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        Diesel generators in the data centre –

        when is bigger better?

        by David Matuseski, Cummins
            inding the best combination
            of generator size and system
       Farchitecture is a goal for all
        data centre designers. Many times, a
        larger generator can provide unique
        advantages. When you combine large
        generators into a paralleling system,
        you can achieve a whole new level of
        advantages. The data centre designer
        should carefully analyse all options to
        optimise the generator system design.                                        For all your advertising
           There are many factors to consider
        when designing the generator system                                          requirements contact:
        for your data centre. Two of the most
        important items to consider in your design   David Matuseski                    Katia dos Santos
        are the optimal size of the generator and
        the architecture of how your generators   system. Various system architectures    076 410 6909
        integrate into the overall power system. In   have been developed to address this
        some installations you have no choice but   challenge. One of the more common
        to go with a larger generator due to the size   architectures is adding tie breakers (or
        constraints of the site.             sometimes tie switches) to the paralleling         or
           This can be especially true when   bus. These tie breakers provide segments
        installing additional power generation   in the bus that allow you to partially shut   Mark Yelland
        into an existing building. Using a   down the switchgear for maintenance.
        greater number of smaller generators   For example, if you have an N+2            074 854-1597
        would not have been a good option    design, you can completely isolate one
        in this example. The higher power    segment of switchgear for maintenance
        density of large generators was the   or repair. This design is also used in an
        better choice. In addition to the unique   N+1 design with tie breakers in-between
        challenges in metropolitan areas,    each generator on the paralleling bus.
        sometimes the footprint advantages of   The protective relaying on a segmented   Visit our Website:
        using large generators are also desired   bus can be designed to eliminate the
        in new construction.                 paralleling bus as a single point of failure.
           Paralleling generators in a data centre   This is most commonly achieved with a
        design can have many advantages. It does   current differential scheme.
        not fit every situation, but paralleling   Another way to achieve concurrent
        does provide many benefits over a single   maintainability is that each generator
        generator design. The advantages have   can be switched from one paralleling bus
        varying degrees of importance in a data   to an alternative paralleling bus. In an
        centre application, but efficiency (reducing   N+1 design, there would be one additional
        your stranded generator power capacity),   generator and corresponding transfer
        can be the most attractive. The generator   switch. Any one component, including
        system is one of the more expensive   the paralleling bus, can be shut down for
        systems to procure, install and maintain.   maintenance and there will still be the full
        Making this system as efficient as possible   ‘N’ capacity available from the generator
        will have a significant effect on reducing   system. There is another architecture for
        data centre cost.                    paralleling generators being used in data
           An important challenge in a       centres. This is sometimes called ‘3 to make
        paralleling system architecture is   2’ (or ‘4 to make 3’, etc.)   n
        achieving concurrent maintainability.
        This is due to the common paralleling   Contact Sbu Gule, Cummins Africa Middle East,
        bus required in a generator paralleling   Tel 011 451-3433,

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