Download TWACS Technology For AMI and Smart Grid Implementation

Low Frequency PLC
Communication
Technology
For AMI and Smart Grid
Applications
Dr. Sioe T. Mak Ph. D. EE
[ IEEE Life Fellow ]
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ADVANCED APPLICATIONS
Enabling Smart Grid Applications
• Smart Meters generate useful information for Smart Grid
applications. They have programmable storage capabilities and
communication interface. Real time can also be down-loaded into
the Smart Meter.
• Two-way communication technologies for utility application is
already available.
• Data bases with huge storage capability coupled with very
sophisticated data management systems are already available.
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ADVANCED APPLICATIONS
The Electric Energy Delivery Infrastructure
• Electric energy is a transitional form of energy which can be
transported in bulk over very large distances through narrow
corridors at the speed of light. The corridors are the transmission
lines, distribution lines, etc.
• It can be easily split into bulk or minute quantities.
• Conversion from electric energy into other forms of energy that can
be readily used is a well-known technology. ( electric motors,
heating elements, light bulbs, etc.)
• The use of alternating currents (50 Hz or 60 Hz) permit voltages to
be converted to high or low voltages using transformers.
• High voltages are used for long distance transmission to reduces
losses in the lines.
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ADVANCED APPLICATIONS
• For added reliability and flexibility, the infrastructure is divided
into regions and segments, such as bulk transmission and
distribution networks.
• The distribution network medium voltages in use in the USA
ranges between 4.0 KV to 34.5 KV and at the service voltage the
range is between 120 V to 488 V.
• MVA ratings are typically between 5.0 MVA to 45 MVA serving 4 to
6 three phase feeders serving 500 to 10,000 customers.
• Between substation bus and customer end there can be multiple
step-down transformers with different types of winding
configurations, overhead and underground cables, capacitor banks
for power factor correction, etc.
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ADVANCED APPLICATIONS
UNIQUE CHARACTERISTICS OF THE NETWORK
• There is phasor correspondence between distribution substation
bus and remote sites. A load drawn at the service voltage has the
same phasor as the load generated at the generator. This unique
phasor correspondence rule is important for designing Smart Grid
control functions.
• The implication is that for comprehensive Smart Grid control
algorithm design, the remotely collected data requires the phasor
for identification of its location in the network.
• Transient oscillatory phenomenon due to a perturbation has a
frequency between 200 Hz to 600 Hz and decays within a half cycle
of the power frequency.
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ADVANCED APPLICATIONS
THE PHYSICAL CHARACTERISTICS OF THE TWACS
COMMUNICATION TECHNOLOGY
• The Low Frequency PLC (TWACS) communication technology uses
the same electric power delivery infrastructure.
• The Outbound signal is generated at the distribution substation bus
by modulating a bus phase voltage.
• The outbound signal propagates into all parts of the distribution
network including the service voltage network served by the
distribution substation.
• Only voltage phasors which correspond to the modulated bus
voltage phasor will see the outbound signal.
• The outbound signal is a distribution network transient oscillatory
response to a perturbation generated by the outbound transmitter.
The transient oscillatory frequency is between 200 Hz to 650 Hz and
does not suffer any attenuation due to line impedances or capacitor
banks. No need for repeaters or line conditioning devices.
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ADVANCED APPLICATIONS
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ADVANCED APPLICATIONS
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ADVANCED APPLICATIONS
• The inbound is a controlled pulse load current generated at a
certain phase angle before the zero-crossing of the phase
voltage which carries the outbound signal.
• For binary encoding, 2 pulses of one polarity and 2 pulses of
the opposite polarity are arranged in certain configurations
allowing the design of multiple simultaneous non-interfering
inbound channels.
• Six simultaneous channels are available. This allows 6 different
transponders to respond simultaneously on the same phase as a
response to a group command.
• To increase data throughput, concurrent phase and
simultaneous feeders are being tested for operational reliability.
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ADVANCED APPLICATIONS
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ADVANCED APPLICATIONS
OPERATIONAL DESIGN
• After a transponder is installed, a search function is used to locate
the transponder.
• If the response from the transponder is captured at the substation,
the path parameters for the transponder is saved for future
communications and transactions.
• The path parameters contain the following information:
1. The substation name, bus number, the voltage phase modulated
for outbound to reach the transponder.
2. The current transformer number and phase connection from
which the inbound response is extracted.
3. Hence each transponder can have the following network
attributes :
Q ( Substation name, Bus number, Phase, Feeder number )
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ADVANCED APPLICATIONS
• Real time for synchronization is broadcasted to all transponders.
The real time can be used to reset registers for starting interval
data collection.
• Each data point collected from the transponder is time stamped
and the interval of data collection is remotely programmable.
• Hence the collected data can be related to location in the electric
distribution network and related to time at which the data is
taken with all other transponders at the distribution network.
• These attributes will prove to be very useful for optimizing
network operation, demand response, load balancing, customer
energy usage profiles and other Smart Grid applications.
• Utilities that have AM-FM systems can also correlate
transponder and monitored data information to geographical
locations.
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ADVANCED APPLICATIONS
Collected Data from Smart Meters and Their Use
Interval Data
• Hourly, half-hourly or 15 minutes, as needed for a specific
application from each customer on each phase and feeder/bus
• Start of data collection is synchronized, hence each interval data
can be correlated by time for all the sites within the service territory
of the distribution substations.
• Hence, for each interval data point the following information will
be available :
1.The magnitude and type of data for the interval (KWH,
average voltage, etc.)
2.The electric network location where the data is taken ( path
parameters of the transponder )
3.The time at which the interval data is taken.
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ADVANCED APPLICATIONS
Customer Services and Demand Response
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Electric energy consumption metering
Gas and water consumption metering
Remote service connect and disconnect
Pre-pay metering
Load management / Demand response
Time of use rates
Etc.
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ADVANCED APPLICATIONS
Improvement of Service Reliability and
Optimization of Energy Delivery
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Outage Management and System Restoration
Integrated VOLT-VAR control
Remote Breaker or Switch control
Feeder Load balancing and Loss Management
Power Quality Monitoring
High Impedance faults detection
Distributed Generation
Hybrid Electric vehicles
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ADVANCED APPLICATIONS
SUPPORTING FUNCTIONS
• Communication Network Monitoring
• Extension of SCADA capability into the Distribution
Network
• AM / FM Systems
• Data Management
• Multi-party Users
• Alarm functions
• Etc.
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ADVANCED APPLICATIONS
DIFFERENT PARTIES REQUIREMENTS
• Customer Service wants timely retrieval of
metering data, handling of customer complaints,
service connect and disconnect, pre-pay
metering, etc.
• Energy management needs load survey data and
perform demand response type functions.
• Maintenance and repair group requires outage
management and distribution control
applications.
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ADVANCED APPLICATIONS
Customer Services and Demand Side Management
Advanced Metering :
1. Electric Energy Metering @ retail wheeling
- Prepay metering
- Service Disconnect
- Gas and Water Metering
2. Load Management
- Time of Use and Load Control
- Averting Rolling Blackouts and Reducing Impact of Cold
Load Pickup
3. Detection of Theft
4. Alarm
5. Etc.
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ADVANCED TWACS APPLICATIONS
Pre-pay Metering
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Customer energy use profile and customer
education
Rate, Start and Duration of Contract
Payment deposit, where and how
Activation
Customer alert to deposit more money
What happens if it is on a holiday
Grace period
Total disconnect
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ADVANCED APPLICATIONS
Remotely Operated Service Disconnect
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Thermal and contact ratings of switch
Short circuit handling capability
Remote checking of switch status
Manual operation
Device address linked to metering transponder
addres
• On site operational testing and switch activation
• Customer alert before opening switch
• Arm the switch and customer activates the switch
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ADVANCED APPLICATIONS
Gas and Water Metering
• Coupled to the electric metering transponders through
short hop RF link or hard wired link
• RF transmitters at the gas and water meters need
batteries
• For hard wired gas meters, safety barriers are required
• Water meters inside metallic manholes can pose problems
for RF
• Gas and water meters can be coupled to one data
concentrator at the electric metering transponder
• Interval gas and water consumption metering has not
taken off yet
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ADVANCED APPLICATIONS
Time-of-Use
• Different rate structure during system peak demand is applied to
qualified customers.
• Small customers with near constant load are excluded.
• Expectation of customers to curtail load
• Charging higher energy prices during peak periods
• Definition of shoulder, peak and valley
• Interval time synchronized meter reading can be used to verify
the effectiveness of the Time-of-Use strategy
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ADVANCED APPLICATIONS
Load Management and Demand Response
To defer or avoid the need to build a peaking unit
Can be considered as dispatching negative generation
Load Control :
• Load survey data are needed
• Load cycling switching schedule for specific appliances have to
be designed to shift system peak demand
• The scram function can be used to drop load in emergency
• Two-way communication system for load control reduces the
cost of reliability
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ADVANCED APPLICATIONS
Time of Use Strategy
• Load survey to determine candidates for Time-of-Use
• Design billing strategy
• Alarm to customers when Time-of –Use rates apply
Prevention of Cold Load Pick-up Problems
• Determine where the cyclic loads are and their load
characteristics
• Determine the effects of outage duration on the inrush
currents due to cold load pickup
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ADVANCED APPLICATIONS
Averting Rolling Blackouts and Reducing
the Impact of Cold Load Pickup
• Brown outs are rolling blackouts to reduce system
demand when the spinning reserve is very low.
• Prolonged disconnect of power to part of a network can
cause cold load pickup problems.
• Load control (some form of scram function) can be
used to reduce the need of applying rolling blackouts.
• Loads can be restored in a staggered fashion to reduce
the effects of cold load pickup.
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ADVANCED APPLICATIONS
DETECTION OF ENERGY THEFT
• Reconciling total coincident demand with coincident
demand of all customers served by the same
distribution transformer in real time [Requires special
box]
• Compare outage counter with adjacent transponders’
outage counter.
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ADVANCED APPLICATIONS
Alarm
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Civil Defense
Traffic routing
Peak load alert to customers to curtail load
Alert to pre-paying customers to deposit
more money
• Alert customers that the service disconnect
is going to be activated
• Peak load alert to smart homes
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ADVANCED APPLICATIONS
Improvement of Service Reliability
And
Optimization of Energy Delivery
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Assets Management
Load Balancing
Improving Power Quality
Integrated VOLT-VAR control
Outage Management
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ADVANCED APPLICATIONS
Distribution Transformer Overload Detection
• Determine coincident peak demand due to all
loads served by a distribution transformer for
regular working days, week-ends and holidays
and monitor seasonal variations.
• Determine magnitude and duration of
transformer overloading
• Decide to replace or not to replace transformer
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ADVANCED APPLICATIONS
FEEDER LOAD BALANCING
• Load imbalance causes unbalanced 3-phase voltages.
• Increase in circuit losses, 3-phase motors overheating,
stray currents, etc.
• Time synchronized hourly meter reading can be used to
determine coincident demand on each phase of a feeder
• Comparing the coincident demand of each phase on the
same feeder can be used to determine which loads can be
shifted to a different phase
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ADVANCED APPLICATIONS
IMPROVING LOAD FACTOR TO REDUCE LINE
LOSSES
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ADVANCED APPLICATIONS
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ADVANCED APPLICATIONS
MONITOR LOAD DISTRIBUTION AND COINCIDENT LOAD
ON EACH PHASE OF A FEEDER.
• Obtain time synchronized interval load and voltage data
from each load on each phase of a feeder.
• Determine coincident peak for each phase
• Determine whether load and voltage imbalance occur
on a feeder, the time and its duration.
• Determine which loads cause the unbalance and can
these loads be redistributed over different phases to
maintain a degree of balance.
• Can load control be used to improve the feeder’s load
factor.
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ADVANCED APPLICATIONS
REDUCE STRAY CURRENTS
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ADVANCED APPLICATIONS
DEFINITION OF VOLTAGE UNBALANCE
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ADVANCED APPLICATIONS
EFFECTS OF VOLTAGE IMBALANCE
• Negative sequence voltages create negative sequence
currents and cause retardation torques. It will cause
an increase in core losses in the motor or generator
resulting additional heating of the motor
• Starting torque is also lower and it takes longer to
bring a motor up to speed.
• Zero sequence currents also cause increase heating
(eddy current losses).
• Motor life is reduced due to aging of insulation.
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ADVANCED APPLICATIONS
INTEGRATED VOLT-VAR CONTROL
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Practical problems :
Voltage level profile along the feeder difficult to determine as
function of time and load
Switching of capacitor banks based on calculated models and
simplified assumptions
New possibilities :
Hourly synchronized meter reading and voltage monitoring
Helps to design more accurate switching algorithm for capacitor
banks
Check effectiveness of the switching algorithm
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ADVANCED APPLICATIONS
Electric Utility Network Outage Management
• Electric utilities already implement selective
coordination of protective devices to isolate faults
• A fault detector at the substation provides the necessary
alarm to trigger polling
• Polling of transponders can be used to determine which
protective device has operated.
• Units that are de-energized will not respond to a polling
command.
• Non-responding transponders have to be related to
physical locations at the network.
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ADVANCED APPLICATIONS
A typical fault scenario
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ADVANCED APPLICATIONS
Power Quality Monitoring
• Distorted voltages and currents affect meter reading accuracy (
DC component in the load current )
• Standard distorted wave-shapes for meter calibration should be
developed by the industry
• They increase system losses and can be damaging to digital
electronic devices
• Polling bell-weather power quality monitoring devices scattered
throughout the network
• Real time patrol to spot harmonic polluters
• Effects of distributed generation on the distribution network
operational reliability
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ADVANCED APPLICATIONS
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ADVANCED APPLICATIONS
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ADVANCED APPLICATIONS
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ADVANCED APPLICATIONS
Communication Network Monitoring and Control
• Determination of de-energized transponders
• Eliminate communications to de-energized
transponders
• Rerouting algorithms to reach transponders that are
alive
• Reestablish normal operating conditions when
everything goes back to normal
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ADVANCED APPLICATIONS
Area Map and Facilities Management systems
• Electric network is very dynamic
• Man made switching due to faults or for
maintenance
• Use AMR capability to update circuit to
the latest conditions using the Outage
Mapping function
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ADVANCED APPLICATIONS
DATA WAREHOUSING
For data to be useful :
• Synchronized interval meter readings, voltage
data, etc. have to be time stamped and can be
related to substation bus, feeder, phase, etc.
• Sufficient historical data have to be kept for
reference and for application and control
strategy algorithm development.
• Data mining should be fast, easy and yet
secured.
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ADVANCED APPLICATIONS
CONCLUSIONS
• System architecture and infrastructure design
determine adaptability to various advanced
Smart Grid applications
• Control and monitoring of infrastructure
prevents system slowdown and loss of data
• Recovery algorithms are an essential part of the
system design
• Added value functions provide synergistic role to
the success of system operation
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