smart grid standards - fau · phasor measurement unit (pmu) “the phasor measurement unit (pmu) is...

Informatik 7

Rechnernetze und

Kommunikationssysteme

Smart Grid Standards

Dr.-Ing. Abdalkarim Awad

13.01.2016

Some Smart Grid Related Standards

IEC 61850 and DNP3: Substation

IEC 61698/61970: Transmission and distribution

IEC 61400: Wind Turbines

IEEE 37.118: PMU

OpenADR: Automated Demand Response

ZigBee: Home Automation

BACnet: Building Automation

Dr.-Ing. Abdalkarim Awad 2

Distributed Network Protocol DNP3

DNP3 becomes IEEE 1815

Set of communication protocols between data acquisition and control equipment

It plays a crucial role in SCADA systems

Used by control centers, RTU and IEDs

It has five layers

Master/slave

Originally the physical layer used serial communication, but now Ethernet can be

Application

Transport

Data Link

Physical

IEC 61850: Substation

IEC: International Electrotechnical Commission

Communication Networks and Systems in Substations

Was developed to provide inter-operability intelligent electronic devices (IEDs) for:

Protection, Monitoring , Control and automation in substations

Addresses Communications and Information modeling

IEC 61850 primary parts

Part 6-1: Substation Configuration Language (SCL)

Part 7-2: Abstract Communications Service Interface (ACSI) and base types

Part 7-3: Common Data Classes (CDC)

Part 7-4: Logical Nodes

Part 8-1: Specific Communications Service Mappings (SCSM) -MMS & Ethernet

Part 9-2: SCSM -Sampled Values over Ethernet

Part 10-1: Conformance Testing

Three IEC61850 Protocols

MMS (Manufacturing Message Specification)

GOOSE (Generic Object Oriented Substation Event)

SV (Sampled Values)

The Power Substation

Circuit Breaker (CB)

Intelligent Electronic Device (IED)

Microprocessor-based controllers of power system equipment

e.g. circuit breaker, protective relay...

Receive digitalized data from sensors and power equipment

Issue control commands in case of anomalies to maintain the desired status of power grid

e.g. tripping circuit breakers

Example

IEC 61850 Standard in Substation Autmation

Sampled Values

Example

Source:

https://www.pacw.org/issue/winter_2008_issue/protection_goose/high_performance_iec_61850_goose_and_protection_relay_t

esting.html

Industrial Ethernet Network

Prioritization

In IEC 61850 control applications, it is required that the control message transfers occur within 3 ms.

Faults can produce a data message storm.

Strict priority.

Generic Substation Events (GSE)

Generic Substation Events (GSE)Control model defined in IEC 61850

Provides a fast and reliable mechanism of transferring event data over the complete substation networks

Multicast

GSE subdivided intoGOOSE (Generic Object Oriented Substation Events)

GSSE (Generic Substation State Events).

SV (Sampled Values)

GOOSE: Generic Object Oriented Substation Event

GOOSE messages are sent when event occurs

Publisher/Subscriber model

Ethernet message (not TCP/IP)

Multicast and priority tagging

To guarantee delivery, GOOSE message is sent several times

No ACK

Examples of GOOSE messages :

- Autoreclosing (between relay and BCU/CB)

- Intertripping (between relay and relay)

- Blocking (between relay and relay/BCU)

- Interlocking (between BCU and BCU)Dr.-Ing. Abdalkarim Awad 16

Sampled Values

Similar to GOOSE

Transmits high speed streams of data set samples encoded in multicast or unicast Ethernet frames.

The protocol uses a publisher/subscriber model, in which a publisher transmits unacknowledged data to subscribers.

Periodic (4000 sample per second)

Communication Stack of IEC 61850

Ethernet Link Layer (with Priority, VLAN)

GOOSESV SNTP

TCP/IP

Time Critical

Ethernet 100 MB/s Fiber

GOOSE and SV messages

Application layer directly accesses link layer for speed – no TCP/IP

Uses Ethernet frame directly with Priority/VLAN 802.1Q tag

Use priority ≥4 due to criticality or messages.

VLAN use is optional.

Fields in payload - source ID, status bits, analog values, time stamp, sequence number, time to live, quality bits, test modes.

Typical packets 200 – 300 bytes long.

Preamble DA SA 1Q tag Type Payload FCS

TPID PCP DEI VID

12 bit 3 bits 1 bit 12 bit

TPID: Tag Protocol Identifier

PCP: Priority Code Point

DIE : Drop Eligible Indicator

VID: VLAN identifier

Drivers for Wide Area Monitoring

To avoid large area disturbances

To improve usage of existing power transfer capacity

To secure power system integrity

20Dr.-Ing. Abdalkarim Awad

Wide Area Monitoring

Structure

Data acquisition, carried by Phasor Measurement Units (PMU)

Data delivery through wide area communication system to PDC-Phasor Data Concentrator

Data Processing, through the system protection Center (SPC)

Command delivery

Command execution

Dr.- Ing. Abdalkarim Awad 23

IEEE C37.188

PDCPhasor

Concentrator

Historian

WANSubstation

Automation

System

Command Datae.g., DNP3

Modbus

IEC60870

e.g., DNP3

Modbus

IEC60870

PDC-Phasor Data Concentrator

HMI -Human Machine Interface

LAN -Local Area Network

PMU -Phasor Measurement Unit

Measures Voltage,

Current , phase

Architecture

PMU PMU PMUPMU

SuperPDC

PDCPDC

Phasor Measurement Unit (PMU)

“The phasor measurement unit (PMU) is a power system device capable of measuring the synchronized voltage and current phasor in a power system. Synchronicity among phasor measurement units (PMUs) is achieved by same-time sampling of voltage and current waveforms using a common synchronizing signal from the global positioning satellite (GPS). The ability to calculate synchronized phasors makes the PMU one of the most important measuring devices in the future of power system monitoring and control”

Synchronized Measurements

A PMU at a substation measures voltage and current phasors:

Very precise synchronization with μs accuracy.

Compute MW/MVAR and frequency.

Measurements are reported at a rate of 20‐60 times

a second.

Can track grid dynamics in real time

Traditional SCADA refresh rate is seconds to minutes

Phasor Data Concentrator (PDC)

Each utility has its own Phasor Data Concentrator (PDC) to:

Aggregate/align data from various PMUs based on time tag

Measurements from each utility’s PDC is sent to the Central Facility:

Where the measurements are synchronized across utilities

OpendPDC

Complete set of applications for processing streaming time-series data in “real-time”

Measured data is gathered with GPS-time from multiple input sources, time-sorted and provided to user defined actions, dispersed to custom output destinations for archival

The openPDC implements a number of standard phasor protocols which can be used to receive data from devices.

The supported protocols:IEEE C37.118,

IEEE 1344, BPA PDCstream, FNET, SEL Fast Message,

PMU for Wide Area Monitoring and Control

Potential PMU Applications

• Wide-Area Visualization and Monitoring;

• Angle and Frequency Monitoring;

• Inter-area Oscillation Detection & Analysis;

• Proximity to Voltage Collapse;

• State Estimation;

• Fast Frequency Regulation;

• Transmission Fault Location Estimation;

• Dynamic Model Validation.29Dr.-Ing. Abdalkarim Awad

PMU Block Diagram

Functional block diagram of the elements in a PMU.

Phasor: reminder

A pure sinusoidal waveform can be represented by a unique complex number known as a ‘phasor’.

A sinusoidal signal

The phasor representation of this sinusoid is given by

)cos()( tXmtx

))sin()(cos(22

Phasor: reminder

Classical Definition of a PhasorThe RMS cosine-reference voltage and current phasors are.

Convention for synchrophasorrepresentation

Phasor

If the sinusoid is not a pure sine wave, the phasoris assumed to represent its fundamental frequency component.

The most commonly used method of calculating phasors from sampled data is that of Discrete Fourier Transform (DFT).

Important of the Phasor Measurement

sin* 21

PMU2PMU1V2

Bus2Bus1XL

Compute MW & MVAR

jVeVV v

jIeII i ||||

)cos( ivVIP

)sin( ivVIQ

Synchronized Measurements

Location 1

Location 2

Phase angular difference between the two buses

can be determined if the two local clocks are

synchronized.

Synchronizing pulses obtained from GPS satellites.

Role of GPS

Constellation of 24 satellites orbiting at 20,200 km Developed by US dept of defenseAvailable for free for civilian useBeyond navigation use, it provides time reference:

Protection systems derive usage of GPS from the timing signal

4 satellites are needed for knowing timing and location position

Satellites have atomic clocksProvides coordinated universal time (UTC) which is international atomic time compensated for leap seconds for slowing of earths rotationscan obtain accurate timing pulse every second

with an accuracy of 1 microsecond

PMU Facts

PMU uses discrete Fourier transform (DFT) to obtain the fundamental frequency components of voltage / current(Half cycle or Full cycle)

Data samples are taken over one cycle / multiple cycles.

Resolution of the A / D converter is 16 bits.

Example

Power Flow= 5 pu

Frequency=50

The power is estimated using bus 1 and 2 (Φ1-Φ2)

Error of time stamp at 1 is 0.1 ms and at bus2 is 0

Find the error in estimated power

PMU2PMU1 V2=1.0V1=1.0

Bus2Bus1j0.1

Example

0.1 ms corresponds to:

∆θ=(0.1ms/20ms)*2π

=0.0314 rad

5)sin(10

5)sin(21

Feq=50 Hz

Example

)sin(21

Signals with 50 and 51 Hz

Blue: Cos(2*π*50*t)

Red: Cos(2*π*51*t)Dr.-Ing. Abdalkarim Awad

Table of synchrophasor values at a 10 fps reporting rate

Fps: Frame per second

Relevant PMU Standards

C37.111-1999

A general transient data recording file format standard

C37.118.1-2005

a complete revision and dealt with issues concerning use of PMUs in electric power systems

C37.118.1-2011

Covers synchrophasor measurements for power systems

Adds frequency & rate of change of frequency (ROCOF) and dynamic operation

C37.118.2-2011

Defines real-time synchronized phasor measurement data exchange method

C37.118.1-2005

Example of frame transmission order

The SYNC word is transmitted first and CHECK word last.

Two- and four-byte words including integer and floating-point numbers are transmitted most significant byte first (network or “big endian” order). All frame types use this same order and format.

Required PMU reporting rates

Word definitions common to all frame types

Sync (2 bytes)

Frame synchronization word.

Leading byte: AA hex

Second byte: Frame type and Version, divided as follows:

Bit 7: Reserved for future definition

Bits 6–4:

000: Data Frame

001: Header Frame

010: Configuration Frame 1

011: Configuration Frame 2

100: Command Frame (received message)

Bits 3–0: Version number, in binary (1–15), version 1 for this initial publication.

Example

A PMU sent a packet that starts with following four bytes (decimal)

170,49,1,198

What is the 170?

Determine the type of frame? Data

Configuration

Command

header

What is the size of the frame?

Example

170=0xAA (0x mean hexadecimal)

It is the SYNC byte

49=0x31=00110001b

0 (Bit 7: Reserved for future definition)

011: configuration frame 2

0001: version 1

It is a configuration frame (Config-2) and the version (1)

Then comes the two bytes size

Size=198+1*256= 454

Configuration frame

Word definitions unique to configuration frame

To send a value (e.g., voltage)

It is possible to send it as a float or integer

If Integer We need to scale it

Example: to send 18.45 as 16 bit integer

Scale it e.g 1000*18.45=18450

At the receiver side: we convert it back using the same scale

18450/1000=18.45

In C37.118, PhasorMag=value*PHUNIT/100000

FORMAT (2 Bytes)

Data format in data frames, 16-bit flag.

Bits 15–4: Unused

Bit 3: 0 = FREQ/DFREQ 16-bit integer, 1 = floating point

Bit 2: 0 = analogs 16-bit integer, 1= floating point

Bit 1: 0 = phasors 16-bit integer, 1 = floating point

Bit 0: 0 = phasor real and imaginary (rectangular), 1 = magnitude and angle (polar)

Example

Explain the following two bytes for FORMAT field

First byte (MSB)= 0

Second byte=8

So we have 0000 0000 0000 1000

Bits 15–4: Unused

Bits 3–0:

Bit 0=0 phasor real and imaginary (rectangular)

Bit1=0 phasors 16-bit integer

Bit2=0 analogs 16-bit integer

Bit3=1 FREQ/DFREQ 32 bit float

PHUNIT (4 bytes)

Conversion factor for phasor channels. Four bytes for each phasor.

Most significant byte: 0 = voltage; 1 = current.

Least significant bytes: An unsigned 24-bit word in 10–5 V or amperes per bit to

scale 16-bit integer data. (If transmitted data is in floating-point format, this 24-bit value should be ignored.)

Data frame organization

Data Frame

PHASORS(4/8)

16-bit integer values:

Rectangular format:Real and imaginary, real value first

16-bit signed integers, range –32 767 to +32 767

Polar format:Magnitude and angle, magnitude first

Magnitude 16-bit unsigned integer range 0 to 65 535

Angle 16-bit signed integer, in radians × 104, range –31 416 to +31 416

PHASORS(4/8)

32-bit values in IEEE floating-point format:

Rectangular format:

— Real and imaginary, in engineering units, real value first

Polar format:

— Magnitude and angle, magnitude first and in engineering units

— Angle in radians, range –π to +π

FREQ(2/4)

Frequency deviation from nominal, in millihertz(mHz)

Range—nominal (50 Hz or 60 Hz) –32.767 to +32.767 Hz

16-bit integer or 32-bit floating point.

16-bit integer:16-bit signed integers, range –32 767 to +32 767.

32-bit floating point: actual frequency value in IEEE floating-point format.

Example

If the voltage is Determine the content of the PHASORS bytes for the same FORMAT in the previous example and the PHUNIT has the following 4 bytes (0,0,47,175)

Based on the format field, we have to send the phasors as 16 bit

Byte0=00 (most significant Byte)

Byte1=00

Byte2=47

Byte3=175

PHUNIT=47*256+175=12207

0 2530.5

Example

Vr=2530.5

Before sending, we have to scale the value

ScaledVr=Vr*100000/12207=20729

This value is 16 bit

We have to send each byte

ScaledVr=20729=0x50F9

ScaledVi=0=0x0000

Example

We have to send the real part and then the imaginary part, therefore

Fist byte=0x50=80

Second byte=0xF9=249

Third byte=0x00

Forth byte=0x00

The PDC will do

80*256+249=20729

20729*12207/100000 =2530.4

Cyclic redundancy codes (CRC)

CRC-CCITT

g(x) = x16 + x12 + x5 +1

Communication options:

• Serial

• IP protocol

37.118.x message

TCP/UDP

header

TCP/UDP

header

TCP/UDP

header

Transp.

header

Transp.

trailer

OPTIONS: TCP only, UDP only, TCP/UDP

Bibliography

High Performance IEC 61850 GOOSE and Protection Relay Testing by Hachidai Ito andKenichiro Ohashi, Toshiba Corporation, Japan

IEEE C37.118 Standard

Smart Grid: Technology and Applications, 2012, ISBN 1119968682, Wiley, by Janaka Ekanayake, Kithsiri Liyanage, Jianzhong Wu, Akihiko Yokoyama, Nick Jenkins

Smart Grid : Applications, Communications, and Security by Lars T. Berger and Krzysztof Iniewski

Hamed Mohsenian-Rad, Communications & Control in Smart Grid (Slides)

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