Multi-Tech Systems 7500 - Manual (Page 299)

ION 7500 / ION 7600 User’s Guide Detailed Behavior
Power Availability Technical Note Page 299
3. Voltage Disturbance Duration: the total number of seconds that the voltage was
outside the envelope determined by the Sag/Swell module. If several sags or
swells occur during one second, only the last one counts toward the total. The
Sag/Swell module settings may be used to control the voltage tolerance. If the
Sag/Swell module is not enabled, no voltage disturbances are counted.
Terminology
For a better understanding of the Availability framework in ION meters, it is
necessary to know the following terms:
Blade-powered meter: the power to run the meter is derived from the Voltage
input terminals that are connected to the monitored system. The meter loses
power if the monitored system is down.
Auxiliary-powered meter: The power to run the meter is derived from an
independent power source. The meter remains powered when the monitored
system is down.
Meter uptime: the time the meter is powered and actively monitoring. The time
is measured by counting 1-second pulses from a periodic timer module.
Meter downtime: the time the meter is not powered. This time is measured by
the meter’s internal clock and made available through the diagnostics module.
The diagnostics module downtime register is reset at the beginning of each
outage.
Availability: the probability of finding a system in the operating state at some
time into the future. Availability is calculated as:
Unavailability: calculated in the framework and then converted to number of
nines, and Availability in percent and parts per million (ppm):
Time the power system is operating within specifications
Total time of operation*
Availability =
* Where total time of observation = uptime + meter downtime
Meter uptime - disturbance time
Meter uptime + meter downtime
=
Time the power system is operating outside specifications
Total time of operation*
Unavailability =
Disturbance time
Meter uptime + meter downtime
=
* Where total time of observation = uptime + meter downtime