BG&E Lifts Power Factor at Seagirt Marine Terminal
A recent partnering between Maryland Port Administration and Baltimore Gas & Electric (BGE) is demonstrating a more customer-friendly approach to resolving reactive power demand than the traditional approach of penalties, expensive dedicated lines and substation installation of mechanically switched or static capacitors.
With the help of on-site adaptive var compensation (AVC) technology from Toronto-based Haefely Trench, power factor at the Port Administration`s Seagirt Marine Terminal has been boosted from an average of 40 percent to a current average of 96 percent, resulting in expected annual demand savings of roughly $220,000. BGE also has increased capacity on its system, two 2,400 kVAR units were installed in January 1997.
Particularly cost-effective for dynamic loading, the AVC technology`s greatest strength is in its speed of response. Combinations of compensating capacitors are switched into the circuit just one-quarter cycle following measurement of the reactive load at the phase-to-neutral voltage zero crossing. Compensation therefore follows the loading extremely closely on a cycle-by-cycle basis.
Timing also is key in the AVC`s prevention of generation of transients. Capacitors are pre-charged to the peak of the supply voltage and remain charged until a triggering signal is applied to the solid state switch (SCR). The triggering signals are synchronized to set the switches into conducting mode only when the system voltage reaches its peak. At this instant, the potential across the SCRs is nearly zero, and corresponds to the natural zero crossing of the capacitor current, hence transients are not generated.
Supplied by two 13.2 kV feeders with cross-tie capability, the Seagirt Terminal`s seven rail-mobile cranes are powered by DC motors controlled by variable speed direct current drives.