Doble TDR900 User Guide
72A-2612-01 Rev. A 09/06
16
There are two basic test types:
•
Overall ( also known as an OCB test or dead tank test)
•
Sectional (also known as an EHV test or live tank test)
An overall test:
A timing test where connections are made at the input terminals to
the breaker and the output terminals from the breaker. The timing
gives the first break in contact for an open measurement, and the
last break to close in a close measurement. Only one cable is
required for an overall measurement.
A sectional test:
This test gives a timing measurement for each break separately. It
is consequently more complex than an overall test as more leads
are needed to connect to each break, but the basic concept is the
same.
4.8.1 Performing an Overall Test (OCB or dead tank)
In an overall test, connections are made to the three separate phases of the breaker. One
side is “common” and grounded. The other side has an input voltage supplied to each
phase.
Contacts closing are determined when current supplied during the test set starts to flow
through the breaker.
The time of “contact opening” is determined when current supplied by the test set stops
flowing.
4.8.2 Performing a Sectional Test (EHV or live tank)
Set up for a sectional test is more complex than an overall test as test leads are needed for
each break.
The TDR900 can perform tests on up to four breaks per phase on three phases at one
time. By using a common connection to all test leads for a single phase, up to 12 breaks
per phase may be measured for each phase. This is usually sufficient as breakers with a
large number of breaks per phase usually have independent pole operation.
4.8.3 Measuring Motion
To measure motion we need a transducer which will change the breaker motion into an
electronic signal which the TDR900 can recognize. This is usually done through a rod
which is attached to the breaker mechanism and then attached to the transducer which is
mounted in a way to allow the rod to move freely when the breaker operates.
One transducer per phase is possible with the TDR900.
Summary of Contents for TDR900
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