Introduction

Thermionic Valve Technology - Disadvantages

<1000 µJ
Thermionic Valve Technology - Advantages

<10 µJ
Discrete Transistor Technology

Integrated Circuitry
<1 µJ

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Down draughts of cold air
Updraughts of warm air
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Negative charged cloud base
Surface rain
Charge accumulation within cloud

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Progression of a stepped leader

 Economic
 $139 Million property damage in
USA
 $40 Million claims to Factory Mutual
 Personal
 Average 70 fatalities
Lightning’s annual cost (USA)

 Surges also cause:
 System down time
 Lost business opportunities
 System unreliability
Less obvious cost of strikes

Day off?
Before

Permanent retirement !

CAPACITIVE
INDUCTIVE
RESISTIVE
Coupling Mechanisms for Transients

Little or no damage occurs to sub-systems within structure
200KA
High local potential
Lightning Strike to Building

200KA
High local potential
Remote ‘ground’
High potential across insulation
Resistive Coupling into Cabled System

IEC 1000-4-5
European std for transients
FCC Part 68, Bellcore TR-NWT-001089
US Telecommunications
BS6651:1992 Appendix C recommendations in UK
IEEE/C62.41:1991 , REA PE-60, UL1449
AC power SPD test standards
Standards for Surge Protection

Static discharges
Switching transients
Power cable induction
Nuclear Electro Magnetic Pulse
Sources of Transients

Source Field Density
Lightning 3V/m
@10km
Static discharge 20kV at impact
NEMP 50 kV/m
@500km
Rise Time
600V/µs
2kV/ns
5kV/ns
Comparison of Transient Sources

 Diverting surge current to earth
 Clamping output voltage to a safe level
 Does NOT prevent lightning but protects against effects
Surge Protection Devices

IEC 1000-4-5
European std for transients
BS6651:1992 Appendix C recommendations in UK
IEEE/C62.41:1991 , REA PE-60, UL1449
AC power SPD test standards
Standards for Surge Protection

90%
50%
10%
8µs
20µs
8/20µs Short-circuit Current Pulse - IEC 60-1 t

V
PK
90%
50%
10%
1.2µs
50µs
1.2/50µs Open-circuit Voltage Pulse t

V
PK
90%
50%
10%
10µs
700µs
10/700µs Open-circuit Voltage Pulse t

• Why install SPDs?
– High likelihood of lightning induced transients
– Combustible gases present
– Uncontrolled flashover may cause ignition
SPDs in Zone 0 - IEC 60079-14

 Installation
 Must be installed in Zone 1
 Must be close to Zone 0
 Must withstand 10kA 8/20µs test to
IEC 60-1
Zone 0 Protection - IEC 60079-14

 Simple Apparatus
 Non-energy storing
 non-voltage producing
 Certified
 Gives greater confidence
IS Applications


 Gives recommendations only
 Splits installations into
Categories
 Lots of real-world data
IEEE C62.41 summary

Service Entrance
Category C3
Panelboard
Category B3
Branch Panel
Category A1
Impulse
10kV(1.2,50µs)
10kA(8/20µs)
Ringwave
6kV(1.2,50µs)
3kA(8/20µs)
6kV/500A 100kHz 6kV/500A 100kHz
IEEE C62.41-1991

Cat C
Cat B
IEEE C62.41 Locations
Cat A

IEC 1312 protection zones

 IEEE C37.90
 Standard Surge Withstand Capability (SWC)
Tests for Protective Relays and Relay Systems
 Applies to a system and not individual components
 SPDs will help comply to the standard
IEEE C37.90 summary

 IEC 1000-4-5 (801-5)
 Testing and measurement techniques - Surge immunity test
 Direct lightning is not considered in this standard
 Highest test level specified is 4kV
IEC 1000-4-5 summary

 BS 6651
 Protection of structures against lightning
 Appendix C covers protection of electronic equipment
 Gives advice on
 how to assess lightning risk for an installation
 the level of protection required
BS 6651 summary

Lightning as a Capacitor

Incoming cables
Local Earth
Common mode surges
Voltage shift is the same for both cables

Incoming cables
Difference mode surges
Voltage difference is between cables

Primary Protection Elements

Spark Gap

1
2
2-electrode Gas Discharge Tube

1
Electronic
Apparatus
2
2-electrode GDT in 2-wire loop

1
Electronic
Apparatus
2
3-electrode gas discharge tube

Secondary Protection Elements

Surge Suppression diode
1500W surge rating
Conventional diode
5W steady state rating
Surge Diodes

Metal oxide particles
Power absorption throughout pellet volume
Multiple current paths
Varistors (MOV)

V V
MOV
I
Surge Diode
I
Secondary Element Characteristics

Device Speed Sensitivity Energy Stability
Air Gap
GDT
Relays
Fuses
Fast
Fast
Poor
Good
Zener V Fast V Good
Transorb V Fast Good
Varistors V Fast Poor
V Slow Good
Slow Fair
High
High
Poor
Good
Low Excellent
Medium Excellent
High Poor
Medium Good
Medium Good
Comparison of Protection Components

1
2
Conventional Hybrid SPD

1
2
Incoming surge
GDT Diode Hybrid
Multi-stage SPD Operation

1
2
Hybrid Device with Steering Diodes

1
2
Continuous Overvoltage Suppression

Incoming Surge
SPD
DC Power
Protection of Panel Equipment

Tx
Surge diversion
Incoming surge
Protection of Transmitters

I/O lines
PSTN
SPDs
Telemetry
Equipment
RF
AC
SPD
Telemetry Outstation


 Let-through or limiting voltage
 Working voltage
 Maximum leakage current
Terminology - SPD basics

Thermocouples
RTDs
RS422
Loadcells
RS232
Switches
Process control loops (4/20mA)
Ultra-sonic level transducers mV
<2V
<12V
<30V
<25V
24V,110Vac
24V/48V
100V
Surge Protector Applications - Selected by Voltage





Terminology - Networks

Thermocouples
RTDs
RS422
Loadcells
RS232
Switches
Process control loops (4/20mA)
Ultra-sonic level transducers
SD07X, TP48
SD07X, TP48
SD16R
LC30
SD16X, SD32X
PC30/D,SD150X
SD32X, TP48
CA350
Surge Protector Applications - Typical solutions

Transmitter protection

Minimal series resistance
1
Two lines plus shield
2
3
4
Replaceable fuse module or loop disconnect
5
6
Automatic grounding via DIN-rail
SD series circuit

 Hybrid SPD
 Shield termination point
 Automatic grounding
 Series fusing
 Line disconnect
 All in 7mm width
 Single component protection
 No shield termination point
 Manual grounding per terminal
 Additional series fusing
 Additional line disconnect
 12-15mm width/loop plus fuse terminal plus knife-edge terminal
SD vs terminal protectors

3-wire transmitter protection

Oil storage tanks
Control computer
Weigh bridge LC30
Load cells
Junction box
Surge Protection of Weighing System
LC30

Compensated
Load Cell
4-Wire Field Cable
LC30
Supply
Signal /
Sense
4-wire Bridge / 4-wire Line

Summation box
Bond
To indicator
Surge protection device Effective system earth
Metal Weighbridge Bonding

VP08 - video protection

Monitoring area Field Installation
VP08 installation

Clipit 100

CA90/CA350 Aerial protector

I/O lines
PSTN
SPDs
Telemetry
Equipment
RF
AC
SPD
Telemetry Outstation

I/O lines
PSTN
SPDs
Telemetry
Equipment
RF
RTU Protection

1c. SPD on subdistribution boards feeding critical areas
1a. SPD on Main
Electrical
Distribution
Board
Mains Power
Cable
SPD
SPD
Main
Computer
SPD
Data
Cable
3. SPD on interbuilding Data
Cables
Telephone
Exchange
SPD
Telephone
Cable
2. SPD on External
Telephone Lines
Building Protection

Damage caused by surge on communications link cable
Local AC supply
Local AC supply
Remote earth
Communications links between buildings

Outside
FL
NP NP
Building 1 Building 2
Protection for Inter-building Network Link

Industrial area within building
Office area 1
NP
High transient overvoltage generated by heavy machinery, welding equipment
& power cables
NP
Network running through Different Building Areas
2





Network characteristics

 Thin ethernet
 NP08/B
 Thick ethernet
 NP08/N
 Token Ring
 NP08/2R
Typical LAN Applications

 RS232
 SD16X, SD16
 DP16/D, DP16
 RS423
 SD16R, SD16X
 PC16/D, PC16
 RS422 / RS485
 SD16/R, SD16X
 NP16/S
Typical industrial network Applications

Allen Bradley data highway plus
Foundation Fieldbus
HART
Honeywell DE
Interbus
Modbus
Profibus
WorldFIP
PC16/D, SD32R
SD32R, SD55R
SD32X, SD32
SD32X, DP30/D
SD32R, NP16/S
SD32R, NP16/S
SD32R, NP16/S
SD32R, NP16/S
Common industrial bus systems

Bus Powered Systems

NP08/N - Thick ethernet

Thick Ethernet installation

NP08/B - Thin ethernet

Thin Ethernet installation

Allen Bradley Data Highway Plus

Category 5 installation

250
200
150
100
50
0
PSTN ringing voltage

 UK jack and socket - office
 DP200/4/I
 Krone strip - exchange
 PX200/10
 Telemetry outstation
 DP200/D
 mSAPN
Typical PSTN Applications

 Krone strip - exchange
 DP16/PX
 Telemetry outstation
 SD16X
 DP16/D
 mSA16
Typical Private Wire Applications

Earth terminal
DP200/4/I

PSTN connection
DP200/4/I installation

DP200/D installation

MOV surge clamping

Power cables transient sources
Lightning
Load switching
Welding equipment
Elevators/lifts
Applicable standards
IEEE Std. 587-1980 (obsolete)
ANSI/IEEE C62.41 1991
IEC 801-4, -5
AC Power Line Protection

L
N
G
SPD
SPD
Spur vs Series Connection
Protected
Load

Fuse protected network
L
N
G
Delta Network of Varistors

Fuses not shown for clarity
L
1
L
2
L
3
N
G
Star-connected Varistors

SPD
L
N
G
SPD
Fusing AC Power SPDs

 MA05/D, MA10/D
 PLC power supply
 Instrument PSU
 MA05/SC, MA10/SC
 Fire/burglar alarm panel
 Computer PSU
 MA05/I, MA10/I
 Fax Machine
 Computer
MA05, MA10 applications

Divert current as soon as possible
Use dedicated low impedance connection
Make sure other systems are bonded to it, once!
Convert series-mode current into commonmode voltage
Grounding for Lightning Protection - Principles

Lightning strike to Aeroplane

 Mains Protective Earth
 Essential for personnel safety
 Carries leakage currents
 Surge Protective Earth
 Must be able to carry huge currents
 Low voltage drop
 Instrument or Computer Earth
 Needs to be kept from ‘dirty’ earth
Different types of Earth

Telecomms
Computers
Instrumentation
Star-connected System Earths

Inductance
Resistance
Cable impedance

Recommended earthing philosophy

Incoming Surge
SPD
DC Power
Common Grounding System
To distribution ground

Incoming Surge
SPD
DC Power
Preferred Grounding System
To distribution ground

Incoming Surge
SPD
DC Power
Disastrous Grounding System
To distribution ground

Hazardous Area
SPD
TX
SPD
Safe Area
IS Barrier
SPDs with IS Barriers

SPDs with Zener Barriers

TX
Hazardous Area
SPD SPD
Safe Area
Galvanic Isolator
SPDs with Galvanic Isolation

Protect equipment;-
Exposed to lightning surges & other transients
With difficult or remote access for maintenance
Critical to plant operation & control
Conclusion

 SRF Range
 High current surge protection and filtering (50 - 120kA)
 Recommend MA230, MA103 or MA2003
 MT Range
 Two terminal device containing 5 MOVs (40 - 120kA)

Recommend MA230, MA103 or MA2003
 MPM Range

Box containing three MT units (50kA L-N)

Recommend MA230, MA103 or MA2003
Critec AC power products

 LAN-TYPE-1E

Token Ring protector

Recommend NP08/2R
 LAN-TW280

TwinAx protector
 Recommend NP16/T
 LAN-BNC
 Thin Ethernet
 Recommend NP08/B
 LAN-N
 Thick Ethernet
 Recommend NP08/N
Critec LAN protectors

 LSAC Range
 4A AC data SPD
 Recommend MA05 or SD150X (higher surge rating)
 LSCP and LSSC Range
 High frequency coaxial SPDs

Recommend CA90 or CA350
 LSJK and LSEK Range

Includes GDT, MOV and surge diode

Recommend SD series
Critec data protectors