Junction Electrical Design Guide

JUNCTION CABLING DESIGN CERTIFICATION667/DS/20664/000

Siemens Traffic Controls,

Sopers Lane,

Poole,

Dorset,

BH17 7ER

SYSTEM/PROJECT/PRODUCT :

Traffic Signal Junction Cabling

Design Certification

THIS DOCUMENT IS ELECTRONICALLY APPROVED

AND HELD IN THE TS DOCUMENT CONTROL TOOL

Issue :Change Ref :Date : dd/mm/yy

Issue 3TS00407918/09/2007

Issue 4TS00650720/03/2012

Issue 5TS006919March 2013

Issue 5 Page 1

JUNCTION CABLING DESIGN CERTIFICATION667/DS/20664/000

Siemens Traffic Controls,

Sopers Lane,

Poole,

Dorset,

BH17 7ER

SYSTEM/PROJECT/PRODUCT :

Site Reference:

Site Address:

Prepared By:

Function :

This Document is fully issued when this page is at a FULL numeric issue and all of the following pages are at the same full numeric issue below and is either signed if provided in paper form, or has the name of the person preparing it added above by the person who has edited the detail / designed the junction cabling layout.

Issue : Change Ref :Date : dd/mm/yy

This is an published work the copyright in which vests in Siemens plc. All rights reserved.

The information contained herein is the property of Siemens plc. and is supplied without liability for errors or omissions. No part may be reproduced or used except as authorised by contract or other written permission. The copyright and the foregoing restriction on reproduction and use extend to all media in which the information may be embodied.

CONTENTS

1.INTRODUCTION

1.1Purpose

1.2Scope

1.3Related Documents

1.4Glossary

1.5Use

2.General NOTES ON INSTALLATION WIRING

2.1Neutral Connections

2.1.1Introduction

2.1.2Context

2.1.3Procedure

3.cABLING

3.1Cable Maximum Loading (Limited by the heating effect)

3.2Loading limited by Cable Voltage Drop (thus associated with cable length)

4.ducting

4.1Capacities

5.CABLE impedances

5.11mm2 Armoured Cable

5.21.5mm2 Armoured Cable

6.COMPLETION OF VERIFICATION CALCULATIONS

7.APPENDIX A Verification Calculations

8.APPENDIX B COMPLEX DUCTING CAPACITIES

LASt Page...... 17

Issue History

Site Reference: ??Issue ? Page 1

JUNCTION CABLING DESIGN CERTIFICATION667/DS/20664/000

1INTRODUCTION

1.1Purpose

This document is intended to allow an assessment to be made on the suitability of the cabling design for a traffic controlled junction installed by STC using STC provided cable. Providing all of the criteria noted in the subsequent sections and sub sections are complied with within the junction design, the cable and terminations design can be certified as complying with BS7671 and Electrical Installation Certificates signed off.

1.2Scope

This document only applies to cables 998/4/70468 and 4/MC832 supplied by STC, and cable terminations supplied in STC traffic controllers and Poles Caps.

1.3Related Documents

BS 7671IEE wiring Regulations

667/SA/20664/000Design and Manufacturer Supplied Information.

1.4Glossary

1.5Use

The tables in the body of the document allow a quick check of the electrical design. For a more detailed check should one be required or if the values or extent of the tables are exceeded the calculation form in the appendix should be used.

The process is to edit the data in this document for the particular customer / site and then provide a paper or magnetic copy to the customer, who should then forward it on to the appropriate installing company. To edit the forms in the appendices of this document, you will need Microsoft Excel, double click on them and they will open up in Excel to allow editing. When you have edited the data, click back on the body of the main word document and the modified tables will be copied back to the word document. Then save the word document in the normal way. Please remember to edit the document series number picking a base number appropriate to your STC base i.e. DEPOT and selecting the next variant in order. The site reference must also be edited in the footer to ensure each page indicates the site for which it is relevant.

2General NOTES ON INSTALLATION WIRING

The standard size of cable drum used in the field by STC is 250M anything else is a special order.

STCs Recommendations are that LV, ELV and detector cabling are run in separate ducts, where ever possible.

2.1Neutral Connections

2.1.1Introduction

Street wiring faults can sometimes affect the display of traffic signals on-street. Poor connections, for example in pole top termination blocks usually leads to the failure of signals to illuminate properly which may be detected by lamp monitoring where this is implemented.

2.1.2Context

Where common neutral connections are used it is possible for the failure of a neutral connection to cause unexpected signal displays, where one or more signals within a given signal head are incorrectly illuminated simultaneously. This lack of neutral connection is not detectable by the controller because the signal voltage presented at the controller terminals does not exceed the required thresholds for conflict or correspondence monitoring.

When incandescent signals are used a cable fault of this type usually causes the signals to be illuminated at a low level and is not particularly noticeable. For LED signals however it is possible for the signals to flash, at least at their 'dim' level. Although the rate of signal flashing is such that they are only typically illuminated for a very short time, less than the conflict / correspondence time defined in TR2500, it can be more noticeable than the display seen with incandescent lamps.

2.1.3Procedure

Normally this type of fault only affects a single signal head or pole and due to other signals displaying correctly is unlikely to cause signalisations that could be considered dangerous, so retrospective action is not essential.

Therefore we are not mandating retrospective action on existing sites, however if the customer wishes to re-wire then we can do this on a chargeable basis

However for new LED sites where it is desired to reduce the likelihood of incorrect displays, particularly involving green signals, it is recommended that individual neutral returns are used for each green signal. For existing incandescent sites where LED signals are being now fitted and spare cables cores are available these may be used to provide additional neutral connections.

3cABLING

3.1Cable Maximum Loading (Limited by the heating effect)

The following is based upon the worst case with all cores carrying the specified current and the maximum number of any type of cable possible, i.e. the worst case condition (thus removing the need to calculate all scenarios),whilst also taking into account the controller maximum load per aspect drive. (See also LIMTS OF LOADING IMPOSED BY MAXIMUM DUCT CAPACITIES). Provided that the loading per core is kept below the maximum number of heads / maximum current value specified below, then the requirements of BS 7671 can be guaranteed. If loadings above these are required then Engineering at Poole should be consulted. This later is extremely unlikely.

3.2Loading limited by Cable Voltage Drop (thus associated with cable length)

Note the following tables are based on the load of a normal tungsten halogen lamp, an LED aspect load, is generally half that of a tungsten halogen lamp and therefore these tables provide a worst case scenario. If all LED aspect are used on a cable run the after careful consideration as to the future use of the cables it is feasible that the lengths could be doubled.

1.0mm2

1.5mm2

The voltage drop in the installation must be no more than 4% of the incoming supply, for a 230 volts supply this is 9.2 volts. The tables above should be checked to ensure that for the selected core size and loading the voltage drop is lower than this maximum. If the voltage drop exceeds the 4% cores / conductors may be paralleled up to reduce it, note NO MORE than 3 cores should be connected in parallel. The numbers in the cells within the tables indicate the number of cores required to meet the voltage drop requirement.

4ducting

4.1Capacities

Based on BS 7671 ‘Selection and Erection’ Appendix A Cable capacities on conduit and trunking section e) the following tables and rule of thumb has been produced.

It should be ensured that none of the conduits in the installation exceed these recommendations.

Ducts should not be over filled with a visual check of the above it would appear as a maximum of 50% filled.

For Detector Feeder Cables The following applies

A mixture of cable sizes i.e. a number of cables in a duct with different numbers of cores in the cables, becomes complex calculation

(and appendix b can be used), however a rule of thumb whithout refering to the spreadsheet in appendix B, would be as follows

NOTE some customers have there own requirements for DUCT capacities and these must be complied with on contracts with those customers, check with customers and /.or their requirements specifications.

An Example would be.

50mm ducts should have no more than 2 armoured cables or 4 non armoured cables. If used in combination in the duct it can be taken that an armoured cable is equivalent to 2 non armoured.

100mm ducts should have no more than 5 armoured cables or 10 non armoured cables. If used in combination in the duct it can be taken that an armoured cable is equivalent to 2 non armoured.

Bend Radii in a Traffic Signal Junction Installation meet the requirements of IEE Regs On Site Guide, provided a) the conduits are not over filled (see earlier paragraphs with reference to duct capacities and, b) standard ‘Slow bends’ are fitted in conduits (e.g. for 50mm conduits 350mm radius, 100mm conduit 450mm radius), or chambers are fitted at such bend points allowing cable minimum bend radii to be met.

Allowable bend Radii are

For Armoured cable min bend radius is 6 X DiaFor Un Armoured Cable min bend radius is 4 X Dia

5CABLE impedances

The approporiate impedances below should be combined and added with the Ze (earth loop impedance at origin) supplied by the Electricity supply authority or Local Authority. Firstly the combined value should not be greater than the required ELI value for the fuse in the controller. Finally these values should be used to cross check the Earth Loop Impedances measured during the testing of the installation. The tables assume 1 core used, at measured at 20˚C, this allows comparison with the max values allowed in 667/HE/20664, as the max values have been reduced by the IEE regs ‘Rule of Thumb’, 0.8 to take into account being measure at 20˚C. Note the impedances below are the loop of 1 core plus the armouring.

5.11mm2 Armoured Cable

5.21.5mm2 Armoured Cable

6COMPLETION OF VERIFICATION CALCULATIONS

It is required that the Verification calculations sheet in appendix A is filled out for the longest cable run and the shortest cable run. Double Click

On the form (this will open it in EXCEL to allow editing), answer yes to macros. Once completed Click back on the Word document page to save it back to the word document. Once Complete the sheets should be checked for the following. NB The TARGET ELI value given in the blank form is that for and ST700 or ST800 with 160 volt dimming, for other scenarios please refer to 667/HE/20664/000

a)Volt drop does not exceed max limit shown.

b)MAX ELI does not exceed target max ELI.

c)Minimum conductor size is less than the size of the cores used (The Steel wiring Armouring will also sufficient).

Note for all of the above extra cores may be used to assist in bringing the design within requirements (no more than 3 dcores in parallel).

The completed sheets sheets should be signed and filed with the design.

Site Reference: ??Issue ? Page 1

JUNCTION CABLING DESIGN CERTIFICATION667/DS/20664/000

7APPENDIX A Verification Calculations

Notes on Design Certification:-

Note 1

Cabling and armouring impedances are based on worst case figures from STC cable suppliers.

Note 2

For the Voltage drop for the designed installation to be acceptable it should be less than 4% as noted in section 525 of the IEE Regs BS7671. The calculations for voltage drop in this document are based on the worst case current for the aspects used in the installtion and a RED/AMBER starting condition. If other than standard Tungsten Halogen lamps are used then you may need to refer to the signal suppliers details to obtain the current required. However if the voltage drop is within the acceptable 4% limit using the figure given for Tungsten Halogen, you need not necessarily consider other lamps types, as in general other lamps have lower current requirements.

Note 3 As noted in Note 1 above the IEE Regs sets the voltage drop limit within an installtion at 4% (section 525) and the value highlighted in red (9.2 volts) is 4% of the nominal 230 volt supply.

Note 4

For the earth loop impedance of the design to be acceptable, the calculated Earth Loop impedance must be less than the target impedance selected from the Installation Handbook for the particular controller and dimming voltage, (handbook 667/HE/20664/000 can be used for STC controllers). (NB As the dimming voltage is taken into account in the target impedance design calculations do not need to consider this).

In the IEE regs all earth loop impedance calculations are normalised to the likely measurement temperature of 20 Celcius (as this allows for comparison when measuring this value during the test and inspection phase of an installation),hence the values calculated here are normalised to this same 20 celcius.

The figures calculated include the impedance as for the supply as given by the electricity board supplier, and thus are higher by this same amount than the loop impedances given in section 5 of this document.

Note 5

For the earth loop impedance of the design to be acceptable, the calculated Earth Loop impedance must be less than the target impedance selected from the Installation Handbook for the particular controller and dimming voltage, (handbook 667/HE/20664/000 can be used for STC controllers). (NB As the dimming voltage is taken into account in the target impedance design calculations do not need to consider this).

Note 6

The minimum cross sectional area for a conductor is calculated as noted in the IEE regs 543-01-03, and provided the conductor size in the cable used is greater than this calculated figure, this part of the design is acceptable.

8APPENDIX B COMPLEX DUCTING CAPACITIES

Site Reference: ??Issue ? Page 1