1. HARDWARE IMPLEMENTATION, REAL TIME TESTING AND DATA
TRACKING USING GSM TECHNOLOGY OF PMU
S. Suresh1, V. Gomathi2
Power Systems Engineering Division,
College Of Engineering, Anna University
1
ssallthebest@gmail.com
2
gomesvg@annauniv.edu
Abstract-Phasor Measurement Unit (PMU) plays a vital role for base and calculating the corresponding phasor [3], this
measuring the Synchronized voltage and current phasor for real time produces an image of the electric system behaviour at a
system. In this work, the hardware implementation of the Phasor particular point in time, delivers information in real time and
Measurement Unit is carried out and is tested in the LabVIEW provides data to be processed by analyzing the irregularities
environment. The main objective of this paper is to measure voltage of the power electric system [7].
(current) magnitude and angle in real time with time tag and to
investigate the performance of PMU with help of Total Vector Error
(TVE). To measure phasor information and track the phasor values of A phasor is a mathematical representation of a
voltage and current synchronously on a power system in real time sinusoidal waveform. The phase angle at a given frequency is
Phasor Measurement Unit (PMU) is used. Hardware for PMU using determined with respect to a time reference. Synchrophasors
DSP microcontroller, GPS receiver and associated supporting are phasor values that represent power system sinusoidal
components has been developed. Three phase voltage and current waveforms referenced to the nominal power system frequency
signals analog data are converted into digital word and transferred and coordinated universal (UTC) time. The phase angle of a
to the computer through RS232 communication link. The outputs synchrophasor is governed by the waveform, the system
signals obtained from the hardware is send via SMS through GSM
frequency, and the instant of measurement [4]. Thus, with a
modem.
universal precise time reference, power system phase angles
can be accurately measured throughout a power system.
Index Terms— Phasor Measurement Unit, DSP
Microcontroller, DFT Algorithm, LabVIEW, Total Vector
The global positioning system (GPS) technology
Error, GSM modem.
provides an economic option for the same. An important
advantage of the GPS technology is that its receiver can
I. INTRODUCTION
automatically detect accurate synchronization. The device
Power systems are large interconnected nonlinear which provides synchronized phasor measurements is called a
systems where system wide instabilities or collapses can Phasor Measurement Unit (PMU). A number of widely
occur when the system is subjected to unusually high stress. distributed PMUs in the power system may be utilized for the
Such system-wide blackouts lead to considerable economic following purpose [8]:
costs as well as adverse impacts on the society. Therefore, the
operational reliability of the electric power system is of • Real time monitoring and control
fundamental importance to power system operation and • State estimation
planning. Operator actions together with automatic control • Protection and control for distributed generation
actions are designed to prevent or minimize the damage • Network congestion management
caused by such outages.
• Angular and voltage stability monitoring
The recently developed WAMS (Wide-Area
Measurement System) technology offers a great potential to
implement dynamic supervision and control of wide-area
II. SYNCHRONIZED PHASOR MEASUREMENT
power system. It helps in monitoring and assessing the
stability, for various preventive and emergency controls and
to increase the transmission capability of the existing assets. Phasor Measurement Units (PMUs) are electronic
As a basic component of WAMS, PMU (Phasor devices that use state-of-the-art digital signal processors that
Measurement Unit) uses highly accurate PPS (one-pulse- can measure 50Hz AC waveforms typically at a rate of 30
per-second) signal of GPS to achieve precise and samples per cycle (1500 samples per second). The analog
synchronous measurement. It has the ability to measure signals are sampled and processed by a recursive phasor
voltage (current) magnitude and angle, frequency and other algorithm to generate voltage and current phasors [5].
parameters, which are transferred to the data control center. Different components of a PMU are shown by a block diagram
These synchronously measured data can then be used for in Figure 1. It measures standardized frequency and rate of
system stability assessment and control. change node voltage and current magnitudes, node voltage and
Synchrophasor technology is currently a widely current phase angles, branch flow magnitudes and angles
accepted technique of measurement in power electric (MW, MVAR, MVA and Current).
systems due to its unique ability to show data, from analog
voltage and current, that is synchronized using the same time

2. Figure 1: Block Diagram of PMU Figure 3: Estimation of phasors from sampled data using
The first commercial PMU was the Macrodyne 1690 Discrete Fourier Transform.
introduced in 1991 that performed only the data recording
function. By the year 1997 PMUs capable of real time The most commonly used method of calculating
measurement were developed. At present the PMUs provide phasors from sampled data is that of Discrete Fourier
data at the rate of about 6-60 samples per second. The lower Transform (DFT). The sampling clocks are usually kept at a
end of the range can represent the inter area power system constant frequency even though the input signal frequency
dynamics while the higher range can cover local oscillations, may vary by a small amount around its nominal value. Other
generator shafts, and controller actions in [2]. options and secondary corrections when the signal frequency
deviates from its nominal value are described in [3]. A more
Algorithms to compute phasors from measured signals computationally efficient method is to compute the estimated
use a recursive moving window of data samples to estimate the phasor recursively by adding the contribution made by the new
phasor parameters. Simple algorithms assume a fixed nominal sample, and subtracting the contribution made by the oldest
frequency value and compute only the magnitude and the sample.
angle of the phasor. Discrete Fourier Transform is one of the
most widely used phasor estimation technique. IV. PMU HARDWARE IMPLEMENTATION AND
TECHNICAL REQUIREMENTS
III. MEASUREMENT TECHNIQUES
The IEEE C37.118 standard has been utilized for
standardizing the Phasor Measurements and for defining the
The basic definition of the phasor representation of a
performance requirements [7]. The block diagram of PMU
sinusoid is illustrated in Figure 2. Assume a single frequency
with LabVIEW is shown in the Figure 4. Three phase voltage
constant sinusoid of frequency ω is observed starting at time
and currents signal from PTs and CTs are connected to the anti
t=0.The sinusoid can be represented by a complex number aliasing filter which is nothing but a low pass filter. Anti-
called ‘Phasor’ which has a magnitude equal to the root-mean- aliasing filter cutoff frequency is 2 KHz. This filter output is
square (rms) value of the sinusoid, and whose angle is equal to given to the DSP micro controller analog input channels which
the angle between the peak of the sinusoid and the t=0 axis. is converted into digital word using ADC converter. Phasor
Measurement Unit technical requirement as follow:
• Input signal range –5v to +5v
• Data resolution not less than 12 bit
• Reporting rate 10-25 reports per second
• Reporting time xx.000000 seconds with time reference
• It should estimate frequency as well as rate of change of
frequency
• Measurement accuracy
Figure 2: Definition of a Phasor, a complex number • Total Vector Error (TVE) should be less than 1%
representation of a constant pure sinusoid.
• Communication protocol
If the sinusoid is not a pure sine wave, the phasor is
assumed to represent its fundamental frequency component
calculated over the data window is illustrated in Figure 3.

3. Block diagram with LabVIEW Three major blocks in the LabVIEW
1. Data reading blocks
GPS 2. Calculating recursive Discrete Fourier Transform
3. Displaying the captured data
IPPS
 Data read block contain a VISA port configuration
PLL
and VISA read, here we can be set serial port
PT1 configurations, while loop configurations, bytes read
Antialiasing
PT2 and also error detection.
dsPIC30 PT3
filter
F4013 CT1
CT2
 Captured data is continues string, this format is
CT3
transferred to substring of single set of six channel
Serial to USB data. In this way all sampled channel information is
converter
connected to waveform chart after bundling.
LabVIEW  From the captured data magnitude and phasor values
Data read Channel
separation
Wave form chart are calculated for all the three phase voltage and
currents using recursive moving window DFT using
LabVIEW. This calculation is updated for every 5ms.
Figure 4: Block Diagram of the PMU VI. LABVIEW FRONT PANEL VIEW FOR ALL SIX
CHANNELS
Using GPS 1PPS signal is generated into 9600 PPS Three phase output was monitored with the help of 50
signal using phase locked loop. Using this 9600 PPS signal all KVA uninterrupted power supply (UPS).To see an input
six channels are samples sequentially. GPS generated time waveform of three phase voltage and current as shown in the
information with resolution of 1µs as well as sample data are Figure 6.
transmitted to LabVIEW through USB port. Magnitude and
phasor information are calculated using recursive DFT
algorithm in LabVIEW. This magnitude and phasor and UTC
information is transported into the central computer through
Ethernet.
V. TESTING THE PMU HARDWARE IN LABVIEW
ENVIRONMENT
LABVIEW DATA CAPTURING LOOP BLOCK DIAGRAM
The PMU hardware has been integrated with LabVIEW
using the port RS 232. The data is being read and processed in Figure 6: Input waveform of three phase Voltage and Current
LabVIEW. The data capturing loop of LabVIEW block
diagram is shown in Figure 5.
FRONT PANEL THREE PHASE WAVEFORM DISPLAY
IN LAB VIEW
Loads are almost balanced and THD was less than 5%.
PMU output waveform is illustrated in Figure 7.
Figure 5: LabVIEW block diagarm
This front panel block diagram shows the typical data
capturing using USB port and displaying the six channels in Figure 7: Output waveform of three phase Voltage and
waveform chart. Current

4. Using this sampled data window with DFT algorithm
the magnitude and phasor values are calculated along with
GPS data of 1µs (xx.000000s) accuracy also transmitted to
PDC (phasor data concentrator) typical one frame data values
are given here. The measurement shows that 49.999265Hz in
Table 1.
TABLE 1
THREE PHASE OUTPUT (VOLTAGE AND CURRENT)
Phases Voltage Current
U phase 441.464524V,10.23432° 68.962153A,26.56465°
V phase 439.178783V,130.47435° 64.176323A,142.17682°
W phase 438.786862V, 254.34252° 71.345982A,266.46534°
Figure 9: PMU setup with GSM Modem
From the Figure 9 it can be inferred that the output values
Phasor values of three phase Voltage and Current are obtained from the hardware can be sent via SMS using GSM
synchronously measured with help of the hardware of Phasor modem.
Measurement unit.
VII. DATA RECEIVING USING BHYPER IX. CONCLUSION
TERMINAL
PMU hardware is build with six analog channels. The
The data available in data read block of LabVIEW is six channels are scanned synchronously using PLL generated
read continuously and can be received using hyper terminal. 9600 Hz signal using one second pulse. The PMU hardware
The received output measurements are shown in the Figure 8. has been integrated and its voltage and current are captured
and it has been realized in Labview. The six channel data is
transferred to LabVIEW. In LabVIEW all six channel
waveforms is observed on waveform chart. The vector from of
voltage and current can be sent as a SMS through GSM
modem.
REFERENCES
[1] Baldwin, T.L., Mili, L., “Power system observability with
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Figure 8: Received voltage and current Outputs using Engineering 2009, 3, 13-17.
hyper terminal
[3] IEEE Standard 1344-1995: “IEEE Standard for
VIII. APPLYING GSM MODEM FOR OBTAINING Synchrophasors for Power Systems”, 2001.
OUTPUT VALUES VIA SMS
[4] IEEE Standard C37.118-2005: “IEEE Standard for
The synchronous measurement of PMU outputs are Synchrophasors for Power Systems”, 2006.
received with the help of hyper terminal and these values are
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BIOGRAPHIES
Suresh Sampath received his Bachelors degree from
Government College of Engineering, Salem in 2010. He is
pursuing his Masters in Power Systems Engineering, College
of Engineering Guindy, Anna University, Chennai. His fields
of interest includes Transmission and distribution, Power
System Analysis and Power System Protection.
Gomathi Venugopal received the Bachelors degree
from University of Madras, in 2002. Received the
Masters degree from College of Engineering, Anna
University Chennai in 2004. She received her Ph.D in the year
2012. She is presently working as an Assistant Professor in
College of Engineering, Anna University, Chennai. Her fields
of interest includes Power System Control and Operation,
Service Oriented Architecture and Web Services.