Trend
Available function keys:
F1
Switch between voltage and current trends, the header shows parameters being
displayed.
F2
Access to Events tables
F3
Access to Cursor
F4
Selection of Cursor move or Zoom
F5
Switch between RUN and HOLD.
Event criteria such as threshold, hysteresis and others are preset, but they may be adjusted. The
adjustment menu is reached via the
【
SETUP
】
key and limits setup.
Events tables
The Events table lists all threshold crossings of phase voltages. Thresholds according to international
standards or user
–definable thresholds can be used. The Events table records major event
characteristics: start time, duration, voltage magnitude, event type, and occurrence phase etc.
Tips and Hints
The occurrence of Dips and Swells may indicate a weak power distribution system. In such a system
voltage will change considerably when a big motor or a welding machine is witched on or off. This may
cause lights to flicker or even show visible dimming. It may cause reset and loss of data in computer
systems and process controllers.
By monitoring the voltage and current trend at the power service entrance, you can find out of the cause
of the voltage dip is inside or outside the building. The cause is inside the building (downstream) when
voltage drops while current rises; it is outside (upstream) when both voltage and current drop.
7.5. Harmonics
Harmonics measure and record harmonics and interharmonics up to the 50th. Related data such as DC
components, (THD) Total Harmonic Distortion, and K-factor are measured. Harmonics are periodic
distortions of voltage, current or power sinewave. A voltage or waveform can be considered as a
combination of various sinewaves with different frequencies and magnitudes. The contribution of each of
these components to the fundamental signal is measured. Readings can be given as a percentage of the
fundamental (%f), or as a percentage of full signal RMS (%r).Results may be viewed in a Bar Graph
display. Harmonics are often caused by non-
linear loads such as DC power supplies in computers, TV’s
and adjustable speed motor drives. Harmonics can cause transformers, conductors, and motors to
overheat.
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