It can be a challenge ensuring that any peninsula has enough alternative sources of electricity to cope with two faults on the system, he said. But that ability to cope with two simultaneous faults without interrupting the flow of electricity is a basic requirement for transmission systems in North America. In Upper Michigan, where two faults could put the local grid at risk, the remedial scheme calls for cuts in the power flowing to a large iron ore mine if there are faults on the connection to Wisconsin. It hasn't been invoked.