MIL-HDBK-1003/7
Critical Loads. To develop a load shedding plan, the critical loads shall be
20.4.1
identified first, along with an estimate of the magnitude of each.
The load shedding plan shall be designed so that critical loads are
shed last. However, in some cases, it may be necessary to divide the critical loads
into two or more categories and assign relative priorities to each category.
20.4.1.1 Mission Critical Loads. Mission critical loads are the loads that are
essential for the operation of the facility and, if shed, would adversely impact the
facility mission. Mission critical loads may also include base security.
20.4.1.2 Life Support Loads. Life support loads include hospitals and similar
facilities where loss of power may endanger life.
20.4.1.3 Cost of Power Outage. In some cases, a power outage, while not endangering
the mission or life support, may result in excessive costs. For instance, the power
supply to a food storage facility may be considered critical because a power outage may
result in food spoilage with inherent loss of money and morale.
20.4.1.4 Political Implications. In some cases, the selection of critical loads must
be made on a purely subjective basis, taking into account the effect on the community of
providing power, or of not providing power, to a specific load during a widespread power
failure.
Time-Critical Loads. In many cases, load criticality will vary with time.
20.4.2
These variations should be taken into account, if possible, when designing the load
shedding plan.
20.4.2.1 Seasonal Variations. In a severely cold climate, a load related to providing
heat could be considered critical during the winter and noncritical during the summer.
Under the same conditions, the power supply to a frozen food storage facility could be
considered critical during the summer and non-critical during the winter.
20.4.2.2 Diurnal Variations. The criticality of some loads may vary from day to night
or from weekday to weekend because of changing usage. Examples may include auditoriums,
theaters, and offices.
20.4.2.3 Interruptible Loads. Some loads can withstand short interruptions but not
lengthy interruptions. Examples may include community facilities with emergency
(battery powered) lighting. These loads can be classified non-critical for load
shedding, but could also be given a high priority for load restitution.
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