Low Frequency PLC Communication Technology For AMI and Smart Grid Applications

1. Low Frequency PLC Communication TechnologyFor AMI and Smart GridApplications Dr. Sioe T. Mak Ph. D. EE [ IEEE Life Fellow ]

2. 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.

3. 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 voltagesare used for long distance transmission to reduces losses in the lines.

4. 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.

5. 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.

6. 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. • Onlyvoltage phasorswhich correspond to themodulated bus voltagephasorwill 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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9. 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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11. 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: • The substation name, bus number, the voltage phase modulated for outbound to reach the transponder. • The current transformer number and phase connection from which the inbound response is extracted. • Hence each transponder can have the following network attributes : Q ( Substation name, Bus number, Phase, Feeder number )

12. 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 electricdistribution 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.

13. 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 : • The magnitude and type of data for the interval (KWH, average voltage, etc.) • The electric network location where the data is taken ( path parameters of the transponder ) • The time at which the interval data is taken.

14. ADVANCED APPLICATIONS Customer Services and Demand Response • 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.

15. ADVANCED APPLICATIONS Improvement of Service Reliability and Optimization of Energy Delivery • 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

16. 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.

17. 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.

18. 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.

19. ADVANCED TWACS APPLICATIONS Pre-pay Metering • 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

20. ADVANCED APPLICATIONS Remotely Operated Service Disconnect • 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

21. 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

22. 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

23. 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

24. 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

25. 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.

26. 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.

27. ADVANCED APPLICATIONS Alarm • 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

28. ADVANCED APPLICATIONS Improvement of Service Reliability And Optimization of Energy Delivery • Assets Management • Load Balancing • Improving Power Quality • Integrated VOLT-VAR control • Outage Management

29. 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

30. 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

31. ADVANCED APPLICATIONS IMPROVING LOAD FACTOR TO REDUCE LINE LOSSES

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33. 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.

34. ADVANCED APPLICATIONS REDUCE STRAY CURRENTS

35. ADVANCED APPLICATIONS DEFINITION OF VOLTAGE UNBALANCE

36. 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.

37. ADVANCED APPLICATIONS INTEGRATED VOLT-VAR CONTROL 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

38. 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.

39. ADVANCED APPLICATIONS A typical fault scenario

40. 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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44. 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

45. 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

46. 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.

47. 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