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Each minute the MLP measures the current passing through phase A. The highest
value from all of the measurements collected over one hour is saved, providing it does not
surpass the value of 1.5 * In or any Zone III unit has activated (DMUZ3).
The hourly register saves the data registered for a week in a circular stack that
when completed, automatically substitutes the oldest data by the newest. Data is saved in
volatile RAM
If the MLP is not set to the right time, the hourly register stores current values every
hour but based on values starting from the date and hour of the last registered event or in
the case it does not exist, from the default date and time (01101/88, 00:00:00).
Through a setting it is possible to change the current log to a voltage log with these
characteristics:
Each minute the active and reactive power is calculated:
P = 3 * (Vx * Ix + Vy * Iy) = 3 * lVl lIl cos (90-α)
Q = 3 * (Vx * Iy - Vy * Ix) = 3 * lVl lIl sin (90-α)
where:
P: Active power
Q: Reactive power
Vx, Vy: Real or imaginary components of the voltage corresponding to phase A.
Ix, Iy: Real or imaginary components of the current corresponding to phase A.
4.16 BREAKER SUPERVISION.
The breakers require maintenance depending on how often they are opened and
with what current during certain periods of time. The MLP supervises the opening of it's
associated breaker for maintenance purposes.
Each time the MLP detects a breaker opening it registers the maximum current of
the phases. If the maximum current does not exceed the rated current, the rated current is
used as the value. The MLP program calculates the square of the current and adds it to the
values obtained In previous openings.
The MLP allows a limit to be set for this sum and when this limit is reached, it
indicates that the breaker requires maintenance. It also allows you to set the value of the
sum when associating a breaker that has been previously opened to the MLP.
GEK-98846A
36
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