Arteche smART P500, Instruction Manual

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7BRELIABILITY INDEXES
PROTECTION, CONTROL AND METERING FUNCTIONS
2.6.12. CBEMA EVENTS
CBEMA Curve is one of the most frequently employed power acceptability curve. It was
developed by the Computer Business Equipment Manufacturers Association in the
1970s, as a guideline for the organization's members in designing their power supplies.
Basically, the CBEMA curve was originally derived to describe the tolerance of
mainframe computer business equipment to the magnitude and duration of voltage
variations on the power system. Also, the association designed the curve to point out
ways in which system reliability could be provided for electronic equipment.
The CBEMA curve was adapted from IEEE Standard 446 (Recommended Practice for
Emergency and Standby Power Systems for Industrial and Commercial Applications -
Orange Book), which is typically used in the analysis of power quality monitoring results.
The relay records the following information regarding such events:

Counter of Hz events: Indicates the number of this kind of events that have been
detected including the present one. This counter has a maximum limit of 100 after
which it changes to zero.

Date and time: Date and time when the event was detected.

Event duration: Time span of the event.

Involved phases: Information about the phases where the event was detected.

Voltages of the three phases : Stores the value of the phase voltages at the
moment of the maximum voltage unbalance.

Current of the three phases: Stores the value of the current for each of the
phases at the moment when the maximum voltage unbalance occurred.

Classification: Classification of the swell according to a nominal scale.
2.7. RELIABILITY INDEXES
The electric utility industry is moving toward a deregulated, competitive environment where
utilities must have accurate information about system performance to ensure that
maintenance dollars are spent wisely and that customer expectations are met.