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GSM Based Remote Bushings Health Monitoring System International Journal of
Wireless Communications and Networking
Article · June 2010
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GSM Based Remote Bushings Health Monitoring System
GSM Based Remote Bushings Health Monitoring System
D. Gopi Krishna1 and K. Mourougayane1
1
SAMEER–Centre for Electromagentics, 2nd Cross Road, CIT Campus, Taramani, Chennai, India
Abstract: An appropriate remote communication connectivity
to monitor and analyze the health condition of the transformer
bushings is suggested. This approach would help to plan
bushing replacement strategies and to provide subsequent
alerts to the respective engineers both at local substation and
at TNEB – HQ during thermal runaway conditions. A
combination of GSM link and RF link were employed to carry
out the experiments for remote data collection.
Keywords: GSM, RF, SMS, BUSHING, TAN DELTA
remote site. Control Terminal (CT) module is used
for monitoring the data periodically or by polling
the RT. The Short Message Service (SMS) based text
message in Protocol Data Unit (PDU) mode is used
for transferring the data from Remote Terminal to
Control Terminal.
I. INTRODUCTION
II. PROPOSED DESIGN AND
ARCHITECTURE
Wireless communication systems are being
employed in many telemetry applications for
remote data collection. GSM based wireless
connectivity becomes low cost solution for SCADA
based applications. One such application is
monitoring the health conditions of transformer
bushings system at the substations of Electricity
Board (EB) through tan delta measurements.
Tamil Nadu Electricity Board (TNEB) has
positioned Intelligent Diagnostic Devices (IDD) at
the sub stations through which the tan delta
measurements have been studied online (i.e. in
energized mode) on hourly basis. These reports
have been collected from the IDD at the field and
the process of analysis and diagnostic steps with
the experts have been carried out off-line.
The present practice of off-line maintenance is
tedious where, the bushings of the transformer need
to be taken out of service to diagnose and to replace
if found to be necessary. This will lead to
interruptions in power supply to the locality and
also time and cost consuming process. In addition
to the above, this may put on to indirect expenses
to the consumers of both domestic and industrial
consumers in terms of alternate usage of power
resources such as generators etc.
To monitor the bushings from the TNEB we
have proposed to establish a GSM link from the EBHQ to the device to be monitored and generate
alerts in the form of SMS to the engineers during
abnormal conditions.
In this project, we have used the GSM based
low cost wireless module developed by SAMEER,
targeted for general SCADA applications.
Necessary hardware and software to support data
acquisition, data transmission and control have
been developed. The Remote Terminal (RT) module
is used for acquiring the data from the devices from
The data transmission medium used here in the
form of SMS is maintained secure by using the PDU
(Protocol Data Unit) format where the data is
analysed in 7-bit hexadecimal octet format during
transmission.
GSM, as an established, reliable cellular radio
network is picked up here since it possesses the
minimum required Bandwidth, offers image service
application and wide coverage.
In order to monitor the bushings from the
control room we have additionally proposed to
International Journal of Wireless Communications and Networking, 2(1) June 2010
57
D. Gopi Krishna & K. Mourougayane
establish an RF link using another low cost 2.4 GHz
RF modems for short distance communication to
the local EB monitoring station.
III. ROLE OF BUSHINGS IN A
TRANSFORMER
Bushing is a device that encloses a conductor and
facilitates connection of the conductor to internal
parts of equipments like Transformers and to
external equipments. The conductor is to be
insulated from the mounting flange which is
normally grounded. The conductor may be an
integral part of the bushing or be drawn into the
central tube of the bushing. In the case of a
Transformer, the Bushing insulates the conductor
from the Transformer tank.
Bushing is the most stressed of all components
in a Power Transformer. It is subjected to normal
working voltage and also abnormal conditions such
as system surges and lightning surges. Also, the
Bushings are subjected to internal apparatus stresses.
Bushing being an Extra High Voltage (EHV)
device, its most vulnerable part is the insulation.
Insulation is constantly stressed over its life period
causing deterioration. Dirt, moisture, oil
contamination, electrical surges and other factors
add up to deteriorate the insulation.
Moisture will cause an increase in the dielectric
losses consequently an increase in Power factor (Tan
delta). As the deterioration in the Bushing
insulation continues there could be a breakdown
in the capacitive layers. Tracking also would take
place producing Partial Discharges.
As sudden Bushing failures cause catastrophic
effect on the Transformer and the connected
network, it is imperative that Bushings need to be
maintained in good condition. Any initial-level
defect should be identified by effective condition
monitoring techniques.
Bushing failures are often violent and lead not
only to Transformer failure but also to Transformer
fires. The transformer being very costly and vital
in a network, the failure of Bushing would prove
costly and damaging. The bushings and its internal
parts are shown in Figure.1
58
Figure 1: Bushing and Parts
IV. DESCRIPTION OF ARCHITECTURE
The proposed system architecture shown in the
Figure 2 comprises of 3 units.
(a) Remote Terminal (RT)
The RT comprises of a GSM chipset along with an
8-bit microcontroller DS89C430 (based on CISC
architecture which is a family of 8051). This
microcontroller constitutes of two independent
UARTS internally.
A customised firmware has been developed to
incorporate the functionality of acquiring the data
from the IDD unit using the proprietary ASCII
protocol from its remote RS232 port and AT
commands to operate the GSM chipset for data
transmission and reception of commands.
The GSM section in the PCB has been
customised and restricted to the SMS alone for this
application by adding the respective electronic
peripherals. It can be further enhanced to allow
GPRS if necessary.
Additionally, this unit comprises of a
rechargeable battery operating at 3.7V /800mAh as
a Standby function. As an alternate power supply,
International Journal of Wireless Communications and Networking, 2(1) June 2010
GSM Based Remote Bushings Health Monitoring System
the data flow can continue uninterrupted for more
than 3 hours during power disruptions at the
remote locations. As an add-on, this can alert the
supervisors of the power disruptions to enable them
to attend to the same early.
To attain the functionality of data acquisition
from the IDD device and data transmission to the
Supervisory Terminal (ST) within the Substation i.e.
between the transformer and the control room, an
RF chipset (operating at frequency range of 2.4GHz)
with low power consumption is used.
(b) Supervisory Terminal (ST)
This unit comprises of a similar RF chipset
(operating at frequency range of 2.4GHz used in
the RT) for data transmission and reception. This
terminal can be directly connected to a system at
the control room to receive the data from the RT.
The average distance that this unit could cover is
approximately 100 meters.
(c) Control Terminal (CT)
This unit comprises of a SIM based unit (i.e. GSM)
and is used to monitor the RT placed at the
substations from long distances i.e. from the TNEB–
HQ.
This has been achieved by operating with the
dedicated application developed, comprising of
Visual Basic 6 in the front end and MS-Access for
database at the backend (Shown in Figure 3). This
has been ported over a PC to communicate with
the Control Terminal (CT). The RT placed near the
transformer is polled continuously from the CT
through SMS with a dedicated identity (ID) to the
substation.
The parameters required for remote monitoring
were evaluated with the engineers of the Electricity
Board and then implemented.
The specifications of the Remote Terminal and
the Supervisory Terminal are provided in the table
below.
Table 1
Specification of RF Modules
Specifications
Remote Terminal
Frequency Range 900 / 1200 / 1800
MHz
RF Power
1W / 30dBm
Technology
GSM
Sensor Interface RS232
Antenna Interface SMA
Power Supply
5V DC / 800mA
Battery
3.7V / 800mAh
Operating
0 to 55 deg C
temperature
Mechanical
3 (W) x 3 (D) x
Dimensions
1.5(H) inches
Supervisory Terminal
2.4 GHz
16dBm / 64mW
RF
RS232
SMA
5V DC / 500mA
3 Volts
0 to 55 deg C
2 (W) x 2 (D) x 1(H)
inches
Figure 2: Architectural Layout of GSM based Remote Bushings Health Monitoring System
International Journal of Wireless Communications and Networking, 2(1) June 2010
59
D. Gopi Krishna & K. Mourougayane
Figure 3: Photo Graph of Remote and Control Terminals
The photographs of the Remote and Control
Terminal are provided in the Figure 3.
V. EVALUATION OF REAL TIME DATA
The parameters at present acquired & remotely
monitored (i.e. using the GSM communication link)
are Leakage Current and Phase angle of all the three
phases, Capacitance (Daily, Weekly & Monthly),
Tan Delta (Daily, Weekly & Monthly), Sum Current
and State code (error codes during any abnormal
conditions) and of the bushings.
3219E839A6836430580E14 9BE96 0301DCCC682
B964391C0BE6CAE57 22C984B4683B160AED
C0DC692D56C2E1B8EC692D9642E18CEC
692D56CAE9B0DC692D9622E5C0DC69A
C140C4707ECE82B964351C8BE 6A2C96E2C9
ACB3693B1602E180CC682B96237180BE6B
2E16C2C19 6DE6CAC958311CCC0583B164339
C0B4763 D160B05808
The actual message when decoded i.e.
converted from Octet to Septet format it would be
in the form of 22 Oct 2009 13:00: 06,0.298,
0.999,0.240,0.970,256.684, 262.086,256.760, 261.850,30
Days,0.258,4.427,4.632, 0.000,0.170,0.686,243.92,
180.00,238.84,4001!
A reusable code with few library functions has
been developed for operating the GSM unit to use
the same for various applications. This has also been
made generic so as to facilitate easy conversion of
data from the PDU string such as 7-bit Septet format
it to the 8-bit Octet format and vice versa etc.
A sample of the data in along with the PDU
string in the form of 7-bit Septet format is shown
below:
The data listed above is then logged into a
database using the above application shown in
figure 4 and displayed respectively segregating into
their respective fields.
07 – Length of the SMSC
91 – Type of address
198948004544 – SMSC No
24 – First Octet of this SMS-DELIVER message
0C – Length (12)
91 – Type of address
198948864508 – Destiny No. (Length-12)
00 – TP-PID
00 – TP-DCS
70800251341122 – Time Stamp
05 – Length
Message in 7-bit Septet format
60
Figure 4: Screen Shot of Remote Online Bushing Monitoring
System
FUTURE ENHANCEMENTS
This system is being enhanced to health monitoring
of 4 transformers (each transformer comprises of 3
bushings). The scope of this system can be further
enlarged in future, so as to cover additional features
such as remote monitoring of DGA (Dissolved Gas
Analysis) and transformer temperature for analysis
and to evaluate the performance of the entire
transformer. Following Wireless Sensor Network
(WSN) based Architecture would further make this
task simple at a later stage when required wireless
International Journal of Wireless Communications and Networking, 2(1) June 2010
GSM Based Remote Bushings Health Monitoring System
nodes are added. It is only matter of time that one
can visualise the entire substation being monitored
for safety and security.
Executive Engineer for their support and coordination to
implement this project. We also acknowledge our thanks to
Mr. S. Karunakaran, Director, SAMEER for the support to
expedite the activity in record time.
CONCLUSION
This project aims at remote online monitoring of
the performance, early detection of abnormalities
and sending alerts to the concerned designated
officials for the required quick action, can bring
down the operational, break down costs, break
down time and enhances the performance and life
of the transformer.
REFERENCES
[1] SMS and PDU information www.dreamfabric.com
[2] http://www.activexperts.com/xmstoolkit/sms
[3] E. P. Dick and C. C. Erven, “Transformer Diagnostic
Testing by Frequency Response Analysis”, IEEE
Transactions on Power Apparatus and Systems, PAS-97(6),
1978.
ACKNOWLEDGMENT
[4] Setayeshmehr, A.; Akbari, A.; Borsi, H.; Gockenbach, E.;
“A Novel Method to On-line Measuring of Power Factor
(tan δ) and Capacitance of Transformers’ Bushings“.
The authors wish to thank TNEB’s R&D team headed by
Mr.K.Gopinath, Executive Engineer and Mr. Prince Xavier,
[5] The Design and Realization of Embedded Wireless Data
Collection System, Springer Boston.
International Journal of Wireless Communications and Networking, 2(1) June 2010
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