The North American Electric Reliability Corporation (NERC), Transmission System Operator Certification (TO) is an intermediate-level credential for professionals who operate bulk electric systems. System Operators monitor power flows, voltages and status of equipment on the transmission system, and ensure the safe and reliable operation of the bulk electric system. Candidates for the TO are expected to have knowledge of resource and demand balancing, transmission, emergency preparedness, contingency analysis and reliability, and managing communications and data.