(2) Reactive power, also known as out-of-phase component. The ratio of the out-of-phase component to the in-phase component is called the dielectric loss tangent tanδ. tanδ=1/WCR (where W is the angular frequency of the alternating electric field; C is the dielectric capacitance; R is the loss resistance). The dielectric loss tangent is a dimensionless physical quantity.
Hysteresis loss
The hysteresis loss is due to the existence of a "hysteresis loop" in the iron core, so that the phase difference between the induced electromotive force and the magnetizing current is not equal to 90 degrees. We know that if it is 90 degrees, the current is "reactive". Now it is not equal to 90 degrees, which is equivalent to connecting an active current component in parallel.
By Steinmetz formula hysteresis loss, Wh =Kh f Bm1.6 w/m3Eddy current loss can be reduced by using an iron core made of thin laminated sheets and material with high electrical resistivity. It reduces the induced EMF and the amount of current flow.
2. Specific explanation:
When the transformer is working normally, the magnetic field generated by the secondary side current and the main part of the primary current are offset. The magnetic field left after cancellation should be roughly equal to the magnetic field at no load (when the secondary current is zero) (assuming resistance and leakage flux are ignored). Therefore, the "magnetizing current" I mentioned above should be equal to the no-load current of the transformer.When the transformer is no-load, if there is no loss, the input characteristics of the primary side should be equivalent to a pure inductance. With loss, the input current is equivalent to adding a resistor in parallel to the inductor. tanδ should be equal to the ratio of the current on this equivalent resistor to the current on the inductor.
Other transformers types:
1. Iron Losses or Core Loss
Total Copper Loss, Pcu = I12R1 + I22R2 ;
The values of Resistance R1 of the primary winding and R2 of the secondary winding are constant.
It occurs in the insulating material and oil of the transformer. The transformer oils are subject to change its parameters such as dielectric strength, tan delta, moisture, chemical parameters (dissolved impurities – dissolution of copper), physical parameters, etc…
Additional points
1.Iron loss (Hysteresis loss, eddy current loss) and dielectric loss are no-load losses which are independent of the transformer load.
2.Whereas the copper loss and stray loss varies with the load current.
3.Iron loss is a constant loss and copper loss is a variable loss.
4.Copper loss is determined by the short circuit test and Iron loss is determined by the open circuit test.
The test items are required for 110kV/220kV substation acceptance and maintenance testing(with corresponding tester types):
Test Object |
Testing Item |
Tester Type |
|
Cable |
Cable AC Hipot Testing |
JYCX |
|
Cable Insulation Resistance Testing |
JYM KYORITSU |
||
Transformer |
Insulation Resistance of Winding |
JYM KYORITSU |
|
DC Leakage Testing in 1min |
JYDHV |
||
Winding Resistance Testing |
JYR50S |
||
Winding Deformation Testing |
JYP |
||
Turns Ratio Testing |
JYT-A |
||
AC Hipot Testing |
JYCX |
||
Short Circuit Impedance Testing |
JYW6300 |
||
Dan Delta Testing |
JYC |
||
Oil Breakdown Voltage (BDV)Testing |
JY6611 |
||
Oil Tan Delta Testing |
GTD-61A |
||
Switchgear |
Circuit Breaker/Disconnector Resistance |
JYL-200B |
|
Relay |
Relay Performance |
JY7003G |
|
On-load |
On-load Switchgear Testing |
JYK-I |
|
Tap Changer Dynamic Testing |
JYK-I |
||
Instrument Transformer |
Current Transformer (CT)Testing |
JYH-C |
|
Potential Transformer (PT)Testing |
JYH-C |
||
Surge Arrestor |
Zinc Oxide Characteristics Testing |
JY6800 |
|
1mA DC Reference Voltage |
JYDHV |
||
Capacitor |
Capacitor Current |
JY6700 |
|
Capacitor Inductance |
JY6700 |
||
Ground Grid |
Grounding Down Lead Earth |
JYD |
Related Articles:
What Test Items are Required for 110kV/220kV Substation Acceptance and Maintenance Testing?
What Tests Must be Done before the Transformer Leaves the Factory?
Main Factors Affecting the Operating Life of Transformers
What is the Purpose of Measuring the DC Resistance of the Transformer Winding?
Points to note in transformer oil breakdown voltage (BDV) test
DC winding resistance tester with 500 times tests on a single charge -JYR9310