Surge Protection Devices

(SPDs)

Samad Khan MEng (Hons) CEng MIET, MIEEE

ABB Furse

Standards committees:

BSi PEL 37/1, GEL 81, CLC TC 37A, JPEL 64/D JPEL 64

IEC SC37A WG3/4/5, IEC TC 64 MT3, TC 81 MT3

Protection against transient overvoltages (surges) in

accordance with BS 7671 and BS EN 62305

BS 7671 Wiring Regulations Covers application (443), selection and erection of

surge protection devices SPDs (534):

For electrical installations to limit transient overvoltages

of atmospheric origin transmitted via the supply

distribution system and against switching overvoltages

For the protection against transient overvoltages caused

by direct lightning strokes or lightning strokes in the

vicinity of buildings

BS 7671 aligns with BS EN 62305

Protection against Lightning replaced BS 6651

What is a transient overvoltage or surge?

Different types of overvoltage

Transient disturbances damage statistics AVIVA

External

35% of all

transients originate

outside the facility

Internal

65% of all

transients originate

inside the facility

Both direct strokes to structure and indirect strokes near structure (up to 1km away)

External - atmospheric over-voltage (lightning)

External - atmospheric over-voltage (lightning)

Direct strike to building NOT required

Direct strike to line NOT required

Lightning Transients

MISCONCEPTION

I have a structural Lightning Protection System (LPS) fitted I do not

need transient protection for my equipment

Fitting structural LPS protects the structure NOT the equipment!

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!

Causes of transient overvoltagesInternal - from switching surges (inductive loads)

Motors lifts, air con

Transformers

Welding equipment

Electrical operation on the distribution grid

The switching of breakers, transformers, motors and inductive

loads in general or the sudden modification of loads causes

sudden current variations (di/dt), generating transitory voltage

surges.

The problems transients cause

Disruption loss of data, RCDs tripping

Degradation reduced equipment lifespan (~95% cases)

Components weakened, until unexplained equipment failure

Will insurance cover this?

Damage immediate loss of equipment (~5% cases)

Damage

Damage

The problems that transients cause

Damage

Degradation

Disruption

DowntimeSize of

transient

overvoltage

No effect0V

6000V

Typical hidden costs of system downtime

Lost business

Delays to customers

Lost productivity

Staff Overtime

Computers

Fire and Burglar Alarms

PABX telephone exchange

Telecom base stations

Data communication network

CCTV equipment

Equipment typically vulnerable to transient overvoltages

Section 534 focuses on 3 Types of surge protection for mains power but any metallic electrical line (data/telecom) is a path for transients 534 recommends protection for these services only

SPD - basic principle of operation

Divert surge currents and limit over-voltages, survive

and repeatedly protect personnel, buildings and

equipment

The need for overvoltage protection - history 534

BS EN 62305 fully replaced BS 6651 in 2008

Protection of electronics now normative part of BS EN 62305

previously only an informative part (Annex C) of BS 6651

Section 443 does not consider direct lightning strokes to the

structure or line and refers to BS EN 62305 BS EN 62305 has a complex software driven risk assessment

Section 534 applies when the need for surge protection is

identified by BS EN 62305 and/or Section 443

Key changes: BS 6651 and BS EN 62305

BS 6651 (withdraw August 2008) BS EN 62305

Simple Risk Assessment

(structural damage)

Comprehensive Risk Management

calculation based on four types

of risk (R1-R4)

Two levels of lightning protection

ordinary and high risk

Four levels (LPL) of

Lightning Protection System

(LPS) I-IV

Transient Overvoltage (Surge) protection

in Appendix C (informative) separate

risk assessment

Transient Overvoltage (Surge) protection

incorporated in main standard

detailed in BS EN 62305-4 AND part of

single lightning risk assessment

(BS EN 62305-2)

BS EN 62305 to address increasing problem

Lightning as a source of harm is a very high-energy phenomenon. Lightning flashes release

many hundreds of mega-joules of energy. When compared with the milli-joules of energy that

may be sufficient to cause damage to sensitive electronic equipment in electrical and electronic

systems within a structure, it is clear that additional protection measures will be necessary to

protect some of this equipment.

The need for this International Standard {BS EN62305-4} has arisen due to the increasing cost

of failures of electrical and electronic systems, caused by electromagnetic effects of lightning.

Of particular importance are electronic systems used in data processing and storage as well as

process control and safety for plants of considerable capital cost, size and complexity (for

which plant outages are very undesirable for cost and safety reasons). BS EN 62305-4

Increased use of electronics,

less able to withstand surges

Section 443 17th Amd

BS EN 62305-1 General Principles

BS EN 62305-2 Risk Management

BS EN 62305-3 Physical damage to structures and life hazard

BS EN 62305-4 Electrical and electronic systems*

*Integral part of the standard

BS EN 62305 Protection against lightning

BS EN 62305 four part series used to provide complete protection (life, building and electronics)

against lightning

BS EN 62305-1 General Principles

BS EN 62305-2 Risk

BS EN 62305 and 61643 series

BS EN 62305-4

Electrical &electronic systems

Where needed, use SPDs tested and applied in accordance to BS EN 61643 series and installed to

the installation rules (BS 7671)

BS EN 62305-3Physical damage & life hazard

Surge current waveforms to BS EN 61643 series

Surges characterised by standardized waveforms (approx time in s to peak/half peak) Direct or partial lightning currents are represented by 10/350 waveform (high energy)

Indirect or induced lightning currents are represented by 8/20 waveform

Type 1 SPDs are tested with 10/350, Type 2 and 3 are tested with 8/20

Surge voltage waveforms (e.g. 1.2/50) are characterized similarly

Damage to electronics occurs from all Sources of Damage S1 to S4

BS EN 62305 Damage Type D3 Failure of internal systems due to Lightning

Sources of damage to a structure

S1 Flashes to a structure

S2 Flashes near a structure

S3 Flashes to services connected to a structure

S4 Flashes near services connected to a structure

S2

S1S3

S4

62305-1

Direct strike to structure (Source S1)

Direct strike to service line (Source S3)

Direct strike near structure (Source S2)

Lightning flash near service line (Source S4)

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

requires use of service entrance Type 1 SPDs for mains

data, signal and telecom lines also require protection

Type 1 SPDs to protect against damage type D2 Physical

damage (fire, explosion, mechanical destruction etc) due to

lightning current effects including dangerous sparking

SPDs and Damage Type D2 to BS EN62305

Fire and electric shock hazards from flashover

Service entrance equipotential/lightning current SPDs (e.g.

Type 1) prevent flashover to preserve life

Used alone, Type 1 SPDs do not protect electronics:

A LPS which only employs equipotential SPDs provides no

effective protection against failure of sensitive electrical or

electronic systems BS EN 62305-4

Transient overvoltage SPDs (Type 2 and 3) needed to

complete a coordinated SPD set for equipment protection

Risk from dangerous sparking

BS EN 62305-4 Protection of electronic systems

SPM (Surge Protection Measures system)

complete system of protection measures for internal systems against surges)

Coordinated Type 2 and 3 SPDs, shielding, bonding measures

R

LPZ0B

LPZ0A

LPZ1

LPZ2

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

Further zones (e.g. LPZ 3) can be created for sensitive equipment

Basic LPZ concept

For LPMS using more than one LPZ, SPD(s) should be located at line entra