Some emergency and standby power applications require the ability to start up and accept electrical loads in less than 10 seconds. If a project has a power restoration time requirement, it is highly recommended that a system level Start Time Analysis (STA) is completed. The STA should look at every aspect of the critical power path, from electrical system component selection to component performance (including settings, time delays, and inherent component processing delays) to site conditions that may impact system performance. The following list offers recommendations to achieve faster generator set starting.
- Avoid unnecessary generator oversizing when configuring generator sets that require a fast start time. Oversized and high voltage generators have a larger rotational inertia than the standard low voltage generator, and will increase generator set start times.
- In a paralleled generator set system, ensure the critical loads are less than the capacity of the smallest generator set and consider energizing all critical loads as soon as the first generator set breaker closes to the bus.
- Consider using a remote radiator with electric driven fans to decrease the inertia during starting on the generator set package, particularly when using an oversized or high voltage generator. Using oversized or high voltage generators in conjunction with engine driven fans may increase start times into an unacceptable range.
- Ensure package electronic controllers are updated to the latest software version.
- Engines equipped with electronic governors should be properly tuned for the site and application. This includes reviewing the ramp rate, and adjusting from the default value to improve start time. Note: increasing the ramp rate will result in increased black smoke on start-up.
- Packages equipped with a Digital Voltage Regulator (DVR) should be properly tuned for the site and application. This includes decreasing the "soft start" feature in the DVR, which will decrease the time it takes the generator to build rated voltage.
Electric Starters & Batteries
- Use heavy duty electric starters with fully charged batteries.
- For generator sets with only a single starter, add a second starter.
- Ensure the electric starter and battery set is able to crank the engine above 110 RPM for ten seconds.
- Use a redundant/back-up battery charger to ensure fully charged batteries.
- Depending on engine model, air starters may increase or decrease cranking speeds and thus affects the overall start time.
- For air start systems, maintain adequate air pressure to crank engine; size air tanks and related lines to crank engine above 110 RPM for at least ten seconds.
- Use jacket water heaters to maintain jacket water temperature at 32°C (90°F) minimum.
- Supply combustion air at 21°C (70°F) minimum.
- Supply battery heaters if ambient temperatures are below 0°C (32°F).
- Have a readily available supply of clean fuel.
- Ensure fuel filters are clean, and there is no air in the fuel system due to leaks.
- Use continuous engine oil pre-lubrication, if available with the engine model.
The parameters listed above cannot guarantee starting in a certain number of seconds, but will certainly improve start time.
- Have you ever performed a Start Time Analysis?
- If the analysis resulted in a start time greater than 10 seconds, how did you resolve the issue?
- When you exercise your genset (weekly/monthly), is start-up time one of the parameters you measure?
- Are there additional measures that you know of that can be taken to improve start time?
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