6 Networking Power Protocols

Intro to Data Communication for the Emerging Smart Grid

Lecture 6

Carl Hauser

Washington State University

February 2014

Power Grid Applications and Protocols Goal: understand the

uses and implementations of data communications in the Grid

Wide variety of requirements and approaches to meeting them

Outline SCADA and DNP3

Communication between control centers: ICCP

PMU communications: C37.118

Substation communications: IEC 61850

Smart metering

Time synchronization

Power Grid Communications 2

SCADA





Smart metering


SCADA is Supervisory Control and Data Acquisition Control:

• control center establishes set points in field devices

• Often manually done by grid operators

• Open-loop

Data acquisition • Usually: slow polling cycle: 2 to 4

seconds

• Sometimes: report by exception

• Data are recorded in Historian Database at control center

• Extracted for use by Energy Management System and display to operators on Human Machine Interface


DNP3: Distributed Network Protocol (www.dnp.org) www.trianglemicroworks.com/documents/DNP3_Overview.pdf

IEEE 1815 Standard

Originated in 1990

Layered Architecture

Physical/low level link: serial over copper, radio, etc.; ethernet; TCP or UDP

Data Link: 256 byte (max) frames; checksums; addressing; acknowledgements

Pseudo-transport: segmentation

Application

• Master-slave

• App level acknowledgements

User code


DNP3 Networking

Operate over variety of link types Speeds of 2400-

9600 bits/sec were fast

slow serial links

multi-drop links

Concentrated links

Not routable!


DNP3 App Layer

“Database” design Numbered data

object groups

Numbered positions in groups

Poll request: send me the value in group NN at position MM


DNP3 and SCADA Deficiencies for Smart Grid No security (but Secure

DNP3 has been developed)

Bump-in-the-wire security device “patch”

Designed for slow links, polling

Awkward data naming and addressing

“Only the control center cares about data” viewpoint

Measurements timestamped when received, not when made


ICCP





Smart metering


Need: > 3000 business entities

run parts of power grid

• Generators, transmission operators, distribution operators

Grid must operate in synchrony—requires coordinated decisions

How do control centers share information?


ICCP/TASE.2: an Internet Application Protocol

Uses TCP for transport

Challenge: achieve high availability communication

Poll-response architecture (several second cycle time)


“Database” Problem

Bilateral agreements between businesses

what do you call the voltage measurement at a particular bus in a particular substation in your database and what do I call it in mine?

Mapping tables and ICCP Associations


ICCP Limitations in Smart Grid

Latency Primary use case is

polling data from correspondent database (Historian) which itself was polled at multi-second intervals

TCP

Security Largely

implemented by the mapping tables

Use secure transport layer (SSL/TLS)

Key management


PMU Communications





Smart metering


PMU: Phasor Measurement Unit Measure voltage and

current 30-240 times per second

Synchrophasor: take each measurement at a precise time (microsecond accuracy)

This is way more and way better data than SCADA devices provide


PMU Protocol: C37.118

IEEE Standard

Application protocol over UDP or TCP transport

Intended use: convey synchrophasor data from PMU to Phasor Data Concentrator and between PDCs


Whither PMU Communications?

Share PMU data among utilities – Naming issue once again!

Send applications only what they need (only some require even 30 measurements /sec)

NASPInet

Improve latency to applications

PMU -> PDC -> application path imposes latency

GridStat


Beyond PMUs

PMUs exemplify modern sensing High rate

Accurately timestamped

With adequate communication these can support the vision of…

Much more automatic, real-time control of the grid for Better reliability

Greater efficiency

Enable integration of highly-variable generation: solar and wind


Substation Communications: IEC 61850 www.ieee.org/portal/cms_docs_pes/pes/.../T.../05TD0235.pdf





Smart metering


Suite of protocols for substation automation More popular in Europe

and Asia than North America

Tries to cover all the needs for substation automation

Also tackles the database and naming problem


Many use cases in substations

Performance needed varies widely Protective relaying: low data

rate and very low latency (<4ms)

SCADA reporting: low data rate and high latency

PMU reporting: high data rate and moderate latency

Use high-performance networking technology: 100 Mbit/s ethernet and better


A new approach to naming

Isolate the “power” services and object models from the communication protocols

2: Application Layer 18

Real-time Communication


Smart Metering - AMS





Smart metering


Main goals

Automated meter reading

Demand response

Remote turn-on/off

More-aware consumers

Technical challenges

Hostile environment

Scale

Privacy (from consumer perspective)

Security of data (from utility perspective)


AMS Architecture


HAN – the home area network

Zigbee – 2.4GHz wireless band (like 802.11b/g/n wireless networking, many wireless phones, …)

“Internet of things” (but not IP!)

“Smart Energy Profile” – customization for metering

Cost matters!

Open vs. proprietary?

Energy monitor display

Smart appliances

http://www.engineeringtv.com/video/Texas-Instruments-ZigBee-Smart









NAN – the Neighborhood Network

Proprietary – no need for open?

Proprietary – don’t think that that means secure!

Mesh routing – radio-based pole-top stations (not much use of the power lines themselves to carry data though it has been done)


Time Synchronization

GPS devices are pretty cheap but installation and interfacing isn’t

Idea: use ubiquitous Ethernet to distribute time

Wide-area time synch Network Time Protocol: RFC 5905

25 years experience

10s of milliseconds accuracy

Local-area time sync Precision Time Protocol: IEEE 1588 2002

Microsecond agreement on LANs


Basic idea

Send a message and get a reply from another host – gives round-trip time

Send a message giving your current time and the round trip time

Other host can estimate the offset between clocks

Problems:

Variability in communication and asymmetric communication times (smaller problem in LANs)

Getting to microsecond level requires timestamping and time capture at a low level in the communication stack (close to the link layer) Power Grid Communications 25

Conclusion

A whirlwind tour: Networking models

IP details at all layers

Power grid communications

Security: Concerns more than solutions

Up next: Computational aspects and distributed systems

(Prof. Bakken)

Security solutions (Prof. Hauser)


Documents

6 Networking Power Protocols