The Siemens static volt ampere reactive (VAR) compensation system (SVC) has strengthened the transmission path from Arizona to California since its completed installation in September 2006. This FACTS installation, currently the largest in North America, was handed over to the customer, Southern California Edison (SCE), after a very short lead time of 13 months for implementation and commissioning. Southern California Edison is one of the nation’s largest electric utilities in the United States, serving a population of more than 13 million via 4.8 million customer accounts in a 50,000-square-mile service area within central, costal and Southern California.
On Aug. 8, 2005, Siemens was awarded the order to furnish, on a complete turnkey basis, all work required to engineer, design, manufacture, assemble, install, test and commission the Devers SVS for Edison’s Transmission and Distribution Business Unit. The initial order was for a 525-kV, three-phase, 60 Hz, -110/+440 MVAR SVS at Devers Substation outside of Palm Springs, California. This included a 110 MVAR Mechanically Switched Capacitor (MSC) and a -110/+330 MVAR SVC.
After signing the contract, SCE requested acceleration and commissioning of the MSC portion of the project by July 1, 2006. With the system operational by the summer peak, SCE was able to strengthen its bulk power 500 kV system. The first change order was signed to energize the MSC early – delivery time of 11 months – and keep the SVC commissioning on the original contract date of Sept. 11, 2006. Successfully meeting the aggressive schedule was directly attributable to teamwork between SCE, Siemens, and Beta Engineering of Pineville (Louisiana), which provided the civil design and site management.
The SVC technology is used to stabilize the voltage at the 500 kV level during normal operation. SCE had previously used manually controlled mechanically switched capacitors and reactors to control fluctuations of the voltage during normal operations. The SVC does this automatically without input from SCE operators.
If a fault occurs within the system during abnormal operations causing contingencies in the transmission system at the 500 kV voltage level, the SVC is switched appropriately in order to mitigate any major voltage fluctuations and damp the system back to normal operation. This can be done on a cycle by cycle basis using Light Fired Thyristors (LTT) as the high speed switching devices.
Siemens FACTS technology has standardized on the LTT Thyristor valves for all projects including these large reactive branch configured SVCs. These offer significant benefits versus the conventional electrically triggered thyristors, e.g. less electronic components at high potential and a substantial increase in reliability.
SVCs are also used to dampen power swings, improve transient stability and reduce system losses by optimizing reactive power control. In the past Siemens has supplied similar projects in the United States such as Entergy’s Ninemile SVC in New Orleans, Louisiana, and its Porter SVC near Houston, Texas. SVCs are one type of flexible alternating current transmission systems (FACTS). FACTS devices are used for the dynamic control of voltage, impedance and phase angle of high voltage AC lines. They also provide strategic benefits for improved transmission system management through better utilization of existing transmission assets; increased transmission system reliability and availability; increased dynamic and transient grid stability; and enabling environmental benefits. FACTS devices are also used to provide increased quality of supply for sensitive industries (e.g. computer chip manufacture).
Siemens met all contract requirements including an aggressive on time delivery schedule in order to meet SCE’s system requirements. The stability of the bulk transmission power system in Southern California is dramatically increased and is based on a microprocessor controlled automatic response by the SVC to maintain the integrity of power flow. The SVC helps keep the lights on in Southern California, especially in the Palm Springs, California, area