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Topic Title: Railway EMC
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Created On: 14 February 2002 04:30 AM
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 14 February 2002 04:30 AM
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deleted_hello73

Posts: 23
Joined: 12 February 2002

Hi,

Currently i am doing a project on railway EMC, but i was not able to proceed due to lack of information. Thus, in the course of doing, i make certain assumption. Do feel free to give your comments on my approach and do enlighten me on my queries.


My project seeks to identify whether there is any interference between the WLAN transmitter and the existing platform/trackside equipment or between the existing platform/trackside with WLAN equipment by using analysis method followed by site measurement.

Objective

Check whether the WLAN transmitter could coexist with the existing equipment in the railway environment.

Check whether the existing transmitter in the railway environment could coexist with the WLAN equipment.

Constraints

The following are the constraints, which are being encountered during the course of work

(i) No information on the transmitter – equipment separation distance and transmitter – cable (for communication and signalling equipment only) separation distance.
(ii) Transmitter Power Level/frequency of railway transmitter is not complete
(iii) Immunity specification of the railway equipment within the range of 80MHz – 1000MHz is either 10V/m or 20V/m (depending on system).
(iv) Immunity specification of the equipment (WLAN and railway equipment) outside the range of 80MHz – 1000MHz is not defined.

Assumption (which I made)

The existing equipment in the railway environment meet the immunity level of 10V/m (within the range of 80MHz – 1000MHz) {worst case as compare to 20V/m}

The existing equipment in the railway environment meet the immunity level of 1V/m (outside the range of 80MHz – 1000MHz) {since no specification is given for this frequency range}

WLAN system specification

Sensitivity = -90dBm
Conforms to the IEEE 802.11b Standard
Operating in ISM Band II (2.4GHz)
Use Direct Sequence Spread Spectrum technology
Data Rate is 11Mbps
13 Operating channel frequencies

EIRP = 100mW (20dBm)
Antenna = Omni-directional
Gain = 2.1dBi

Approach

My approach basically is to break down the EMC problem into different categories as shown below:

(i) Existing transmitter (operating within 80MHz – 1000MHz) – WLAN equipment

(ii) Existing transmitter (operating outside 80MHz – 1000MHz) – WLAN equipment

(iii) Existing transmitter (operating in WLAN band) – WLAN equipment

(iv) WLAN transmitter (2.4GHz) – existing equipment

Then by using Friss formula to compute the radius of the transmitter radiating field (in each case) which is equal to the immunity level of the equipment before deciding whether to perform measurement. For equipment falling within the computed radius, measurement will be done

In our measurement only inter-operative test will be done (since this will test the entire system including the interconnecting cables), no conducting or radiating test is performed (since the specification of the equipment is not complete and thus there won’t be any specification to compare with).


(i) What should the minimum distance of the cable away from the transmitter be in order to classify that it will not pick up and signal and conduct it into the communication/ signaling system.

(ii) Can normal shielded (communication/ signaling) cable be exempted from the test if the WLAN transmitter is transmitting a power of 100mW.

(iii) Can the we assume that for receiver frequency up to ±10fo from the transmitter frequency (fo) be included in the test only as other frequency will be too insignificant (This is because I have come across the case that even if the frequency is ±15fo away, significant amplitude level of the transmitter may saturate the receiver even though it is not in band. What should be the minimum amplitude level before we claim that the frequency doesn’t come into play (assuming the WLAN receiver sensitivity is –90dBm)
(iv) What about for the case of WLAN transmitter – equipment, is there a way where we can claim that certain frequency will not affect the equipment.

(v) Can I conclude that the beacon of the signalling transmitter will not affect the WLAN equipment (even though they are inband) since it exists only for a short duration.

I was wondering is there anybody who have any document related to the above and could share with me

Thanks



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hello73
 18 March 2002 12:47 PM
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amccallum

Posts: 28
Joined: 18 October 2001

Suggest you obtain copies of :

EN 50121-1 - Railway Applications EMC
EN 50121 -2
EN 50121-3-1
EN 50121-3-2
EN 50121-4
EN 50121-5

May also be worth looking at

GS/ES 1914 - Electromagnetic Susceptibility Data for Track Circuits and AWS

CCITT Specifications Vol V recommendations P53 - Psophometric Analysis

Once you have read/understood all that let me know if u have any further questions
and any progress you have made

Regards

Andy

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Andy McCallum
 03 April 2002 08:52 AM
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deleted_hello73

Posts: 23
Joined: 12 February 2002

Btw, can i know where to obtain those standards

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hello73
 10 April 2002 02:37 PM
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amccallum

Posts: 28
Joined: 18 October 2001

Try your library - the IEE library or the BSI Website

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Andy McCallum
 24 February 2011 12:05 PM
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RogerMee

Posts: 1
Joined: 24 February 2011

The illegal copying and distribution of standards is theft. Standards must be paid for!
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