文档介绍：Testing Items、Methods 、Procedure and Formulas:
No.
Testing Items
Testing Methods Procedure and Formulas
1
Voltage ratio
measurement and
check of vector
group
Adjust the tap changer, and measuring voltage ratio error of each tap of HV-LV. The test result of error at the nominal tap should be ≤±%. The vector group should be formula is as following:
K=U1/U2
No.
Testing Items
Testing Methods Procedure and Formulas
2
Winding .
resistance
measurement
To measure . resistance of HV and LV windings at winding end by HS305, The test result of error: phase <4%,line<2%.
K=(Rmax-Rmin.)/Rave.
K is the unbalanced rate of three-phase DC resistance.
3
Measurement of
insulation
resistance
Transformer enclosure should be well grounded,then to measure insulation resistance。By measurement meter ZC11D-5,2500V. (HV:>1000MΩ; LV:>50MΩ)
Connection diagram of insulation resistance measurement is as following:
No.
Testing Items
Testing Methods Procedure and Formulas
4
. voltage
withstand test
Applied voltage withstand test uses 50Hz sine-wave single-phase . voltage, tested winding of transformer is
shorted and energized, the other non-tested windings are shorted grounding, also the core, clamp and tank are grounded. This test is considered to be qualified, if there is no discharge, breakdown and no sudden decrease of testing voltage. The testing voltages are:
HV & neutral-38kV 60s, LV-3kV 60s.()
HV & neutral-50kV 60s, LV-3kV 60s.(22KV/)
No.
Testing Items
Testing Methods Procedure and Formulas
5
Induce withstand voltage
1、induce withstand voltage
The wiring diagram of induce withstand voltage test is as following:
ac surge ism,HV side is open-circuit.
Wiring diagram is following:
induce withstand voltage:( kV×2 ;22kV×2)
Use 50kVA、200Hz generator set three-phase output to winding of tested transformer. tap position is at 3 step, Test lasts for 30s (Formula: test time=120*50/200=30