What is TTR test of transformer?
Transformer Turns Ratio (TTR) testing is one of the most common ways of assessing the condition of a transformer’s windings and core. Throughout the life of a transformer, TTR results are compared against the nameplate ratings to reveal insulation deterioration, shorted turns, core heating or other abnormalities.
What is the IR value of transformer?
IR Value of Transformers
| Voltage | Test Voltage (DC) LV side | Min IR Value |
|---|---|---|
| Up to 6.6KV | 500V | 200MΩ |
| 6.6KV to 11KV | 500V | 400MΩ |
| 11KV to 33KV | 1000V | 500MΩ |
| 33KV to 66KV | 1000V | 600MΩ |
How do you test a power supply for a transformer?
To test your transformer, simply touch the red and black pins of your ohmmeter to the opposite ends of the transformer’s wiring. Read the display and compare the resistance on your ohmmeter to the resistance stated on the transformer’s data sheet. This is sometimes listed on the transformer’s enclosure.
What is Megger test of transformer?
The insulation resistance test (meggering) is of value for future comparison and also for determining if the transformer is to be subjected to the applied voltage test. The winding insulation resistance test is a DC high voltage test used to determine the dryness of winding insulation system.
How is TTR ratio calculated?
type-token ratio = (number of types/number of tokens) * 100 = (62/87) * 100 = 71.3% ABSTRACT: The type-token ratio (TTR) is a measure of vocabulary variation within a written text or a person’s speech.
How do you perform a TTR test?
Procedure of Transformer Ratio Test
- First, the tap changer of transformer is kept in the lowest position and LV terminals are kept open.
- Then apply 3-phase 415 V supply on HV terminals.
- After measuring the voltages at HV and LV terminals, the tap changer of transformer should be raised by one position and repeat test.
What is pi test of transformer?
If a transformer passes the insulation resistance test, before applying any overvoltage test, it is recommended to do a Polarization Index (PI) test….Insulation Resistance and Polarization Index.
| Polarization Index | Insulation Condition |
|---|---|
| 1.1 – 1.25 | Questionable |
| 1.25 – 2.0 | Fair |
| Above 2.0 | Good |
How many types of transformer testing are there?
Transformer manufacturers perform two main types of transformer testing – type test of transformer and routine test of transformer. Some transformer tests are also carried out at the consumer site before commissioning and also periodically in regular and emergency basis throughout its service life.
Can you use a megger on a transformer?
Megger leads to connecting to HV bushing studs and earth point transformer tanks to calculate the importance of IR insulation resistance between HV windings and earth.
What is average TTR?
Window Size. Obviously, the moving-average TTR of a text varies with the window size more or less the same way that the conventional TTR varies with the text length. Empirically, for typical English text, MATTR ≈ 2 W −0.2, so with window sizes of 100 and 500 words, typical MATTRs are 0.8 and 0.6 respectively.
What is tan delta test in transformer?
A Tan Delta test is performed by applying an ac voltage to a test cell of known gap, measuring the total current flow through the oil, and separating and comparing the reactive and resistance portions of the current passing through the oil.
Which test is done in transformer?
These tests include winding insulation resistance test, winding resistance test, vector group test, tan delta test, no-load test or iron losses, load test or copper losses, temperature rise test, partial discharge test, frequency response analysis test, and transformer oil breakdown test.
What is Type test of transformer?
Type tests of transformer include: Measurement of impedance voltage/short circuit impedance (principal tap) and load loss (Short circuit test) Measurement of no-load loss and current (Open circuit test) Dielectric tests of transformer. Measurement of insulation resistance.
What is good PI value?
The Polarization Index is derived by the ratio between the one minute reading and the ten minute reading. Recommended minimum PI results for suitability for service (or implementation of high voltage testing) is widely accepted as 2:1 or greater. Any reading lower than this minimum value is a concern.
What is IR and PI test?
Insulation Resistance (IR) and Polarization Index (PI) are two universally accepted diagnostic tests for insulation tests. These are in use for more than 75 years. The IR test measures the resistance of the electrical insulation between the copper conductors and the core of the stator or rotor.
Which is special test on transformer?
Special Tests of transformer include Dielectric tests. Measurement of the harmonics of the no-load current. Measurement of the power taken by the fans and oil pumps. Tests on bought-out components/accessories such as Buchholz relay, temperature indicators, pressure relief devices, oil preservation system, etc.