1 BROKEN RAIL DETECTOR FOR CBTC/PTC APPLICATIONS Victor F. Grappone, P.E. President December 2, 2003

2 OVERVIEW Commercial Power Frequency Electrical Solution. Detects Complete Rail Breaks. Does Not Require Insulated Joints. Simple Hardware Design. Track-Mounted Detection Coil. Commercial Off-The-Shelf (COTS) Programmable Logic Controllers (PLC’s). Detection Provided In Complex Trackwork. Closure Rails. Crossovers.

3 STATUS U. S. Patent Application Has Been Allowed. Issuance Expected By December 15, Preliminary Tests On Hardware Have Been Performed. Detection Coil. Preliminary PLC Programming Complete. Funding For Development Being Sought. Government Agencies. Signal/Train Control Suppliers. Or Anyone Else.

4 TRACK CONFIGURATION Track Is Divided Into Detection Sections. (1) Range Of Length Is Several Feet To 2-3 Miles. (2) Hardwired Shunts Are Applied At Section Boundaries. (3) Each Section Forms A Current Loop. (4)

5 DESIGN 60 Hz. Power Is Applied To The Approximate Center Of The Section. (1) A “Figure-8” Shaped Detection Coil Is Mounted Between The Rails. (2) Approximately Six Feet Long. The Detection Coil Is Connected To A PLC (3) Via An Amplifier (4)

6 OPERATION (RAILS INTACT) Current Flows About Equally In Each Half Of The Section. (1) Proportional Currents Are Induced In The Coil. (2) Induced Voltages From All Four Quadrants Are Oriented In The Same Direction Relative To The Coil, Therefore They Add Together To Produce A Relatively High Voltage. The High Voltage Is Detected By The PLC (3), And Interpreted As “Rails Intact”

7 OPERATION (RAIL BROKEN) A Rail Breaks. (1) Current Now Flows In Only Two Of The Previous Four Quadrants. (2) The Voltage In The Coil Is Now About Half Of What It Was. (3) The PLC (4) Detects The Voltage Drop And Deduces A Broken Rail

8 EMI IMMUNITY Interfering And Unequal Currents Can Flow In Either Rail. (1) Current (2) Is Equal To Current (3). Due To Coil Symmetry, Induced Voltages (4) And (5) Are Equal In Magnitude. However, They Are Oriented In Opposing Directions With Respect To The Coil. Therefore, No Net Interfering Voltage Is Induced

9 COMPLEX TRACKWORK Current Loops Need Not Be Comprised Of Paired Running Rails. Train Detection Is Not Provided. Loops May Be Applied To Cover Difficult Rail Sections. Closure Rails. (1) “Inside” Rails Of Adjacent Tracks At Multiple Crossovers. (2) 1 2

10 RELIABILITY As Just Demonstrated, The Design Is Inherently EMI Immune. Three PLC’s Are Provided In A Two-Out-Of-Three (“2 oo 3”) Configuration. Two Are Required For Normal Operation. The Third Provides Redundancy. Compensation Methods Provided To Deal With The Real-World Environment. Varying Ballast Impedance. Presence Of Foreign Metallic Objects. Source Voltage Variation.

11 BALLAST IMPEDANCE COMPENSATION Voltage Setpoints Are Set With Rails Intact And Under Otherwise Normal Conditions. Voltage Changes Due To In Ballast Conditions Variation Will Occur At A Slow Rate. Setpoints Are Dynamically Varied Provided That The Expected Maximum Rate Of Change Is Not Exceeded.

12 FORIEGN OBJECT COMPENSATION Unlike Varying Ballast Conditions, Metallic Foreign Objects Can Only Cause The Coil Voltage To Increase. A Rapid Increase In Coil Voltage Will Be Detected And The Safe State (Rail Broken) Assumed.

13 VITALITY Electrical Signals Are Interpreted By The PLC’s. Each Interpretation Is Performed At Least Twice By Each PLC. Two Instances Must Agree For The “Rails Intact” State To Be Assumed. Two Of The Three PLC’s Must Agree For The “Rails Intact” State To Be Assumed. Predefined Setpoints Will Be Transparent To Users.

14 QUESTIONS? Thank You.