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Zigbee Based Wireless Sensing of Zonal Electrical Parameters Using State-of-theart Metering System towards Smart Grid Management Dr. J. N. Bera Department of Applied Physics University of Calcutta First International Conference on Intelligent Infrastructure December 1-2, 2012 Energy Measurement: Modern Perspectives Must perform all standard measurements accurately like Active and reactive Power and energy consumption, Power Factor, Direction of power flow etc. Must have communication modules for two way communication between customers and utilities for providing data on energy usage to customers to help control cost and consumption and to utilities for load factor control, peak-load requirements, determination of tariff strategies etc. Must help in faster outage detection and restoration by the utility Must include remote connect/disconnect of users, appliance control and monitoring, prepaid metering etc. Department of Applied Physics, University of Calcutta 01.12.2012 Energy Measurement: Modern Perspectives (2) Must be intelligent enough to manage the emergency situation Must have control over Smart Appliances like Air Conditioners, Space heaters, Water heaters, Refrigerators, Washers and Dryers (consume ~ 20% of load) It can cater the need for Advance Metering Infrastructure Hence, these meters must be designed using digital processors with embedded coding of intelligent program to make them smart enough Department of Applied Physics, University of Calcutta 01.12.2012 Advance Metering Infrastructure (AMI) It is basically the convergences of Modern energy meters, communication Infrastructure and the supporting information infrastructure Three major categories of AMI functions – like Market Applications: To reduce labour, transportation, infrastructure cost associated with meter reading and maintenance To increase accuracy of billing To allow for time based tariff Department of Applied Physics, University of Calcutta 01.12.2012 Advance Metering Infrastructure (2) Customer Applications: To increase customer awareness about load reduction, provides demand response and load management improve system reliability and performance and thus enhances customer convenience and satisfaction Distribution Operations: better customer load management identification of location of outage and quicker restoration, reduction in outage duration etc. management Department of Applied Physics, University of Calcutta 01.12.2012 Objective To describe a state-of-the-art development of electrical parameter monitoring system for modern power grid applications with the help of energy meters The networking and automatic meter reading (AMR) facility is incorporated using Zigbee and IEEE 802.11 based WLAN at 2.4 GHz and 5.8 GHz ISM bands respectively To describe the measurement features of a voltage, current, direction of power flow and supply frequency using the samples To measure the energy consumption for both active and reactive power using a unique sample shifting technique An energy management system (EMS) software at the central control room to collect the data from different meters for zonal management and efficient running of the grid Department of Applied Physics, University of Calcutta 01.12.2012 Sensing of Directions of power flow Principle Power Directio n Load Angle range Positive slope zero crossing angles Quadra nt Forward 0°<θ<-90° (lag) 0°<θ<90° First •The load angle θ is evaluated from their zero crossing instants Forward 0°<θ<90° (lead) 270°< θ <360° Fourth •The lagging or leading states will be computed from the slope of the Reverse 90°<θ<180° (lag) 180°<θ<270 ° Third waveforms. Reverse -180°< θ <-90° (lead) 90°< θ <180° Second •Sensing of direction of power flow is done from the sample values of the voltage and current signals • Forward direction of power flow is. from power grid to the load while from the load to power grid is reverse flow • For forward power θ belong to first (lag) or fourth (lead) quadrant while third (lag) or second (lead) I V V I(lag) I(lead) I(lead) V V I I(lag) I V Power flow positive negative quadrant for reverse power Department of Applied Physics, University of Calcutta phasors 01.12.2012 V Islanding Schemes for Reverse Power Flow The firmware of the microcontroller is intelligent enough to diagnose under voltage over voltage under frequency over frequency the rate of change in frequency with respect to a cycle (df/dt) If this df/dt exceeds a limiting value or set value, the huge disturbance in the grid will be indicated and a corresponding trip signal may trip the zone for its islanding purposes As the disturbance is dangerous for the inner grid while exporting the power, this df/dt will automatically be implemented while reverse power flow i.e. export of power will be in operation Department of Applied Physics, University of Calcutta 01.12.2012 Zigbee based LR-WPAN Features Structure Low Cost Low power wireless devices High data security Networks range single-hop star topologies to more complex multi-hop mesh networks ISM Band Department of Applied Physics, University of Calcutta 01.12.2012 ZigBee Components ZigBee devices are of two types Reduced Function Devices (RFD): These are reduced complexity nodes with relatively limited memory, processing, and power capabilities Full Function Devices (FFD): These devices have the resources to perform more complex task such as Coordinator or Router but can also be an End Device in a network The primary components of ZigBee LR-WPAN •ZigBee Coordinator, ZigBee Router, ZigBee Trust Center (ZTC) •ZigBee End Device (ZED): An End Device can be an RFD or an FFD •ZigBee Gateway: A gateway node serves as a bridge between a ZigBee network and another network (such as a wired Ethernet network) and performs protocol conversion as necessary Department of Applied Physics, University of Calcutta 01.12.2012 Typical Smart meter with Zigbee based Energy Measurement Unit (ZEU) Features •All standard measurement •Store consumed energy w.r.t. RTC •Intelligent enough to indicate a probable tapping using Statistical Analysis •Automatic Meter Reading facility Suppl y LCD Display RTC uC2 On/Of f contro l Load EMH uC1 Zigbee Module Memory •Keeps record of power interruption Department of Applied Physics, University of Calcutta 01.12.2012 Smart meters in Zigbee Basic Service Set for Networking ZEU 3 Zonal Networking Features ZEU 2 Zonal Meters’ Networked with Zigbee BSS Zigbee Coordination System (ZCS) keeps track of all the ZEUs within a range of ~ 1-2 KM ZEU 4 ZEU 1 ZEU 5 Pktconv ZC communicates with ZEUs in unicast mode by sending the MAC address of the intended ZEU in the request packet The intended ZEU, whose MAC matches, will respond only by sending the reuired data packet ZCS ZEU 7 WLAN+ ES Ethernet Switch (ES) RS232 to Ethernet Converter WLAN+ ES /PC ZEU 6 Zigbee Coordinator µC Department of Applied Physics, University of Calcutta Data packet Zigbee to WLAN or vice versa conversion 01.12.2012 WPAN using ZBSS with WLAN WPAN Features •Two layers of networking – IEEE 802.15.4 based ZBSS & IEEE 802.11b based WLAN WLAN + ES (LOS) (Zone) •WLAN is of LOS communication for better spectral efficiency •Emergency situations can well be managed with these metering WLAN + ES (LOS) Central •Customer care can be handled in a better way WPAN monitoring scheme •Zonal energy consumption can be known at any time Department of Applied Physics, University of Calcutta 01.12.2012 Wide Area Monitoring Scheme WAM Features •Wide area is divided into several zones •Each zone has dedicated WPAN with IEEE 802.15.4 based ZBSS & IEEE 802.11b based WLAN •Energy management software has the zone selection features to collect Zonal data in a predefined schedule •The overall energy consumption can be computed from different zonal consumptions WLAN + ES (LOS) Zone2 WLAN + ES (LOS) Zone1 WLAN + ES (LOS) Central WLAN + ES (LOS) Zone3 Wide area monitoring scheme •The server based storage facility is incorporated to store the data on RTC basis Department of Applied Physics, University of Calcutta 01.12.2012 Data Packet Format Since this WSN system is designed with two layer of communication, two basic kind of data packet format is essential Following are the data packet format which can be utilized at different levels of communication. Header Target MAC addr Sender MAC addr Requested Requested Type Byte 2 bytes 2 bytes 2 byte 1 byte 2 byte Data packets format from ZC to ZEU Department of Applied Physics, University of Calcutta 01.12.2012 Data Packet Format (2) Header Target MAC addr Sender MAC addr Sent data Type Sent Byte no. Data 2 byte 2 byte 2 byte 1 byte 2 byte 54 byte Data packets format from ZEU to ZC Header Zone TCP/IP addr EMS TCP/IP addr Target MAC addr Requested Type Requested Byte 2 bytes 6 byte 6 bytes 2 byte 1 byte 2 byte Data packets format from EMS to ZC Department of Applied Physics, University of Calcutta 01.12.2012 Data Packet Format (3) Header Zone TCP/IP addr EMS TCP/IP addr Sender MAC addr Sent data Type Sent Byte no. Data 2 bytes 6 byte 6 bytes 2 byte 1 byte 2 byte 54 byte Data packets format from ZC to EMS Department of Applied Physics, University of Calcutta 01.12.2012 EMS System EMS Features One Front End web application for the visual interaction with • Meter Setup Module • Zone Setup Module • Consumer Maintenance Module • Connection Maintenance Module • Data Acquisition Module • Audit & Reporting module • Assets Management system • Customer Care Module etc. WLAN + ES (LOS) Central Server GUI Ethernet Switch Client Terminal GUI Switch Ethernet Switch Data Base EMS system with necessary hardware as per the MIB information Department of Applied Physics, University of Calcutta 01.12.2012 EMS System (2) It is to be used by the admin and part of it will be used by any authorized client Another Back End server application for managing the MIB and communication schedule with energy meters The design of the EMS includes the formulation of data structure in order to cater all of the above features and the pages are designed with .net framework environment and the data structure is designed with SQL database environment Department of Applied Physics, University of Calcutta 01.12.2012 Energy Management Software GUI Database Application GUI Network or Web enabled PC at Central Location Conclusion A centralized monitoring of measured electrical parameters of different corners of the grid through wireless sensor network based on Zigbee and IEEE 802.11 based WLAN networking protocols are proposed It can be used for grid protection by islanding the zone with under voltage, over voltage, over load, different faults, short circuit and df/dt schemes, part of which can be implemented in the ZEU and in the PC EMS software as well From the EMS software an online load flow at different branches of the grid can be visualized at a glance and hence this can also be used for state estimation of the grid Power flow direction sensing helps in determining the import or export of power from or to the grid to be in commensurate with modern electricity act Department of Applied Physics, University of Calcutta 01.12.2012 Acknowledgement The author acknowledges the auspices of ongoing Research Scheme on Power (RSOP) project funded by Central Power Research Institute (CPRI), Bangalore, under Ministry of Power, Govt. of India and UGC SAP DRS-I project for providing the required infrastructural facilities The author also acknowledges Mr. Ranjit Pal and Mr. Tarun Sahoo for their technical support in implementing this proposal Department of Applied Physics, University of Calcutta 01.12.2012 THANK YOU Department of Applied Physics, University of Calcutta 01.12.2012