Voltage Channels; Voltage Aux (V Dc) - Novatech Bitronics PowerPlex II User Manual

5.3 Voltage Channels

The PPX II uses a unique voltage connection method, which is combined with
simultaneous sampling to provide an extremely flexible voltage measurement system.
All voltage inputs are measured relative to a common reference level (essentially
panel ground). See Appendix 1 for input connection information. Because all signals
are sampled at the same instant in time, common mode signals can be removed by
subtraction of samples in the DSP, instead of the more traditional difference amplifier
approach. This greatly simplifies the external analog circuitry, increases the accuracy,
and allows measurement of the Neutral-to-Ground voltage at the panel. The 7kV input
divider resistors are accurate to within +/- 25ppm/DegC, and have a range of
600V , from any input to panel ground. Each sample is corrected for offset and
PEAK
gain using factory calibration values stored in non-volatile memory on the board.
Additionally, a continuous DC removal is performed on all inputs.
The PPX II calculates voltages in PRIMARY units, based on the VT Ratio entered.
There is one VT Ratio that covers all inputs on both buses. Ratio can be entered via a
network and protocol (refer to the specific protocol manual for details) or via the web
interface.
The advantages of this method of voltage measurement are apparent when the PPX II
is used on the common 2, 2-1/2, and 3 element systems (refer to Section 5.6). The
PPX II is always calculating Line-to-Neutral, Line-to-Line, and Bus-to-Bus voltages
with equal accuracy. On 2 element connections, any phase can serve as the
reference phase. Further, the PPX II can accommodate WYE connections on one
Bus, and DELTA connections on the other Bus.
On 2-1/2 element systems, one of the phase-to-neutral voltages is missing, and the
PPX II must create it from the vector sum of the other two phase-to-neutral voltages.
In order to configure the PPX II for 2-1/2 element mode and which phase voltage is
missing, a "0" is written to the phase-to-neutral VT Ratio for the missing phase
voltage.
The average of the 3 voltage phases ((Va + Vb + Vc)/3) is also available for bus 1 and
2, and is made available on a per cycle basis.

5.4 Voltage Aux (V DC)

The PPX II provides a measurement for the voltage connected to the power supply
terminals. This is a differential voltage. The DC value measured depends upon the
power supply voltage source.
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ML0047 December 1, 2017 Copyright 2017 Bitronics, LLC