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Last Mile Connectivity Challenges in Smart Grid

Cigre Colloquium, Mysore, November 13-15

Chander B Goel

Texas Instruments India

Smart Grid Advantages

• Omits human Errors

• Reduced Man Power and Quicker Billing

• Increase the resiliency of the grid.

• Helps in implementation of Dynamic Tariffing

• Helps to catch power theft directly from power lines

• Helps to catch tampering of Energy Meters

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Smart Meter & Automated Meter Reading

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Meter communicates via wired or wireless interfaces to the outside world. Level of smartness depends on the exact capabilities of the meter

–1-way communication or Automated Meter Reading (AMR)

–2-way communication or Advanced Metering Infrastructure (AMI)

Expectations from AMR

• Reliability and sustained connectivity

• Interoperability

• Security

• Ease of Installing and Commissioning

• Lower Cost

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AMR Technologies

• Wireless Technologies– Zigbee SE– 6LowPAN– Wireless M-Bus– Wifi

• Wired technologies– M-BUS with RS485– Power Line

Communications

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Choosing the ISM frequency band for LPRF

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• Most of the countries of the world allow 2.4GHz band free of licensing requirements but there are limitations with this band because of lower range and interference.

• Most countries now allow a sub 1 GHz band for license free use for AMR applications

Comparing LPRF technologies

• Zigbee with SE– Pros

• Mesh based self healing networks• Mature specification. Interoperability guarenteed.• Smart Energy profile available.• Good for Home Area Network

– Cons• Limited support for sub 1 GHz bands. 2.4GHz implementations limit range.• The stacks have a big footprint.

• 6LowPAN– Pros

• The meters can be merged into internet.• Standardization at RFC level.

– Cons• Application layer is still open. Interoperability can be challenging.

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Comparing LPRF technologies.

• Wireless M-Bus– Pros

• Standardized in Europe as EN13757• Operates at 868MHz. Can provide better range coverage.

– Cons• Does not support mesh topology.• Security is not inherently available in the specification.

• WiFi Direct– Pros

• Ubiquotus. Mobile phones or Tablets can be used to read meters

– Cons• The transceivers consume higher power.• Limited range due to 2.4GHz frequency band.

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Wired AMR - Power Line Communication

• Power Line Communications Refers to a Method of Narrow Band Communications that uses the Existing Power Lines as the Communication Medium

• Based on S-FSK or OFDM

• Reduces System Cost

• Increases System Reliability

High-Voltage Side(110-380kV)

Medium-Voltage Side

(10-30kV)Backbone Telecommunications

Network

Utility Customer

Utility Company

Low-Voltage Side (110-240V)

Concentrator

MV router

Meter/modem

Transformer

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PLC Frequency Bands, Standards and Regulations

• PLC frequency bands in Europe– Defined by the CENELEC:

• CENELEC-A (3 kHz – 95 kHz) are exclusively for energy providers

• CENELEC-B, C, D bands are open for end-user applications

– Bands A, B and D protocol layer is defined by standards or proprietarily defined

– Band C is regulated – CSMA access

• PLC frequency bands in USA– Single wide band – from 150 to 450 kHz– FCC band 10 kHz – 490 kHz– Access protocol defined by standard– HomePlug broadband: 2–30 MHz

• PLC frequency bands in Japan– ARIB band 10 kHz – 450 kHz

• PLC frequency bands in China– 3–90 kHz preferred by EPRI– 3–500 kHz single-band not regulated

A3–95 kHz

B C D

Energy suppliers Consumers Future

Standard/Proprietary protocol

CSMAStandardprotocol

95–1

25 k

Hz12

5–14

0 kH

z14

0–14

8.5

kHz

Standards Prime G3 IEC 61334

Regulations CENELEC FCC ARIB

PLC for Smart Grid AMI Worldwide

• Countries with PLC deployment for Smart Grid– Spain ( PRIME on CENELAC band)

– France (G3 on CENELAC band)

– Taiwan (G3 on FCC band)

– Korea (IEEE P1901.2 on broadband)

• Countries with PLC pilots deployment for Smart Grid– China ( SFSK on EPRI band)

– Mexico (PRIME on CENELAC band)

– Japan (ITU-T G.9955 on ARIB band)

– Turkey (G3 on CENELAC band)

– Polland ( PRIME on CENELAC band)

– USA (Propreitry for Home Plug)

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Power Line Communication Challenges

• Frequency dependent attenuation– Line Attenuation due to conductor material properties and branching

– Echos and interference due to Multipath propagation.

• Noise due to Loads– Colored background noise due to Computers, Dimmers, Hair Dryers

– Narrowband Interference

– Synchronous periodic impulsive noise from Thyristor based DC power supplies

– Asynchronous periodic impulsive noise due to switching transients

– Asynchronous impulsive noise in Industrial environments due to Arc welding etc.

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The latest PLC technology based on OFDM is looking to be well immune to all the above factors.

Hybrid Networks - PLC/RF Combo

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Benefits:

• Robust network

• Smaller network diameter

• Lower latency

1. Concrete wall: blocks radio, but penetrated by PLC

To backbone network

Sink

Hybrid

Wireless

2. PLC blocked by noise, use wireless to get around

Wired

A single noise source barely affect both networks

Simulation Platform for The Study of Large Hybrid Sensor Networks

Extended COOJA simulator for the study of large networks with hybrid nodes

An RF Link used by RPLAn RF Link used by RPL

A PLC Link used by RPLA PLC Link used by RPL

PLC NodePLC Node

RF NodeRF Node

Hybrid Nodes Increase Robustness and Shorten Network Diameter

Extended RPL and MAC protocols for networks with hybrid nodes

Two RF nodes replaced by hybrid nodesTwo RF nodes replaced by hybrid nodes

Open Challenges in AMR

• Sustained Connectivity – Guarenteed ??

• Isolation of PAN – Commissioning Challenge.

• AMR Standards and Technologies – Matured ?? Proven ??

• Field Software Upgradability – Should be mandatory.

• Security – Guarenteed ??

• Database management and maintenance – Expertise to be developed.

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Thank You

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