Despite a threat of potential power outages, the national grid operator says the power system worked as expected, but analysts argue the whole market is not fit for purpose.

A fault with equipment on the cable system that takes power from the South to North Island lead to an emergency situation where Transpower was forced to ask consumers to reduce power use amid increased pressure from cold weather.

Power systems consultant Bryan Leyland owns a small hydro power station - and he said the current system works in an ideal world but it was not that simple.

He spoke to Māni Dunlop.