New European Standards Regarding Lightning

and Surge Protection

Joe Ellwood
 New European Standards Regarding
Lightning and Surge Protection
•Lightning facts and characteristics
•Direct effects and damage

•Secondary lightning effects – surges/transient overvoltages

•How do they damage equipment?
•The problems transients cause and why protection is required

•Recognised protection measures

•BS 6651/BS EN 62305 - comparisons

•Where to apply protection

•Key requirements for a protector

•Questions & Answers

 Lightning Characteristics

• Lightning strikes the earth 100 times a second

• Discharges in excess of 200,000 amps
•Can energize half a million 100 watt light bulbs!

• Direct damage is obvious and immediately apparent

•Damaged buildings, trees, fires
•Personal injuries, death

•Tendency to strike taller structures and objects

• However ground strikes are common where distance between

structures is greater than twice their individual height
 Direct Lightning Damage

Physical damage (fire, explosion, mechanical

destruction etc) due to lightning current effects
 Direct Lightning Damage

Injuries/death to living beings due to high voltages

(step and touch voltage)
 Secondary effects of lightning

• The secondary effects of lightning causes surges or transient overvoltages

“A transient overvoltage (surge) is a short

duration increase in voltage measured
between two or more conductors”

• Resistive coupling is the most common form of damage

• Inductive coupling can also occur
 What are Transient Overvoltages (surges)?

Normal mains power supply

Big

• Up to 6,000 volts
(Almost 20 times mains supply)

Transient overvoltage

Fast

•Typically 50 microseconds duration (20,000

transients per second)
Resistive coupling
Inductive coupling
 Lightning Transients

• Direct strike to building NOT required

• Direct strike to line NOT required

• Transients can pass through HV network

 Equipment that cause switching transients

• Motors – lifts, air con

• Transformers

• Welding equipment
 The problems transients cause

• Disruption – loss of data, RCD’s tripping

• Degradation – reduced equipment lifespan
• Damage – loss of equipment
 The problems that transients cause

6000V
Damage

Degradation
Damage Downtime
Size of
transient
overvoltage
Disruption
Damage

0V No effect
 Downtime – the biggest cost!

• Losses due to downtime often far exceed

hardware losses Cost
Cost
• Typical hidden costs of system downtime
• Lost business
• Delays to customers
• Lost productivity
• Staff Overtime
Time
Equipment typically vulnerable to transient overvoltages

• Computers

• Fire and Burglar Alarms

• PABX telephone exchange

• Telecom base stations

• Data communication network

• CCTV equipment
Critical equipment for vital services

Old Trafford
Home of Manchester United
 Transients - the growing threat!

Increase in transient losses

due to electronics becoming
•Cheaper - more utilised
LOSS

•Smaller - more sensitive

Year
Losses due to direct strikes
Losses due to transient overvoltages
Comparison of losses due to direct strikes
against losses due to transient overvoltages
 Why protection is required

Effective transient overvoltage protection can prevent:

• lost or destroyed data

• equipment damage
• repair work for remote and unmanned stations

• sales lost to competitors

• loss of production
• health and safety hazards caused by plant instability, after loss of
control
•LOSS OF LIFE
British standards: Protection of structures against lightning

(BS) CP1 1947

(BS) CP326 1965

BS6651 1985
BS6651 1992
Appendix C – equipment protection added

BS6651 1999

BS6651 2000 Corrigendum No 1

BS6651 2005 Amendment No 1
BS 6651 : Protection of structures against lightning

• Main body of standard covers protection of structures

• Need for protection determined by simple risk assessment
• Protection measures consist of “Faraday cage” principles

• Protection of electronic equipment covered separately

• Guidance given in Informative Annex C
• Separate risk assessment to structural protection
• Protection measures consist of transient/surge protection
Risk Assessment – consider direct
strike to structure
 Collection area for a
direct strike to structure
Risk assessment considerations - transients

• A lightning strike up to 1 km away can have devastating

consequences
• Both buried and overhead cables are vulnerable
• Need to additionally allow for
• surrounding ground
• associated buildings
• lines between buildings
• lines leaving the site
• Collection area MUCH bigger than for a direct strike
• risk to equipment therefore MUCH bigger!
Risk Assessment – threat from
transient overvoltages
 Collection area for
transient overvoltages/surges
 Protection measures - realities

• BS 6651’s risk assessment for protection of equipment not utilised in practice

COMMON MISCONCEPTION –

“I have a structural Lightning Protection System (LPS) fitted –

I do not need transient protection for my equipment”

• Fitting structural LP system protects the structure NOT the equipment!

 Direct strike to building – with NO LPS fitted

Physical damage to structure through mechanical

forces and heat
Inductive coupling can still cause transient
problems for equipment
 Direct strike to building – structural LPS fitted

LPS provides safe low resistance path but surges have higher
energy. Structure is SAFE, equipment is NOT!
Fit transient protection on all cables that enter/leave buildings and
critical external equipment (CCTV). Fit protection local to critical
equipment within building.
 INDIRECT STRIKES
Most common cause of lightning transient problems

Indirect strike as far as 1km away cause transient

problems irrespective of whether structural LPS
fitted or not!
From BS 6651 to BS EN 62305 - CENELEC

• Harmonisation of European standards has led to new industry standards

• BS EN62305 series “Protection against lightning” published in September 2006
• Over 15 years of work by world experts including 28 European member states
• Over 4 times more information than BS 6651
• CENELEC standards have priority over “conflicting” National Standards
• Both the BS 6651 and BS EN62305 series will run in parallel for 24 months
• BS 6651 will be withdrawn in August 2008
Key changes: BS 6651 and BS EN 62305
BS 6651 BS EN 62305

Simple Risk Assessment Comprehensive Risk

(structural damage) Management Calculation
based on four type of risk
(R1-R4)
Two levels of lightning Four levels of Lightning
protection – ordinary and high Protection System (LPS)
risk I-IV

Transient Overvoltage (Surge) Transient Overvoltage (Surge)

protection in Appendix C protection incorporated in
(informative) main standard – detailed in
BS EN 62305-4
 BS EN 62305 – four parts
BS EN 62305-1 General Principles
BS EN 62305-2 Risk

BS EN 62305-3 BS EN 62305-4
Physical damage Electrical &
& life hazard electronic systems
Scope – BS EN 62305 - 1
Provides general principles for protection against
lightning of:
• structures, their installations, contents and persons
• services connected to a structure
BS EN 62305-2 – Risk Management

Identify the structure to be protected

• Complex document embracing many more factors

than the BS 6651 risk assessment.
Identify the types of loss relevant to
the structure to be protected Rn

R1 risk of loss of human life

R2 risk of loss of service to the public
R3 risk of loss of cultural heritage

For each loss to be considered

• By working through series of formulae the process

Identify the tolerable level of risk
RT

allows the user to decide on what protection is required

For each loss to be considered

to reduce the actual Risk (R) below the tolerable level

Identify and calculate the risk
components RX that make up risk Rn

(RT).
RA, RB, RC, RM, RU, RV, RW, RZ,

Calculate

Rn = Σ R X

• Protection may be the installation of an LPS system or

Rn = RT
No Install protection
measures in order to

transient/surge protection or both – a significant

reduce Rn
Yes

deviation from BS 6651.

Structure is adequately protected for
this type of loss
BS EN 62305-2 – Risk Management

Need to assess each relevant risk (R)

according to corresponding types of loss (L)

R1 – risk of loss of human life (L1)

R2 – risk of loss of service to the public (L2)

R3 – risk of loss of cultural heritage (L3)

R4 – risk of loss of economic value (L4)

BS EN 62305-2 – Risk Management

Protection against lightning is required if the

calculated risk Rn(whether R1 or R2 or R3) is greater
than the tolerable level of risk RT
ie Rn > RT
Types of loss RT
/annum
Loss of human life or permanent injuries 1 x 10-5

Loss of service to the public 1 x 10-4

Loss of cultural heritage 1 x 10-4

• LPS (Lightning Protection System) – BS EN 62305-3
- complete system used to reduce physical damages to
a structure.
Consists of external and internal lightning protection
systems.
• BS EN 62305-4 Protection of electronic systems
-LPMS (LEMP Protection Measures System)
- complete system of protection measures for internal
systems against LEMP.
 LPZ0A
R
LPZ1

LPZ2
LPZ0B

• LPZ (Lightning Protection Zone)

- zone (area) where lightning electromagnetic environment is defined
0A Full current, full magnetic field, 0B Partial/induced current full magnetic field
1 Limited induced current damped magnetic field
2 Limited induced current, further damped magnetic field
Basic Lightning Protection Zone LPZ concept – BS EN 62305-4

LPZ 0 - most severe

Cross bond metallic services
Transient protection (SPDs)
installed on services entering
each zone

SPD (Surge Protection Device)

- device which limits transient
overvoltages and diverts
surge currents.
Zoned concept or “Location Categories” – BS 6651 Appendix C
 Where to Protect

• Transients enter buildings via metallic conductors

– Through both underground and overhead cables

• Protect all cables which enter or the leave building

– Different systems require different protectors

• Protect critical equipment locally

– Examples include Fire Alarm Panels, PLCs, Computers, Servers

• Comprehensive product range required to protect all systems

– Mains protectors cannot protect a telephone line
Where to apply protection
 Where to apply protection

Where to protect
• All cables that enter or leave the building:
- Mains power
Where to apply protection

Mains protectors
Where to apply protection

Mains protectors
 Where to apply protection
Where to protect

• All cables that enter or leave the building:

- Mains power
- Data communication and local
area network cables
Where to apply protection
Data communication and local
area network cables
 Where to apply protection
Where to protect

• All cables that enter or leave the building:

- Mains power
- Data communication and local
area network cables
- Telephone lines
Where to apply protection

Telephone lines
 Where to apply protection

Where to protect

• All cables that enter or leave the building:

- Mains power
- Data communication and local
area network cables
- Telephone lines

- CCTV, Satellite, TV and antenna cables

Where to apply protection
CCTV protectors
(Mains power, CCTV video & telemetry lines)
Where to apply protection

RF protectors
 Where to apply protection

Where to protect

• All cables that enter or leave the building:

- Mains power
- Data communication and local
area network cables
- Telephone lines
- CCTV, Satellite, TV and antenna cables
• The power supply local to important
equipment
Where to apply protection

The power supply local to

important equipment
 Where to apply protection

Where to protect

• All cables that enter or leave the building:

- Mains power
- Data communication and local
area network cables
- Telephone lines
- CCTV, Satellite, TV and antenna cables

• The power supply local to important

equipment
• Electronic equipment outside the main
buildings
Where to apply protection
Protect electronic equipment
outside the building
 Key requirements for a protector

For effective protection, a transient overvoltage protector should:

• be compatible with the system it is protecting

• survive repeatedly
• be properly installed
• not leave the user unprotected, as a result of failure
• have a low let-through voltage for all combinations of conductors
• Lower let-through voltage = better equipment protection
 Low let-through voltage

6,000V 600V
 Summary

• Transient overvoltages present a growing threat

• Most modern systems are affected
• Structural LP systems do not protect equipment
• LP systems need to be complemented with surge protection to
protect both the structure and equipment
• Recognised in new BS EN 62305 standard
• Risk and protection measures now include both LPS and SPDs
• All incoming/outgoing cables should be protected
• Also provide local protection to critical equipment
• Choose protectors that have a low let-through voltage in all modes
Questions & Answers