Design and Implement of a Frequency Response Analysis System

Transcription

1 ECE 4600 GROUP DESIGN PROJECT PROPOSAL Design and Implement of a Frequency Response Analysis System GROUP 02 GROUP MEMBERS Alan Mark Hao Liang Deng Naima Shahzadi Tong Shu DEPARTMENT SUPERVISOR Dr. Behzad Kordi INDUSTRY SUPERVISOR Nathan Jacob P. Eng. September 26, 2014

2 Table of Contents Introduction... 1 Specifications Microcontroller Variable- Frequency Oscillator (VFO) Amplifier Gain & Phase Comparator System Interface... 5 Tasks & Milestones Project Milestones Task Assignments... 7 Gantt Chart... 9 Budget Conclusion References... 11

3 Introduction Frequency Response Analysis (FRA) is the most common method for diagnosing mechanical and electrical faults and displacements within a power transformer. Since Power transformers are one of the most important elements in the power system network, accurate diagnostics and proper maintenance of power transformers is crucial. Frequency response analysis works by determining the transfer function, V out /V in, and the phase difference between the input and output waveform over a range of frequencies [1]. The FRA test results are also known as the fingerprint of the transformer. These fingerprints are compared with previous ones and any discrepancies would indicate a deformation within the system that will require repair [2]. The goal of this project is to design a frequency response analysis system that will determine the magnitude and phase of the transfer function over a frequency range of a two- port network. The project will be a cost effective solution to FRA because the current market devices are in excess of thousands of dollars. To achieve this goal, a computer- interfacing program will communicate with the FRA system to create a variable frequency sinusoidal waveform. This waveform will then be amplified to ensure that the amplitude is above noise level. After amplification, the waveform will be injected into the input of the test unit. After allowing steady state to be reached, the input and output of the test unit will be measured to determine the amplitude of V out /V in and phase difference. These results will then be displayed on the computer- interface program. To achieve accurate results, the system requirements are as follows. The variable frequency output power source must provide consistent power over the entire frequency range to ensure consistent measurements of the transfer function. The frequency range must be variable from 10 Hz to 2 MHz. The test result, which includes the phase difference and the amplitude of V out /V in over the entire frequency range, will be stored in a comma- separated values (CSV) file. Finally, the computer- interfacing program will allow user inputs and data acquisition for the whole system. GROUP DESIGN PROJECT PROPOSAL Page 1

4 Specifications The designed FRA system will require multiple hardware components to operate. The system flow chart is shown in Figure 1 and depicts how the hardware components will be utilized in the flow of operation within the system. Further details of each hardware component can be found below. Figure 1: FRA System Flow Chart 2.1 Microcontroller A microcontroller will act as a brain for the entire FRA system. Firstly, this microcontroller will accept user inputs from a system interface program. User inputs include start analysis, store analysis results and plot results function. Secondly, the microcontroller will communicate with the variable- frequency oscillator (VFO) through 4 digital Input/Output channels to begin the FRA test. Finally, the microcontroller will store the measured gain and phase difference data to the PC through 2 analog input channels. The GROUP DESIGN PROJECT PROPOSAL Page 2

5 microcontroller will be required to have a USB port in order to communicate to the PC. The frequency response analysis system will collect about 1400 samples and each sample will be 6 bytes, thusly a 16 KB flash memory will be sufficient. Table 1 summarizes the required specifications of the microcontroller. Table 1: Microcontroller Specifications Value Notes Digital I/O 4 Channels Min Analog Input 2 Channels Min Output voltage 5 V p Nominal Flash Memory 16 KB Min 2.2 Variable- Frequency Oscillator (VFO) The variable- frequency oscillator (VFO) will produce sinusoidal waveforms with a range of frequencies beginning at 10 Hz and ending at 2 MHz. The VFO s output frequency range and frequency step will be controlled by the microcontroller. An advanced function generator was measured to have a frequency stability error of.1%, resulting in the same requirement for the VFO. Table 2 below displays these required specifications for the function generator. Table 2: Function Generator Specifications Value Notes Output Wave Form Sinusoid Frequency Range 10 Hz to 2 MHz Minimum range Frequency Step 1Hz Min Output Voltage Level 1Vpp Min Frequency Stability Error 0.1% Min GROUP DESIGN PROJECT PROPOSAL Page 3

6 2.3 Amplifier An amplifier will be used to increase the power level of the VFO s output signal so that the signal injected into the test unit is strong enough that the measured response is well above the noise floor level. A 5 V/V gain will be sufficient based on the 1 V pp output voltage of the VFO. The amplifier s frequency bandwidth will be at least 4 MHz to accommodate the high- end frequency at 2 MHz. For a sine wave not to be affected by slew rate limitation, the slew rate (SR) will have to be larger than 2πf Vpeak. Based on the output requirement of the VFO, V peak is 0.5V and highest frequency is 2 MHz, which yields a minimum SR of 6.3 V/μs. Table 3 summarizes the required specifications of the amplifier. Table 3: Amplifier Specifications Value Notes Amplifier Type Power Amplifier Gain 5V/V Min Frequency Bandwidth 2 MHz Min Slew Rate 6.3 V/µμs Min Output Voltage level 5 to 50 V p Nominal 2.4 Gain & Phase Comparator The gain and phase comparator will be used to determine the phase difference and gain of the test specimen. The detector will have input signals from the test specimen output and VFO, the latter being used as the reference signal. The detector will determine the difference in phase of the input signals, and the gain will be the ratio of the test specimen amplitude to the reference signal amplitude. The gain and phase will be the GROUP DESIGN PROJECT PROPOSAL Page 4

7 output of the comparator to the microcontroller. The required range of the phase and input voltages for the detector are listed below in table 4. Table 4: Comparator Specifications Value Notes Phase difference range 0 to 180⁰ Minimum range Input voltage range 1 V rms 2.5 System Interface The interface program will control the microcontroller based on user inputs. The user will have an option of starting the FRA test, storing and plotting the FRA test results. The interface program will collect the digital data of gain and phase difference from the detector, and will store the data into a comma- separated values (CSV) file. In addition, the interface program will generate a Bode plot of the test unit based on the data of gain, and phase difference. A processing development environment will be used to build the interface program. The required functions of the system interface program are listed below in table 5. Table 5 System Interface Functions Summary Development Environment Programming Language Operating System Function 1 Function 2 Function 3 Processing Processing Mac OS X, Windows Start FRA test Data Storage to CSV format Bode plot GROUP DESIGN PROJECT PROPOSAL Page 5

8 Tasks & Milestones 3.1 Project Milestones The project is divided into four milestones. Milestone 1: Research, Part Acquisition, and Draft Design Research will be completed by each team member in order to design the FRA system. Afterwards, the team will agree upon an FRA system design and the necessary components will be researched to ensure that the most optimal choice of parts is made. All the parts will then be ordered. Milestone 2: Component Testing and Simulation Upon acquisition of the parts, each part will be tested independently to verify that it meets the project needs and specifications. Computer simulations will be made to verify any designed components to ensure they meet project needs. Milestone 3: Micro Controller Coding for all components A beta program of the User Interface program will be written and tested for proper functionality. The data acquisition portion of the beta program will be tested in conjunction with the microcontroller when the microcontroller is supplied with predetermined data from a known filter test unit. Milestone 4: System Assembly and Test This final milestone will require the assembly and test of the entire system. Tests will be completed on a simple filter unit with known results and further tests will then be completed on an audio transformer and then on a power transformer. Calibrations and adjustments will be made if there are any discrepancies in the test results with the known results after each test stage. GROUP DESIGN PROJECT PROPOSAL Page 6

9 3.2 Task Assignments Component Task Task Responsibilities Milestone 1: Research, Part Acquisition, Draft Design Micro - Controller Research and selection Tong Shu [TS] & Hao Liang Deng [HD] Micro - Controller Study on Program Language TS & HD Function Generator Research and selection Alan Mark [AM] & Naima Shahzadi [NS] Amplifier Determine the specification AM & NS Amplifier Schematics Design AM & NS Comparator Research phase and gain detection method TS & HD Comparator Schematics Circuit Design TS & HD Comparator Component build or selection TS & HD Interface Selection on interface programing environment AM & NS Interface General design on interface system AM & NS Data Acquisition Research data acquisition program. All Milestone 2: Component Testing and Simulation Micro - Controller Basic Function Test TS & HD Function Generator Connect with the Micro- Controller TS & HD Function Generator Performance Test TS & HD Amplifier Simulation of draft design AM & NS Amplifier Build real circuit and test AM & NS Comparator Unit Test for a range of frequencies AM & NS GROUP DESIGN PROJECT PROPOSAL Page 7

10 Component Task Task Responsibilities Milestone 3: Micro Controller Coding for all components Programing Build the coding for whole system All Interface Build and test a Beta Program All Milestone 4: System Assembly and Test All Component Assemble the system and test All Data Acquisition System test with data acquisition program All Testing on Transformer Compare the results with transformer finger print All Documentation and Presentation Proposal Progress Report Oral Progress Report Final Report Final Presentation All All All All All GROUP DESIGN PROJECT PROPOSAL Page 8

11 GROUP 02 ECE 4600 Gantt Chart The project phases and tasks assigned are scheduled into a timeline as shown in the Gantt chart. GROUP DESIGN PROJECT PROPOSAL Page 9

12 Budget The budget was compiled based on research of standard components. Taxes and brokerage fees are included in the estimated costs. System Component Parts Estimate Cost Element Input source Micro- controller Arduino Yun $74 Variable- frequency AD9850 Module $10 oscillator (VFO) Amplifier Power Amplifier THS309X high- speed $50 amplifier module DC Power Supply +/- 15V DC power supply 0$ (Borrow from ECE Department) Comparator Phase Comparator AD8302 $30 Amplitude AD8302 $30 Comparator Interface Coding Processing $0 Environment Circuit Wire Wrap Wire Wrap Board $50 Component Print Circuit Board PCB $20 Circuit Element Resistor, Capacitor, $50 Wire Simulation Circuit Simulation Software NI Multisim 0$ (Borrow from ECE Department) Shipping Cost $40 Tax $46 Grand Total $400 Conclusion The proposed project is the design and implementation of the voltage frequency response of a two- port network. The necessary tasks will be performed so that the final goals of the project can be accomplished within the given timeframe and within our budget. GROUP DESIGN PROJECT PROPOSAL Page 10

13 References [1] IEEE Power and Energy Society, IEEE Guide for the Application and Interpretation of Frequency Response Analysis for Oil- Immersed Transformers, IEEE Std C57.149, The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY , USA, Mar. 8, [2] Naser Hashemnia et al, Characterization of Transformer FRA Signature under Various Winding Faults, in 2012 IEEE International Conference on Condition Monitoring and Diagnosis, Bali, Indonesia, 2012, pp GROUP DESIGN PROJECT PROPOSAL Page 11