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Ethernet Surge Protective Device (SPD) Electrical Design Considerations Presented by: Mick Maytum ICT Surge Protection Expert ictsp-essays.info Contents • Surge types Common-mode, Differential-mode unbalanced and balanced • Ethernet system • Unexpected consequences Surge generators, Protective functions • General Port connections, Protective function • Surge tests Common-mode, Differential-mode, Common-mode to differentialmode conversion, Durability, Cable screen terminal • DC tests Insulation resistance, Voltage drop • References 2/19/2017 Ethernet SPD Electrical Design Considerations 2 Surge Types - Common-mode voltage Equipotential conductor group Reference potential surge appearing equally on all conductors of a group at a given location 2/19/2017 Ethernet SPD Electrical Design Considerations 3 Surge Types - Differential-mode voltage a) balanced and b) unbalanced Equipotential conductor group 1 Equipotential conductor group 1 A Equipotential conductor group 2 Link Reference potential a) Equipotential conductor group 2 B b) surge occurring between any two conductors or two groups of conductors at a given location 2/19/2017 Ethernet SPD Electrical Design Considerations 4 Surge Types - Differential-mode voltage in an Ethernet system 1 PoE mode A powering feed pair PoE mode B powering feed pair Signal twisted pair conductor to conductor differential-mode surge 1 2 2 3 3 6 6 4 4 5 5 7 7 8 8 Powering pairs pair to pair differential-mode surge Ref: Surges and their mitigation Modes of PROTECTION and SURGE 2/19/2017 Ethernet SPD Electrical Design Considerations 5 Ethernet system • At surge frequencies the port loading is effectively resistive capacitive and non-linear. • The port Ethernet transformer presents a d.c. load of about 1 W + 1 W • The PoE PD circuits consists of a diode bridge, avalanche diode and capacitance. • The PoE PSE circuits consists of a regulating IC, series pass element, some protection and capacitance. • Most of the PoE PD and PSE ICs are rated about 100 V 2/19/2017 Ethernet SPD Electrical Design Considerations 6 Unexpected consequences - Surge generators 1 Differential surge on Ethernet signal port <2/>10, 800 V, 100 A 100 A 90 A 80 A Generator current (green) 70 A 60 A 50 A ≠ (not the same result) 40 A 30 A Secondary current (blue) 20 A 10 A 0A 0 µs 1 µs 2 µs 3 µs 4 µs 5 µs 6 µs 7 µs 8 µs 9 µs 10 µs 100 A 90 A 80 A 1.2/50-8/20 , 800 V, 100 A Generator current (green) 70 A 60 A 50 A 40 A 30 A Secondary current (blue) 20 A (shorted secondary) 10 A 0A 0 µs 1 µs 2/19/2017 2 µs 3 µs 4 µs 5 µs 6 µs 7 µs 8 µs 9 µs 10 µs Ethernet SPD Electrical Design Considerations 7 Unexpected consequences - Surge generators 2 40 A 30 A 36 A 3) Secondary winding energy dump 1) Linear 20 A 33 A 30 A 27 A 2) Core saturation 10 A 24 A 21 A 0A 0 µs 1 µs 2 µs 3 µs 4 µs 5 µs 18 A 15 A 40 A 1.2/50-8/20 (blue) <2/>10 (red) <2/>10 (red) 12 A 30 A 9A 20 A 6A 3A 10 A 1.2/50-8/20 (blue) 0A 0A 0 µs 0 µs 1 µs 2 µs 3 µs 4 µs 1 µs 2 µs 3 µs 4 µs 5 µs 5 µs <2/>10, 800 V & 1.2/50-8/20, 1214 V Refs: Ethernet differential surge testing - di/dt Differential surge stress reduction by Ethernet magnetics 2/19/2017 Ethernet SPD Electrical Design Considerations 8 Unexpected consequences – Gas Discharge Tubes - 1 RA Equipment port A RA Equipment port A RAB RB RAB RB B Impulse B IB IA GDTB GDTA Impulse GDTB C GDTA C 9) 10) GDTB conducts and hogs both conductor currents, IA & IB. The summation of GDTB arc voltage and low voltage drop IA x RAB prevents GDTA sparkover . Equipment port suffers a differential surge of IA. 2/19/2017 Ethernet SPD Electrical Design Considerations 9 Unexpected consequences – Gas Discharge Tubes 2 RA Equipment port A RAB RB B IB IA Impulse GDTAB C 11) When the two outer GDT electrodes are independently surged, conduction of both halves occurs in well under 1 µs. Low resistance Ethernet signal ports bridge the two outer electrodes lowering the non-conducting GDT section voltage. The lower electric field voltage field takes longer to attract the conducting section plasma. As a result it can take many microseconds before both GDT sections conduct. Before simultaneous conduction occurs, a major portion of the surge front is applied differentially to the equipment port. 2/19/2017 Ethernet SPD Electrical Design Considerations 10 Unexpected consequences – Gas Discharge Tubes 3 • • • 2/19/2017 Differential port voltage (cyan line, difference between electrode voltages) and surge current (yellow line) for generator voltages of 600 V, 1.5 kV, 2.5 kV and 6 kV. Nominal GDT sparkover 1.1 kV. Graphics created by Tatjana Gazivoda-Nikolic and kindly supplied by Bourns Inc. Ethernet SPD Electrical Design Considerations 11 Unexpected consequences – Gas Discharge Tubes 4 RA RA Equipment port A Equipment port IA A RAB LAB RB B RAB RB IB D1 D3 RD D5 ID D Impulse LDE GDTAB RE RDE E Impulse D2 C D4 D6 IE GDTABDE 12) C Many simultaneous voltage limiting circuit solutions are available. The above two diagrams show circuits using a multi-phase diode bridge and centre-tapped choke approaches. 2/19/2017 Ethernet SPD Electrical Design Considerations 12 General - Port connections • An SPD performance specification should comprehend the connector capability and not just the internal component capability. • A hard-wire connector may be required when the RJ45 contact currents exceed 1 kA or voltages between adjacent contacts will exceed 4 kV. 2/19/2017 Twisted-pair (1, 2) signal 1 Twisted-pair (3, 6) signal 3 Twisted-pair (4, 5) signal 4 Twisted-pair (7, 8) signal 7 Cable screen if present 2 1, 2 & 3, 6 PoE mode A powering feed pair 6 5 4, 5 & 7, 8 PoE mode B powering feed pair 8 Screen Protective earth/ common Ethernet RJ45 contact connections Ethernet SPD Electrical Design Considerations 13 General - Protective function A generic Ethernet SPD performance specification should try to be technology neutral on the surge protective components (SPCs) used in the SPD. SPD 1W SPD 10 nF 10 nF 1W 75 W 1W 75 W Termination circuit 1 nF Termination circuit 1 nF GDT common-mode voltage limiting (partial circuit for only one twisted pair) 2/19/2017 1W Isolating transformer common-mode voltage blocking (partial circuit for only one twisted pair) Ethernet SPD Electrical Design Considerations 14 Surge tests - Common-mode R1 through R8 = 1 W C1 through C4 = 10 nF, 300V Cable port R11 through R14= 75 W Equipment port 1 1 2 2 3 3 6 6 • R1 C1 R11 C2 R12 C3 R13 • • R2 R3 R6 R9 = 5 W SPD • R4 4 4 5 5 7 7 8 8 R5 Generator charge voltage kV 2.5 6 12 Manufacturer defined R7 1.2/50-8/20 combination wave generator C4 R14 R8 C5 PE Screen Screen Termination circuit 1 nF 3 kV reference bar Generator return/Earth 2/19/2017 a b c Common source for maximum stress on breakdown paths Simulated Equipment port Voltage limiting and isolation technologies covered DC tested after impulses Maximum equipment impulse limiting voltage kV 1.0 1.5 2.0 Manufacturer defined d Ethernet SPD Electrical Design Considerations 15 Surge tests - Differential-mode single pair R1 through R8 = 1 W C1 through C4 = 10 nF, 300V SW (1-2) R11 through R14= 75 W Equipment port Cable port 1 R1 1 C1 R11 C2 R12 R2 2 2 3 3 • • • R3 SW (3-6) • R6 6 R9 = 10 W 6 Differential voltage SPD 4 SW (4-5) R4 4 C3 R13 C4 R14 Generator charge voltage kV R5 5 5 7 7 8 8 R7 1.2/50-8/20 Generator R10 = 10 W SW (7-8) R8 Screen C5 PE Screen Termination circuit 1 nF 3 kV reference bar Generator return/Earth 2/19/2017 Individual twisted pair tests Simulated Equipment port Simulated generator current division DC tested after impulses a b c d Ethernet SPD Electrical Design Considerations 2.5 6 12 Manufacturer defined Preferred measured values for 1-2, 3-6, 4-5 & 7-8 Termination peak voltage V 100 200 300 Manufacturer defined Termination peak current A 50 100 150 Manufacturer defined 16 Surge tests - Differential-mode PoE pairs PoE port termination Equipment port Cable port 1 D1 D2 D3 D4 1 2 2 3 3 A 6 R9 = 10 W C1 6 D5 A SPD B SW 4 4 5 5 7 7 • • • D6 D7 D8 D9 • Individual PoE pair tests Simulated Equipment port Simulated generator current division DC tested after impulses B A 1.2/50-8/20 Generator R10 = 10 W B 8 Screen C2 8 PE Screen D10 reference bar Generator return/Earth 2/19/2017 a b c Ethernet SPD Electrical Design Considerations Generator charge voltage kV 2.5 6 12 Manufacturer defined Preferred Peak mode A or mode B termination voltage V 90 95 100 Manufacturer defined 17 Surge tests - Common-mode to differential-mode conversion – single pair Generator current sharing network Equipment port Cable port 1 R1 = 40 W Twisted pair differential voltage Termination circuit R12 = 150 W 1 • • R2 = 40 W 2 2 3 3 6 6 R3 = 40 W R36 = 150 W R6 = 40 W R4 = 40 W SPD 4 4 5 5 7 7 • • Individual twisted pair measurements High impedance equipment port to measure source voltage Equalised generator current division DC tested after impulses R45 = 150 W R5 = 40 W R7 = 40 W 1.2/50-8/20 Generator R78 = 150 W R8 = 40 W 8 8 Screen PE Screen reference bar Generator return/Earth 2/19/2017 a b c Ethernet SPD Electrical Design Considerations Generator charge voltage kV 2.5 6 12 Manufacturer defined Preferred values of differential voltage V 100 200 300 Manufacturer defined 18 Surge tests - Common-mode to differential-mode conversion – PoE pairs Generator current sharing network Cable port 1 R1 = 40 W Termination circuit Equipment port R11 = 1 W 1 R2 = 40 W • • R12 = 1 W 2 2 R3 = 40 W R13 = 1 W 3 3 R6 = 40 W R16 = 1 W 6 6 R4 = 40 W Mode A differential voltage • • Individual twisted pair measurements High impedance equipment port to measure source voltage Equalised generator current division DC tested after impulses R14 = 1 W SPD 4 4 5 5 R5 = 40 W R15 = 1 W R7 = 40 W 1.2/50-8/20 Generator PoE differential voltage R17 = 1 W 7 7 8 8 R8 = 40 W Mode B differential voltage R18 = 1 W Screen PE Screen reference bar Generator return/Earth 2/19/2017 a b c Ethernet SPD Electrical Design Considerations Generator charge voltage kV 2.5 6 12 Manufacturer defined Preferred values of differential voltage V 90 95 100 Manufacturer defined 19 Surge tests - Durability • Little attention is given to impulse durability rather than big number single impulse ratings • Over life SPDs may experience many thousands of surges not just one big one • Further depending on the technology the single and multi-impulse ratings maybe the same (silicon junction) or require major rating reduction due to wear-out (MOVs) • It makes sense to know what the SPD 100 impulse or more impulse rating is 2/19/2017 Ethernet SPD Electrical Design Considerations 20 Surge tests - Cable screen terminal Equipment port Cable port 1 R9 = 5 W SW 1 2 3 1 2 3 1.2/50-8/20 Generator 1 2 2 3 3 6 6 4 5 5 7 7 8 PE Screen Screen reference bar 2/19/2017 • SPD 4 8 Generator return/Earth • • b • Values based on IEC 60603-7-7 SW position 1 checks cable port screen terminal to protective earth (PE) terminal bonding SW position 2 checks equipment port screen terminal to protective earth (PE) terminal bonding SW position 3 checks cable port screen terminal to the equipment port screen terminal. Generator charge voltage kV 2.5 6 12 Manufacturer defined Ethernet SPD Electrical Design Considerations Maximum screen to PE voltage, SW positions 1 & 2 V 40 90 180 Manufacturer defined Maximum screen to screen voltage, SW position 3 V 80 180 360 Manufacturer defined 21 DC tests - Insulation resistance 500 V >2 MW 1, 2 3, 6 SW 7, 8 4, 5 1 1 2 2 3 3 1, 2 6 6 SW 3, 6 2 2 3 3 6 6 SPD SPD W Equipment port Cable port 1 Equipment port Cable port 1 4 4 5 5 7 7 W 7, 8 4, 5 4 4 5 5 7 7 8 8 8 PE Screen Screen Screen 8 Screen reference bar reference bar b Isolating transformer SPD Voltage limiting SPD 2/19/2017 Ethernet SPD Electrical Design Considerations 22 DC tests - Voltage drop Equipment port Cable port 1 1 V12 2 2 3 3 6 6 V36 0.5 A current source SPD 4 4 5 5 7 7 V45 V78 8 8 Screen 2/19/2017 • Important for PoE • Preferred value < 0.5 V • Then total d.c. power feed mode A or B series resistance of the SPD < 0.5 W PE Screen Ethernet SPD Electrical Design Considerations 23 References 1 of 3 Ethernet differential surge testing - di/dt Differential surge stress reduction by Ethernet magnetics Surges and their mitigation Modes of PROTECTION and SURGE Voltages and currents in Ethernet cables due to lightning strokes ETHERNET port surge testing – Test levels and configurations Ethernet Surge Protective Device (SPD) design considerations Recommendation ITU-T K.117 : Primary protector parameters for the surge protection of equipment Ethernet ports 2/19/2017 Ethernet SPD Electrical Design Considerations 24 References 2 of 3 Ethernet ATIS PEG Conference Papers 1999-2012 CD currently available of all 1999-2012 papers ATIS PEG Conference 1999 Papers 10Base-T Surge Protection: Nisar Chaudhry ATIS PEG Conference 2007 Papers Power Over Ethernet (POE) – What is it? How to Protect it?: Mick Maytum ATIS PEG Conference 2008 Papers Ethernet Protection (Once it has Left the Building; Inside the Cell Site): Nisar Chaudhry ATIS PEG Conference 2009 Papers Electrical Protection Considerations for the Deployment of Ethernet Services in the Outside Plant: Larry Payne ATIS PEG Conference 2010 Papers Evolving Ethernet Applications and Protection: Jim Wiese Ethernet Protection: Nisar Chaudhry ATIS PEG Conference 2011 Papers A Comparison of Various Ethernet Protection Solutions: Ben Huang Lightning Damage of the Home Network Ports: Mick Maytum IEEE Std. 802.3 Ethernet ports — Types, Surge Capability and Applications: Mick Maytum ATIS PEG Conference 2012 Papers ONT Damage: Jim Wiese 2/19/2017 Ethernet SPD Electrical Design Considerations 25 References 3 of 3 Ethernet ATIS PEG Conference Papers 2013-2016 Currently downloadable at the PEG Library ATIS PEG Conference 2013 Papers Ground or Not to Ground Ethernet Protection, Part 2: Nisar Chaudhry Optical Network Terminations (ONTs): Lightning Damage and Standards – What’s the Latest Information?: Jim Weise The Ethernet Port Maze, Part 1: Michael (Mick) Maytum The Ethernet Port Maze, Part 2: Michael (Mick) Maytum ATIS PEG Conference 2014 Papers Ethernet Protection-Latest Standards Work: Jim Wiese GbE Port Protection in Exposed Environments: Len Stencel ATIS PEG Conference 2015 Papers Power Over Ethernet (PoE) Part 1- What Is It, How It Is Used, and Lightning Field Failure Analysis: Jim Wiese Power Over Ethernet (PoE) Part 2 – Protecting PoE Against Intra-Building and OSP Environments: Tim Ardley Latest ITU-T Surge Protection K Recommendations: Michael “Mick” Maytum Direct Lightning Strike Surge Propagation in Customer Premises Wiring: Michael “Mick” Maytum Lightning Surge Damage to Ethernet and POTS Ports Connected to Inside Wiring: Joe Randolph ATIS PEG Conference 2016 Papers Protecting PoE PSE and Ethernet to the Latest International OSP Standards: Tim Ardley 2/19/2017 Ethernet SPD Electrical Design Considerations 26