Atec Megger-TTR100 - Manual (Page 2)

TTR™100
Handheld TTR
APPLICATIONS
The proper operation of a transformer relies almost
entirely on the electrical properties of its windings. To
ensure continued proper operation, transformers are tested
to verify that their electrical properties have not changed
from design specifications. A TTR is an extremely useful
instrument for testing transformer windings because it can
locate several types of problems within a single- or a
three-phase transformer. It is also ideal to use for testing in
meter shops for the inspection of CTs and PTs. It can
determine the no-load accuracy of CTs and PTs and also
determine the need to further test faulty CTs and PTs.
The TTR100 applies voltage, with voltage ratio being
directly proportional to turns ratio, to the high-voltage
winding of a transformer and accurately measures the
resulting voltage from the low voltage winding. In addition
to turns ratio, the unit measures excitation current, phase
angle deviation between the high and low voltage
windings, percent ratio error, dc winding resistance and
polarity.
Transformer Turns Ratio
Transformer Turns Ratio is the ratio of the number of turns
in the high voltage winding to that in the low voltage
winding.
A Transformer Turns Ratio Test Set such as the TTR100 can
directly measure the ratio of single phase, as well as three
phase transformers. Transformer ratio can change due to
several factors, including physical damage from faults,
deteriorated insulation, contamination and shipping
damage. If a transformer ratio deviates more than 0.5
percent from the rated voltage ratio, it may not operate
reliably. To measure small ratio changes such as this, the
accuracy of a Megger TTR100 is needed.
Excitation Current
The TTR100 is capable of measuring exciting current by
applying voltage to one of the transformers windings. An
accurate measurement of exciting current can provide
information about the condition of a transformer’s core.
Unwanted circulating currents or unintentional grounds
can affect the exciting current and indicate a problem.
Phase Angle Deviation
The phase angle deviation is the relationship between the
voltage signal applied to the high voltage winding and the
voltage signal extracted from the low voltage winding.
The phase deviation between the high and low side of a
transformer is generally very small. However, the phase
deviation can change significantly if there is deterioration
or damage in the transformer core. The TTR100 can
measure this phase relationship with the resolution
necessary to detect a problem.
Additional information about a transformer’s electrical
properties can be found in the IEEE Standard Test Code
for Transformers, C57.12.90, or by contacting Megger’s
technical support group.
Winding Resistance
Measuring the DC resistance of transformer windings will
aid in identifying problems such as shorted or open
windings, as well as loose connections.
The Megger TTR100 can measure the DC resistance of
both single phase and three phase transformer windings.
Transformer Polarity
Polarity of a distribution transformer becomes of interest in
order to determine its proper connection within a power
network.
The Megger TTR100 will identify subtractive and additive
polarity of the single-phase distribution transformers.
FEATURES AND BENEFITS
■ Faster, easier handheld operation. User no longer has to
kneel or bend down to operate the instrument.
■ Powered by rechargeable battery, provides up to fifteen
hours of field operation.
■ Report header information such as company name,
substation name, transformer manufacturer, transformer
ratio, operator, temperature and %RH can be entered
and saved via the alphanumeric keypad.
■ Measures the widest turns ratio range in the industry
(20,000:1) with the highest accuracy (±0.1%, 0.8 to 2000)
at a low excitation voltage.
■ Enables the operator to enter the ratio of the transformer
and all of its taps. This allows the operator to know
immediately when a tap is outside the acceptable limits
so that problem taps can be easily identified.
■ Records ratio errors for bushing CTs to an accuracy of
±0.1% nameplate. This reduces the need for additional
test equipment and improves set-up time.
■ Measures the phase deviation (in minutes, degrees or
centiradians) of the transformer primary versus
secondary. This quickly indicates problems in the
transformer such as partial shorted turns and core faults.
This measurement is also useful in verifying phase errors
in all types of PTs and CTs.
■ Perfect for meter shops, the TTR100 can be used for
inspection purposes by using it to determine the no-load
accuracy of most CTs and PTs. It also can be used to
determine the need to further test potentially faulty CTs
and PTs.
■ The TTR100 is ideal for use by transformer
manufacturers. Its unique testing procedures and storage
capability allows an operator to set up and test single
and three-phase transformers (with multiple tap
changers and bushing CTs) in minimal time.
■ A “Quick Test” mode provides a fast determination of
the turns ratio, excitation current, phase angle deviation,
and winding resistance in single- and three-phase
transformers and CTs. In addition, polarity is provided
for CTs and single-phase transformers.
■ Displays all measured and calculated values for each test
including ratio, excitation current, ratio error, phase
angle deviation, transformer vector group, winding
resistance and polarity thus providing comprehensive
and conclusive data