byPower-Pop03-25-201410:28 AM - edited 04-15-201401:23 PM
We don’t always think about our emergency power supply setup until it’s needed. However, managers of critical power applications, like hospitals and data centers, need to be prepared for any duration of power loss. Not only is the reliability of the backup system crucial, quick start times are required before an electrical load can be accepted. The longer it takes for the system to start, the longer a critical application goes without power.
The National Fire Protection Agency’s (NFPA) 110 standard requires a 10-minute start up time for life-safety systems. Managers of critical power applications should complete a system-level start time analysis (STA) to ensure power restoration time requirements are being met. The STA covers every aspect of the critical power path from component selection and performance (including settings, time delays, and inherent component processing delays) to site conditions that may impact system performance. It’s possible that the STA may reveal a start-up time that takes longer than 10 minutes for an emergency power supply system. In this case, the following considerations can help managers achieve a faster generator set start-up time.
Examine rotational inertia: Oversized and high voltage generators have a larger rotational inertia than the standard low voltage generator, which will increase start times.
Energize critical loads: Ensure the critical loads are less than the capacity of the smallest generator set for paralleled systems. Energizing all critical loads as soon as the first breaker closes to the bus can increase start times.
Test engine-driven fans: Remote radiators with electric-driven fans will decrease inertia during start-up, particularly when using an oversized or high-voltage generator.
Consider a software upgrade: The latest software version will provide the best start-up time for system controls.
Review the ramp rate: Match the ramp rate to the site and application needs, as adjustments from the default value will improve start time. You’ll notice that increasing the ramp rate will result in more black smoke on start-up.
Regulate DVR: Decreasing the soft start feature in the digital voltage regulator (DVR) will decrease the time it takes the generator to build rated voltage.
Electric Starters & Batteries
Test the battery charge: Use heavy-duty electric starters and back-up starters with fully charged batteries for faster start times.
Consider a second starter: Single-starter generator sets provide slower start-up times.
Check crank speed: Ensure the electric starter and battery set is able to crank the engine above 10 rpm for 10 seconds.
Examine engine model: Air starters may increase or decrease cranking speeds depending on engine model.
Maintain air pressure: Size the air tanks and related lines to crank the engine above 110 rpm for at least 10 seconds.
Maintain water temperature: Use a water jacket heater to keep water temperature at 32°C (90°F) minimum.
Combustion air supply: This should be kept at 21°C (70°F) minimum.
Consider a battery heater:If ambient temperatures are below 0°C (32°F), use a battery heater to avoid longer start-up times.
Use clean fuel: Change fuel filters regularly and monitor fuel system tubing to avoid air intake and leaks.
Consider pre-lubrication: If available with the engine model, use continuous engine oil pre-lubrication to ensure smooth flow.
When every second counts in emergency backup system start times, managers can implement an STA report to determine whether or not the system meets the 10-second standard. Unfortunately, each system requires individual assessment, but the good news is that applying any combination of these options will likely improve start time.
For more information on reducing backup system start time and other Caterpillar Product Support services, visit us online.
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