Transformers component 

Temperature rise limit K

Measuring method

Items

Allowable degree of deviation (%)

Coil

B

80

No-load loss

+15

F

100

Load loss

+15

Iron core and surface of the structural components

The max. value shall not exceed the allowable temperature rise limit of the contact insulation material

thermometry or thermocouple method

Total loss

+10

Insulation level:
The transformer withstands 2000V power frequency testing voltage without breakdown or flashover in 1 minute
At frequency and voltage multiplying in 1 minute. The performance of transformer shall not exceed the allowable deviation value in the following table.

No-load current

+30

Impedance voltage

±10

Transformer ratio

±0.5

DC resistance unbalanced ratio

Iine

2

Phase

4

Remarks: If the DC resistance unbalanced ratio of three-phase transformer exceeds the specified range in Form 2 due by the reason of material of coil and structure, the measured value shall be recorded in the delivery test record and the very reasons also be noted.