SMART GRIDS DEFINITIONS AND MEASUREMENT ISSUES

LORENZO PERETTO

UNIVERSITY OF BOLOGNA

T&M 2012 – DURBAN, SOUTH AFRICA

2-5 SEPTEMBER 2012

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• Changing Power & Energy World

• Challenges and Opportunities

• Smart Grid Technologies

• Standards

• Policies

• Smart Meters

• Measurement issues - challenges

TALK OUTLINE

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Today

Courtesy from Dr. Wanda Reder, S&C Electric, USA

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2030

Courtesy from Dr. Wanda Reder, S&C Electric, USA

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RECOGNIZING THE NEED FOR POWER

Consumer electronics

represent the largest single

use for domestic electricity

Computers and gadgets will

account for 45% of electricity

used in the home by 2020

Increases demand good

power quality and

uninterrupted power

availability

AND, THE RESPONSE

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Business as usual

– Losses are 7% to 15% in the

grid and much more with

generation

– Generation ~50-70% of capacity

Investments lag peak growth

–Makes peak difficult to manage

–Creates vulnerability

–Living with operational risk

• Grid grossly underutilized

• Peaks occur ≤ 1% of the time

United States

Annual Average Growth in

Transmission vs Summer

Peak Demand

Courtesy from Dr. Wanda Reder, S&C Electric, USA

THE RAMIFICATION

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Assets are aging

R&D spending is limited

US outages up over last 15

years

Grid modernization is

inevitable

Need to invest “intelligently”

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BUSINESS IS CHANGING

Then:

• Large generation stations

• Centralized dispatch

• Outages “tolerated“

• Grid “over designed”

• Radial distribution

• Uni-directional powerflow

Future:

• Emerging “customer choice”

• Distributed & green resources

• Less tolerance of outages

• Looped or meshed distribution

• Mixing old with new

• Multi-directional powerflow

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WHAT DOES SMART GRID MEAN???

Seven characteristics (as defined by US DOE)

1. Enable Active Participation by Consumers (Prosumers)

2. Accommodate all Generation and Storage Options

3. Enable New Products, Services and Markets (internet model)

4. Provide Power Quality for the Digital Economy

5. Optimize Asset Utilization and Operate Efficiently

6. Anticipate & Respond to System Disturbances (Self-Heal)

7. Operate Resiliently Against Attack and/or Natural Disaster

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Distributed Energy Resources (DER)

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Graphics adapted from an EPRI Presentation

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• United States

-Investing ~$7 Billion

-Standards framework

-200 PMUs installed

• China

- Investing $7.3 billion;

- 700 PMUs in operation.

Aiming to install on all 500

and 300 kV lines in 5 years

• South Korea

- Investing nearly $1 Billion

• Brazil

- Forecasting 60% growth in

electricity consumption

between 2007 and 2017

- 16-34% increase in

renewables

- PMU pilots recording widearea

disturbances

MAIN COUNTRIES AROUND THE GLOBE (PMU)

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PMU OPERATING PRINCIPLE

The method consists of measuring voltage and/or current

phasors with high accuracy in different nodes of the power

network (synchrophasors) by using proper measuring

systems (PMU) which are synchronized to a common time

reference, usually the GPS.

Im

Re

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…PMU OPERATING PRINCIPLE

Typical parameters of synchrophasors are frequency,

amplitude and phase.

Requirements for the sensors

o phase error less than 1 mrad

o ratio error on the order of 0.1%

WORLD-WIDE PMU DEPLOYMENT

15 Source: IEEE Power & Energy Magazine January 2009 “Measurements Get Together”

by Saikat Chakrabarti and more

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Advancements are needed

Design, monitoring, and control is increasingly complex

Technology development is needed:

– Visualization, warning systems, pre/post disturbance analysis

– Monitoring of power system oscillations

– Flexibility to accommodate changes, adaptive solutions

– Protocols for synchronized devices

– Interoperability: information from various sources

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Electric Vehicles

The electric vehicle will grow in the next years It requires new infrastructure.

Plug-in-Hybrid-Electric Vehicles (PHEVs)

Battery-Electric-Vehicles (BEVs)

small SUV segment at first (low weight, less expensive battery, good

3.2 Million Plug-in Electric Vehicles to be Sold Worldwide by 2015

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DoE Forecasts

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Renewable Energy

Renewable energy

– Environmental Benefits

– Indefinite Supply

– Jobs and Economic Growth

– Energy Security

European Renewable Energy Council studies show that

by 2090 the world can halt fossil fuel use, saving

$18 trillions

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Renewable Energy: Progress

o Renewable energy consumption in the US increased by

8% between 2008 and 2009; Renewable energy provides

18% of total net electricity generation worldwide

o China added 37 GW of renewable power capacity, more

than any other country in the world;

o Wind power reached a record high of 38 GW. China leads

with more than one-third of the world market

o Solar PV additions reached a record high of 7 GW.

Germany leads with more than half the global market

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Emerging Policy Implications

Policy and market development

– New technologies: storage, electric

vehicles

– New markets and incentives

Consumer engagement

– Awareness, acceptance, education

– Consumer choice and privacy

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European Smart Grid Policy

European Directive 2009/28/CE dated April 23rd 2009

which encourages and promotes the use of energy from

renewable sources.

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European Smart Grid Policy

20-20-20 objectives.

20 percent reduction in greenhouse gas emissions;

20 percent cut in energy consumption;

20 percent increase in the use of renewable energy;

by 2020

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Governments Invest Worldwide

China: $7,323

US: $7,092

Japan: $849

South Korea: $824

Spain: $807

Germany: $397

Australia: $360

UK: $290

France: $265

Brazil: $204

Zpryme Research & Consulting, Jan. 2010

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Smart Grids-related Standards IEEE

IEEE 2030

IEEE 2030 Guide for Smart Grid Interoperability of Energy Technology and Information Technology Operation with

the Electric Power System and End-Use Applications and Loads

IEEE 2030.2 Guide for Interoperability of Energy Storage Systems Integrated with

Electric Power Infrastructure

IEEE 2030.1 Guide for Electric-Sourced Transportation Infrastructure

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Work in progress……

IEEE C37.239 COMFEDE standard contributes to improving

Smart Grid reliability

IEEE C37.242 Guide for Synchronization, Calibration, Testing,

and Installation of (PMU) for power system protection and

control

Smart Grids-related Standards IEEE

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Core IEC Standards for Smart Grid

IEC/TR 62357: Service Oriented Architecture (SAO)

IEC 61970: Common Information Model (CIM) / Energy Management

IEC 61850: Substation Automation

IEC 61968: Common Information Model (CIM) / Distribution

Management

IEC 62351: Security

IEC 62056: Data exchange for meter reading, tariff and load control

IEC 61508: Functional safety of electrical/electronic/programmable

electronic safety-related systems

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SMART METERING, SMART GRIDS &

STANDARDIZATION

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SMART METER

A SMART METER IS A MEASUREMENT SYSTEM THAT

SHOWS TO BOTH USERS AND DISTRIBUTORS HOW MUCH

ELECTRICITY IS BEING USED AT EACH CONSUMPTION

POINT, IN REAL TIME.

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SMART METERS

Europe America

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SMART METERS

•The instant control of the power flowing into the network

branches requires sensors to provide the most accurate

power measurements possible.

•The uncertainty affecting the measurement results will

propagate through the control algorithms and significantly

influence the position of the working point

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With the event of Smart Grids, Measurements issues

are turning into Measurement Challenges

- Metrological issues in Smart Grids needs more and even

new answers

New measurement models (functions)

New measurement methods

New calibration procedures

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New measurement models

Distributed measurement systems - used for

- PMU – state estimation

- Renewable energy control (prosumers)

- Power Network Diagnostic

Target Uncertainty (Specific Limit) on values S

GUM - Supplement 2 will be used

Measurement

function

implemented

into a P

PMU1

PMU2

PMUn

S1

S2

Sn

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New measurement methods

Online measurement of the loss factor (tan) in Power

Transformers

Partial Discharges measurements in cables beyond 2 km from

the position of the sensor

State of knowledge of the operator can be poor: mistake or

uncertainty?

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New measurement methods

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New calibration procedures in HV and MV power systems

o Onsite - Online calibration of sensors and measurement

Instruments

o Nonlinear behavior of sensors (ratio and phase errors at

fundamental depend on the THD of input quantity)

o The advent of digital measurement devices makes the

access to large volumes of “measurement data” very easy.

Is it possible to operate a calibration of a given sensor?

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We have redundancy in the measurement system, and we should

be able to find out if a measurement associated to a specific

network node is correct (within the associated uncertainty interval)

or not

Challenge:

“playing” with the uncertainty evaluation, arriving to the concept of

“on-line uncertainty evaluation” and, hence, “on-line measurement

system calibration”

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Moreover it is time now that measurement-related tems,

definitions and procedures comply with reference

Standards

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According to IEC Smart Grid Standardization Roadmap

document

“Legal metrology: Among all the functions in the scope of smart

grids, smart metering is the only one under metrological control.

There are strict requirements set by legal metrology bodies

concerning allowable errors, repeatability, durability, reliability,

suitability and protection against corruption”

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Example: Type B evaluation of Standard uncertainty:

- IEC 61000-4-30, which refers to the power quality assessment,

defines the uncertainty in terms of a maximum deviation

- Guide of the Expression of the Uncertainty in Measurement

(GUM), although it is an ISO/IEC standard, defines uncertainty in

the form of standard deviation for an assumed probability

distribution

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Therefore, the values of uncertainty obtained from the accuracy

specifications of a measurement instrument are obtained in terms

of standard deviation (GUM), but are interpreted by the user as

maximum deviation (IEC 61000-4-30).

For a rectangular distribution, this turns into an erroneous

interpretation of the specification by a factor of 3

Maximum deviation

Standard uncertainty

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Smart Sensors (voltage and current) differ from “Non Smart

Sensors” for:

- Higher accuracy than in the past (r.e.< 1/1000, ph.e.<1mrad)

- Light (3-6 kg)

- Compact (typ. height 360mm – diameter 150mm)

- Bandwith (up to 4 Mhz or up to 80 Mhz for PD meas.)

- Reliability (250.000 – 300.000 h now)

- Communication interface (analog as well as digital)

Smart Sensors: what’s new?

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New Smart Sensors can be either passive or active

In both cases their output is “low voltage” (100mV to 2V) or

“low current” (80-200mA)

Typical instrumentation requires voltage and current inputs:

typ. 100V and 1-5A !!

How to make sensors and instrumentation compatible?

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- New IEC Standards are going to be issued: IEC 61869-x

“Instrument Transformers“

- Works are still active for the revision of the IEEE C57.13

“Instrument Transformers”

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In all documents there is not any theroretical as well as

technical information on how to Evaluate and Express

Uncertainty in measurements on power systems

This leads to use different methods for evaluating the

uncertainty and, hence, to manage different numbers about

the measurement errors and uncertainties.

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Recently an ad-hoc IEEE WG for a new Standard:

Measurements on Electric Power Systems: uncertainty

evaluation and expression

TC-39 of IEEE Instrumentation and Measurements Society

On August 29th 2012 it has been approved

It is expected to be completed by the end of 2014

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Scope

To provide guidance and procedures for assessing the

uncertainty affecting measurements on power systems.

The theory reported in the Standard ISO/IEC “Uncertainty of

measurement: Guide to the expression of uncertainty in

measurement” and supplements will be used for evaluating and

expressing uncertainty affecting the measurement results.

The guidelines included in the document could be used to

evaluate the uncertainty when performing the measurement of

a given quantity on electric power systems as well as to

correctly write their value in official documents (like

specifications) and test reports…..

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Thank you very much

Lorenzo Peretto

University of Bologna

Department of Electrical Engineering

IEEE Smart Grid Steering Committee member

lorenzo.peretto@unibo.it

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Content

Measurement theory

Measurement Uncertainty

Guide to the expression of Uncertainty in

Measurements (GUM)

Signal conditioning and analog processing

Digital signal processing

Measurement Instruments

Voltage and Current Sensors

Distributed Measurement Systems (DMS)

Measurement Management Systems (MMS)

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Content

How to evaluate uncertainty in measurements on Power

Systems

-Uncertainty sources in Power Systems

-Propagation of the effects of uncertainty sources in

the measurement algorithms

-How to express and interpret uncertainty affecting

the measurement result (instrument reading)

Many examples will be included