Complex sentence: Oil filled transformers with conservators (an oil tank above the transformer) tend to be equipped with Buchholz relays-safety devices that sense gas buildup inside the transformer (a side effect of corona or an electric arc inside the windings) and switching off the transformer.
Split into simpler sentences: Oil filled transformers with conservators (an oil tank above the transformer) tend to be equipped with Buchholz relays. These are safety devices that can sense gas buildup inside the transformer (a side effect of corona or an electric arc inside the windings) and then switch off the transformer.