Current limiting for jacob's ladder?
What has worked well for me with such transformers is 100 watt light bulbs in series with the primary voltage. Add more bulbs in parallel for more current.

The reason is that incandescent light bulbs are very non-linear about current consumption. As the current rises the filament in the bulb get much hotter and its resistance goes way up, limiting the maximum current flow.

If the transformer shorted the lights would come ON full brightness. As it is they will flicker with changing loads on the high-voltage side. Do NOT try resistors as they will simply get hot as a linear device. Do NOT try them on the high-voltage side as the voltage will just arc across the resistor and burn it up.

I know farmers who do this for their electrified fences to protect the transformer, and to limit the current when cattle or horses touch the wire.