Class II Based Signalling Power Supplies. Tahir Ayub Senior Design Authority Engineer IP Signalling, Signalling Innovations Group

Transcription

1 Class Based Signalling Power Supplies Tahir Ayub Senior Design Authority Engineer P Signalling, Signalling nnovations Group 1

2 Signalling Power Systems Utility ntakes Signalling Supply Point (SSP), Principal Supply Point (PSP) Signalling Power Distribution System nterface to final Signalling Loads Date Tahir Ayub Railway LV Systems 2

3 Signalling Distribution System Utility PSP SP LOC Asset

4 T System Operation Line side Equipment PSP/SSP 650V PSP 400/650 TX Power Enclosure C e C e C e C e C e C e 650/110 Tx 325V 325V Signaling Load Earthing System (R A )

5 T ndividual irst ault (ECP) Line side Equipment 650V R PSP 400/650 TX Power Enclosure C e C e C e C e C e C e 650/110 Tx Signaling Load Earthing System (R A ) Elevated Voltage between exposed conductive part and earth dependant on cable length and impedance of Ra. Very unlikely to exceed 60V.

6 T ndividual irst ault (Cable) Line side Equipment 650V PSP 400/650 TX R Power Enclosure C e C e C e C e C e C e 650/110 Tx Signaling Load Earthing System (R A ) Very Small Residual risk of Direct Contact on exposed cables. The risk is consistent with installations with unarmoured cables

7 T ndividual Second ault R PSP 400/650 TX R Residual risk of Direct Contact on exposed cables. The risk is consistent with installations with unarmoured cables

8 T ndividual Second ault (ECP) R PSP 400/650 TX R Vt Vt Vt Touch Voltage ault Current Elevated Voltage between Exposed Conductive Part and Earth likely to be very small (<60V)

9 T ndividual Second ault (Same ECP) R PSP 400/650 TX R Vt System protection not rated to disconnect on L-L or 2 L-E fault Vt Touch Voltage ault Current Elevated Voltage between exposed conductive parts and earth likely to be > 60V

10 T ndividual Line to Line ault R PSP 400/650 TX Protection must operate before thermal damage Vt Touch Voltage ault Current

11 T Collective System Line side Equipment 1 Line side Equipment X R PSP 400/650 TX Collective earth Power Enclosure 650/110 Tx Circuit Protective Conductor (CPC) Other LOC or REB nstallations Power Enclosure 650/110 Tx CPC PSP Earthing System Signaling Load Signaling Load Earthing System Typically 10 Ohms (SS8503) Earthing System Typically 10 Ohms (SS8503)

12 T Collective irst ault (Cable) R PSP 400/650 TX CPC Vt Vt Vt Vt Vt Touch Voltage ault Current Elevated Voltage between Exposed Conductive Part and Earth likely to be very small (<60V). All location cases will see an elevated voltage. Vt dependant on local earth impedance and cable distribution length

13 T Collective Second ault R R PSP 400/650 TX CPC Protection must operate to manage lethal touch voltages Vt Vt Vt Vt Vt Touch Voltage ault Current Elevated Voltage between Exposed Conductive Part and Earth likely to be very lethal (>60V) and is dependant on voltage divider produced by current passing through the CPC and Local earth. This could reach half system voltage depending on all location cases. Vt dependant on local earth impedance and cable distribution length

14 T Collective Second ault (CPC Optimisation) R R PSP 400/650 TX CPC Protection must operate to manage lethal touch voltages Vt Vt Vt Vt Local Earth mpedance utilised to optimise CPC Vt Touch Voltage ault Current Elevated Voltage between Exposed Conductive Part and Earth likely to be very lethal (>60V) and is dependant on voltage divider produced by current passing through the CPC and Local earth. This could reach half system voltage depending on all location cases. Vt dependant on local earth impedance and cable distribution length. f Local earth is not maintained then the elevated voltage could be lethal at the ECP.

15 T Collective Line to Line ault R PSP 400/650 TX CPC Protection must operate before thermal damage Vt Touch Voltage ault Current

16 Class Engineering Strategy Engineering Strategy Reduced CAPEX costs without reducing safety mprovement in Personnel Safety Reduction in System Risk Compliant to Standards Reduced Maintenance Burden Greater Tolerability to DC Corrosion Simplified Earthing and Bonding in AC Electrified Areas Ability to integrate into Legacy Systems

17 Class Proposal Reduce the probability of insulation failure in the LOCs and REBs to a negligible level so that power supply equipment enclosures need not be earthed for protection, so earthing or bonding to a CPC is not necessary. Utilising Class Equipment as a protective measure against electric shock Utilising a 2-core cable Distribution Strategy in place of a 3-core Strategy Realise the opportunity of complying with the requirements of BS 7671 Realise the opportunity of reducing costs associated with signalling power supplies

18 Class Strategy No Circuit Protective Conductor (CPC)

19 Class Strategy Double nsulation or Reinforced nsulation

20 Class Scope The Class Based Design Solution is to be implemented into: New Build Signalling Power Distribution Systems Existing Signalling Power Distribution Systems [3-core Armoured cable - CPC based system] Legacy Signalling Power Distribution Systems [2-core Unarmoured cable system]

21 Design Strategy Location Case/REB Equipment Class Switchgear Housings Class Signalling Transformers Encased Cabling between Class Switchgear and Class Signalling Transformer Cable Consumables (Glands, Joints, Terminations etc) Distribution Equipment 2 Core Enhanced Unarmoured Cable OR 2 Core Armoured Solid Bonded Cable

22 Solid Bonded Armoured Cable Solution EPR M Line side Equipment 1 BS 5467 Armoured Cable Line side Equipment X PSP 400/650 TX Gapped MET Class Power Enclosure Class 650/110 TX MET Class Power Enclosure Class 650/110 TX Signaling Load Signaling Load Earthing System (R A ) Earthing System (R A )

23 Enhanced Unarmoured Cable Solution EPR M Line side Equipment 1 Enhanced Unarmoured Cable Line side Equipment X PSP 400/650 TX Class Power Enclosure Class Power Enclosure MET Class 650/110 TX MET Class 650/110 TX Signaling Load Signaling Load Earthing System (R A ) Earthing System (R A )

24 Risk Assessment Results Risk of electrocution inside the LOC will, in practical terms, be removed by the introduction of Class equipment. Power cable options ranked in order of safety are as follows: 1.Armoured, solid bonded (=1 st ) 2.Enhanced unarmoured (=1 st ) 3.Armoured, resistance bonded 4.Armoured, direct bonded Other performance factors considered: Conclusion Reliability, Availability, Maintainability, Logistics and Whole-Life Costs. The Enhanced Unarmoured Cable option presents the highest overall level of Safety.

25 Legacy, Existing and Class Schemes Stage 1 Basic Comparison Table eature Legacy Existing Class Safety < Norm > Availability of supply = Norm > Compliance with Standards N Y Y Maintenance burden > Norm* < Ease of fault location = Norm = Resilience to corrosion > Norm > mmunity to stray a.c. currents > Norm > * Assumes design relies on earth electrodes as well as CPC to control touch voltages 25 Document Title 18 ebruary 2014

26 Maintenance Comparisons with Legacy and Existing Systems Maintenance factor Solid Bonded Armoured Cable (Class ) Enhanced Unarmoured Cable (Class ) 1 st inspection Reduced dependency on LOC electrode condition No dependency on LOC electrode condition Periodic inspection Reduced dependency on LOC electrode condition Armour continuity/loop impedance test required No dependency on LOC electrode condition Mid life degradation Reduced dependency on LOC electrode condition Armour/gland corrosion No dependency on LOC electrode condition Cable troughs and ducts maintained in good order mpact of possession restriction No impact No impact

27 PRAMS Conclusion Cable options ranked in descending order of preference PRAMS ranking of cable options 0 = lower, 1 = higher Performance Reliability/Availability Maintainability Personnel Safety System Enh UnArm Arm solid

28 Cable mpact & Crush Tests mpact Tests Crush Tests

29 Cable Damage Tests mpact Tests Armoured Cables maximum 6 impacts to failure Enhanced Unarmoured Cables 26 impacts, no failure Crushing tests Armoured Cables maximum 1.2 tonnes to failure Enhanced Unarmoured Cables, minimum 2.2 tonnes to failure The tests showed that the Enhanced Unarmoured Cable design has greater resistance to impact and crushing faults than a standard Armoured cable.

30 Safety Case The update of the Safety Case from Stage 1 was undertaken to incorporate the results of the MECA and PRAMS analysis The report presents evidence that the project has reached a stage where the identified design options, may be selected for detailed design. Conclusions There is no identified safety reason to prevent the design development stage of Class Equipment using Enhanced Unarmoured Cable proceeding. t is important to recognise that Armoured Solid Bonded Cables remain a viable alternative both in terms of risk and standards compliance however, MECA analysis identified the highest failure mode criticality is associated with the use of Armoured Cable.

31 New Standards NR/L2/ELP/27408 Product Specification for Signalling Power Distribution Cables NR/L2/ELP/27409 Product Specification for unctional Supply Points (SP) NR/L2/SG/30007 [ssue: 2] Product Specification for Power Transformers for Signalling Systems NR/L2/ELP/27410 Specification for Class Based Signalling Power Distribution Systems

32 solating Overcurrent TX Device System Transformation nsulation Monitor Enhanced Unarmoured Cable Enhanced Unarmoured Cable Enhanced Unarmoured Cable PSP nstallation Class SP Switchgear Assembly Conduit System Class Hybrid SP solating Transformer Signalling Load Signalling Load PSP Earthing System Signalling Earthing System Signalling Earthing System Date

33 nnovating through Collaboration Date