This is a voltage measuring transformer, 35000/100 V. It's name is Bobo.

It is old and useless, but it can generate high voltage and nice sparks. It is able to check small power and telephone Insulators, how and where the spark runs by vice-versa using.

I gives power to it's secundary points by a toroid transformer, when I begin increase the voltage from zero, it shows the high voltage effect. By the 10 V it generated 3.5 kV and the crown effect voice begins. In dark, when I give 30 V, the blue crown effect is visible and the voice is alike what you hear from the transmission lines. I put there 3 cm of spark space, and from 70-80 V, 25-30 kV primay, the spark jumps. (the air is wet...)

When the spark is lighting, the secondary coil drains huge current, 20-25 A toroid primary on 230 V, it is high, thre spark can lives only 1-2 sec, my toroid can't pass it longly.

I am thinking about a high frequency injector circuit to convert it to a safe Tesla transformer but the voltage transformer's iron core is not so able for the very high frequency.. It needs a try :-)