University of Manitoba Department of Electrical & Computer Engineering ECE 4600 Group Design Project Progress Report Wireless High-Voltage Power Line Sensor by Group 11 Jordan Bartel Thomas Neusitzer Sailen Kara Qian Song Academic Supervisor Dr. Gregory Bridges Industry Supervisor Dr. Miodrag Kandic Manitoba Hydro Date of Submission January 12, 2015 Copyright 2015 Jordan Bartel, Sailen Kara, Thomas Neusitzer, Qian Song
TABLE OF CONTENTS Table of Contents List of Abbreviations....................................... ii 1 Introduction......................................... 1 2 Project Progress...................................... 1 2.1 Energy Harvesting System (Qian Song)..................... 1 2.2 Power Storage System (Sailen Kara)....................... 2 2.3 Data Acquisition System (Thomas Neusitzer).................. 3 2.4 Wireless Communication System (Jordan Bartel)................ 4 3 Future Work........................................ 4 3.1 Hardware System.................................. 4 3.2 Software System.................................. 5 4 Conclusion......................................... 5 Appendix A Updated Gantt Chart.............................. 6 Appendix B Updated Budget................................. 8 i
List of Abbreviations Abbreviation CT DAQS DRA EHS LAT PSS SEPIC WCS WPLS Description Current Transformer. Data Acquisition System. Digital Recording Ammeter. Energy Harvesting System. Linear Active Thermistor. Power Storage System. Single Ended Primary Inductor Converter. Wireless Communication System. Wireless High-Voltage Power Line Sensor. ii
1 Introduction 1 Introduction The purpose of this project is to design and implement an energy harvesting, wireless highvoltage power line sensor (WPLS) as an alternative to the battery reliant, non-wireless digital recording ammeters (DRAs) currently utilized by Manitoba Hydro. Similar to a DRA, the WPLS is placed directly on a high-voltage power line to monitor the line current. Additionally, the WPLS is capable of measuring the line temperature, ambient temperature, line sag angle and motion of the power line. This project was divided into four subsystems: the Energy Harvesting System (EHS), Power Storage System (PSS), Data Acquisition System (DAQS) and Wireless Communication System (WCS). While some parts of the EHS and PSS subsystems are slightly behind schedule, the modular design approach helped to keep the overall progress of the project on track. An updated Gantt Chart with the current progress is shown in Appendix A. 2 Project Progress The EHS and PSS subsystems are still being developed individually, while the DAQS and WCS have entered the integration phase. All of the main components for each subsystem have been purchased for a total of $322 as shown in Appendix B, which falls within the allotted project budget of $400. The project progress for each subsystem is described in the following sections, with the name of the design lead shown in parentheses. 2.1 Energy Harvesting System (Qian Song) The EHS is responsible for supplying power to the WPLS by harvesting energy from the power line s magnetic field. There are three main components for the EHS: the energy harvester, the rectifier and the regulator. The energy harvester presented a major challenge because commercial energy harvesting chips 1
2 Project Progress did not provide enough power to supply the other subsystems. Two main options were explored: 1. Use a current transformer (CT) and modify its secondary windings 2. Custom design and build an air core transformer Some problems were encountered for both options. The CT has a very high output current that can damage the subsystem components, and the air core transformer can only provide enough voltage by using an impractical number of turns. Ultimately, a Mastercraft digital current clamp meter was modified to be used as the energy harvester. The meter is similar to a CT but outputs less power, and the harvested energy is in the hundreds of milliwatts range required by the WPLS. Testing with two parallel clamps demonstrated that the microcontroller can be powered on and successfully transmit information with its antenna. The rectifier and regulator have been built, tested individually, and function properly. However, the regulator does not output the required voltage when combined with the harvester and rectifier circuits. This issue is expected to be resolved by replacing the regulator chip with a zener diode regulator. The EHS will then be ready for the integration phase. 2.2 Power Storage System (Sailen Kara) The EHS cannot supply power below a line current of approximately 200 A, and therefore rechargeable batteries are used as an alternate power source for the microcontroller. During high line current conditions (above 200 A), the batteries will be charged using the excess power generated by the EHS. Two different charger topologies were considered and simulated: a voltage regulator and a voltage converter. An LM317 voltage regulator was used to adjust the voltage. However, this design required the input voltage of the charger to be higher than that provided by the EHS. The LM317 is also sensitive to temperature changes, and the output voltage varies at different temperatures, which is a drawback to using this method since the environmental conditions are highly variable in 2
2 Project Progress Manitoba. The alternate design is a DC-DC converter with the single ended primary inductor converter (SEPIC) topology. The SEPIC topology is used to give a non-inverted output using the LT1512 chip. Using a converter gives the flexibility of having input voltage lower than the output voltage, and there is less voltage variation due to ambient temperature. Due to the input voltage flexibility and its lesser dependency on temperature changes, a DC-DC converter topology has been implemented to build the charger. 2.3 Data Acquisition System (Thomas Neusitzer) The DAQS consists of a microcontroller interfaced with several electrical sensors and is responsible for the measurement of critical characteristics of the power line. These critical characteristics include the line current, line temperature, line sag angle, ambient temperature and the motion of the power line. An Arduino Uno was selected for implementing the data collection protocol because it is a low cost embedded systems implementation with significant online resources. In addition, there are many Arduino compatible devices, including antennas, for use in the WCS. Software for the data collection protocol was written using the open source Arduino IDE. Several options were considered to measure the line current, including a Hall-Effect sensor, a Rogowski coil, a CT and a custom current sensor. The first three alternatives were deemed impractical since the Hall-Effect sensors cannot be physically attached onto a power line, the Rogowski coils are not rated to operate below 0 C, and the CTs are cost prohibitive and exceed the project budget. Therefore, the custom current sensor was implemented using a modified Mastercraft digital current clamp meter and a rectifying circuit. The rectifying circuit was constructed to limit the sensor output voltage between 0 and 5 V in order to protect the Arduino. A Linear Active Thermistor (LAT) was implemented to measure the line temperature. The LAT was selected because it is inexpensive and satisfied the temperature sensing specification of -40 to 125 C. An identical LAT was implemented to measure the ambient temperature since the temperature in Manitoba has the potential to range from -40 to 40 C. 3
3 Future Work In order to measure the sag angle of the power line, a 3-axis accelerometer was implemented. Initially, a 3-axis gyroscope had been used for this purpose, but it skewed the results due to gyroscope drift. Utilizing an accelerometer in place of the gyroscope enabled the collection of acceleration data, which describes the motion of the power line. This motion data can be used to evaluate the performance of the power line when subject to high winds. 2.4 Wireless Communication System (Jordan Bartel) An Arduino Uno paired with an XBee transceiver was chosen to implement the WCS. This decision was made because the XBee transceiver is compact, omni-directional, power efficient and very easy to connect to the Arduino using an SD shield. Software has been created to read collected data from the SD card and write the information to the serial port of the XBee antenna configured as a coordinator device. To save power and reduce packet drop rates, this device has been programmed to transmit only to the desired end device, which is the base station. The program has been tested, resulting in successful transmission of collected data to the end device. The data is then stored in a text file where it can be viewed as raw data or graphed using a program such as MATLAB or Microsoft Excel. 3 Future Work In the next two months, the main tasks are integrating the EHS and PSS to complete the hardware system, and combining the DAQS and WCS for the software system. Once the hardware and software systems are functional, they will be combined and tested to ensure project specifications are met. 3.1 Hardware System The EHS and PSS will first need to be completed and then consolidated. Once the two subsystems are combined, a switching interface based on the line current must be developed to determine 4
4 Conclusion the situations in which the EHS or PSS will act as a power source for the WPLS. Additionally, all breadboard circuits will need to be built on a prototype board for the final implementation. Finally, a suitable housing for the WPLS will need to be built or purchased. 3.2 Software System While most of the software is complete, some issues have arisen from the limited amount of SRAM of the Arduino UNO. Since there is only 2 kb of SRAM, there is insufficient space to hold the raw data. Further work is required in order to store some raw data on an external micro SD card to solve this issue. The WCS will be modified to save received data in a visually appealing and usable form on the base station. This will be done using the program Maker Plot, which takes incoming ASCII characters from a USB port and filters through the data to appropriately graph different data types on their own scale. The data will also be saved in a text file to allow for further analysis. 4 Conclusion The WPLS is intended to be used as an alternative to the DRAs currently being utilized by Manitoba Hydro to monitor line current. In addition, the WPLS is capable of measuring the line temperature, ambient temperature, line sag angle and the motion of the power line. Currently, the project is on schedule and under budget. The subsystem integration phase is nearly complete, and system testing is expected to begin at the end of January. Overall, the project is on track to meet and exceed the specifications upon its completion on March 4, 2015. 5
Appendix A Updated Gantt Chart Figure A.1 shows the updated project Gantt chart. The blue sections denote the projected duration of each task while the green sections denote the actual task duration; the vertical red line is used to denote the current date in the project. As shown by the Gantt chart, some tasks have taken more time to complete than others, but the project remains on schedule. 6
Fig. A.1: Updated Gantt Chart for the Wireless High-Voltage Power Line Sensor. 7
Appendix B Updated Budget The updated project budget is shown in table I. All of the parts listed have been purchased and received, or are readily available from the Department of Electrical & Computer Engineering Technology Shop. The total project cost is currently $321.99, which is within the $400.00 budget supplied by the Department of Electrical & Computer Engineering. 8
Table I: Updated Budget for the Wireless High-Voltage Power Line Sensor. Notes: * The Arduino Uno Rev. 3 was provided by Dr. Greg Bridges ** The 3-axis Accelerometer was provided by the Dept. of Electrical & Computer Engineering Tech. Shop *** The Prototype Board has not yet been acquired from the Dept. of Electrical & Computer Engineering Tech. Shop 9