Eaton Power Xpert PXM 4000, User And Installation Manual

Page: 138 / 292

Page 130
IM02601004E
www.eaton.
8 Setup on the Web Server Pages
SUBCYCLE DISTURBANCE
The Power Xpert Meter captures subcycle disturbances with its regular metering hardware, which
samples at 30.72 ksps. You can set the dv/dt Threshold and Absolute Threshold for Van, Vbn, Vcn,
Vab, Vbc, and Vca. In addition, you can select the kind of action that will occur when one of the
thresholds has been reached; Capture Waveform, Capture Parameters and/or Send E-mail.
The Absolute Threshold Voltage setting is intended
to trigger on Voltage spikes that exceed the normal
positive and negative peak values, which are typi-
cally 1.4 times the rms line-to-ground Voltage. It is
important to set this threshold safely above the ex-
pected peaks. The Setup page suggests a threshold
that is 20% above the Nominal L-L Voltage (divided
by the PT ratio). For example, a 120V/208V system
has a 120V rms and 170V peak (line-to-ground), and
so a 250V threshold is appropriate (i.e. 208 + 20%).
The dv/dt Threshold setting is entered in dv while the
dt is fixed at the hardware sampling rate. The Setup
page suggests an aggressive threshold. Specifically,
the setup page suggests a threshold that is 5% of
the Nominal L-L Voltage (divided by the PT ratio).
To calculate the volts per microsecond, multiply the threshold Volts by 0.03072. For example, if the
dv/dt Threshold is set at 20V, the Volts per micro second would be 0.744 (i.e. 20V x 0.0372 Msps =
0.744 V/ microsecond).
A 30.72 ksps sampling rate and a pure 120V sine wave would result in a dv of 1.5V per sample at
the zero crossing. A disturbed waveform would have a much higher dv/dt.
Note: To notify Power Xpert software of subcycle disturbances, select the Send Web Services
Notification box.