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SMART GRIDS DEFINITIONS AND MEASUREMENT ISSUES
LORENZO PERETTO
UNIVERSITY OF BOLOGNA
T&M 2012 – DURBAN, SOUTH AFRICA
2-5 SEPTEMBER 2012
2
• Changing Power & Energy World
• Challenges and Opportunities
• Smart Grid Technologies
• Standards
• Policies
• Smart Meters
• Measurement issues - challenges
TALK OUTLINE
3
Today
Courtesy from Dr. Wanda Reder, S&C Electric, USA
4
2030
Courtesy from Dr. Wanda Reder, S&C Electric, USA
5
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
6
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
7
Assets are aging
R&D spending is limited
US outages up over last 15
years
Grid modernization is
inevitable
Need to invest “intelligently”
8
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
9
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
10
Distributed Energy Resources (DER)
11
Graphics adapted from an EPRI Presentation
12
• 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)
13
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
14
…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
16
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
17
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
18
DoE Forecasts
19
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
20
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
21
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
22
European Smart Grid Policy
European Directive 2009/28/CE dated April 23rd 2009
which encourages and promotes the use of energy from
renewable sources.
23
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
24
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
25
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
26
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
27
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
28
SMART METERING, SMART GRIDS &
STANDARDIZATION
29
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.
30
SMART METERS
Europe America
31
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
32
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
33
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
34
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?
35
New measurement methods
36
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?
37
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”
38
Moreover it is time now that measurement-related tems,
definitions and procedures comply with reference
Standards
39
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”
40
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
41
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
42
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?
43
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?
44
- 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”
45
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.
46
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
47
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…..
48
Thank you very much
Lorenzo Peretto
University of Bologna
Department of Electrical Engineering
IEEE Smart Grid Steering Committee member
49
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)
50
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