Power quality problems in heavily loaded radial systems, with multiple static VAr compensators, expanded bundle transmission lines and dynamic active loads

The transmission of large amounts of power using radial systems through long distances with acceptable power quality levels represents a big challenge, specially when transmission system expansion is delayed by financial constraints. This appears on CHESF North transmission system where the high length of transmission lines, the presence of a great number of small industrial loads, the high levels of power transmitted, long fault clearing times on subtransmission system fed by 230 kV substations and elevated shunt capacitances of expanded bundle transmission lines (EBTL) used to increase the transmission capability, produce long duration voltage sags on fault clearing, followed by high voltage swells. To quantify these effects and propose actions to minimize their impact over the transmission system, as the use of special protection schemes, dynamic and transient studies were performed and compared with site tests, with detailed modeling of the involved elements, such as static VAr compensators, motor loads and EBTL