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TRANSCRIPT
SMART GRID MEASUREMENTS
Saikat ChakrabartiProfessor
Department of Electrical Engineering
Indian Institute of Technology Kanpur
UP 208016
Email: [email protected]
1
Characteristics of modern power systems
Wide geographical spread
Large number of interconnections
Rapid growth in the demand of electricity
Power system components operated closer to their
designed limits
High penetration of renewable energy sources
Competitive electricity market
2
Need for monitoring the system3
To take preventive and corrective control actions to
avoid any potentially dangerous operating condition
To analyse the vulnerability of the system against credible
contingencies
To facilitate economic operation of the system by
controlling the generator outputs and line flows based on
the information obtained from the monitoring system
To ensure acceptable quality of the power supplied to
the consumers
Need for real-time monitoring4
Power system is dynamic, and the operating conditions
are changing continuously
System topology (network interconnections) also may
change
Uncertainties in the demand for electricity
Power system components are being operated closer to
their designed limits
High penetration of renewable energy sources adds to
power quality and control problems.
How do we monitor?5
Remote terminal units (RTUs) and intelligent electronic devices (IEDs) placed at substations
Measurements from these RTUs and IEDs are telemetered to the control centre
Dedicated communication channels, such as optical fibre network are typically used for transmitting the measurements
Above monitoring mechanism is a part of the so-called
supervisory control and data acquisition (SCADA) system
Source: A. Abur and A. Exposito,
“Power System State Estimation: Theory
and Implementation"
What do we measure?6
In SCADA, two types of measurements are collected by
the RTUs and the IEDs, and telemetered to the control
centre:
Analog measurements (power flow, power
measurement, voltage magnitude, and current
magnitude)
Logic measurements (status of circuit breakers,
switches etc.)
What is done with the measurements?7
Measurements are telemetered to
the control centre
A state estimator constructs the
single line diagram of the system,
and estimates the states, after
detecting, identifying, and
processing bad data, if any, in the
measurements
By states, we usually mean the magnitude and phase angle
of the bus voltages
Control centre: source: internet
Measurement systems8
Two measurement technologies are revolutionizing the way
we monitor and control the power system
At the distribution level:
Advanced metering infrastructure (AMI), including smart meters and
the associated ICT infrastructure
At the transmission level:
Wide area measurement system (WAMS), including phasor
measurement units (PMUs) and the associated ICT infrastructure
Wide area measurement system (WAMS)
Measurements
from widely
dispersed
locations are
synchronized
with respect to a
common clock
9
Source: Internet
Synchrophasor measurements 10
1 pps time signals are obtained from GPS
Phase angle of a sinusoidal signal 𝑥(𝑡) will be taken as 0°, if the
peak of the signal coincides with the UTC seconds rollover
The phase angle is taken as 90° if the positive zero-crossing of the
signal coincides with the UTC seconds rollover.
Convention for
synchrophasor
representation
Phasor measurement units (PMUs) 11
Phasor represents a sinusoidal signal with a magnitude and a phase
angle (with respect to a reference)
Phasor measurement technology enables measurement of voltage
and current phasors with respect to a reference signal from a
satellite clock.
Source: http://www.phasor-rtdms.com/
Potential applications of WAMS12
Real-time visualization of power systems
Improved state estimation
Online estimation of load models
Online monitoring of power system stability
Analysis of the causes of a total or partial blackout
Real-time congestion management
Design of an adaptive protection system
Detection of faults on transmission lines
Advanced metering infrastructure (AMI) 13
AMI is comprised of the state-of-the-art electronic/digital hardware and software, which combine interval data measurement with continuously available remote communications
AMI typically refers to the full measurement and collection system that includes:
meters at the customer site
communication networks between the customer and a service provider, such as an electric, gas, or water utility
data reception and management systems that make the information available to the service provider
AMI components…contd. 15
Meters: electricity/gas/water meters
Fixed network: commonly available networks are Broadband over Power Line (BPL), Power Line Communications (PLC), Fixed Radio Frequency (RF) networks, and public networks (e.g., landline, cellular, paging)
The AMI host system (servers) that receives the meter data and sends to the Meter Data Management System (MDMS)
MDMS manages data storage and analyses to provide useful information to the utility
Functional requirements of AMI 16
The main objectives of AMI are:
to enable two way communication between smart
energy meter and Head End System (HES)
to enable remote reading, monitoring & control of
electrical energy meters (consumer, feeder, DT meters
etc.)
to serve as repository of record for all raw, validated and
edited data.
The sanitized data may be subscribed by other utility
function for higher order analysis, billing, and collection.
AMI system requirement 17
Smart Meter at consumer end: Single phase whole current, Three phase whole current, CT & PT operated three phase meters and CT operated three phase meters
Smart meter network: usually Radio Frequency (RF) mesh in license free frequency band/ Power Line Carrier Communication (PLCC) or GPRS/3G/4G communication technology or combination of these technologies as per the site requirement
Data Concentrator Units (DCUs): The smart meter data using RF mesh/PLCC is collected by DCUs or Access points
Head End System (HES): data collected by the DCUs transported to HES through Wide Area Network (WAN); data from smart meters using GPRS/3G/4G technology may be transported directly to HES through WAN
AMI system requirement…contd. 18
Meter Data Management System (MDM): required for managing, analyzing, reporting, and securing the meter data
Web application: updated on-line data of consumers, consumer portal etc.
Mobile app: to enable consumer to log in through android/iOS/Window based mobile app to see information related to his/her energy consumption. App should also provide platform for implementation of peak load management functionality by providing existing tariff & incentives rates, participation options etc.
The AMI Implementing Agency (AIA): responsible for proper data exchange among Smart meter, DCU, MDM, HES and other operational/requisite software as part of fully functional AMI system.
Distribution system state estimator (DSSE) 19
Deployment of SE at the distribution level needed for:
handling massive penetration DGs
managing demand response
manage EVs and storage
Challenges in DSSE:
Unbalanced system – requiring 3-phase formulation
High R/X ratio
Large number of nodes
Incomplete observability – possibility of utilizing smart meter
data along with SCADA measurements
Conclusion 20
Measurement and sensing technologies are going to play
a major role in smart grids.
In the distribution systems, AMI including smart meters will
be a key enabler for efficient operation.
In generation and transmission segment, WAMS is going
to play a major role.
Managing the large amount of information and ensuring
its security will be a big challenge. Cyber-security and
cloud computing applications are bound to get
increased importance.