|Starting operation, recorded from 7UT512|
At magnetizing inrush treads one significant component 100Hz (2. Harmonic).It will be measured and used for stabilisation.
1. Amplitude matching
- Nominal Power (from there primary and secondary nominal current)
- Current transformer ration primary and secondary
2. Phase position matching
- connection group e.g. Yd 5
3. At automatically regulated Transformers
- Control range e.g. +/- 10%
4. Two- or Three windings transformer
- One critical event for the differential protection of transformer is the starting.
- Current flows in the transformer and it is used for magnetizing the core,but no current flows out on secondary side.
- For prevention of tripping of the protection device special actions are to be taken.
- The magnetizing current is identificated by a high component 2.Harmonics (100Hz).
- It will be filtered-out and used for stabilisation. With that the transformer can be started safely.
but also in normal operation:
I1 is not I2 !
because of actual transfrormation ratio of the transformer
because of connection group of the transformers
Phase position matching
- at conventional and analog devices: matching transformers
- at digital devices computationaly in protection device