Download - Tvss Design
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Section 5: TVSS Design & Application
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TVSS Design Concept for AC Applications
LOAD
Incoming Transient Superimposed on Sinewave
AC Power from Utility
$$$Equipment Costs Downtime
Line
N-G Bond/Transformer
Neutral
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TVSS Design Concept for AC Applications
TVSS LOAD
Incoming Transient Superimposed on Sinewave
AC Power from Utility
Suppress HarmfulTransient EnergyBefore ReachingCritical Loads
Line
Neutral
N-G Bond/Transformer
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uTwo Main Goals of TVSS Design:uMinimize clamp (let-through) voltage to the load
uMaximize peak amperage handling capability
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AC TVSS Design Considerations
Time
Vrms
Vpeak
Vclamp
Voltage
u Vclamp must allow for utility voltage variations, but
remain low enough to be effective against transients.
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AC TVSS Design Considerations
u Factors That Affect TVSS Let-Through Voltage:
u Type and quality of components
u Nominal clamp voltage of components
u TVSS design efficiency
u System voltage configuration
u Amount of peak amperage passed through the system
u Rise time of transient waveform
u Installation of the TVSS device
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Installation Option: Parallel Connection
M
TransferSwitch
Generator Feed
Meter/Disconnect
MDP
TVSS
To Critical Loads:RectifiersComputersEtc.
N-G Bond
Ground Rod
Install with:*Minimum Lead-Length*Maximum Wire Size*No Tight Bends, Crimps
VerifyIntegrity
60 A
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Connection Method: Parallel
L1 Load
L2 Load
Additional Lead-Lengthwith Parallel Connection
TVSS
Equivalent CircuitPhase Busses
N
N
L1
L2
TVSS
MDP
u Features:u Easily installed with existing systemu To service, may disconnect only power to TVSSu If TVSS sacrifices, down line load is still powered
u Concerns:u Requires some extra lead-length for parallel connection
240/120 V 1ΦΦL1 L2
N
L1
L2
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TVSS Operation: Let-Through Voltage
Z|| Path = R|| Path + L|| Path
Z“ON” = R “ON” + L“ON”
VLet-Through
VLet-Through = VClamp + IT (R|| Path + R“ON”) + (L|| Path + L“ON”)
Transient Voltage
Normal Utility Voltage
Line
Neutral
IT
N-G Bond
LOAD
TVSS
dIT
dtPage 5 - 7
Note: || = Parallel
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Let-Through Voltage Components
VLet-Through
VClamp
IT
Peak Voltage Seen by Critical Equipment
Initial Clamp Voltage of TVSS Device (tested at 1 mA)
Transient Current Diverted Through Suppressor
Impedance of Wires/Connections To/From Parallel TVSS Device
Finite Resistance of TVSS Technology when Suppressing Current
Factors include: Lead-Length, Wire Gauge, Bends in Wire Path….
*Yields UL 1449 Rating
VLet-Through = VClamp + IT (R|| Path + R“ON”) + (L|| Path + L“ON”)dIT
dt
Z|| Path=R|| Path+L|| Path
Z“ON”=R “ON”+ L“ON”
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AC TVSS Install Issues
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AC TVSS Install Issues
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Installation Option: Kelvin Connection
M
TransferSwitch
Generator Feed
Meter/Disconnect
MDP /TVSS
To Critical Loads:RectifiersComputersEtc.
N-G Bond
Ground Rod
VerifyIntegrity
Optimum Installation:Kelvin-Type ConnectionAllows ZParallel Path ≅ 0
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Connection Method: Kelvin
L1
L2
L1 Load
L2 Load
Equivalent CircuitFeed-Through TVSS
TVSS
MDP
Neutral Buss
PhaseBusses
u Features:u Minimum Parallel suppression path only through modulesu If TVSS sacrifices, down line load is still powered
u Concerns:u May have to reconfigure existing electrical systemu Input terminals & enclosure must be sized for rated source current
(requires larger panels)u To service TVSS, may have to de-energize downline MDP and loads
N
240/120 V 1ΦΦN
L1 L2
N L1L2
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Installation Options: Series Connection
M
TransferSwitch
Generator Feed
Meter/Disconnect
MDPTVSS
To Critical Loads:RectifiersComputersEtc.
N-G Bond
Ground Rod
VerifyIntegrity
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Connection Method: Series
L1 Load
L2 Load
Equivalent Circuit
TVSS
u Features:u Series Impedance to “Dampen” Incoming Transientu Allows more control over parallel path impedance
u Concerns:u May have to reconfigure existing electrical systemu TVSS doesn’t suppress load-switching transients (it’s upline)u To service TVSS, complete replacement required and downline MDP
and loads must be de-energizedu Larger, heavier panels required for matching rated source current
N L1L2
L
L
L1
L2
Series TVSS(Still has parallel elements)
MDP
Neutral Buss
Phase BussesN
240/120 V 1ΦΦ N
L1 L2
Series Inductors
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Summary of Installation Options
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Features Concerns
Parallel: • Simple Installation• Servicing requires only disconnecting TVSS• If TVSS sacrifices, the load is still powered
• Installation sensitive/ conductor length concerns
Series:
Kelvin: • Minimizes conductor length• If TVSS sacrifices, the load is still powered
• May have to reconfigure existing electrical system• Enclosure size increases• May have to de-energize loads to service unit
• Improved transient response• Minimizes conductor length
• Must reconfigure system• Enclosure size increases• May have to de-energize loads to service or replace the complete unit
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“Common/Normal” Mode Disturbances
Hot (Line)
Neutral
Ground
Time
Normal Mode*Disturbances
Common Mode Disturbances
Disturbance occurring betweenthe phase or neutral conductor,but not at the same moment intime.
Disturbance occurring on both the phase and neutral conductorssimultaneously.
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*Also called Transverse or Differential Mode
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Modes of Protection
u Line-to-Neutral (L-N) Suppression
u Line-to-Ground (L-G) Suppression
u Neutral-to-Ground (N-G) Suppression
u Line-to-Line (L-L) Suppression [Not Shown]
Phase Lines(ΦΦ Lines)
Neutral (N)
Ground (G)ΦΦ Lines - Neutral ΦΦ Lines - Ground Neutral - Ground
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Service Entrance TVSS (N-G Bond)
CriticalEquipment
Close toService
Entrance
Meter/SiteDisconnect
*N-G Bond
TVSS
MDP
Neutral and Ground are Bonded (Therefore, at the Same Potential)Phase - Neutral TVSS RequiredNeutral - Ground TVSS Not Required (Neutral bonded to Ground)Phase - Ground TVSS Redundant (Neutral bonded to Ground)
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Remote Ground TVSS
CriticalEquipmentFar From
ServiceEntrance
Meter/SiteDisconnect
*N-G Bond(if present)
TVSS
MDP
Resistance/Inductancefrom Conductor Length
Where there is a Remote Ground or N-G Bond does not exist:There may be a significant difference in Neutral and Ground Potentials.Therefore, all modes of suppression may be used (Φ-N, Φ-G, N-G).* Φ-N along with N-G protection may make Φ-G redundant
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AC Electrical Protection
TVSS
TVSS
HVAC
Computers
TVSS
Gen
M
Meter
ACDisconnect
BuildingDisconnect
TransferSwitch
MainDistribution Panel
SubDistribution Panels
Disconnect
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Summary of Protection Modes
u Systems With Neutral (Grounded) Conductoru Line to Neutral (L-N) protection is a must!
u N-G may be necessary if far away from a system N-G bond.
u L-L will be redundant and often not recommended.
u L-G may be necessary if far away from a system N-G bond, butraises safety issues.
u Systems Without a Neutral (Grounded) Conductoru Line to Line (L-L) protection is a must!
u L-G may be unnecessary and may raise safety issues.
u Effectiveness of Protection Modes Depends on theType, Coordination and Quality of the ComponentsTherein!
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MOV Applications: Simplest Design
u Features:u Possible High Joule / Peak Amperage Rating
(Joules=Energy=Volts*Amps*Time)u Concerns:
u MOV Degradation Leads to Device Failureu Wide Clamp Voltage Range - Typically 10 - 12%u One Current Path - Clamp Voltage Rises as Current
Increases
Indicator Light
MOV
Line
Neutral
Fuse
LOAD
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MOV Applications: Matrix Design
u MOV Matrix Benefitsu Parallel paths increase joule/peak amperage handling
(Joules=Energy=Volts*Amps*Time)
u Less current per path = less degradation of each MOV
u Series MOVs allow for precise nominal clamp selection
MOV
Line
Neutral
LOAD
MOV
MOV
MOV
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SAD Applications: Matrix Design
R x (VoltageComponent)Yields Initial VoltageClamp Level
C x (CurrentComponent) Yields Current Handling
R x C Matrix for TVSS Design
R: # of RowsC: # of Columns
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SAD/MOV Applications
u Typical Abilities:u SAD clamps lower than MOV to take most transientsu SAD clamping characteristics and response timeu MOV backup for “insurance” against large eventsu Independent primary and secondary fuses and alarmsu Remote status and easy field repairability
Fuse
SAD Matrix MOV Matrix
Fuse
P
Primary Stage
Secondary Stage
S
Line
Neutral
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Telco/Data TVSS Design Considerations
u Various signal levels require specific clamp voltagesu Plain Old Telephone Service (POTS) = 120 - 190 Vpeak
u T-1 (data) = 3 - 8 Vpeak
u Twisted pair, coax, PC connections = 5 - 50 Vpeak
u Operating frequency will affect TVSS design usedu Applications range from DC to GHz
u Method of interfacing will depend on your equipmentu POTS / T-1 / Data connect via RJ jack, twisted pairs, M66
block…
u TV / Cable / Radios utilize coax, twisted pairs, customcabling...
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Typical Telco (T1) Signal Types and Levels
Vpk
t (sec)
Vpk
t (sec)
Vpk
t (sec)
Vpk
t (sec)
Tip Voltage Ringer Voltage
~50 VDC
~100 Vup to ~150 V
Sum
Digital-Level Signal (After Smartjack)
~ ±3-8 V
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T1 TVSS Installation Guidelines
DSX
M66 BlockTelco Service Entrance
Install with:*Minimum Lead-Length*Maximum Wire Size*No Tight Bends, Crimps
TVSS Channel Bank
Radios
DC PowerRect
To Interior Halo andMaster Ground Bar (MGB)
4-WireT-Span
Network Interface Unit (NIU)
Wireless Communications Facility T-1 Service
Buried Ground Ring (Sometimes via Master Ground Bar)
Telco Ground Bar (TGB)
Telco Termination
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TVSS Ground
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Telco (T1) TVSS Design
Gas Tube
Designed Clamp Voltage of SAD Depends on Peak Signal Level
Modes of Protection:Tip - RingTip - GroundRing - Ground
SAD
Blocking Diodes
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RSeries= 0.5 ΩΩ
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Radio Frequency (RF) TVSS Concepts
u Protect Coaxial Cable Sheath
u Typically done with grounding kits on tower and at RF entrance of building
u Protect Center Conductor
Protect ALL Conduction Paths for Coaxial Cable
Grounding Kits
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RF TVSS Designs: Tuned Isolated Center Conductor
u Featuresu Electrical Isolation of Input/Output Center Conductor
u Concernsu Limited Lifetime of TVSS Componentsu No Indication when TVSS Components Failu Design may be Power Limited (Higher Insertion Losses)u Filters Any DC-Injected Transmission
Discrete TVSS Components:Gas Tubes, MOV’s, etc.
Heliax Superflex
TVSS Device
Chassis Grounded
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RF TVSS Designs: Quarter Wave Short (QWS)
λλ4
t (sec)
λλCenter Frequency ( f ) Cellular: 860 MHz Paging: 920 MHz Lightning: 40-100 kHz
λ = λ = f
c
c = speed of light ≅ ≅ 3.0x108 [m/s]
λλ = wavelength [m]
InitialVoltage Wave
InitialCurrent Wave
Band-Pass Filter
Heliax Superflex
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u Featuresu Purely Physical Device - No Components to Failu Sandia Tests at 800,000 V: N-Type - 48,000 A; DIN-Type - 93,000 Au Not Power Limited - Insertion Losses Extremely Low (≤ ≤ 0.05 dB)
u Concernsu Filters Any DC-Injected Transmission
Band-Pass Filter
RF TVSS Designs: Quarter Wave Short (QWS)
Heliax Superflex
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DC-Injected Center Conductor Protection
Gas Tube Device
Tower Radio Equipment
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u Featuresu Passes DC-Injected Transmission to Power
External Amplifiers
u Concernsu Limited Lifetime and Response Time of TVSS
Components (Maintenance Required)u No Indication when TVSS Components Fail