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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