Basin Electric Power Cooperative is one of the few utilities that supply electricity on both sides of the national electric system separation. The two systems arose because the transmission system developed from the population centers on the coasts inward.
Direct-current (DC) ties or interties bridge the national electric system separation by taking alternating current electricity on one side, converting it to direct current, and then converting it back to alternating current so that it is in sync with the alternating current of the other side of the system separation.
Every generator east of the electrical transmission separation drives and affects that system and every generator west of the separation drives and affects that system. Electricity is generally transmitted at alternating current of 60 Hertz (cycles) per second. The slightest upset such as an electric generating unit abruptly separating from the system changes the standard 60 Hertz per second just slightly so the two systems are not synchronized and therefore cannot be connected directly. Connecting the systems would cause several system disconnects because protective devices for the facilities that are basically big circuit breakers would activate.
The focus of the North America Electric Reliability Corporation's (NERC) compliance program is to improve the reliability of the bulk power system in North America by fairly and consistently enforcing compliance with NERC standards. Specifically, the program is designed to ensure that the right practices are in place so that the likelihood and severity of future system disturbances are substantially reduced, while recognizing that no standards or enforcement process can fully prevent all such disturbances from occurring.
In the United States, NERC and the eight regional entities charged with compliance enforcement monitor compliance via a number of methods, including regular and scheduled compliance audits, random spot checks, and specific investigations as warranted by indications that a standard may have been violated.