1 Darrin Marr Marcie Webb Brad Zarikoff Digital Input Power Meter

2 Introduction Background Design and operation Progress and problems encountered

3 Project Goals To design a Power Meter that accepts a digital input Reduce the redundancy in conventional technology Improve on Power Measurement for Utility Industry

4 Application Overview Power Meters are typically used in substations Current and voltage transducers feed power meters You cannot connect an oscilloscope to volts

5 Conventional Technology IPP tap from utility breakers Analogue Meter (Analogue Metering) 120V analogue signal Current Sensor Voltage Sensor NXVCT IPP owned equipment 138 kV 13.8 kV Stn. Service Xfmr. 475 kW load Utility owned equipment Gas Turbine Generators 225 MVA 13.8 kV, 60 Hz Optical Current Electronics DAC, Amplifier Optical Voltage Electronics DAC, Amplifier - 0.2% accuracy over 2 – 3000A range

6 Metering with Digital Input Meter with digital input (Digital Metering) Current Sensor Voltage Sensor NXVCT Optical Current Electronics Optical Voltage Electronics IPP owned equipment 138 kV 13.8 kV Stn. Service Xfmr. 475 kW load Utility owned equipment Gas Turbine Generators 225 MVA 13.8 kV, 60 Hz IPP tap from utility breakers Merging Unit

7 Meters

8 Corporate Sponsorship NxtPhase is a company that makes Voltage and Current Transducers NxtPhase uses optics to measure the line voltage or current Optical signal is transduced to voltage and digitized Dedicated to “Digitizing the Grid”

9 Keeping NxtPhase Happy NxtPhase does not make Power Meters Want to interface to next generation Digital Input Power Meters and Protection Relays Need to develop a Merging Unit to IEC standard

10 Current and voltage emulation Current and voltage data merging unit Receiving and data decoding unit Data display Digital Input Power Meter

11 Digital Input Power Meter Layout

12 Sine Wave Generator Used to generate three-phase voltage and current received from NxtPhase equipment Simulates three voltage and current signals Output at NxtPhase proprietary data and sampling rate as TDM signal

13 Merging Unit Takes TDM data of six sinusoids and packetizes them into data stream for transmission Outputs packets at 2.5Mbps at 4.8kHz sampling rate Continuous packet output (no idle) Averages samples (NxtPhase sampling rate much faster than IEC standard)

14 Packet Standard Packetized in accordance with IEC standard Packet standard incorporates three- phase metering, protection, and unit data, error control (CRC)

15 Merging Unit

16 Buffer Board Transmission along data line to allow for remote monitoring Buffer board decodes data packet and buffers data (0.2s worth) for burst transmission National Instrument DAQ card dumps data into file on PC to be used by meter display

17 Data Display Visual Basic in Excel application Retrieves voltage and current data from data file every x seconds Formats and displays current and voltage information Calculates voltage and current spectrum, power factor, and RMS values

18 Digital Interface Meter

19 Project Status Verification stage at present All design and implementation complete Currently testing to ensure reliable operation Visit our demo on Friday in ELW

20 Problems Encountered No copy of Matlab for meter display development –Would have been excellent tool for data display and manipulation Now using Visual Basic in Excel –Limited mathematical capabilities –Slow graphing capabilities

21 Problems Encountered Original design included fiber optic link between Merging Unit and Digital Meter Researched options available –Found inexpensive development kit Lack of time forced us to abandon testing and implementation Fiber optics used to avoid EMI

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23 Error Detection IEC standard includes CRC error detection code –Uses three 16-bit CRC checks Possible to have better error detection with less CRC bits required –One 32-bit CRC check would have better detection capabilities

24 Conclusions Digital input power meter currently not available commercially –NxtPhase has interest because need to connect PT’s to digital meters Realizable with more time NxtPhase will be able to use Merging Unit design as step towards useable product

25 Questions?