Communication Technologies and Standards for Smart Grids EE 772 : - - PowerPoint PPT Presentation

Communication Technologies and Standards for Smart Grids

EE 772 : Smart Grids

• Prof. S. A. Khaparde

Indian Institute of Technology Bombay

Smart Grid Communications

• 1. Bi-directional flow of information (along with electricity) – for effective

control of generation and consumption

• 2. Real-time information: Paves way for active consumer participation
• 3. Technologies used at each level of operation to be in sync with data rate,

permissible latency, security and timing requirement of respective application

• 4. Communication protocols must account for specific needs of the power

system applications

Smart Grid Communication Requirements

• 1. Security - Ensure secure information storage, transportation, privacy,

avoid cyber attacks

• 2. Reliability, Robustness and Availability - Timely availability of time

critical information, robustness to distortions and channel noise

• 3. Scalability - It should be flexible enough to add on new web services and

protocols with increasing penetration of renewables and modernization

• 4. Quality of Service (QoS) - Reduce packet drops, minimize latency and

delays

Smart Grid Communications: Key Considerations

• 1. Availability during power outage – more so during natural calamities –

ensure observability of the network not on outage

• 2. The technology in use should in itself have low power requirement
• 3. Secured and resilient to attacks and intrusions
• 4. Scope for open standards and enable interoperability
• 5. Choice of technology based on density of nodes, last mile connectivity,

cost of deployment

• 6. Choice of technology: Licensed versus Unlicensed

Information flows in Smart Grid

Two way information flow between -

• 1. Sensors and electrical appliances to smart meters
• HAN
• Wireless : ZigBee, 6LowPAN, Z-Wave
• Wired: Powerline communication
• (Mostly) Unliscensed technologies
• 2. Smart meters to utility’s data center
• WAN, NAN
• Internet, Cellular Technologies (2G,3G, 4G)
• (Mostly) Liscensed technologies

Smart Grid Communication Infrastructure

• 1. Customer: Home Area Network (HAN)

Devices - Smart meters, thermostats, PCs, building automation, pumps Technology - ZigBee, WiFi, OpenHAN, HomePlug

• 2. Distribution: Neighborhood Area Network (NAN)

Devices - Smart meters, relays, distribution automation Technology - WiMAX, PLC, Cellular

• 3. Transmission and Operations: Wide Area Network (WAN)

Devices - EMS, WAMS, lines, towers, sensors and actuators Technology - IEC 61850, DNP3, SANET, Satellite

• 4. Markets - Enterprise and external

Participants - Retailers, Aggregators, Regulators, Customers Technology - Internet protocols

Dedicated and Shared Communication Channels

Dedicated - secured communication, exclusive link between source and destination, lesser latency, expensive Example: Differential protection of transmission lines - communication between differential relays (blocking signals) Shared - Message sent by the source is received by all devices connected to the shared channel. An address field in the message specifies for whom it is intended.

• higher latency but economic, higher utilization of available resource

Example: Communication network inside a substation, star or ring connection

• f bay controllers and monitoring equipments (CT, PT)

Dedicated and Shared Channels

• Dedicated link for differential

Relays

• Shared Medium - Nodes and routers

Wired Communication

Power Line Carrier Communication (PLCC) -

• Sending data simultaneously with electricity over same medium
• Minimal added installation
• Line matching unit injects signals

Into HV Transmission lines or LV and MV Distribution lines

• Message captured by line traps
• Originally used for low-rate SCADA,

now being used in Home Automation

Wired Communication

• Power Line Carrier Communication (PLCC)
• High data rate and capacity: 200 Mbps within homes, but low bandwidth

for NAN restricts usage

• Challenge from discontinuity- transformers, circuit breakers, faults
• Shared medium – data transmissions are broadcast in nature- security

and privacy issues

• Transmission medium is harsh and noisy – adds coloured noise, severe

signal distortions. Channel modelling is a challenge.

Wired Communication

• Power Line Carrier Communication (PLCC)
• Ultra Narrow band (UNB): below 3KHz, low data rate, high connectivity
• ver long distances
• Low Data Rate (LDR) Narrow Band (NB): Between 3-500KHz, single

carrier based, upto 10kbps

• High Data Rate (HDR) Narrow Band (NB): Upto 1 Mbps, for NAN

communication

• Broadband PLC: Above 1.8MHz, short range, used in HAN

Wired Communication

Twisted Pair - two twisted copper cables each with outer PVC or plastic insulator - upto 1.2 GBps - broadband services Coaxial Cables - Outer coaxial conductor provides effective shielding from external interference - reduced losses from skin effect - upto 10 MBps Optical Fibres - Core, cladding and buffer coating - internal reflection - less signal degradation than copper wires, no interference (EMI)

• lesser weight than copper but high cost of installation
• used for long distance transmission – no need for repeaters upto 100 Km
• high capacities upto 1 Tbps
• security high because of obscurity

Wired Solutions

DSL (Digital Subscriber Lines): High-speed digital data transmission technology that uses the wires of the voice telephone network, Frequency band 0 - 2.208 MHz, inexpensive, scalable, poor data security, high latency, same applications as PLC Ethernet: Frequencies - 16 MHz, 100 MHz, 250 MHz, 500 MHz, 600 MHz, 1 GHz, 1.6-2.0 GHz.

Wireless Communication

Radio Communication - Alternative to expensive fibre optic and copper wire for long range, limited bandwidth

• 1. Ultra High Frequency (300 MHz - 3 GHz)
• 2. Microwave (3 GHz - 30 GHz)

Cellular Technology - service area divided into cells, each cell has a transceiver to control and communicate with users within a cell, operates on CDMA, communication between mobile objects - even when the object moves across different cells. Technologies - 3G, GPRS, GSM.

• In India 900, 1800, 2100 and 2300 MHz, short technology life cycle

Satellite Communication - Widely adopted for SCADA, microwave network with satellites acting as repeater, key challenge is delay

Short Range Wireless Solutions - 6LoWPAN

• Low power RF in 800 MHz, 900 MHz and 2400 MHz bands
• Applications: AMI (NAN), SCADA/EMS (NAN), SCADA/DMS(NAN), Building

automation, Microgrids, Distributed generation, Electric Vehicles

• Lightweight, versatile - can be used with any physical and data link layer
• Scalable
• Low power RF unreliable due to uncertain radio connectivity, battery

drain, physical tampering

Short Range Wireless Solutions - ZigBee

• Short range solution (10-100m), same application areas as 6LoWPAN
• Low data rates: 20kbps, 250 kbps
• Frequency bands ~ 868 MHz (20 kbps) for EU, 915 MHz (40 kbps) for US

and AUS and 2.4 GHz (250 kbps) worldwide

• High market penetration in home automation ~ Low cost of modules
• Low reliability, poor interoperability with non-ZigBee devices
• Low power consumption compared to other sub GHz protocols

Short Range Wireless Solutions - ZigBee

• Ideal technology for smart lightning, energy monitoring, home

automation, and automatic meter reading

• Capable of being connected in a mesh of large number of devices ~ 1000

nodes and more

• low processing capabilities, small memory size
• Interference from other devices using the license free ISM frequency

band (2.4GHz) like WiFi, Bluetooth and Microwave

Short Range Wireless Solutions - WiFi

• Frequency 2.4 GHz, limited range, low power RF
• Applications: Automatic meter reading (AMR), AMI -NAN, home automation
• Higher power consumption than ZigBee (WiFi ~ 700 mW, ZigBee ~ 100 mW)
• Based on IEEE 802.11 standard for WLAN, optimized for fast data rates -

higher than other RF technologies

• Cost effective

Other Low Power Short Range Wireless Technologies

• 1. Bluetooth - 2.4 GHz, only connects two devices at any time, extremely

short range, applied mostly for reading meter data

• 2. Infrared - 2.4 GHz, extremely short range, line of sight communication,

inexpensive, low power consumption, application- meter reading

• 3. Z Wave - 865 MHz to 956 MHz, compared to ZigBee expensive and not

scalable, poor penetration in India Applications: SCADA/EMS, SCADA/DMS, microgrids, substation automation

Long Range Wireless Solutions

• 1. WiMAX: typically coverage of 20kms or more for 1.8 GHz link, based on

IEEE 802.16 standard, Data rates up to 140 Mbps, low latency (10-50 ms)

• 2. Low Power Wide Area (LPWA): Frequency -TV spectrum, 900 MHz, 2.4

GHz, 5 GHz, Applications: SCADA/EMS, SCADA/DMS, Substation automation

• 3. Satellite Communication: Frequency - 1 to 40 GHz, affected by weather,

WAMS application

• 4. Long Wave Radio: Typically 100 -200 kHz, extremely high range, reliable,

propagation affected by obstacles

Comparison of commonly used technologies

Priority of Data

• 1. Priority level 1:
• Critical for safe operation and control
• Eg : Inter-control center communication (IEC 60870), PMU communication

(C37.118), Substation automation (IEC 61850), Cyber security (NERC CIP 00X)

• Latency : very low (relaying), medium (distribution)
• Level of assurance (LOA): High
• 2. Priority level 2:
• Eg : Building automation (BACnet ANSI), Substation and feeder device

automation (DNP3), Revenue metering (ANSI C12.19)

• Latency : Medium, LOA :Medium

Selection of Communication Technology for an Application

• For mission critical applications (such as SCADA/DMS, Wide Area

Monitoring System, Distribution Automation etc), security, reliability and latency will be the key criteria for deciding a communication technology. Cost will be of lesser priority.

• For non-critical applications (such as AMI, connectivity for Distributed

Generation, etc) cost will be decisive.

Communication Standards and Protocols

• 1. A communications protocol is a standard rule for data representation and

data transfer over a communication channel.

• 2. If devices use different protocols they will not be able to share data with each
• ther.This was a problem in earlier versions of SCADA networks where

devices from different vendors used different manufacturer specific protocols (proprietary protocols).

• 3. Open standards for communications enables seamless interoperability

between devices, this brings many advantages. Vendors can supply off-the- shelf SCADA solutions that can be easily modified and used.

Open Standards for Smart Grid

• 1. Open System Interconnection (OSI) Model was introduced in 1984
• 2. The OSI model divides the data communications process into seven

independent layers and each of the layers describes how the data is handled in the different stages of transmission

• 3. Following protocols are commonly used for SCADA applications:

IEC-60870-104 IEC-61850-GOOSE DNP3

Standards for Information Exchange

DNP3:

• Distributed Networking Protocol
• Communication between substation data acquisition and control

equipments

• Used by control centers, RTUs, IEDs
• Reliable but not secure from attacks
• Master DNP3 station sends request and Slave DNP3 stations respond to

these request, slave can also transmit message without request

• Recently adopted as IEEE standard 1815-2010

Standards for Information Exchange

IEC 61850

• Framework for substation automation, addresses interoperability of IEDs
• Uses an object model to describe the information available from different

pieces of substation equipments

• In addition to defining a protocol, specifies a data structure
• For every physical device, logical devices within it are specified. Each

logical device is then mapped to 86 different classes of logical nodes as defined in IEC 61850. For a IED with protection logic, the logical nodes could be - distance, overcurrent, differential, etc.

Standards for Information Exchange

IEC 61850 Data Structure