Design and implementation of the monitoring and control systems for ...

Electrical Power and Energy Systems 74 (2016) 36–41

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Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes

Design and implementation of the monitoring and control systems for distribution transformer by using GSM network Maisam Jalilian a, Hossein Sariri b, Fariborz Parandin b, Mohammad Mehdi Karkhanehchi c, Mohsen Hookari a, Mehdi Ahmadi Jirdehi d, Reza Hemmati d,⇑ a

Young Researchers and Elite Club, Eslam Abade-E-Gharb Branch, Isalmic Azad University, Eslam Abade-E-Gharb, Kermanshah, Iran Department of Electrical and Electronics Engineering, Eslam Abade-E-Gharb Branch, Isalmic Azad University, Eslam Abade-E-Gharb, Kermanshah, Iran Department of Electronic Engineering, Faculty of Engineering, Razi University, Kermanshah, Iran d Department of Electrical Engineering, Kermanshah University of Technology, Kermanshah, Iran b c

a r t i c l e

i n f o

Article history: Received 25 October 2014 Received in revised form 10 July 2015 Accepted 13 July 2015

Keywords: Electrical distribution transformer GSM network Monitoring system Practical design and implementation Transformer tap changer

a b s t r a c t This paper designs and implements the monitoring and control systems for tap changer of the distribution transformers by using GSM (global system for mobile) network. The proposed method comprises an embedded system which collects and processes the transformer parameters such as temperature, humidity, silicone gel color, Buchholz relay status, the status of input and output phases, the current flow in each phase and power of each phase. If the parameters exceed the permitted level, the system sends all parameters using the GSM modem through GSM network to the control center, and the center receives and processes them by the GSM modem, and then they are displayed on computer. Furthermore, some commands are sent from the center to change the tap changer position, denoting the transformer position and making report on the transformer parameters. Some advantages of this system can be denoted as extending the lifetime of the transformer, consumers, wires and facilities, no need to the operator, simplifying the troubleshooting in distribution network, balancing the loads and providing customers with proper service. Ó 2015 Elsevier Ltd. All rights reserved.

Introduction One of the most important equipment in electrical distribution networks is electrical distribution transformer which is installed in various powers and voltage rates in different points of the network. Monitoring and protecting the distribution transformers is very important. The transformer parameters are regularly monitored by technicians, and the detected problems are accurately resolved [1]. Distribution transformers are monitored in a continuous and appropriate way, they could be utilized for a very long time. Economic issues are very important in electrical power systems and cost reduction is mainly defined for high quality and reliable power generation. In the recent years, some studies have been carried out to preserve and prolong the utility life of high reliability of the monitoring [2]. Tap changer is one of the main components of ⇑ Corresponding author at: Kermanshah University of Technology, P.O. Box: 63766-67178, Kermanshah, Iran. Tel.: +98 831 7259980x2; fax: +98 831 7244201. E-mail addresses: [email protected] (M. Jalilian), [email protected] (H. Sariri), [email protected] (F. Parandin), [email protected] (M.M. Karkhanehchi), [email protected] (M. Hookari), m.ahmadi@ kut.ac.ir (M.A. Jirdehi), [email protected] (R. Hemmati). http://dx.doi.org/10.1016/j.ijepes.2015.07.022 0142-0615/Ó 2015 Elsevier Ltd. All rights reserved.

transformer which is highly beneficial to stabilize output voltage [3,4]. Along with dielectric and electric states, a defective tab changer can damage transformer [5,6]. The life of a transformer depends on its internal states and it can lead to considerable damages and losses [7]; supervising the transformers condition and electrical machines from a remote distance in order to prolong their utility life is today recognized and done by different practices [4,8,9]. The monitoring performs on the main parameters of a transformer such as temperature, voltage and current and monitoring parameters are further explained in [10,11]. The power transformer is one of the greatest and most important facilities in power systems. The humidity in the oil of transformers is a very important parameter because it can increase dielectric losses. The previous papers have proposed some systems for monitoring the transformer parameters such as temperature and voltage for change of tap changer [12]. The typical examples includes power transformer sampling and monitoring system for the change of tap changer using optical fiber [13] and the system designed to monitor load current temperature and transformer oil and transformer oils in power plants and also sending parameters to operator [14].

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M. Jalilian et al. / Electrical Power and Energy Systems 74 (2016) 36–41

Sensors group

Embedded system

GSM modem1

GSM modem2

Fig. 1. The monitoring system of Tap changers including sensors, embedded system and GSM modems.

Magnetic sensors

Mechanical system

IR sensors

Temperature sensor

Wet sensor

Current sensors

The embedded system (Atmega 128 microcontroller)

Voltage sensors

The level of oil sensor

Source of system

GSM modeme

Fig. 2. Connection of the embedded system to the transformer sensors and equipment in order to making the monitoring and control systems.

Fig. 4. Printed circuit board of the embedded system which has been shown in Fig. 3.

GSM modem2

RS232

FTD232

Computer

Fig. 5. Block diagram of the control center system which denotes the procedure of connection between GSM modem and computer.

Fig. 3. Practical circuit of monitoring and control systems for transformer tap changer including embedded system, supplementary elements and monitoring system.

This paper addresses the monitoring and controlling systems for distribution transformers by using GSM network. This system records key operation parameters of a distribution transformer

such as temperature, humidity, silicone gel color, Buchholz relay status, the status of input and output phases, the current flow in each phase and power of each phase. The paper is organized as follow; Section ‘‘Hardware of the proposed method’’ briefly describes the hardware of the proposed method. Section ‘‘Transformer system software design’’ describes the transformer system software design. Section ‘‘Results’’ presents the result of the system output, followed by conclusion in Section ‘‘Conclusions’’.

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START

START

Receive data related to sensorsand GSM modem

Receiving data from GSM modeme1 and GSM modeme 2

Data processing and decision making

Receiving message

Display of parameters on a graphical LCD

No Yes Encoding of the receive data

Yes Exceed the allowed amounts No Sending data through GSM modem

Transformers data coding

Fig. 6. Flowchart of the proposed methodology in order to monitoring and control for transformer tap changer.

Hardware of the proposed method The hardware of the system is composed of two parts; the first part is a group of sensors attached to the transformer. The second part which is located at the center of the control is composed of a GSM module for connecting Max 232 chip. This chip is applied to transfer the data between 232 Max standard (computer) and TTL standard, and the chip FTD 232 as a USB-to-serial converter is applied to establish a link between non-synchronic serial, computer and external facilities through a USB. The sensors send the transformer data to the embedded system and the embedded system processes such data and displays them on a graphical display screen. Then, using GSM modem, the transformer’s GSM

The display of transformer parameters Fig. 8. Flowchart of the monitoring system for transformer tap changer.

parameters are sent for GSM network system. In the control center system, these data are received and processed by GSM modem and displayed on a computer screen. The structure of the hardware is displayed in Fig. 1. The hardware attached to the transformer This system attached to the transformer is composed of a group of sensors, embedded system (designing and building a microprocessor as an integral part of system or device), GSM modem, mechanical system, graphical LCD (Liquid Crystal Display) and feeders which are situated near the transformers and oversee its performance. The transformer system diagram block is shown in Fig. 2.

Fig. 7. The designed software to control the hardware and practical circuits.

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Embedded system In this system, the microcontroller ATmega128 equipped with an internal analog-to-digital converter is used. This microcontroller receives and then processes the sensors’ data and finally establishes a link between data through a USART port and GSM modem in a serial way. The graphical LCD is implemented by an initiation system and all transformers parameters are digitally displayed on it. DC double motor control is done by the embedded system which has the duty of changing the transformer’s tap changer.

allowed levels some commands are sent to GSM modem. The applied GSM modem is of a SIM 900 type and it has USART communication protocol and is able to communicate with the embedded system serially; this modem is used to send data by GSM network. The mechanical system is applied to change the tap changer of the transformer and is composed of two DC 12-V motors, which one is used for changing the tab changer and another for inserting or excluding transformer from the distribution network. Fig. 3 shows the device. The printed circuit board of the embedded system is designed by the Altium Designer Software and it is shown in Fig. 4.

The group of sensors

The control center system hardware

Temperature sensor receives transformer’s temperature and sends it for microcontroller’s analog-to-digital converter. The humidity sensor transfers humidity inside transformer to the system. Using three infrared sensors, this sensor receives silicone gel color in three levels including low, middle and high, and when the silicone gel is specified and then immediately replaced, any increase in transformer’s humidity is prevented and the utility life of the transformer is prolonged. Using Hall impact sensors, it is possible to become aware of the current gone through three input and output phases of transformer and to recognize failure of each phase in the network. In addition, it is possible to prevent stealing the electricity cables. Using a buoyant, the level of oil in a transformer tank could be also measured and then it is converted into an electrical signal and sent to the embedded system to be analyzed. The oil is lower than the standard level in this case the signal sent to the embedded system is changed and then embedded system issues the controlling commands. The current and voltage modules are required to measure the current and voltage in three output phases. In the feeding block, solar cell and lithium battery are used. A 12 V voltage with 5 A current is applied to feed GSM model; some motors are applied to change tap changer and, also a 5 V voltage is used for feeding the micro-controller using a switching regulator. All the parameters are collected and processed by the embedded system and displayed on a graphical LCD. Then the parameters are compared with allowed values, if they exceed

The control center system is composed of three parts including GSM modem2, RS 232 Chip and FTD 232 Chip. The message sent by the transformer system is received by GSM modem2 and then transferred by RS 232 Chip and FTD 232 Chip to a computer. RS 232 Chip is applied to transfer data between RS 232 (computer) and TTL standard (GMS modem2) because the level of voltage in the TTL logic ranges from 0 to 5 and in the RS 232 protocol it ranges between 15 to +15 V. As the Port com in computer is outdated, FTD 232 Chip is used for creating a virtual port and connecting to computer USB. The block diagram of the control center is shown in Fig. 5.

Transformer system software design Transformer system program has been scripted by Bascom AVR program. First, data system receives different sensors. Then data are processed and sensors data exceed the allowed amounts, in this case the parameters are encoded. So the beginning and end of each parameter, three characters are added to that particular parameter. The system sends data transfer command to GSM modem and the measured parameters are sent for controlling center system through GSM. In addition, if a control command is sent for transforming system in the form of a message, the message is received and data encoded and processed. Then, control commands sent by

Table 1 Transformer temperature, voltage, current and consumption rate within 24 h. Hour

Temp (C)

Current Phase A (A)

Voltage Phase A (V)

Power Phase A (kw)

Current Phase B (A)

Voltage Phase B (V)

Power Phase B (kw)

Current Phase C (A)

Voltage Phase C (V)

Power Phase C (kw)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

18 18 18 19 19 19 19 20 22 23 26 28 33 34 34 35 34 34 34 33 31 26 24 20

121 105 90 93 97 102 112 121 130 132 150 152 143 162 170 175 179 190 194 195 200 202 190 154

218 220 219 219 218 217 217 217 216 216 215 215 216 216 216 215 215 212 211 210 210 210 211 216

26 23 19 20 21 22 24 26 28 29 32 33 31 35 36 38 38 40 40 41 42 42 40 33

125 127 96 82 81 97 106 116 127 133 155 153 148 153 172 174 180 189 187 192 199 205 198 177

218 218 220 219 219 219 217 217 216 216 216 216 217 215 215 214 213 213 213 212 212 211 212 214

27 28 21 18 18 21 23 25 27 29 33 33 32 33 37 37 38 40 40 41 42 43 42 37

118 121 101 97 96 97 102 107 117 127 141 143 144 155 163 171 178 178 181 185 192 197 183 181

219 219 219 220 220 220 219 219 217 216 215 215 215 215 215 214 213 213 213 213 212 212 213 213

26 26 22 21 21 21 22 23 25 27 30 30 31 33 35 36 38 38 38 39 41 42 39 38


250

Voltage (V),Current (A),Power (W)


40

200 150

Current Voltage Power

100 50 0

0

5

10

15

20

25

250 200 150

Current Voltage power

100 50 0

0

5

15

20

25

(B) Values of phase b

220

36

200

34

180

Temperature (C)


(A) V alues of phase a

160 140 Current Voltage Power

120 100 80

32 30 28 26 24

60

22

40

20

20

10

Time (Hours)

Time (Hours)

0

5

10

15

20

25

18

0

5

10

15

20

25

Time (Hours)

Time (Hours)

(D) Transformer temperature within 24 hours

(C) Values of phase c

Fig. 9. Voltage–current of all phases and transformer temperature for 24 h.

control center system are implemented. Fig. 6 shows the flowchart of transformer system software. The design of control center system software The control center program is designed by the software Visual Basic. First, the message sent by transformer system is received, processed and then encoded by GSM modem2. Then sending parameters of the transformer are analyzed and the amount of each parameter is displayed on LCD. The picture of the system software is shown in Fig. 7. Also, the commands related to reporting, change of tap changer, or inserting or excluding transformer from the distribution network is initially encoded and then it is sent for transforming system through GSM modem2. The flowchart of the control center system program is shown in Fig. 8. Results By measuring the transformer parameters such as transformer temperature and current–voltage and power at each three output phases by the system attached to transformer and processing and sending these parameters for controlling center system, it is possible to effectively monitor distribution transformers and also to observe consumption rate in three outlet phases within 24 h. The transformer parameters shown in Table1. The transformer parameters such as temperature and current–voltage and power at each three output phases within 24 h shown in Fig. 9. By measuring current and power at each phase and based on the Eq. (1), the consumption power in each phase is obtained.

P ¼ I V

ð1Þ

Given the graph of temperature in some hours transformer temperature rise to two causes, an increase in ambient temperature and load current increases that increase the load current will cause the winding temperature rise then transformer temperature rise. According to graph of current, voltage and power of each phases with increasing load current to reduce voltage that in the summer reduces more voltage and increases current load more because load is induction and by using this system can be changed of tap changer and can keep changing the voltage standard. Conclusions In the present study, the results from the application of the distribution transformers monitoring and controlling system are investigated. This system plays significant roles in the security of power distribution network, prolonging the utility life of the distribution transformers and monitoring transformer parameters (such as temperature, humidity, silicone gel color, Bocholt’s relay state, input and output phase state, output phase state, the current passing each phase, the power per phase). By monitoring the consumption power at each three output phases of transformer, the consumption rate at per part of distribution network could be supervised and it is possible to become aware of the current voltage and power at three phases within 24 h. The sensors embedded in the input and output phases of a transformer to detect current passing provide the opportunity to become aware of current gone through each phase and to prevent stealing power wires and facilities. The defects to the distribution system are immediately recognized by using this system and it is possible to provide users with the best and fastest services. Another main characteristic of the system is to change tap changer in different seasons by a remote


controlling way and from the control center, which can increase the output of the transformers. Also, by stabilizing standard voltage in the distribution network, the utility life of the consumers is also increased. Given the control system, distribution transformers could be entered and le from the distribution network through GSM network. This state can create a balance in marginal parts while an excessive load occurs. References [1] Papadopoulos TA, Chrysochos AI, Nousdilis AI, Papagiannis GK. Simplified measurement-based black-box modeling of distribution transformers using transfer functions. Electric Power Syst Res 2015;121:77–88. [2] Bengtsson C. Status and trends in transformer monitoring. IEEE Trans Power Deliv 1996;11:1379–84. [3] Samet H, Ghanbari T, Ghaisari J. Maximum performance of electric arc furnace by optimal setting of the series reactor and transformer taps using a nonlinear model. IEEE Trans Power Deliv 2015;30:764–72. [4] Pires RC, Mili L, Lemos FAB. Constrained robust estimation of power system state variables and transformer tap positions under erroneous zero-injections. IEEE Trans Power Syst 2014;29:1144–52. [5] Foata M, Rajotte C, Jolicoeur A. On-load tap changer reliability and maintenance strategy. Cigré Int Coun Large Electric Syst, Paris France 2006;28.

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