The design and implementation of circuit breaker on-line monitoring ...

ITEC Asia-Pacific 2014 1569889171 ITEC (IEEE Transportation Electrification Conference and Expo), Asia-Pacific, 2014

The design and implementation of circuit breaker on-line monitoring device Wei Wang1, Leting Lin2, Wei Pang2,Ming Xuan2, Jingyi Liu1, Wei Ma1, Rui Li1 1 National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China, 010-51684873, [email protected] 2 Overhaul Department of Jilin Electric Power Company,Changchun, 130021, China Abstract: This paper designed a circuit breaker on-line monitoring system based on S3C2440A core controller. With the high speed and high precision extended A/D, this device can sample signals on real time. It is fast, easy networking and convenient for remote data transmission by Ethernet. The embedded linux operating system, which can be cut arbitrarily and easy to translate, is used in this device. This monitoring system has complete functions, and has the advantages of user management and real-time multitasking. Tests show that the system can sample quickly and accurately, and transmit data fast and safely. System’s anti-interference ability is strong, performance is stabilized and the bit error rate is low. So, it is better than the traditional 485 communication way.

The mechanical robustness of circuit breaker’s component is extremely important. Mechanical failures of circuit breaker can be caused by: operating mechanism and the transmission system fault, electrical control circuit fault. In order to anticipate and show the fault in real time, we need to monitor stroke, speed, and mechanical vibration signal of dynamic contact during it closing and opening. 2. Online monitoring of circuit breaker opening coil. By monitoring current of opening coil, we can get coil status information and mechanical properties. 3. Online monitoring of primary side current. We can get the degree of wear through the primary side current. 4. Online monitoring of voltage and current of energy storage electrical machine. Monitoring the current, voltage and working time of circuit breaker energy-storage motor is used as getting the information of energy storage electrical machine, through data statistics and comprehensive analysis; we can know the evaluation of the working state of the energy storage system. Finally, we can infer the fault type of circuit breaker, combined with the operation of historical data. 5. Communication function We can transmit data to the master station by the Ethernet based on specific communication protocols, so that the master station and slave station can share information. 6. Display function We can use the LCD to display data in real time.

Keywords: Circuit breaker; On-line monitoring; ARM; Linux;

I. INTRODUCTION Most failures of circuit breaker are mechanical operation mechanism failure[1], to keep the circuit breaker running safely, the operations management need to repair it periodically. In this way, it is not only affects the normal operation and increases operating costs, but also causes circuit breaker artificial damage. So it’s a good idea to design a circuit breaker on-line monitoring system to solve these problems [2-3]. The common way to design a circuit breaker monitoring system mainly based on Micro Controller Unit, but its function relatively single, hard to extend and doesn’t have the operating system, visualization and maneuverability are relatively poor. So in this design we choose the pattern of ARM + Linux, besides functions that Micro Controller Unit can achieve, the visualization is stronger and network communication function is also powerful [4- 5]. This monitoring system mainly uses the ARM9-S3C2440 micro controller chips as the carrier and runs Linux operation system on it, We try to check the circuit breaker operation status and improve the reliability of circuit breaker through on-line monitoring and data analysis .In this way, we can save cost and provide reliable scientific basis for power supply scheduling, operation and maintenance.

B. System ensemble design The design of hardware based on utu2440 core board and monitoring system structure diagram is shown in figure1.

II. THE INTRODUCTION OF SYSTEM FUNCTION AND ENSEMBLE DESIGN

A. The introduction of system function According to the requirement of system circuit breaker on-line monitoring, system should implement the following functions: 1. Circuit breaker on-line monitoring for mechanical characteristics

Fig.1 Structure of breaker monitoring device

III. THE DESIGN OF SYSTEM HARDWARE

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ITEC (IEEE Transportation Electrification Conference and Expo), Asia-Pacific, 2014

E. AD conversion In this design, the AD conversion chip is 14 bits MAX125, it can sample four channels at the same time, but you need to write your own driver program. Each channel is independent of others, so when any channel failed it will not affect the operation of other channels [10].

A. Analog signal measurement The analog signals that system needs to sample, including: current of opening coil, primary side current, the voltage of opening and closing control power, the voltage of energy storage electrical, the voltage of AC control power, the vibration signal and stroke signal. So measurement module is shown as follows: 1. Measure current of opening coil This design selects the hall current sensor, which can measure AC or DC current. Schematic diagram is shown in figure 2.

Fig.4 MAX125 operation sequence diagram

The sampling mode is determined by address, and the extend CONVST signal can start sampling and converting, S/H circuit will track the input before the rising edge coming. Each channel conversion time is 3 us, so if all four channels need to be converted, a conversion cycle is 12 us. Before the transformation completed, all input CONVST signals will be ignored. When the last channel completed, the INT signal will be generated, its falling edge marks the end of the conversion process, and the conversion results will be stored in RAM of 14 * 4. If INT signal change into low level, the S/H circuit will back to tracking state, preparing for the next sample. In the process of reading data, the first read operation will make the INT signal change into high level. When system read the results of digital quantity, the CS, RD need to be low level at the same time. Each RD signal correspond to a channel data, four successive pulses can complete the process of reading data from data bus [11].

Fig.2 Wiring diagram of hall circuit sensor

2. Measure current of primary side. The phase current of main circuit is ac signal, it can be converted as weak current signal directly by hall current sensor, the schematic diagram is same as figure 2.1 3. Measure voltages We use hall voltage sensor KV25A/P to measure he voltage of opening and closing control power, the voltage of energy storage electrical and the voltage of AC control power. 4. Measure vibration signal We use acceleration sensor YD-1 to measure vibration signal, vibration charge amplifier is DHF-7.

F. Function of external device After main controller has read the measured data, we choose internal SDRAM memory to store data, so if power is cut it can prevent loss of data. At the same time, the electricity parameter data will be displayed on the LCD. To make sure the system work safely, the system provide the 5V power supply. Core board frequency is selected as 400 MHZ, and power supply module will provide 3.3V,.+5V,-5V,+15V and -15V.

B. Measure switch signal Switch signals of system including: circuit breaker auxiliary nodes, the location of isolating switch auxiliary node, the location of the car, and the state of the energy storage system. In this design, we choose optical coupling . C. Conditioning circuit There high frequency signals may be mixed in normal signals that came from the sensor, so we need low pass filter circuit to suppress external high frequency signal. In this design, the low pass filter is second-order Sallen - Key lowpass filter, and its schematic diagram is shown in figure 3.

IV. THE DESIGN EMBEDDED LINUX DRIVER This design chooses extended ADC to complete data sampling, and the data communication is based on the Socket Ethernet. We need to complete the design of the AD converter driver, network card driver and socket communication program [13]. A. The build of Linux development environment The embedded system doesn’t have the ability of independent development itself, so we need to build a development environment, completing the following content: 1. Establish a cross-compilation environment; 2. Establish the kernel environment; 3. Establish application integration development environment; 4. Installed Linux system on ARM board.

Fig.3 Low-pass filter circuit

D. Multiple switches In this design, two pieces of multiple switches MAX333 are chosen to constitute a 16-channel input and 8-channel output to AD conversion chip.

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B. The design of the AD converter driver and transplant Figure 5 is schematic diagram of the AD converter driver, Linux calls driver of AD to get the sample data between the kernel and hardware, then transmit data to the users.

receiving part is the key of the communication of the server and client, so the data that must follow the protocol of service can be read and return the result [14]. In this design, we use the TCP/IP protocol in Linux operating system itself; it can call the underlying function directly and drive the Socket communication module. The details of Socket programming is shown in figure 7.

Fig.6 The socket listening process flow chart Fig.5 A schematic diagram of ADC driver

C. Communication protocol In this monitoring device, communication protocols are completely followed the national standard of the telecontrol equipment and systems part 5 of transmission code 101 of basic telecontrol tasks standard ". This standard specifies the frame format, the link layer transfer rules, service primitives, structure of application data, encoding of application data, application function and message format. D. The design of the socket and transplant In this design, we write the application program based on protocol of TCP/IP Ethernet, by calling the socket function to achieve various functions, including the receiving and sending data, data checking etc. [7]. The Socket is used to describe the IP address and port. Applications usually send the request or response to network through a socket. Server uses Server Socket to listen the specified port, waiting for the client connection request, after client connection, the conversation will be get, after the completion of the session the connection will be closed. Therefore, server and the client can send data to each other by the Socket interface, and two sides follow the protocol of data interactive communication, data transmission format and time sequence. The memory in the core board is SDRAM it is equivalent to the Socket server, which including the Socket listening and Socket receiving treatment. The part of socket listening is working in multithreaded way, and the process of listening is in a fixed port. If server received the request then start to response, otherwise it will listen the port continually. Socket

Fig.7 Programming diagram in detail

E. Applications transplant to Linux hardware There are many methods to download the applications to hardware board, but here we registered ADC as misc equipment. We use the methods of Linux NFS Share server to complete the Socket communication program loading. After the success of the NFS establish, we will download TCP program to the development board, and waiting for the final test [15]. V. SYSTEM TEST

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A. Test environment and test conditions

1500

1. Test environment The local PC runs two operating systems at the same time, and connects computer and development board with cable and serial port line. The test environment is divided into two parts: a. Installing Linux system in the virtual machine of the Windows platform, and testing programs of server-side in the Linux terminal. b. Checking the status of operation in local HyperTerminal.

a/m/s^2

1000

0 0

Fig.8 Waveform of vibration signal

Fig. 9 Server connection state diagram

Running client program, the client can connect to the server successfully as shown in figure 10.

Fig. 10 The client connection status

By figure 9 and 10, you can make a conclusion that the data transmission is correct. 4. The speed of Ethernet data transmission test. We measure the time of data transmission from the host computer to control module by Ethernet, we got the actual transmission speed, which is shown in table 2.

Tab. 1 Data sampling precision

relative

voltage/V

analog

error

t/us

-1000

B. Test environment and test conditions 1. Functions and data test We change the input voltage by adjust rheostat resistance to test the AD, from table 4.1 we can get the result that input voltage value and the AD conversion voltage value have a biggest difference is less than 0.01 V, so the relative error is within 1%. Converted to

50000 100000 150000 200000 250000 300000 350000 400000

-500

2. The methods of test a. Start Linux OS, set up a new user terminal and run the server program. b. Start the development board , configure IP. c. Run client program on Linux operating system. d. Test system.

Input

500

Tab. 2 Ethernet data transmission speed of the experimental data

Size of data

/V

transmission

time（μs）

speed(Mbps)

46

36.4032

9.6407

74

57.5819

9.8047

102

85.6873

9.0818

0.196%

130

107.8838

9.1934

2.831

0.106%

158

136.0749

8.8587

3.557

3.562

0.140%

186

157.4103

9.0151

4.376

4.380

0.091%

0.471

0.470

0.212%

(Bytes)

0.701

0.702

0.142%

1.076

1.082

0.557%

1.534

1.539

0.356%

2.040

2.044

2.828

According to the experiment data above, we can calculate the actual transmission speed is about 9.2657 Mbps

2. The result of sample To simulate the actual waveform, this study also uses the software, which named digital dynamic testing in real time, to simulate the actual waveform. Figure 4.1 is the waveform of circuit breaker closing vibration signal, figure 8 is the waveform of circuit breaker closing coil current signal. The experiment proves that this system can sample correctly, and get a ready for the next step of data processing and fault diagnosis.

5. Ethernet test results analysis According to the experiment data above, it shows the Ethernet data transmission rate can reach nearly 10 MBPS, and much higher than the traditional communication transmission speed of 485; Through the bit error rate test shows it almost no error problem; A single node error has no effect on the whole network, the security of system network structure is good, stability is nice, easy to debug, low maintenance cost.

3. Ethernet access test Server program reads a word from customer and increase his value, and then write it back. Server is running, it creates a socket and begins waiting for customer connection. As shown in figure 9.

VI. CONCLUSIONS In this work, we have designed a on-line monitoring system of circuit breaker, we take advantages of ARM and Linux system, so we got a greatly improve of the performance of the circuit breaker on-line monitoring system,

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and make data sampling more accurately, more safely and quickly to transmit data. Besides the system has a powerful function, easy to management and handle multitasking in real-time. System can provide reliable scientific for power equipment overhaul and this system has a very good application value and popularization value. Acknowledgment This work is supported by Science and technology project of State Grid (JLJX13KJ-2-1). References [1] [2] [3] [4] [5]

[6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

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