Research and development of online - Realtime supervising system for low voltage grids

Electronics & Automation 
N. H. Duc, N. T. Minh, “Research and development of  for low voltage grids.” 30 
RESEARCH AND DEVELOPMENT OF ONLINE-REALTIME 
SUPERVISING SYSTEM FOR LOW VOLTAGE GRIDS 
Nguyen Huu Duc
1*
, Nguyen Thanh Minh
2
Abstract: This paper presents some results of fabrication and experiment of an 
online-realtime supervising system for low voltage grids. The experiment results 
show that, for the proposed system, important operating parameters of the low 
voltage grid such as voltage, current, power, temperatures of oil, cable are 
supervised and analyzed. Additionally, alarming messages are sent to operators 
immediately when there are abnormal phenomenon occurring at the grid. This 
proposed system can help improve reliability of electric supply and reduce SAIDI, 
SAIFI, as well as enhance safety of human being and equipment. 
Keywords: Smart grid; Smart transformer; Supervising; Managmement; Low voltage. 
1. INTRODUCTION 
The recent trend of Smart Grid in the world has been applied to the 
management, supervision of transformers and low voltage grid [1-4]. Monitoring 
systems for distribution transformer and energy monitoring systems (BEMS) have 
been used in some countries such as USA, Korea, India. However, these systems 
are still expensive [5-9]. 
Vietnam currently has no specific regulation or model on low-voltage grid 
monitoring and management system. In urban areas of Vietnam, distribution 
substations often were installed near residential areas, markets and crowded places, 
which pose a potential risk of unsafe operation. 
Checking and measuring operating parameters of substations have mainly been 
done by manual methods. Thus, it leads to labor-intensive, unsafe, incomplete - 
inaccuracy data. Additionally, alarming & warning devices such as oil temperature 
of transformer, oil level, steam relays, underground cable breakdown alarms are 
on-site reading devices. Moreover, these devices are not able to store and transfer 
data by themselves. 
Currently, there is a meter data management system (MDMS) in electric power 
grids of Vietnam; However, it still has several disadvantages as follows: Only 
electrical parameters of transformer such as active power, voltage, current can be 
measured and the sampling frequency is 30 minutes or one hour per time, thus 
leading to no guarantee of updating the online operation status of the transformer. 
Additionally, MDMS could not monitor non-electrical parameters and operation 
status such as oil temperature, oil level, relay effect, fault indicator and alarming 
status, so on. Therefore, it is impossible for MDMS to send warning signals to 
operators. Moreover, this MDMS is to calculate electricity bills for customers, thus 
it has its own specific safety and security. It should be separated from the operation 
management system. 
Based on current operation of transformer at distribution grids of Vietnam, there 
is a necessity to development a so-called online-realtime supervising system 
(STrS) of the transformer. The proposed main tasks of the STrS will (1) collect 
online all necessary data of the transformer; (2) send data to center operation room 
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Journal of Military Science and Technology, Special Issue, No.72A, 5 - 2021 31 
and (3) analysis of data. This STrS will bring several core merits such as: (1) limit 
risk of electrical safety for operators; (2) cut down labor resource; (3) reduce 
operating and maintenance cost; (4) increase management efficiency; and (5) 
modernize electrical distribution grids. 
The paper is organized as follows. Section 2 shows overview of the proposed 
STrS system. Fabrication of the proposed system is described in Section 3. 
Experiment results and analysis of the installed system are discussed in Section 4. 
Finally, conclusion is drawn in Section 5. 
2. OVERVIEW OF THE PROPOSED STRS SYSTEM 
Schematic of the STrS system is shown in fig. 1. It is composed of a terminal 
unit, different sensors, a server. Its characteristics are presented in detail as follows. 
Figure 1. Overview of the proposed STrS System. 
(1) Terminal unit: It is a measuring and monitoring equipment. Its functions are 
receiveing, measuring and processing signals from peripheral devices and 
transformer stations. This device can monitor the electrical quantities such as 
voltage, current, cosφ. It can also read temperature parameters, namely oil 
temperature in the transformer, temperatures at bus bar. Additionally, it can 
receive data from alarming devices such as oil level, stream relay status, so 
on. In order to make easy for operators supervising at field, it should display 
collected data on its LCD screen. Afterward, it will transfer supervising data 
to webserver that can be access everywhere by the operators with only a 
personal computer. 
(2) Server system (server): Its functions are managing and analyzing collected 
data. This server system includes a server that stored all collected data and a 
software that helps operators for their management. In order to support 
operators, the software can display data from all peripheral devices 
connected to the terminal unit. Additionally, it can generate statistics report; 
Electronics & Automation 
N. H. Duc, N. T. Minh, “Research and development of  for low voltage grids.” 32 
alerts or alarming message. Moreover, it is possible to extend its system with 
other software. 
(3) Data transmission channel: There are several ways to transmit supervised data 
such as wireline (ADSL, Optical cable, so on); radio (GPRS/3G, SMS, RF, 
WIFI, so on). 
(4) Device receiving and displaying information could be a personal computer or 
portable mobile device. 
3. FABRICATION OF THE PROPOSED SYSTEM 
A main device SGMV of the system is a terminal device located near a 
transformer. This device SGMV has its aim as: (1) collect data from field sensors 
such as current transformers, voltage transformers, oil temperature and pressure, 
warning/alarm states; (2) supervise the parameters (phase current, voltage, 
indicator capacity is instantaneous and within a range period of time); and (3) 
process and transfer collected data to a server. 
Figure 2. Diagram of SGMV equipment block principle. 
The principles diagram of SGMV equipment shown as in figure 2 is divided 
into 4 parts: (1) LCD circuit; (2) ADE circuit; (3) TOP circuit and (4) PSU circuit. 
The part of electronic measurement is to measure parameters U, I, P, Q, f, cosφ, 
energy consumption, and send measurement data to it RTU via RS485 is set at 
the station. Other measurement elements are thermometric sensors; temperature, 
humidity, and smoke sensor. Sensors collect operating parameters of the 
transformer and low voltage grid, then transfer to the SGMV at the distribution 
cabinet. The SGMV is designed to include a processor central logic, digital I/O, 
analog order, communication modules. Figure 5 shows a power unit (DC/DC) 
which has the switch duty DC power input. Levels of Output voltage +5V, 3.3V, 
2.5V supply to the central processing, input circuits, output, communication. A 
power supply with 5V/3A use an electronic switching source IC LM2576HV with 
an input voltage 12-60 VDC [3]. 
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Journal of Military Science and Technology, Special Issue, No.72A, 5 - 2021 33 
a) LCD circuit b) ADE circuit 
b) TOP circuit d) PSU circuit 
Figure 3. Design of block circuits: a) LCD circuit; b) ADE circuit; 
c) Top circuit; d) PSU circuit. 
Figure 4. Design of the printed circuit. 
Figure 3.a: Includes 1 LCD, 4 buttons and 3 single LEDs. The circuit is 
supplied with a voltage of 5V. The circuit has the function of displaying through 
LCD, led and interacting with the device through 4 push buttons. Figure 3.b 
Includes 4 ADE 7758; - Operating voltage: 5V; - The circuit has the function of 
Electronics & Automation 
N. H. Duc, N. T. Minh, “Research and development of  for low voltage grids.” 34 
reading the values: Current, voltage, accumulated capacity,... Figure 3.c The design 
circuit includes blocks: Ethernet, SIM, RS232, source SIM. The SIM uses 3.8V 
power. Figure 3.d includes: Source, Real-time, EEP rom, memory card, ADE, 
Microcontroller. The power unit generates 3.3V and 5V DC. 
Figure 4 shown the complete design of the printed circuit. All parts are designed 
on the same board. Components are arranged on both the top and bottom of the 
circuit. The part arrangement and wiring ensure standards of size and distance. As 
a result, the finished product of SGMV is shown as in figure 5. 
Figure 5. Photo of the finished product. 
4. EXPERIMENT RESULTS AND ANALYSIS 
Figure 6. Overview of the human interface of the system. 
The proposed system is applied to the LV grid of Dong Da, Hanoi from 
18/3/2020 to 05/11/2020. In this pilot project, this system has been normal 
operated and good functioned as follows. Figure 6 shows the overview of the 
human interface of the system. Figure 7 shows the location of the installed system 
at Lang Thuong, Dong Da, HaNoi. The proposed system is installed and includes 
key functions as follows: 
 Monitoring operating parameters to the branches behind Moulded Case 
Circuit Breakers (MCCB) at the distribution cabinet (maximum 9 branches). 
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Journal of Military Science and Technology, Special Issue, No.72A, 5 - 2021 35 
 Monitoring oil temperature parameters, contact temperature at the low 
voltage terminal on the top of the transformer. 
 Monitoring parameters of contact temperature at the extreme of Aptomat 
(ATM- bus bar total). 
 Integrating most of the existing state sensors at the transformer (MBA) and 
distribution cabinets (sensors of device opening and closing state, oil level, 
gas relays, cable head failure alarms,...). 
 Detect incidents that short-circuit the distribution cabinet. 
 Data sending cycle can be flexibly set to minute unit, for example 5-minute 
sample time. 
 Operation alerts, status alerts are set according to the operational status of 
each substation to ensure early detection of potential risks. 
 All of the above functions are integrated in a compact device, the optimal, 
open Web server system makes it easy to operate and integrate the system. 
Operating parameters of the grid is shown as in figure 8, including voltages, 
currents, powers, cosφ as well as other state parameters. As seen in figure 8, all 
operating parameters are collected and supervised with 5 minutes sampling time by 
operators. It is also noticed that the grid is in normal state. 
Figure 7. Location of the installed system 
at Lang Thuong, Dong Da, Hanoi. 
Figure 8. Operating parameters 
of the grid. 
Another merit of this system is to draw charts of supervising parameters such as 
voltage, current, power and oil temperatures, and so on, as shown in figure 9. In 
addition, the system can immediately send notification to operators when the grid 
has abnormal states as illustrated by figure 10. 
Electronics & Automation 
N. H. Duc, N. T. Minh, “Research and development of  for low voltage grids.” 36 
Figure 9. Charts of supervising parameters. 
Figure 10. Alarms of abnormal states of the grid. 
As a result, after utilizing the installed system, the grid can achieve several 
merits as follow: 
 Reduce the risk of transformers, low voltage grids of distribution substations, 
especially substations located in densely populated areas (due to the potential 
danger of transformers such as the phenomenon of short-circuiting a single-
phase winding, poor contact in the transformer, deteriorating insulation 
causing internal discharges and so on). This also helps reduce 
troubleshooting costs because preventive treatment costs are often quite 
small compared to when the incident occurred. 
 Reducing power loss: Due to the technical losses of substation and the 
distribution grid, it is mainly due to the transformers and the grid operating at 
full load, overload, phase shift or contact at the terminals. Therefore, the 
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Journal of Military Science and Technology, Special Issue, No.72A, 5 - 2021 37 
proposed system can reduce operational technical losses for the substation, it 
is estimated that it can be reduced by 0.2% to 2% (depending on the actual 
operational situation such as the transformer and the number of phase-
shifting low voltage lines, how much overload and for how long,...). 
 Modernizing the electricity grid towards to the smart grid: Measurement, 
monitoring and management online and remotely; Modernize the 
management and operation. 
 Increasing management efficiency: Improving the reliability index of 
electricity supply (Saidi, Saifi, Maifi); Minimize the risk of power outages; 
Reduce time outages. 
 Operating data: real-time, complete, accurate and synchronized; The operator 
is warned promptly and fully. 
 Reducing manpower and operating costs: Reducing manpower in 
measurement and inspection of grid operation; Reduce maintenance costs. 
 Reducing the risk of electricity unsafety for operators: No direct contact with 
electricity; Limit checking when the grid is operating. 
5. CONCLUSIONS 
The STrS system supply a comprehensive automation solution for LV grid 
operation, replace the existing operation systems, save labor cost, and improve 
safety conditions for equipment, grid and operators. S3M systems supply the 
online, comprehensive and high accuracy measurement, monitoring and operation 
management data. 
The STrS system including: 
1. Monitoring equipment (SGMV). 
2. Webserver (S3M-WS4.0). 
3. Sensors and measuring instruments. 
Sensors and measuring instruments (installed at substation) send real-time data 
to a monitoring equipment (SGMV). Through the transmitted channels, measured 
data will be processed, stored and sent to webserver by the SGMV device. 
The STrS system can be installed, operated, tested and maintained easily, 
independently and will not affect the operation of existing power grid. 
This subject is in the field of research and implementation of smart solutions 
towards smart grids in Vietnam. Therefore, this topic is essential for Vietnam's 
high-tech and sustainable economic development strategy. 
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[1]. James Momoh, “Smart Grid-Fundamental of Design and Analysis”, 
IEEE Press, March 2012. 
[2]. “Smart Energy Grid, Energy & Power Magazine”, Volume 9 Issue 19, 
March 16, 2012. Available online:  
[3]. “The Smart Grid: An Introduction, prepared for the U.S”. Department 
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[4]. European Technology Platform Smart Grid, “Strategic research agenda for 
Europe‘s electricity networks for the future”, European Commission, 
Directorate General for Research, Directorate Energy, 2007. 
[5]. A. Q. Huang, "Medium-voltage solid-state transformer: Technology for a 
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3, pp. 29-42, Sept 2016. 
[6]. M. Liserre, G. Buticchi, M. Andresen, G. D. Carne, L. F. Costa and Z. X. Zou, 
"The smart transformer: Impact on the electric grid and technology 
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June 2016. 
[7]. C. Kumar, Z. Zou and M. Liserre, "Smart transformer-based hybrid grid loads 
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[8]. “Operation and control of smart transformer for improving performance of 
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[9]. Bunn M., Das B. P, Baguley C. “Smart Supervisory System for Distribution 
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TÓM TẮT 
NGHIÊN CỨU CHẾ TẠO HỆ THỐNG GIÁM SÁT THỜI GIAN THỰC 
CHO LƯỚI ĐIỆN HẠ ÁP 
Bài báo trình bày một số kết quả chế tạo và thử nghiệm hệ thống giám sát 
trực tuyến thời gian thực cho lưới điện hạ áp. Kết quả thí nghiệm cho thấy, 
đối với hệ thống đề xuất, các thông số vận hành quan trọng của lưới điện hạ 
áp như điện áp, dòng điện, công suất, nhiệt độ dầu, cáp đều được giám sát 
liên tục và phân tích. Ngoài ra, các cảnh báo trong quá trình vận hành của 
lưới điện được gửi đến người vận hành ngay lập tức khi có hiện tượng bất 
thường xảy ra trên lưới điện. Hệ thống này có thể giúp cải thiện độ tin cậy 
cung cấp điện và giảm SAIDI, SAIFI, cũng như tăng cường an toàn cho con 
người và thiết bị. 
Từ khóa: Lưới điện thông minh; Lưới điện hạ áp; Máy biến áp, Giám sát thời gian thực; Cảnh báo. 
Received Mar 16
th
 2021 
Revised Apr 29
th
 2021 
Published May 10
th 
2021 
Author affiliations: 
1
Department of Renewable Energy, Faculty of Energy Technology, Electric Power University, 
235-Hoang Quoc Viet, Ha Noi, Viet Nam; 
2
Smart Electric Solution Company, 210-Le Trong Tan, Hanoi, Vietnam. 
*
Corresponding author: ducnh@epu.edu.vn.