Download - 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, 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.
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)
1 1 1
2 2
3 3 34
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).
1
2
1
4 3
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”.
2
1
11
12
2
2
3
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.
3
2
1
2
3
4
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.
4
32
51
1
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.