TVSS
Transient Voltage Surge
Suppression Devices
Thomas Greer
Senior Director – Engineering Services
TLG Services
Agenda
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What is the problem?
Why?
IEEE Recommended
Practices
TVSS Modeling
Q&A
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Voltage Transient
Question:
1.
2.
3.
4.
What is the primary source of
most transient voltages?
Lightning
Circuit switching
Short circuits and outages
All the above
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IEEE Emerald Book, Std. 1100-1999
Transient Surge Impact
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“…Load switching is a common cause of surges in power wiring.”
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“…Depending on the severity of the surge and the susceptibility of the
equipment, three types of occurrences are possible…: data disruption,
hardware stress, and hardware destruction.”
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“…effects ranging from simple data upset and corruption to actual
equipment damage.”
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“A single lightning or switching surge often causes immediate, but not
readily apparent physical damage to semiconductor devices. This
damage then finally appears at some later time…”
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“Immediate and obvious total destruction of hardware components in
a single incident.”
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Power Quality Strategy
99.999??
Redundancy
Generator
Battery Back-up
Surge Protective
Devices (SPD/TVSS)
Noise Filters
Wiring
Grounding & Bonding
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IEEE Emerald Book, Std. 1100-1999*
“…a listed and properly
rated surge protective
device should be
applied to each
individual or set of
electrical conductors
(e.g. power, voice,
data) penetrating ... a
structure”
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Telecom Building
Surge
Protection
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z Generator
Input
z T1 Lines
z RF
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Clamping Action of Transient Voltage Surge
Suppressor
TVSS
Surge
Current
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“Protected”
Load
Equipment
Clamped
Surge
Voltage
Criteria for Suppressor Selection
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Surge current
Redundancy
UL suppression voltage
Modes of suppression
EMI / RFI filtering
Life cycle testing
Monitoring
Application Analysis
Warranty
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AC Power SPD’s (Surge Protective Devices)
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Automatic Transfer Switches
Question: Which lines on an automatic transfer
switch should have TVSS installed ?
1.
2.
3.
4.
The primary input
The secondary input
The output
All the above
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Typical Telecom Switchgear
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What Are Low Voltage Lines ?
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Telephone lines
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Ethernet, Cat 5, Cat 6
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Security Panel Circuits
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Fire Alarm Circuits
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1 – 300 Volts DC
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Why Protect Low Voltage Lines
LIGHTNING - Enters through telephone, power or buried cable
lines.
ELECTROSTATIC DISCHARGE - Caused by build-up and
discharge of energy in dry climates.
POWER CROSS - Communications line comes in physical contact
with an electrical power line
INDUCTION - Induced from magnetic fields surrounding power
and other lines near communications cables.
POWER FAULTS - Currents introduced into power line neutral
bonded to TELCO cables, transferred to communications
equipment.
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IEEE Recommended Practice
8.6.6 . “Electronic
equipment containing
both ac power and data
cabling should also be
properly protected via
surge protective devices
on both the ac power and
data cables.”
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What is Primary Protection
Voltage Clamp
500 – 750 Vdc
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What is Secondary Protection
• UL 497A Secondary Protectors: A
secondary protection system must be
listed for and be installed in series
between the primary protector and the
protected equipment. All secondary
protector systems must safely limit overcurrents to less than the current carrying
capacity of the telephone cables and
equipment.
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What is Secondary Protection
Voltage Clamp 6 – 200 Vdc
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Normal Condiions
A
B
Low Voltage / Data Lines
0 Volts
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0 Volts
Transient Strike
A
B
Low Voltage / Data Lines
0 Volts
Sneak Currents Travel
Point B to A
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3000
Volts
Protection Devices
Question: What components are used in hybrid Surge
Protective Devices ?
1.
2.
3.
4.
MOV’s and SAD’s (Metal Oxide Varistors &
Silicon Avalanche Diodes)
GDT’s (Gas Discharge Tubes)
PTC’s (Positive Temperature Coefficient
Thermistor)
All of the above
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Metal Oxide Varistor - MOV
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Silicon Avalanche Diode - SAD
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Gas Discharge Tube - GDT
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TVSS Modeling
Clamping Voltage Vs. Level of Technology
250
200
Clamping
Voltage
Gas Tubes
MOV
SAD
Hybrid
150
100
50
0
Technology
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TVSS Modeling
Surge Current Capability as a Function of Technology
Current (I)
AMPS
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
Gas Tubes
MOV
SAD
Hybrid
Technology
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Fuse
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Positive Temperature Coefficient
Thermistor - PTC
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TVSS Modeling
Durational Overcurrent / Sneak Currents
5000
1000
Number of
Occurrences
Before Failure
1
0
1/2 Amp Durational Current
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PTC
Glass Fuse
TVSS Modeling
SAD
Extremely Fast
Clamping
GDT
Very High Surge
Current Rating
Over-Current Protection
PTC
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Separates Components
TVSS Modeling
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Low Voltage Line Protectors
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How To Select
•
Operating Voltage ?
•
Steady State Current ?
•
Data Rate ?
•
Type of Termination ?
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Conclusion:
Implement your Power Quality Strategy
99.999??
Redundancy
Generator
Battery Back-up
Surge Protective
Devices (SPD/TVSS)
Noise Filters
Wiring
Grounding & Bonding
Emerson Confidential