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BROKEN RAIL DETECTORFOR

CBTC/PTC APPLICATIONS

Victor F. Grappone, P.E.President

December 2, 2003

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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.

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STATUS

• U. S. Patent Application Has Been Allowed.• Issuance Expected By December 15, 2003.

• 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.

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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)

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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).

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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”.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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QUESTIONS?

• Thank You.