Creating a Custom Power Monitoring Application with Python and the IHVM ...

TECH NOTES

Creating a Custom Power Monitoring Application with Python and the IHVM-4P Module

Turn your Daxus? DXS-100 or SmartCorder? DDX-100 into a power analyzer with the IHVM-4P High Voltage Input Module and PythonTM

TECH NOTES

This note is an update to one published in February 2018 describing a Power Monitoring system based on the IHVM-4P and the Python programming language. The original application has been refined and expanded to use Data Capture so that no waveform data is lost. A second application was created to perform the same analysis function with Data Capture Review. Both of the applications can run on a Windows computer connected to either a Daxus? DXS-100 or a SmartCorder? DDX-100.

Figure 1 Real-time Power Monitor

IHVM-4P SUMMARY The IHVM-4P is a high voltage input module for the Daxus DXS-100 and SmartCorder DDX-100 data acquisition systems that is well suited to monitor electrical power. One or two of these modules can be installed in a standard Daxus DXS-100 or SmartCorder DDX-100 and each module provides 4 isolated, high voltage inputs for up to 600 Vrms. Each input channel can be sampled independently up to 50,000 times per second. The IHVM-4P includes a Digital Signal Processor (DSP) which generates 16 output waveform channels from the 4 analog inputs.

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In this case, we made use of the Power Mode with the following outputs:

? Voltage ? RMS Voltage ? Current ? RMS Current ? Frequency ? True Power ? Apparent Power ? Power Factor

Voltage from an AC power line can be connected directly or obtained from a transformer. Current inputs are conditioned to a voltage using a current probe or a shunt. The module is fully supported by the standard Daxus or DDX-100 Windows application which must be used to set up the module prior to running the Python application. The built-in Daxus DXS-100 or SmartCorder DDX-100 software application provides flexible gain control, user unit scaling and filtering as required to suit the measurement conditions.

The true value of the IHVM-4P in this type of application is its ability to perform complex mathematical operations on the inputs in real-time and at the full sample rate. This on-board signal processing significantly reduces the processing load on the Windows application.

PYTHON SUMMARY The Power Monitor application described was developed and tested using Python 2.7.12. Python is attractive as a means of implementing Daxus DXS-100 or SmartCorder DDX-100 functions because it is open source, free and supported by a large community of users. Python can also be enhanced with robust libraries for graphics and scientific computation. AstroNova provides a library of functions to simplify using Daxus DXS-100 and SmartCorder DDX-100 modules as input for a Python application.

POWER MONITOR APPLICATIONS OVERVIEW The Power Monitor outlined in this note consists of two different applications. The Real-Time Power Monitor application (shown in Figure 1) runs in real-time and replaces the built-in Daxus DXS-100 or SmartCorder DDX-100 software application. The Data Capture Review (DCR) Power Analysis application (shown in Figure 2) runs

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as a function under the built-in Daxus DXS-100 or SmartCorder DDX-100 software application in Review Mode.

Figure 2 DCR Power Analysis Application

The basic presentation of both applications are identical but there are differences in how the programs operate. In a typical application, a user would first run the standard Daxus DXS-100 or SmartCorder DDX-100 application to set up the module mode and spans and verify signal quality. The user would then close the standard Daxus or SmartCorder DDX-100 application and run the Real-Time Power Monitor application to monitor power in real-time for as long as required. This application allows the user to run a continuous data capture in the background so that nothing is missed.

This version of the Real-Time Power Monitor is designed for studying single phase power systems so only 2 inputs are required (voltage and current). All other measurements are derived by computation. Figure 1 shows the real-time displays and numeric values provided by the system. Frequency, RMS values, power measurements and power factor are obtained directly from the IHVM-4P. Other calculations are performed in the Python application.

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To view previously acquired data, the user can run the standard Daxus DXS-100 or SmartCorder DDX-100 application and select the capture record acquired during real-time monitoring.

While in Review Mode, the user can launch the Power Analysis function from the Analysis pull down menu (Analysis > Custom > Power). The Power Analysis function will analyze the section of the record on the left side of the screen and present the results as shown in Figure 2. If the user moves to another portion of the record, the anaylsis can be done again by pressing the Update button. If Cursor A is active on the Review screen, the user can select Auto Update and the analysis will be repeated every time the cursor position is changed.

SETTING UP THE IHVM-4P The standard Daxus DXS-100 or SmartCorder DDX-100 application is particularly helpful in setting up the IHVM4P because it has such a large number of features. When using the module to measure AC power systems, the Advanced Module Settings menu should be used first to simplify subsequent menu choices. This menu is shown in Figure 3 for a Daxus with only one IHVM-4P installed. By selecting Power Mode, IHVM-4P is automatically configured for the most common power measurements. The ratio settings provide a convenient means of indicating scaling associated with power transducers such as transformers, shunts and current loops.

Figure 3 Advanced Module Setting Menu

When the IHVM-4P is placed in Power Mode, each pair of inputs is capable of monitoring a single AC phase with voltage connected to one input and the current waveform connected to the other. Figure 4 displays a portion of the Channel Settings menu for a single IHVM-4P when in Power Mode. The inputs are referenced by the letters A,

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