Turn to Turn Fault Detection for Air Core Reactors

The goal of this project is to create a small scale model of a 3 phase air core reactor in order to test for inter-turn faults, as well as an RTDS model of the system to further test more in depth fault scenarios.

Background
Avista deployed a system of air core reactors at their Noxon Rapids Dam in Montana in order to drop the bus voltage at the dam to help keep voltage levels even across the grid. Although the reactors have common protection schemes deployed already, there is currently no way for a protective relay to detect an inter-turn fault within a single phase of an air core reactor; a situation which could lead to complete failure and destruction of a reactor.

Deliverables
The goal of this project is to develop a protective relaying algorithm which will enable an IED, specifically an SEL 487E, to detect inter-turn faults within a single phase of an air core reactor.

Specifications





 * Project Specifications (As of 2/20/2015)
 * Length: 6-7 inches
 * Width: 4-5 inches
 * Weight: Approximately 6 oz.
 * Power Capacity: 5.33-7.2 W/H
 * Capacitance: Approximately 1.82 Farads at 120 Vrms
 * Needs to carry a charge for twice the time it take to charge the phone. (About 3 hours)
 * Discharge Time: 80 minutes
 * Two minutes to charge device
 * Create a USB interface for the charger based on USB specifications

Client Interview

 * Wrote a list of technical, budget, and miscellaneous questions for client to make sure we approached this project fitting our client's needs
 * From the answers we obtained, we were able to build a better foundation for starting this project
 * [[File:VARsity_Client_Question_Whiteboard.pdf]]

Lead Instructor and Technical Advisor Meetings

 * Every week we meet with our lead instructor and our technical advisor to go over the progress of the project
 * Topics such as due dates, technical progress, budgets, and brainstorming are all discussed during these meetings

Calculations

 * [[File:Calculations_VARsity.PNG]]

Scaled Test Circuit
In order to create an environment for testing, it will be necessary to build a scaled test circuit that can operate at 120V which we can use to manipulate in order to test for inter-turn faults.

RTDS Model
In order to correlate data, it is necessary to have an RTDS model simulation program to see if certain test points give the same data during a fault condition.

The RTDS model also makes it easier to show the magnitude of the fault current that would flow through a shorted winding.

Future Work
The following are problems that need to be addressed in the future:
 * Getting the isolated gate driver to work properly – Under voltage lockout? Incorrect size of Bootstrap Capacitor? Circulating currents from charging supercapacitors? Interference with power supplies? Do we need a power supply with enough DC voltage and amperage to test circuit (170 V dc with up to 27 Amps)?
 * Miniaturization – need smaller components (inductors especially - some have up to a 24 week lead time)
 * Assembly of 2nd prototype – printed circuit board and surface mount components picked and assembled. Install of Vishay supercapacitors.
 * Possible thermal issues with surface mount components (especially the N channel power mosfet)
 * Feedback isolation for microcontroller. Needs op amps or other isolation on voltage divider input signals.
 * Feedback code or circuit for shutting microcontroller off when fully charged
 * Self powered. Right now requires a 20Vdc source in addition to a USB cable hooked up to the microcontroller.

Minutes

 * [[File:9.14.16_Meeting_Minutes.pdf]]
 * [[File:9.20.16_Meeting_Minutes.pdf]]
 * [[File:9.28.16_Meeting_Minutes.pdf]]
 * [[File:10.4.16_Meeting_Minutes.pdf]]
 * [[File:10.21.16_Meeting_Minutes.pdf]]
 * [[File:10.25.16_Meeting_Minutes.pdf]]

Client Interview

 * [[File:VARsity_Client_Question_Whiteboard.pdf]]

Design Review

 * [[File:2015 AirCap Design Review.pdf]]
 * [[File:2015 AirCap Design Review ppt.pdf]]

Final Report

 * [[File:2015 AirCap Final Report.pdf]]