Download Swedish train detector system

LABORATORY INVESTIGATION OF THE SWEDISH
TRAIN DETECTION SYSTEM
Åke Wisten
Luleå University of Technology
Service check of the train detector
system
When the voltage between the rails is close to 6 V DC, the
section is considered to be clear, ”NO TRAIN ON THE SECTION”
Service check-no train
Service check of the voltage level for ”NO TRAIN ON THE SECTION”
Service check: train on the section
Service check of the voltage level for ”TRAIN ON THE SECTION”
Lab tests of the train detector system
• The Swedish train detection system has been
tested in a laboratory.
• 1. Testing the delay times for switching the
signals : red to green, green to red
• 2. Testing the influence of a lightning strike in
the neighbourhood of the rails
1. Testing delay times
• Testing delay times for switching the relays,
corresponding to the entrance of a train, and
the departure of a train, from an I-railsection.
Feeding voltage of the I-rail
• Voltage feeding of the I-rail: The I-rail is always
connected to a 6 V DC battery, with very low
internal impedance, and a very big inductance
(0.3 Henry) in series. The low voltage side of the
inductor is permanently connected to the I-rail.
The negative pole of the battery is connected to
ground (ground = the S-rail).
• During the lab-test the breaking of the I-rail
feeding circuit was done between the battery +
6VDC pole and the inductor. The voltage was
measured between the battery and the inductor.
The train detector circuit
• The I-rail voltage is controlling a relay. The I-rail is
connected to the primary port of the relay. When the Irail voltage is 6 V, the secondary contacts are closed.
When the I-rail voltage is 0 V, the secondary ports are
open.
• In the detector circuit there is an adjustable resistor,
and a very big inductor in series with the primary port
of the relay. The adjustable resistor is needed for
adjusting the switching voltage level. The inductor is
needed to protect the relay from fast changes in
currents. For safety reasons there are two relays on
each I-rail section.
Breaking the 6 V feeding voltage
Voltage measured at the I-rail feeding 6VDC circuit. The
primary 6 V DC-circuit is opened at time 0.1 seconds. A spark is
closing the circuit again for a short moment (shows as an 8 V
peak). Then the circuit is definitely broken – and the voltage
goes to zero.
A train is entering the section
Voltage at an output port of the relay. Delay time for
switching from ”no train on the section ” to ”train on the
section”: 0.33 – 0.1 s = 0.23 seconds
The train is leaving the section
Voltage at an output port of the relay. Delay time for switching from
”train on the section” to ”no train on the section”: 1.45 – 0.1 s = 1.35
seconds
2. Testing lightning strikes
• Testing implications of a high voltage
discharge, similar to an indirect hit by
lightning in the neighbourhood of the I-rail
• A 30 kV, 6.2 nF capacitor was discharged
against the I-rail. The purpose was to
investigate if the train detection relays were
influenced by the “lightning strike”.
Testing lightning strikes
• When the 30 kV capacitor was decharged at
the I-rail a 3 cm spark was generated. The
time-duration of the spark was measured by
means of an optical fiber between the spark
and a photodiode.
Duration of the lightning spark
Measuring duration time of a spark. The signal from the photo diode, showing the
duration of the spark. The duration of the spark was about: 4 us.
Duration of spark in detail
Measuring duration time of a spark. The duration of the spark was
measured by means of a photodiode. The duration of the spark was
approximately 0.4*10 us = 4 us. The rise time was approx. 0.2 us.
Sparc interference on left relay output
Voltage at a secondary port of the left relay, when the spark was hitting the I-rail.
The maximum interference-voltage was 15 V.
Sparc interference on right relay
output
Voltage at a secondary port of the right relay when the spark was hitting the I-rail. The
maximum interference-voltage was 18 V
Sparc interference on relay input
Voltage at the input port of the left relay when the 30 kV discharge was applied at the
I–rail. The maximum voltage in this case was 12.5 kV. The width of the pulse was about
0.1 ms.
Test conclusions
• Conclusions.
• The delay time for switching green light to red
light was 0.21 seconds, and from red to green
1.35 seconds
• When a very strong lightning-discharge was
applied on the I-rail no disturbance on the
functioning of the train detection relays was
noticed.
• The experimental lab setup can be used for
checking computer models of the train detection
system.