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BEIJING DAELIM GREEN EP TECH CO., LTD.
operation.Impedancevoltageisusuallyexpressedinperunitorinpercentoftheratedvoltageofthewinding
across which the voltage is applied and measured
Dielectric Strength
Thedielectrictest of thetransformer is intended to checkthe abilityof main insulation to earth,inter turn and
line end insulation to earth. It is generally performed in two different steps, likewise, Separate applied voltage
withstand test (Hi-Pot) and induced voltage withstand test
8.2 Special/Design Tests
Insulation Power Factor (Tan δ)
Theinsulationpowerfactoristhe ratioofthepowerdissipatedin theinsulation inwattstotheproduct of
The effective voltage and current in volt-amperes when tested under a sinusoidal voltage and prescribed
Conditions.
Insulation Resistance
Insulation resistance tests are made to determine the insulation resistance from individual windings to ground
or between individual windings. Insulation resistance tests are commonly measured in mega ohms or may be
calculated from measurements of applied voltage and leakage current.
Temperature Rise
Atemperature-risetestisdefinedasatesttodeterminethetemperatureriseaboveambientofoneormore
ofthetransformer’swindings,asmeasuredattheterminals.Theresultforagiventerminalpairorwindingis
the average value of the temperature of the entire circuit; it is not the temperature at any given point in a
specificwinding.Thetermaveragetemperaturerisereferstothevaluedeterminedbymeasurementsona
given terminal pair of the winding. It does not refer to the arithmetic average of results determined from
different terminal pairs of the transformer
Lightning Impulse
Lightningimpulsetestsshallconsistofandbe appliedinthefollowingorder: onereducedfullwave, two
chopped waves, and one full wave. The time interval between applications of the last chopped wave and the
finalfullwave shouldbeminimized withoutintentionaldelays, toavoid recoveryofdielectricstrength if a
failure were to occur prior to the final full wave. Impulse tests shall be made without excitation.
Please refer to IEEE Standard C57.98-2011.