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- Single- and three-phase
transformer testing
- Fully automatic; fast; easy-to-use;
robust; lightweight
- Battery powered
- Tests turns ratio, excitation current,
and polarity
- Simple, one-button operation
- Quick-start guide on front panel
- Operator-selectable languages
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The Megger TTR25 is an automatic hand-held battery
operated transformer turns ratio test set. It is used to
measure the turns ratio, excitation current and polarity of
windings in single- and three-phase distribution and power
transformers (tested phase by phase), potential & current
transformers, and tapped transformers.
The unique design of the TTR25 allows the user to operate
the test set while holding it in one hand. It effectively
eliminates the user from having to kneel or bend down to
operate the instrument and speeds up testing time.
Realizing the extreme environments in which the TTR25
must operate, special attention has been paid to making it
extra rugged, with a high impact, shock resistant case, yet
incredibly lightweight at a mere 870 g (1.9 lbs).
Its design makes this instrument well suited for use in a
variety of harsh environments. The TTR25 is particularly
suited for testing in substations, transformer-manufacturing
environments, and meter shops. It features a high-contrast,
backlit LCD screen which can be seen in bright or ambient
light.
This unit measures a high turns ratio of 20,000:1 accurately
with the lowest excitation voltage. The excellent
repeatability of the TTR25 helps the users to determine the
condition of transformers under test. It is designed for
simple, one button operation with the measured results
displayed directly on the easy to read LCD or printed to
the optional printer. The TTR25 needs no additional
software and comes ready to use complete out of the box. |
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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
help locate several types of problems within single- and
three-phase transformers.
It it used to determine the no-load accuracy of CTs and
PTs and also determine the need to further test faulty CTs
and PTs. The TTR25 applies voltage to the high-voltage
winding of a transformer and accurately measures the
resulting voltage from the low voltage winding. The ratio
of voltages is directly proportional to turns ratio. In
addition, the unit measures excitation current and polarity.
Transformer Turns Ratio
A Transformer Turns Ratio Test Set such as the TTR25 can
directly measure the turns ratio of single-phase
transformers as well as three-phase transformers.
Deviations in these measurements will quickly indicate
problems in transformer windings and in the magnetic
core circuits. 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
TTR25 is needed.
Transformer Polarity
Polarity of a distribution transformer becomes of interest in
order to determine its proper connection within a power
network. The Megger TTR25 will identify normal (in
phase) and reverse polarity of the single-phase
transformers.
FEATURES AND BENEFITS
- Fast, easy hand-held operation. No need to kneel or
bend down to operate the instrument.
- Powered by six standard “AA” alkaline batteries; no
charger needed. Provides up to 12 hours of field
operation.
- Measures turns ratio range of 20,000:1, with a high
accuracy (±0.1%, 0.8 to 2000) at a low excitation voltage.
- 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.
- Perfect for meter shops, the TTR25 can be used for
inspection purposes to determine the no-load accuracy
of most CTs and PTs. It also can be used to determine
the need to test potentially faulty CTs and PTs.
- Automatic self-calibration for each test.
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| Excitation Voltage: |
8 V rms for testing distribution or power transformers and PTs;
0.5, 1.5, or 8 V ac rms for testing CTs.
The excitation voltage is switched automatically if excitation
current exceeds a preset value. |
| Test Frequency: |
55 Hz internally generated providing a universal 50/60 Hz test set |
| Excitation Current Range: |
0 to 100 mA, 4-digit resolution |
| Turns Ratio Range
: |
0.8 to 20,000, 5 digit resolution |
| Transformer Winding Phase Relationship: |
ANSI C57.12.70-1978
CEI/IEC 76-1:1993 and Publication 616:1978
AS-2374, Part 4-1982 (Australian Standard) |
| Current (rms) accuracy: |
(2% of reading + 1 digit) |
| Turns Ratio Accuracy
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0.1% (0.8 to 2000)
0.15% (2001 to 4000)
0.25% (4001 to 10,000)
0.5% (10,001 to 20,000) |
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| Display full graphics
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LCD module, adjustable back-lighting, wide temperature range,
128 x 64 dots (21 characters by 8 lines) |
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Type of Power
Six standard “AA” (IEC LR-6) alkaline batteries
Battery Life
12 hours of field operation
Safety/EMC/Vibration
Meets the requirements of IEC-1010-1, CE and ASTM D999.75
Temperature Range
Operating: -20º C to 55º C (-5º F to 130º F)
Storage: -50º C to 60º C (-55º F to 140º F)
Relative humidity
Operating: 0 to 90% noncondensing
Storage: 0 to 95% noncondensing
Protective Devices
High voltage side shorting relay, transient voltage suppressors and
gas surge voltage protectors
Measuring Time
Less than 5 seconds
Measurement Method
ANSI/IEEE C57.12.90
Dimensions:
240 H x 115 W x 50 D mm (9.5 H x 4.5 W x 1.9 D in.)
Weight:
Approximately 1.3 kg
(2.8 lb), including leads
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