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8 Configuring the Recorder
8-30 TESLA LITE User Manual D03283R01.10
8.11 Watts and Vars Channels
Description
The Watts/Vars Channels calculate apparent power (volt-amps), real power
(watts) and reactive power (vars) from voltage input and current inputs. The
channel can produce either single phase or three phase values.
Input
Analog Input Channels, Summation Channels or Sequence Component chan-
nel can be used as inputs to a Watts/Vars Channel. Using a Sequence Compo-
nent as an input results in three-phase Watts and Vars.
Calculation
Voltage and current are multiplied to calculate apparent power, real power and
reactive power.
Triggers
• Watts: high and low level (2)
• Watts: positive and negative rate of change (2)
• Vars: high and low level
• Vars: positive and negative rate of change
• Dual triggers for Watts allows fault and swing recordings to be triggered
by different settings (e.g. Rate of Change Interval), if desired.
To prevent multiple triggers on threshold conditions, an hysteresis of 2% of
setting is applied to magnitude triggers.
Recording
High Speed : Watt and Var values at a rate of eight values per cycle (regardless
of the system sample rate).
Low Speed : Watt and Var values at a rate of one value per cycle.
Number of
Channels
5 Watts/Vars Channels are available.
Types
W/V
Notes
The primary to secondary scale factor used by the Watts/Vars Channel is based
on those of its voltage and current input channels.
Watts, Vars, and Volt-Amp magnitudes are also available to the metering dis-
play, SCADA and the long term trending function.