Expected test results section 7 consists of sections specific to each particular type of equipment.
Transformer insulation resistance test values.
Insulation resistance decreases in temperature or moisture.
The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms.
Value at 60 seconds after application of the test voltage is referred to as the insulation resistance of the transformer at the test temperature.
After the required connections are made you apply the test voltage for a period of one min.
Before conducting a transformer winding resistance test it is important to observe all safety warnings and take proper precautions ensure that all equipment to be tested is properly grounded and treat all high voltage power equipment as energized until proven otherwise by using the proper lockout tagout procedures.
Within those sections there are typically three main bodies of information.
Use the megger test at a low voltage side.
Calculation of the i 2 r losses in transformer.
A rated line to line voltage for three phase ac machines line to ground voltage for single phase machines and rated direct voltage for dc machines or field windings.
Use caution when testing.
Basically there are three different tests that can be done using a megohmmeter.
Measure insulation resistance between low voltage windings and the main body of the transformer.
B kv is the rated machine terminal to terminal voltage.
In the factory it helps in determining the following.
That this document list how to test specific pieces of equipment or systems.
A winding resistance test of a transformer is carried out as a type test routine test and also as a field test.
Apply the test voltage and note the reading.
Values based on ieee std 43 2013.
The transformer neutral bushing is to be disconnected from earth during the test.
Ansi neta mts 2015 table 100 11 insulation resistance test values rotating machinery for one minute at 40 c.
Clean the terminals of the transformer.
Megger insulation resistance test device.
The transformer neutral bushing is to be disconnected from earth during the test.
Calculation of winding temperature at the end of temperature rise test of transformer.
Insulation resistance test of transformer is divided into three parts.
Value at 60 seconds after application of the test voltage is referred to as the insulation resistance of the transformer at the test temperature.
Visual and mechanical inspection 2.
Apply the test voltage and note the reading.
Adjust megger tester at 1000 v dc.
With a little record keeping and common sense however you can get a good picture of the insulation condition from values that are only relative.
