10 Class II Based Power Supplies - IRSE II Based Power... · IT System Operation PSP/SSP Line side...
Transcript of 10 Class II Based Power Supplies - IRSE II Based Power... · IT System Operation PSP/SSP Line side...
Class II Based Signalling Power SuppliesTahir Ayub
1
Senior Design Authority EngineerIP Signalling, Signalling Innovations Group
Date 18.08.10 Tahir Ayub Railway LV Systems 2
Signalling Power SystemsUtility Intakes
Signalling Supply Point (SSP), Principal Supply Point (PSP)
Signalling Power Distribution System
Interface to final Signalling Loads
Signalling Distribution System
Utility PSP FSP LOC Asset
IT System Operation
PSP/SSP
Line side Equipment
650/110 Tx
Signaling Load
Power Enclosure
PSP 400/650 TX
Earthing System (RA)
325V 325V
Ce Ce Ce Ce Ce Ce
650V
IT Individual – First Fault (ECP)
Line side Equipment
650/110 Tx
Signaling Load
Power Enclosure
Ce Ce Ce Ce Ce Ce
650V
IF
IF
IFIFIFIFIF
IF IFIF
IF IF IF
RF
Earthing System (RA)
PSP 400/650 TX
Elevated Voltage between exposed conductive part and earth dependant on cable length and impedance of Ra. Very unlikely to exceed 60V.
IT Individual – First Fault (Cable)
Line side Equipment
650/110 Tx
Signaling Load
Power Enclosure
Ce Ce Ce Ce Ce Ce
650V
IF
IF
IFIF
IF IFIF
IF IF IF
RF
Earthing System (RA)
PSP 400/650 TX
Residual risk of Direct Contact on exposed cables. The risk is consistent with installations with unarmoured cablesIF Very Small
IT Individual – Second Fault
PSP 400/650 TX
IF
IF
IF
IF
RF
RF
Residual risk of Direct Contact on exposed cables. The risk is consistent with installations with unarmoured cables
IF IF IF
IT Individual – Second Fault (ECP)
PSP 400/650 TX
IF
IF
IF
IF
RF
RF
Elevated Voltage between Exposed Conductive Part and Earth likely to be very small (<60V)
IF
IF IF IF
Vt Vt
Vt Touch VoltageIF Fault Current
IT Individual–Second Fault (Same ECP)
PSP 400/650 TX
IF
IF
IF
IF
RF
RF
Elevated Voltage between exposed conductive parts and earth likely to be > 60V
IF
IF IF IF
Vt
Vt Touch VoltageIF Fault Current
IFIF
System protection not rated to disconnect on L-L or 2 L-E fault
IT Individual – Line to Line Fault
PSP 400/650 TX
IF
IF
IF
IF
RFIF
IF IF IF
Vt Touch VoltageIF Fault Current
IFIF
Protection must operate before thermal damage
IT Collective – System
650/110 Tx
Signaling Load
Power Enclosure
Earthing System Typically 10 Ohms (SSI8503)
RF
Line side Equipment X
650/110 Tx
Signaling Load
Power Enclosure
Earthing System Typically 10 Ohms (SSI8503)
Other LOC or REB Installations
Circuit Protective Conductor (CPC)Collective earth
CPC
Line side Equipment 1
PSP Earthing System
PSP 400/650 TX
IT Collective – First Fault (Cable)
PSP 400/650 TX
IF
IF
IF
IF
RF
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
IF
IF IF
Vt Vt
Vt Touch VoltageIF Fault Current
CPC
VtVt
IT Collective – Second Fault
PSP 400/650 TX
IF
IF
IF
IF
RF
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
IF
IF IF
Vt Vt
Vt Touch VoltageIF Fault Current
CPC
VtVt
RF
Protection must operate to manage lethal touch voltages
IF
IT Collective–Second Fault (CPC Optimisation)
PSP 400/650 TX
IF
IF
IF
IF
RF
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. If Local earth is not maintained then the elevated voltage could be lethal at the ECP.
IF
IF IF
Vt Vt
Vt Touch VoltageIF Fault Current
CPC
VtVt
RF
Protection must operate to manage lethal touch voltages
IF
Local Earth Impedance utilised to optimise CPC
IT Collective – Line to Line Fault
PSP 400/650 TX
IF
IF
IF
IF
IF
IF IF
Vt Touch VoltageIF Fault Current
CPC
RF
Protection must operate before thermal damage
Class II Engineering Strategy
Engineering Strategy Reduced CAPEX costs without reducing safety Improvement 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
Class II 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 II 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
Class II Strategy
No Circuit Protective Conductor (CPC)
Class II Strategy
Double Insulation or Reinforced Insulation
Class II ScopeThe Class II 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]
Design Strategy
Location Case/REB Equipment
Class II Switchgear Housings
Class II Signalling Transformers
Encased Cabling between Class II Switchgear and Class II Signalling Transformer
Cable Consumables (Glands, Joints, Terminations etc)
Distribution Equipment 2 Core Enhanced Unarmoured Cable
OR 2 Core Armoured Solid Bonded Cable
Solid Bonded Armoured Cable SolutionE
PR
PSP 400/650 TX
Line side Equipment X
Class II 650/110 TX
Signaling Load
Class II Power
Enclosure
IM Line side Equipment 1
Class II 650/110 TX
Signaling Load
Class II Power
Enclosure
Earthing System (RA) Earthing System (RA)
BS 5467 Armoured Cable
MET MET
Gapped
Enhanced Unarmoured Cable SolutionE
PR
PSP 400/650 TX
Line side Equipment X
Class II 650/110 TX
Signaling Load
Class II Power
Enclosure
IM Line side Equipment 1
Class II 650/110 TX
Signaling Load
Class II Power
Enclosure
Earthing System (RA) Earthing System (RA)
MET MET
Enhanced Un-armoured Cable
Risk Assessment Results Risk of electrocution inside the LOC will, in practical terms, be removed by the
introduction of Class II equipment.
Power cable options ranked in order of safety are as follows:
1.Armoured, solid bonded (=1st)
2.Enhanced unarmoured (=1st)
3.Armoured, resistance bonded
4.Armoured, direct bonded
Other performance factors considered:
• Reliability, Availability, Maintainability,
• Logistics and Whole-Life Costs.
ConclusionThe Enhanced Unarmoured Cable option presents the highest overall level of Safety.
18 February 2014Document Title25
Legacy, Existing and Class II Schemes
Feature Legacy Existing Class II
Safety < Norm >Availability of supply = Norm >
Compliance with Standards N Y Y
Maintenance burden > Norm* <
Ease of fault location = Norm =
Resilience to corrosion > Norm >
Immunity to stray a.c. currents > Norm >
* Assumes design relies on earth electrodes as well as CPC to control touch voltages
Stage 1 Basic Comparison Table
Maintenance Comparisons with Legacy and Existing Systems
Maintenance factor
Solid Bonded Armoured Cable(Class II)
Enhanced Unarmoured Cable(Class II)
1st 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 requiredNo dependency on LOC electrode condition
Mid life degradation
Reduced dependency on LOC electrode condition
Armour/gland corrosion
No dependency on LOC electrode conditionCable troughs and ducts maintained in good order
Impact of possession restriction
No impact No impact
PRAMS Conclusion
Cable options
ranked in descending
order of preference
PRAMS ranking of cable options0 = lower, 1 = higher
Performance Reliability/Availability Maintainability
Safety
Personnel System
Enh UnArm
1 1 1 1 1
Arm solid 0 0 0 0 0
Cable Impact & Crush Tests
Impact Tests Crush Tests
Cable Damage Tests
Impact 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.
Safety Case
The update of the Safety Case from Stage 1 was undertaken to incorporate the results of the FMECA 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 II Equipment using Enhanced Unarmoured Cable proceeding.
• It is important to recognise that Armoured Solid Bonded Cables remain a viable alternative both in terms of risk and standards compliance however, FMECA analysis identified the highest failure mode criticality is associated with the use of Armoured Cable.
New Standards
NR/L2/ELP/27408 Product Specification for Signalling Power Distribution Cables
NR/L2/ELP/27409 Product Specification for Functional Supply Points (FSP)
NR/L2/SIG/30007 [Issue: 2] Product Specification for Power Transformers for Signalling Systems
NR/L2/ELP/27410 Specification for Class II Based Signalling Power Distribution Systems
Date 08.11.12 32
System Transformation
PSP Installation
Signalling Earthing System
OvercurrentDevice
Enhanced Unarmoured Cable
Insulation Monitor
Class II FSP Switchgear Assembly
Conduit System
Class II Hybrid FSP Isolating Transformer
PSP Earthing System
Enhanced Unarmoured Cable
Signalling Earthing System
Enhanced Unarmoured Cable
IsolatingTX
Signalling Load Signalling Load
Date 08.11.12 33
Innovating through Collaboration