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PSERC Power Systems Engineering Research Center

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					Wireless Data Communication
       in Substations


       Mladen Kezunovic (P.I.)

          Alireza Shapoury


       Texas A&M University
          College Station
          PSerc Meeting

           November, 2002        PSERC
                OUTLINE
                                                                        PSERC


   Introduction

   Overview of the Problem

   Objectives

   Projects Tasks (Technical Approach)

   Results

   Conclusions


PSerc Meeting    Texas A&M University at College Station   November, 2002       2
                INTRODUCTION
                                                                         PSERC

• Use real-time and off-line data for better
    maintenance management
•   Utilize new technologies of wireless
    communications and mobile agents
•   As an example, improve efficiency of circuit
    breaker maintenance assessment
•   Demonstrate the benefits of new communication
    and software technologies using utility
    maintenance management scenarios


PSerc Meeting     Texas A&M University at College Station   November, 2002       3
                INTRODUCTION
                                                                              PSERC

• Pros of Wireless Network
                • Cheaper than (often-expensive) cabling version
                • More relaxed constraint on isolation level and
                    clearances
                •   Portability/mobility
                •   Reduced susceptibility to unstable grounds
                •   Convenience and ease of installation
                •   Easier implementation of higher Insulation
                    Protection (IP) of instruments
                •   Extends the range of data acquisition and I/O
                    (large scale operation)


PSerc Meeting          Texas A&M University at College Station   November, 2002       4
OVERVIEW OF THE PROBLEM
                                                                               PSERC


• THE FIRST GLANCE
  • Known
                 • Use License-exempt ISM (Industrial,scientific and Medical)
                   Band (Cost-free to use the spectrum)
                 • FCC Allows Higher RF Power If Spread Spectrum (3-4 times
                   improvement in transmit range)
                 • Upper Network Layers Already Developed (No need to
                   reinvent the wheel)
  • Not Sure
                 • Suitability of Existing Solutions For This Particular Application
  • Sure
                 • Solutions Not Tested/Evaluated for This Application

 PSerc Meeting          Texas A&M University at College Station   November, 2002       5
OVERVIEW OF THE PROBLEM
                                                                              PSERC

•    Already Well-developed Wireless Network
     Standards
         •      IEEE 802.11
         •      IEEE 802.16
         •      More on Appendix A
•    What is the difference?
         •      Their Physical (PHY) and/or Medium Access Control
                (MAC) Are Not Optimized/Assessed to Operate in The:
                • FIXED LOCATION
                • IMMEDIATE VICINITY OF HIGH TRANSIENT
                    SOURCE
         •      Adopt Other Standards for Upper Layers

PSerc Meeting          Texas A&M University at College Station   November, 2002       6
                OBJECTIVES
                                                                        PSERC

• Identifying the Probable Impacts of the
    Environment (What Should We Look for?)
•   Design Measurement Setup Plans
•   Conduct Series of Measurements to Probe Our a
    Priori Knowledge
•   Process the Data to Acquire Relevant and More
    Comprehensive Understanding
•   Defining the Most Appropriate Wireless Strategy
    for Substation Environment

PSerc Meeting    Texas A&M University at College Station   November, 2002       7
                  PROJECT TASKS
                                                                             PSERC


I.        Theoretical Analysis and Technical
          Observations
II.       Field Measurement Setup Plans
III. Data Analysis and Post-Processing
IV. Identifying Reliable System
    Characteristics
V.        Documentation
      PSerc Meeting   Texas A&M University at College Station   November, 2002       8
I. THEORETICAL ANALYSIS AND
   TECHNICAL OBSERVATIONS                                                      PSERC

•    Impulsive noises and EMI Impact On Wireless
     Channel
•    Noise Sources In Substations
•    Review of The Noise Impact On the Core Spread
     Spectrum Schemes
•    Crude Comparison Of DSSS And FHSS
                 •   Worst-case Analysis
                 •   Worst-case happens under different noise profiles for
                     DSSS and FHSS



 PSerc Meeting          Texas A&M University at College Station   November, 2002       9
    I. THEORETICAL ANALYSIS AND
       TECHNICAL OBSERVATIONS                                                   PSERC


•    DSSS indicates
     approximately 5dB
     superior to that of FHSS
     under worst-case noise
     profile of their own



•    Assessment of the
     likelihood of the
     Worst-case situations
     necessitates
     measurement



     PSerc Meeting       Texas A&M University at College Station   November, 2002       10
II. FIELD MEASUREMENT SETUP
    PLANS
                                                                        PSERC

        Measuring Parameters (Statistics)
           • Average Noise Power
           • Average Signal Power
           • Average Packet Error
           • Temperature
        Measurement Devices, Configurations and
         Operation Modes
        Investigating Practical Issues (E.g. Antenna
         Type and Location, Proper Output Power)


PSerc Meeting    Texas A&M University at College Station   November, 2002       11
 II. FIELD MEASUREMENT SETUP
     PLANS
                                                                       PSERC


I.      Propagation Profile Measurement
II.     IEEE802.11 Based Site-Specific
        Measurement
III. 900MHz Long-Term Site Survey
IV. 2.4GHz Long-Term Site Survey


PSerc Meeting   Texas A&M University at College Station   November, 2002       12
    III.DATA ANALYSIS AND
        POST-PROCESSING
                                                                           PSERC

•     IEEE Has a Recommended Practice for Site
      Survey
•     The Measured Data Has a Strong Non-random
      Component With Long-time Memory and a
      Stationary Internal Structure, Which Calls for
      Time Series Analysis.
•     Our Statistical Analysis Suggests That The
      Mostly-Used Classical Distributional Analysis Is
      Not Appropriate Unless Incorporated With Time
      Series Analysis.

    PSerc Meeting   Texas A&M University at College Station   November, 2002       13
IV. IDENTIFYING RELIABLE
    SYSTEM CHARACTERISTICS
                                                                       PSERC


       Achievable Baud Rate For Wireless Channel
       Maximum BER For Data Devices
       Necessary Response Time For The Wireless
        Device
       Choice and design of Antenna
       Power Supply And Isolation
       Adequate Data Security



PSerc Meeting   Texas A&M University at College Station   November, 2002       14
V. DOCUMENTATION
                                                                       PSERC



       Progress Reports

       Final Report

       Preparing Some Publications




PSerc Meeting   Texas A&M University at College Station   November, 2002       15
    CONCLUSION                                                                   PSERC

    Accomplishments
                       Identification of Noise Sources in Substation
                       Worst-case Analysis for Two Core SS
                        Modulation Formats
                       Extraction of the Necessary Parameters (to
                        Be Measured)
                       Measurement Setup (Modifications,
                        Verifications and Programming )
                       Conducting Several Long-term Measurement
                        Runs


    PSerc Meeting         Texas A&M University at College Station   November, 2002       16
    CONCLUSION                                                                   PSERC

    Accomplishments (Cont.)

                       Presenting a Methodology for Post Processing
                        of Data
                       Investigating the Impacts of Substation
                        Electrical Parameters (E.G. Voltage Levels,
                        Power, Etc) on Wireless Link Quality
                       General Requirements and
                        Recommendations for the Wireless System
                        Candidates



    PSerc Meeting         Texas A&M University at College Station   November, 2002       17
CONCLUSION                                                                     PSERC

       Results in a Nutshell
                   Noise Analysis in This application requires
                    time series analysis
                   Impacts of Slow-Varying processes in
                    Substation
                          Load pattern and even Voltage levels have no or little
                           impact over the link quality on Average
                          Ambient and Transformer Temperatures have no or
                           little impact on the link quality on Average
                          Transformer Temperature has no or little impact on
                           the link quality on Average




PSerc Meeting           Texas A&M University at College Station   November, 2002       18
CONCLUSION                                                                     PSERC

       Results in a Nutshell (Cont.)
                   Impacts of Fast-varying Processes in
                    Substation
                          Sharp Peaks and Troughs May Cause Link Disruption
                          The Existence of the Impulsive Signal Level Variation
                           Should Be Considered by Wireless Designer (Increasing
                           the TR Power Settings)
                                ~14 dB Variation (900 MHz)
                                ~20 dB Variation (2.4 GHz)
                   Signal Level variation seems to be strongly
                    depending on the location of the substation i.e.
                    Rural, Industrial,etc (almost 6 dB difference in
                    link quality)


PSerc Meeting           Texas A&M University at College Station   November, 2002       19

				
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