed
so it can be easily attached to Doble and other test sets.
Reliable performance
The Lapp-Doble test terminal has a proven track record when
it comes to reliable performance. In fact, over the last 25
years more than 15,000 Lapp-Doble test terminals have been
installed worldwide in both new construction and in upgrade
projects at existing substations.
Models, fittings available for multiple applications
through 765 kV and 6000 amps
The Lapp-Doble test terminal may be used with any substation
equipment which can benefit from periodic measurement of power
factor or dissipation factor, including:
• Bushings on power transformers
• Bushings on SF6 gas circuit breakers (both live and dead
tank versions)
• Bushings on air blast breakers
• Bushings on bulk oil circuit breakers
• Lightning arresters
• Current transformers
• Voltage transformers
Different terminal configurations are available for the
top and bottom copper castings to tailor the test terminal
for each application. Terminal configurations include spades
with custom drillings, smooth and threaded studs, smooth and
threaded female stud connectors, and custom drillings in the
face of the top and bottom copper castings. Through system
voltages of 230 kV, the Lapp-Doble test terminal is used without
corona rings. At 345 kV, one corona ring is recommended. At
550 and 765 kV, two rings are recommended.
Lapp-Doble test terminal on an SF6 gas circuit
breaker (dead tank version)
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