Three-Phase TTR®
Transformer Turns Ratio Test Set
Three-Phase TTR®
Transformer Turns Ratio Test Set
■ Fully automatic operation
■ Measures three phases simultaneously
■ Highest ratio measurement (20,000:1); highest accuracy (0.1%)
■ Built-in storage and downloading capabilities
■ Measures ALL power transformers,
PTs and CTs
■ Displays % error vs. name plate and pass/fail limits
■ Operator choice of “quick” test or complete “full” test
DESCRIPTION
The Three-Phase Automatic TTR is designed to measure the turns ratio of power, instrument, and distribution transformers in a substation or manufacturing environment. At 16.5 lbs (7.5 kg), it weighs less than any other commercially available instrument. A rugged and robust design makes this TTR well suited for use in a variety of harsh environments. The TTR is also particularly suited for testing in power transformer manufacturing environments where testing of complex, three-phase substation power transformers can be performed quickly while minimizing the possibility of errors.
This new TTR measures the highest turns ratio range in the industry (10,000:1) and also provides the highest accuracy (0.1%). No other instrument’s performance is comparable that is commercially available today.
Another excellent feature of this new TTR is the ability to measure phase deviation (in minutes or centiradians) of the transformer primary versus secondary. This will quickly indicate problems in a transformer such as partial shorted turns and core faults. This measurement is also useful in verifying phase errors of all types of PTs and CTs.
The TTR also features special software capabilities. The TTR comes equipped with sufficient onboard memory to store up to 200 test results in the field for later retrieval in the office. Test results can be printed on an optional serial printer whenever a hard copy is desired, or the data can be downloaded to a PC. Identification of individual test readings is also easily done. The system software allows entry of the transformer alphanumeric serial number,
transformer type and tap information for each test performed.
This new TTR also comes with a unique optional, remote control software program. This Windows® based program permits control and operation from a PC keyboard, download of test data from the TTR to a PC, print out a test results report and assist in the preparation of management and/or analysis reports using either Excel® or Access®.
Realizing the extreme environments in which the TTR must operate, special attention has been paid to making it extra rugged (with a hard, shock resistant case), yet incredibly light weight (16.5 lbs). It features a high contrast LCD screen which can be seen in bright or ambient light and comes equipped with specially designed leads which provide the necessary flexibility needed in cold weather conditions.
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 transformer. It is also ideal to use for testing in Meter shops for the upcoming inspection of CTs and PTs. It can determine the no load accuracy of all CTs and PTs and also determine the need to further test faulty CTs and PTs.
The new TTR applies voltage 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 and percent ratio error.
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 Three-phase Automatic TTR can directly measure the ratio of most types of transformers. Transformer ratio can change due to several factors, including physical damage from faults, deteriorated insulation, contamination and shipping damage. If a transformer ratio changes 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 Biddle TTR is needed.
Exciting Current
The exciting current is the current that maintains the magnetic flux excitation in the core of a transformer.
A Transformer Turns Ratio Test Set such as the Three-phase Automatic TTR is capable of measuring exciting current because they apply 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. If there is deterioration or damage in the transformer core, however, the phase deviation can change significantly. The Three-phase TTR can measure this phase relationship with the resolution necessary to detect a problem.
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THREE PHASE TRANSFORMER TEST |
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TEST: 105 |
ID: A13579CV0246 |
DIAG: 31 |
Yzn11 |
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TAPS TESTED: |
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3 - 16 R |
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H VOLTAGE: |
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25000 |
X VOLTAGE: 5000 |
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CALCULATED TURNS RATIO: |
5.000 |
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TEST VOLTAGE: |
80 V |
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A |
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B |
C |
RATIO |
5.102 |
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5.015 |
4.986 |
% DEVIATION |
2.04 |
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0.30 |
-0.28 |
PHASE (min.) |
1.2 |
|
2.4 |
1.8 |
lexc (mA) |
20.6 |
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10.5 |
7.78 |
SELECT: 1 - PRINT 2 - STORE |
3 - NEXT TEST |
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4 - PRINT TEST |
5 - MAIN MENU |
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Example of the TTR LCD screen which shows test data from a three-phase transformer test.
Three-Phase TTR®
Transformer Turns Ratio Test Set
More 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.
FEATURES AND BENEFITS
■Measures the widest turns ratio range in the industry (10,000:1) and also provides the highest accuracy (0.1%).
■Enables the operator to enter the ratio of the transformer and all of it’s taps. This allows the operator to know immediately when a tap is outside the acceptable limits. Also allows for a pass/fail limit so problem taps can be easily flagged.
■Comes equipped with “remote-control” switch for single person testing. This allows the operator to test transformers with “LTCs” very quickly.
■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) 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 TTR can be used for inspection purposes by using it to determine the no-load accuracy of most CTs and PTs. Also, it can be used to determine the need to further test potentially faulty CTs and PTs.
■This instrument is also ideal for use by power transformer manufacturers. Its unique testing procedures and storage capability allows an operator to set up and test difficult three-phase transformers (with multiple tap changers and bushing CTs) in a quarter of the time than it used to take with the former Biddle TTR. This test also includes a pass/fail limit of individual ratios.
■A “Quick Test” Mode provides a fast determination of the turns ratio for single and three-phase transformers, thus saving time.
■Displays all values for each test including measured and calculated ratio, exciting current, ratio error, and phase angle deviation, thus providing comprehensive and conclusive data.
■Automatic self-calibration for each test.
■Rugged, lightweight design ideally suited for a harsh field and substation environment.
■Three user selectable standards: ANSI, IEC, and Australian. Also meets IEC 1010 as well as other safety standards such as CSA and UL.
■Six user selectable languages: French, German, Italian, Portuguese, Spanish and English.
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