electronic protection systems for direct current...

Electronic Protection Systems for Direct Current Railways

The Future for RailwaysMade in Germany

Table ofContent

Made-in-Germany 1

Witt at a Glance 2

Systems for Direct Current railways – Overview 3

Earth Potential Meter EPM 4

Earth Short-Circuiting Device ESC / Voltage Limiter 5

Driving Voltage Monitor DVM 6

Cable Fault Monitoring Device CFM 7

Transducer TD 8

Surge Arrestor Monitoring SAM 9

Monitoring of Overhead Catenary Wires MCW 10

Monitoring of Stray Currents 11

References & Contact 12

Do You know:Made inGermany?

Witt IndustrieElektronik fulfils everything that you can expect from a German company:

We are absolutely on-time and reliable, we plan exactly and act efficiently, we keep dead lines and target cost, we deliver consistent high quality.

We are typical German engineers: our knowledge is exhaustive, and we strive for innovation. And we find it too.

But after forty years in operation and working together in partnership with our customers we know that it needs more to be successful:

Only the fair cooperation between our customers and us is enabling us to deliver „tailor-made“ solutions. We work together with a large number of our customers for decades.

Also partnership means: Made in Germany

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Witt IndustrieElektronik at a glance

Successfully developed

systems and devices

Installations

of Witt products

Since 1972 we are developing products in the fields of rail electronics and industrial electronics. Especially for metrological application, specifically for the requirements of the customers. And innovative – as our experience shows us how to find new pathways. More than 400 devices and systems Witt IndustrieElektronik has developed. They were implemented more than 5,000 times. Deutsche Bahn and Daimler AG belong to our content customers.

Our offer for the Rail Industry

For our customers building, operating or maintaining rail bound transport systems our experienced team has developed customer specific electronic systems from the areas

Safety systems for DC railroads like ground short-circuiting devices

Monitoring of railroad infrastructure like supervision systems for overhead traction lines

Measuring systems for railway infrastructure, wheel alignment, wheel condition monitoring, measurement systems for switches, rail condition diagnostics, etc.

All systems have been created in close cooperation with our customers. Jointly they are tested and put into operation in the real environment. This way it is assured that the environmental influences of the daily operation - wet, dry, hot, cold, dusty, vibrations - are tolerated and that the results are reliable. In addition it is guaranteed that the goal of the customer is fulfilled - be it cost savings, increased life span of systems or protection of persons and infrastructure.

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Systems for Direct Current RailwaysOverview

For Direct Current (DC) railways Witt IndustrieElektronik develops and implements a wide range of protective and measurement systems.

Operating DC railways there is always the risk that unacceptable high contact voltages evolve - typically between rolling assets and the infrastructure like bridges or platforms. The Witt IndustrieElektronik product family for this field measures the voltages and initiates further actions.

One example is the development of a short circuiting device (ESC) developed for the Berlin subway. This protects passengers from harmful contact voltages and the subwayassets against corrosion because of stray currents.

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All systems were developed with Deutsche Bahn or Berlin Public Transport System BVG.

Earth Potential Meter

While operating DC railways with running rails as return conductor, various ground resistances generate voltages that might be dangerous for humans or buildings. One of the requirements of DIN EN 50122-1 is the continuous monitoring of the earth potentials.

This measurement device monitors the potentials of the connected grounds and evaluates the occurring voltages (referring to technical specifications). The voltage between the earth systems or the return conductor respectively that are to be monitored is continuously measured.

By exceeding the threshold setting a switching command is given via a potential-free changeover for the activation of further devices such as an earth short circuiting device or isolation switch.

Witt Products for Direct Current RailwaysSafety Systems

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Earth Short-Circuiting Device ESC/Voltage Limiter

Rail system with DC traction use the running rail as return conductor for the traction current. For several reasons the rail is insulated against ground.

The return current flowing through the rail generates a potential against earth through the electric resistance of the rail. This electric potential can be measured as a voltage between the rail or the carriage respectively and buildings and other infrastructure or earth. This voltage is potentially dangerous for persons. Because of that in DIN EN 50122 it is stipulated that this voltage has to be removed if it exceeds defined thresholds. This is facilitated by a temporary short circuit between rail and earth.

ESC is an automatically resettable earthing short-circuiting device according to EN 50122. It is programmable and is monitoring the voltage differences between the return conductor and the earth. The combination of thyristors arranged anti-parallel and a power contactor ensures a short switching period and high current carrying capacity.

If the set voltage waveform is exceeded, the earth short-circuiting device is activated, i.e. if the criteria of a closing operation are fulfilled, the thyristors are triggered and simultaneously the contactor is switched. The thyristors switch in a few microseconds, the contactor closes in approx. 90 ms. When the thyristors have been triggered, the voltage collapses to a few volts. The thyristors remain triggered until the contactor has been closed, which is detected by way of the position of the auxiliary contacts of the contactor. Thereafter, the thyristors are turned off and the contactor takes over the load.

Newer, faster contactors allow to omit the thyristor group.

The main assemblies of the earthing short-circuiting device are in a dual-channel redundancy design. Moreover, the earth short-circuiting device has got self-testing functions. In that way it is ensured that malfunctions hardly occur. If a malfunction occurs despite this provision it is always reported.

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Witt Products for Direct Current RailwaysSafety Systems

U = I2 x RR-W

RR-WI0

I1 I2 RWRR

Railearth(RE)

Waterearth(WE)

I0 = Derivative traction currentI1 = Partial current to railearth

= (I0 x RB) / (RB-W + RW)I2 = Partial current to waterearthRR,W = Earth resistance railearth, waterearth

Driving Voltage Monitor

The catenary voltage of DC railways must be measured before individual sections can be connected. An electrical connection of those sections may only take place in case all voltage values are within a certain range.

The devices monitor the driving voltage of individual sections and supply information about the voltage values and show if they are within the allowed range.

If all catenary voltages of the track sections that are to be interconnected lie within the allowed ranges, the interconnection between the track sections can be enabled.

The device does not need any auxiliary power supply and is intended for top-head rail mounting.

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Witt Products for Direct Current RailwaysMeasurement Systems

Cable Fault Monitoring Device

The CFM is a self-resetting cable monitoring device for the detection of cable errors. It is used for the monitoring of the insulation of DC cable systems. It works without auxiliary power supply. The connection is made between the insulating outer shell and a reference ground.

For the reporting, there are two potential free changeover contacts available. The device is integrated in a plastic housing that is made for the mounting on top-hat railways.

Between signal and triggering a time delay of 4.8 sec is integrated.

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The voltage between a cable sheath and the earth is measured by a rectifier. If the voltage limit is exceeded a signalling relay is addressed.

The circuit operates with the constant-current principle. This means that even after the voltage increases to more than 1000 V the demand for electricity is not increasing. The leakage current flowing to earth is dimensioned with only 2 mA. Only in cases of failure the current load will be increased to 6 mA. The state of switching is displayed locally by a signal lamp.

Transducer

The transducers of Witt enable a very accurate measurement of driving voltages and currents in electrical isolation.

The transducers are used in DC-powered vehicles as well as in stationary facilities. The voltage that falls off an external current shunt is transmitted potential-free. Thus, it is possible to measure on the "hot" side of the traction power supply.

It is possible to measure the absorbed power by the pantograph in the inside of the railway engine. The device can also measure the power delivered by a substation or a sectionalizer.

The entire electronic is placed in a fully isolated plastic housing. The 4-20 mA outlet is wired in a way that in case of a fault 0 mA will flow and such the following stages can detect an error.

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The voltage that drops out of the current shunt is limited (transient protection) and filtered by the device. Next this voltage is transduced into a high proportional frequency (60-800 kHz) and transferred by a optic fibre cable which is completely galvanically isolated. A subsequent frequency/voltage converter generates a proportional voltage that will - after a filtering in a final stage - be converted into electricity.

The necessary auxiliary voltage is provided in two separate transducers to the primary and the secondary side.

Surge Arrestor Monitoring

The device monitors the surge arrestor (SA) within a certain railway section and reports broken SA via an integrated GSM-Modem. It requires no external power supply. The integrated high-performance battery has a maximum uptime of 5 years.

The SA-monitoring device detects the condition of the fuse through contactless current- and voltage measurements. A defective fuse causes a report which will be transmitted by the GSM module. The device requires no auxiliary power supply and no signal lines.

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The monitoring device measures the current and the voltage curve across the fuse. The measurements are made with an altering current transmitter. The current pulse generated by melting fuses triggers an irreversible signalling contact. The voltage measurement additionally monitors the triggering criteria. An SMS will be send by the GSM-Module if it gets a report.

Monitoring of Overhead Catenary Wires

Catenary wires may break and if they fall to the ground and on the tracks the danger exists that a rail becomes electrified which could also endanger persons who are in the area.

To supervise this, an electrically insulated and non-conductive link is mechanically coupled to the contact wire. In case of a rupture of the catenary this connection will also fail and a message will be send to an operations centre.

The device consists of three modules:

Transmitter: Transmits a defined signal over the control line

Monitoring Line: Transmits the information from the transmitter

Receiver: Receives information of the transmitter and compares these with the basic information

Advantages

No other manufacturer provides a similar system with the functions as described.

Installation and maintenance costs are very low; the operational work can be executed by the own employees after a short briefing. A built-in electronic monitoring system in the receiver module additionally secures the proper function of the system.

Witt Products for MonitoringRail Infrastructure

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Seite 11

Stray Current Monitoring

In a rail system powered by DC,unwanted electric potentials and stray currents can occur because typically the running rail is used as a return conductor. Due to unavoidable isolation issues of the running rails to earth these electric potentials and stray currents occur, which can endanger passengers and can damage the infrastructure because of electro-chemical corrosion.

To monitor the potentials and the stray currents measurement systems are located at dedicated positions in the rail network.

The measurement systems can be designed as stand-alone systems (e.g. the earth potential meter of Witt) or in combination with an earth short circuiting device (e.g. ESC 100).

The measurement stations collect the data and transfers it to a central evaluation station. The data transmission is done automatically and formatted using TCP / IP protocol via a modem connection or another communication procedure.

The display of the information can be done using a map of the network:


Witt IndustrieElektronik

References (Excerpts)

Diagnostics of points and tracks,

voltage limiter, ground short-

circuiting device

Railways

Diagnostics of points and tracks, voltage

limiter

Swiss Federal

Railroad

Public Transport Systems

Partners for Railway Projects

Concept for energy conservation,

cable error measuring device, noise

measurement, cable error detection,

components for sub-stations

Components for control of high

voltage test field, high voltage

switches

Diagnostics of points

Test beds for components

Diagnostics of wheels, stations,

obstacle detection on tracks

Traction cable monitoring

Concept for energy conservation

Monitoring system for grounding

issues (in preparation)

Netherlands

Railroad

German

Railraod

Austrian Federal

Railroad

Voltage limiter, ground short-

circuiting device

BerlinDresden

Munich Hamburg

Earth short-circuiting device

Berlin

Earth short-circuiting device

ContactIf you have further interest in our systems:Do not hesitate to contact us!

Witt IndustrieElektronik

Weststr. 1

13405 Berlin

Germany

Phone: +49 30 794 884 0

[email protected]

www.witt-online.com

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