1. ASEA Model UZBLN 250/300 UZB , One resistor – asymmetrical
3MVA trafo, 44kV tap changer
UZB , One resistor – asymmetrical
L – Linear regulation N- at neutral
250kV impulse
300A rated

2. Asymmetrical pennant

3. Raising the voltage = up

4. Lowering the voltage = down

5. Linear regulation Linear = adding the turns or subtracting the turns
for DC testing this is important, because :
Raising voltage
when subtracting turns, you are switching onto position with voltage but lower resistance (due to the voltage drop) and current is higher each position (UP)
Peak up - current jumps, when connecting to the point with voltage

6. Lowering - DOWN Lowering voltage Peak down - current drops
when adding turns, you switch onto the position without voltage but higher resistance, and the current is lower each position (DOWN)
Peak down - current drops
when connecting with point without voltage

7. Peak-up : going up
T breaks
S makes
T makes

8. up
T breaks
S makes
T makes

9. up
T breaks
S makes
T makes

10. up
T breaks
S makes
T makes

11. Peak-down : going down
T breaks
T makes
S breaks

12. down
T breaks
T makes
S breaks

13. down
T breaks
T makes
S breaks

14. down
T breaks
T makes
S breaks

15. Photos found on the internet

16. Before repair

17. After repair