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DNV GL © 2014 SAFER, SMARTER, GREENER DNV GL © 2014

KEMA Laboratories, now part of DNV GL

DNV GL KEMA Laboratories

1

•Tutorial on HV Circuit Breaker Testing and Certification

IEEE Switchgear Committee, St. Pete Beach, FLA

April 30, 2015

KEMA Laboratories, now part of DNV GL

DNV GL © 2014

Your speakers of today

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Director Marketing and Sales KEMA Laboratories, Chalfont, Pa DNV GL Energy Chairman of STL-NA Member of IEEE SG Committee WG’s Founder of battery storage labs in US Was GM of KEMA High Power Lab, NL Former business management consultant Been active in R&D of cables, switchgear

Service Area Leader and Innovation KEMA Laboratories the Netherlands DNV GL Energy Fellow of IEEE, PhD Professor in Netherlands, China Convener of CIGRE WGs Convener of IEC maintenance teams Chairman of Current Zero Club Worked in Toshiba, Japan

Paul Leufkens paul.leufkens@dnvgl.com

René Smeets rene.smeets@dnvgl.com

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DNV GL © 2014

Agenda

Trends in T&D equipment

Risks to TSOs / DSOs

How do outages arise?

Certification: reducing your risks and liabilities

Testing: the cornerstone of certification

High-voltage testing

Testing circuit breakers and switchgear

Arc resistance testing (internal arc)

Standard and certification

Conclusions

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DNV GL © 2014

Trends in T&D equipment

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Expanding grids

Increased interconnectedness

Higher fault currents, DC time constant, out-of-phase management

Phase-shifting transformers

Local generation

Increased transmission capacity needed

Conventional generation more concentrated

Generator equipment (breaker, busduct)

Increased reliability, short-circuit limitation, large fault levels

Long distance transmission

More (series) capacitor banks, compensation, protection devices

Gas-insulated lines

HV DC grids

Meshed DC grids need circuit breakers

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DNV GL © 2014

Additional issues

Smart grids

IT integration

New control, metering and management needs

Energy storage: hydro pumping, batteries, LN2, SMES, UPS, etc..

Hydrogen as an energy carrier

Superconducting technology

Intelligent reactive power management

HV power electronic devices (SVC, FACTS, Statcom)

Intelligence closer to equipment level

Controlled switching, adaptive switchgear drive technology

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Higher performance demands

Equipment hardening and increased performance

Increased (di)electrical, mechanical, thermal and pneumatic endurance

Cable / line ampacity, temperature rise issues

New protection concepts

Inflexible earthing no longer enough

Faster protection

Power quality

Transient management, surge arresters, voltage dip control, harmonics

Industrial and medium-voltage DC applications

New measurement systems

Optical current and voltage measurement

Directly linked to IT systems (digital output)

Calibration

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DNV GL © 2014

Equipment design and construction

Space limitations

More GIS, underground station and stations

in buildings

Mobile substations

Switchgear with combined functionality

New materials

Nano, composite and solid-state materials

for insulators

Cable insulation

Avoiding SF6, HV vacuum switchgear

Biodegradable transformer oil Amorphous

transformer cores

Low loss materials

Increased HSE awareness

Fault arc management, internal arc detection

and handling

Reducing fire risks

Low magnetic field equipment design

Controlling sound levels, RI and EM

emissions

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Risks to TSOs/ DSOs

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The threat of blackouts

Modern society depends on electricity

Power outages (blackouts) are not acceptable

Social unrest

Health hazards

Damage to local / national economy

Interrupts electricity trade

Yet number of large outages is growing

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E.g. number of outages affecting 50,000 people or more in US

2009 42

2010 52

2011 109

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When blackouts occur

Damage to your reputation

Public increasingly vocal in expressing dissatisfaction

Reduced investor and stakeholder confidence

Lower position in performance benchmark

Financial penalties

Claims from customers

Fines from regulators and authorities

Your responsibility

Must provide adequate response to (legal) claims

Information on quality processes must be recorded

Must be fully transparent, well regulated and

accountable

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Power testing, inspections and certification

Lost time if a blackout disrupts IT systems

48 hours to reconfigure a network

Days or weeks to re-enter lost data

> 33% of companies take more than a day to recover

10% of companies take more than a week

Financial losses

33% of companies lose between $20,000 and $500,000

20% of companies lose between $500,000 and $2 million

5% of companies lose more than $2 million

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Total loss to US economy: $80 billion to $188 billion per year

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How do outages arise?

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Equipment causes blackouts

Most avoidable outages are equipment related

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35

24

21

13

4 2 1

Foreign objects Scheduled outages

Equipment or apparatus Weather events

Lost of supply Environmental factors

Human error

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148

4

15

51

2 20

UK 2011 (Eaton Corp.)

USA 2011 (Eaton Corp.)

Hydro Quebec 2006-2007

208

767

138

28

456 245

1229

Animal Faulty Equipment / Human Error

Planned Theft / Vandalism

Unknown Vehicle Accident

Weather / Falling Trees

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Faults in power systems

Faults can’t be avoided

Circuit breakers must minimize the duration of the fault

All HV equipment must be capable of withstanding the stresses that faults cause

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What causes faults?

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Effects of faults

Fault current

Causes very high forces between nearby conductors

– Felt by all equipment but transformer most sensitive

– Complicated pattern in three-phase systems

Impact of arc on fault location

Thermal stresses to personnel and equipment

Pressure rise in enclosed volumes

– Risk of explosion and fire

Can cause instability to power system if lasts too long

Risk of problem spreading and wide-scale blackouts

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DNV GL © 2014

Fault currents

Very high current

Causes forces on conductors

Induces currents in unexpected areas

Examples

Fault current through closed disconnector

Impact of overhead line conductors

Impact on line trap

Induced current by extreme busbar current

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Thermal effects of faults

Fault arcs cause

Pressure rises

Explosions

Fires

Examples

Underground pressure rise (cables)

Pressure rise in switchgear panel

Power arc near string insulator

Fault arc in current transformer

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How often do faults occur?

Wide regional variations

– Global average: 1.7 faults per year

on an overhead line

90th percentile: 3.3 faults per year

on an overhead line

– Lower voltage systems suffer

more faults

90% of faults happen in overhead lines

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0

2

4

6

8

10

12

14

16

18

20

< 100 100-200200-300300-500500-700 ≥700

system voltage class

nr. of faults per 100 km

OH line per year

average

90percentile

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International fault statistics

Very large regional variations

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0

3

6

9

12

15

18

Number of short-circuits per 100km*year OH line

<100 kV 100-200 kV 200-300 kV

300-500 kV 500-700 kV >700 kV

Europe Canada USA Brazil Japan India

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Most faults are single phase

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0

20

40

60

80

100

<100kV 100-200 kV 200-300 kV 300-500 kV 500-700 kV >700 kV

Number of phases involved in fault

3 phase

2 phase

1 phase

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Most faults are not persistent

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0

20

40

60

80

100

<100kV 100-200 kV 200-300 kV 300-500 kV 500-700 kV >700 kV

Fault removal rate by OC, O-CO-C or O-CO-CO-C operation

OC O-CO-C O-CO-CO-C

DNV GL © 2014

Best practices increase reliability

Quality assurance reduces failures

Specification

Procurement

Factory acceptance tests

Best practices accepted by major utilities

Asset management by

– Technology

– Processes

– Organization

Equipment certification is key to quality

assurance and reliable service to customers

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1

0,8

0,6

0,4

0,2

0

MaF fr / Type of Enclosure / Total, CIGRE 2012

MaF f

requency

[per

100 C

B-y

ears

]

live tank metal clad total

new survey old survey

Figure 1-8 Distribution of CB MaF frequencies per type of enclosure

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Certification: reducing your risks and liabilities

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The three foundations of certification

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International standards Skilled personnel Adequate

test laboratories

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International standards

Created by standards committees

– Include people from across the value

chain - Including you!

Are constantly renewed

You’ll hear more later

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Skilled personnel

Ongoing training and education

Experience counts

Dissemination

DNV KEMA Academy

Publications in leading journals

Books

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HQ and flagship lab at DNV GL Arnhem

switchyard (245

kV) generator

building

(8400 MVA)

on-board

transformer testing

MV test lab

(40 kV)

synthetic

installation

(720 kV)

high-power

labs open-air test

site

high-voltage

lab

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DNV GL Powertest, Chalfont, Pa, USA

Synthetic testing at 245 kV

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DNV GL ZKU, Prague, Czech Republic

Power arc testing (40 kA, 0.2 s)

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Testing: the cornerstone of certification

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Types of tests (1): reasons for testing

Development tests

Testing prototypes

Ordered by manufacturer

Performed at manufacturer’s site according to client’s instructions

Type tests (for certification)

Verify that an example product meets the requirements of a specific standard

Ordered by manufacturer

Performed at independent lab according to international standards

Acceptance tests

Verify a specific product meets application and user-defined requirements

Ordered by equipment user

Performed at independent lab according to user’s specifications

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Types of tests (2): properties tested

Electrical

Functional performance

Dielectric performance

Load performance

Non-electrical

Mechanical

Dynamic

Thermal

Climate and environmental

Seismic

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Types of tests (3): test objective

Types of tests (3): test objective

Functional testing

Does the apparatus fulfill its function?

– Circuit breakers making and breaking of short-circuit current

– Switchgear switching of load current (inductive, capacitive)

Requires high current and high voltage

Withstand testing

Does the apparatus withstand the stresses of normal / abnormal operating conditions?

– continuous current and voltage (thermal, dielectric)

– short-circuit current

– lightning and switching voltages

– mechanical (no load switching, electro dynamical forces)

– thermal (pressure rise due to fault arcs)

Requires high current, high voltage or high power

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Components to be tested

Circuit breakers

Switchgear

Transformers

Cables

Accessory

Isolators

Surge arresters

Fuses

Busbars

Conductors

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High-voltage testing

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Focus on High voltage testing

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High voltage test arrangement for a cable system Source: DNV GL

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What makes high voltage special: high electric field stresses

Common insulating materials:

– vacuum, Air, N2, SF6, oil, paper, resin, PE, rubber, porcelain, glass

High electric field stresses in insulating materials (dielectrics)

– must be of proper design and high quality to withstand these stresses:

– thickness, electric field distribution, free of impurities, ageing resilience

Especially apparent at the interface between dielectrics

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Electric field stresses have to be managed

DNV GL © 2014

What is the disadvantage of applying high voltage

Risks of flashover, insulation breakdown and short circuit between phases

or to earth:

Ageing of dielectrics

– Humidity, (salty)fog, frost, sunlight (UV), current, voltage

– Temperature influence on dielectrics

Breaking of support insulators by mechanical forces

Etc…

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Ageing by climatic influences with electrical stresses Source: DNV GL

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How to ensure compliance to safety and reliability

Insulation quality must be verified before operation

Determination of quality and condition, primarily non-destructive

– Withstand tests under increased test parameters

– Temperature tests to simulate working conditions

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Daily power demand example Source: mpoweruk.com

Temperature cycle on a cable Source: DNV GL

Conductor

Sheet

Ambient

DNV GL © 2014

How to ensure compliance to safety and reliability

Additional diagnostic tools:

– measurement of partial discharges, in order to detect defects

– measurement of dielectric loss factor (Tan δ)

– determination of water treeing, especially in XLPE

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A three-phase partial discharge pattern Source: DNV GL

Water treeing can lead into

major breakdown

Source: ee.washington.edu

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Testing circuit breakers and switchgear

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Circuit breakers

Circuit breakers must interrupt the current during a short circuit

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Fault current interruption sequence

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2

1

0

-1

-2

1

0

-1

-2

1

0

-2

-2

-10 0 10 20 30 40 50 60

current in second-pole-to-clear

current in first-pole- to-clear

current in last-pole- to-clear

relay time opening time arcing time

break time

trip signal from relay

contact separation

interruption fault starts

minimum arcing time

DNV GL © 2014

Current interruption process

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current

power

frequency

voltage

current zero

contact separation

arcing time

Transient Recovery

Voltage (TRV)

Recovery Voltage

(RV)

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Voltages stresses in the breaker

Immediately after interruption, hot gases

remain in the gap and feel fast rising voltage:

thermal stresses

A little later, a very high voltage is reached

across the open gap: dielectric stresses

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Direct testing

Current and voltage from single source

Directly on the power grid

– pro: high power available

– con: difficult to match with test object, poor availability, risk of damage

With generator-fed power supply

– pro: high flexibility, easy to adjust, safe for test object, no grid interaction

– con: high investment

With capacitor bank supply

– pro: low investment

– con: only for low power

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Direct testing set-ups

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On the grid

Generator fed

DNV GL © 2014

Direct testing layout

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generator master

breaker

current

limiting coils

TRV

generating

circuit

voltage

measurement

current

measurement

test object transformers

Making

switch

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However…

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DNV GL direct three/phase power in test-bay at 50 Hz

GVA / break 550 kV, 63 kA

20

15

10

5

1950 1960 1970 1980 1990 2000

SF6 circuit-breakers

Air blast circuit-breakers

Interruption capability per break [GVA]

2010

DNV GL © 2014

Example: short-circuit testing a circuit breaker (three phase)

Voltage: 420 kV

Fault current: 63 kA

Frequency: 50 Hz

Power required = 420 kV x 63 kA x 3 = 45830 MVA

– Exceeds direct power available at any test lab (e.g. DNV GL: 8400 MVA)

Possible solutions

– Single phase testing: power required = 45380 MVA / 3 = 15277 MVA

– Half-pole testing: power required = 15277 MVA / 2 = 7638 MVA

Still exceeds power-voltage characteristics of the most powerful labs

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A different method is required

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Requirements for testing a circuit breaker

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after interruption: only need a sufficiently high

voltage

- from pre-charged capacitor

special circuit needed to reignite the arc

before interruption: need enough power to maintain the full (arc) current at moderate voltage (< 60 kV)

- from generators

short-circuit current

reignition

interruption

contact separation

arcing time

transient recovery voltage

DNV GL © 2014

Synthetic testing

Current and voltage from multiple sources

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generator circuit capacitor circuit

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Synthetic testing

Current and voltage from multiple sources

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55/68

Synthetic circuit (with parallel current injection)

DNV GL © 2014

Current injection

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Generator current

Injected current

Current through test-CB

Delayed current zero

tpo tHS tj

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Synthetic testing at DNV GL

2 x cap. bank

720 kV - 1.7 MJ

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Installation “West”(1980) up to 500 kV rated voltage

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Synthetic testing at DNV GL

Installation “East”(2012) up to 1200 kV rated voltage

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Combined synthetic tests

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Initial TRV

Breaker under test

Short-circuit current supply circuit

Second synthetic stage

First synthetic stage

DNV GL © 2014

Example: 800 kV full-pole test

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0 0.5 1 1.5 2 2.5 3 0

200

400

600

800

1000

1200

Am

plitu

de [kV

]

Time [ms]

second synthetic stage

first synthetic stage

resulting TRV

IEC envelope

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Example: 1100 kV full-pole test

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Test-set up for 1100 kV

TRV > 2000 kV

-200 0 200

400

600

800

1000 -1000

-500

0

500

1000

1500

2000

time (us)

current (10% of 50 kA)

IEC reference lines

T10 TRV

TRV (

kV),

curr

ent

(A)

DNV GL © 2014

Why is full-pole testing essential?

In service, voltage is shared approx. 50/50

across the two chambers,

In service, there is 100% dielectrical stress

between internal parts and enclosure

Hot and ionized exhaust gases from breaker

compartment weaken dielectrical strength.

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2

½ U

U

½ U

U

A

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Half- vs. full-pole testing for enclosed switchgear

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½ U

½ U

½ U

hot exhaust gas from breaker

Full-pole test: interrupter stress OK internal stress OK Half-pole test:

interrupter stress OK internal stress not OK

½ U

U

½ U

U

DNV GL © 2014

Three-phase synthetic testing

In three-phase circuits, the current in each phase is interrupted at a different time

The conditions for the three interruptions are different

– The first circuit breaker pole to interrupt experiences the highest TRV

– The last pole to interrupt experiences the longest arc duration

These stresses have to be imposed realistically in a test

A three-phase synthetic test

– needs three separately controllable synthetic installations

– Is hugely complex

– is essential for switchgear with three breakers in a common enclosure

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cs

1st

2nd

3rd

highest TRV

longest arc duration

Example: three-phase synthetic test with three injections

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‘Making’ tests

Circuit breakers also experience severe stresses during

‘making’ (closing into a short-circuit)

Pre-arc will establish during closing in the contact gap

Severe pressure shock in the interrupter and possible damage

to the contact system

This function must be verified in full-power test

Full voltage and current is needed

– Synthetic make

– voltage from capacitors to breakdown the gap at full voltage

– detection of breakdown and make-gaps initiate current flow

– full current from generators

– by-pass the make-gaps using fast switches

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Example: full-pole synthetic make test up to 1100 kV

‘make’ gap

‘make’ test

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Single-phase testing of three-pole circuit breakers

Single-phase testing is often used when test laboratory has insufficient power

– BUT should be done with care

Verification test (for making and breaking) demonstrates single-phase tests are acceptable on

three-pole device with common drive

Beware of three-phase interactions that single-phase circuits can’t represent

Three-phase testing of three-phase devices is always preferred!

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Three-phase testing of three-phase devices

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recovery voltage contact separation

current

no-load contact

movement

three-phase test contact movement

single-phase test contact movement

voltage: 80 kV/div

current: 111kA/div

time: 10 ms/div

DNV GL © 2014

HV making / breaking testing needs sufficient supply power

Many arcs in series

High total arc voltage counteracts source voltage

Especially with

Synthetic testing (auxiliary breakers)

Testing breakers with multiple arcing chambers

Tests with long arcs (tall arresters, power arcs)

Current sources must have as high a terminal voltage as possible

Guarantees adequate arcing stresses

Risk is to apply too little energy in the fault current arc

Testing is then not strenuous enough

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Load current switching testing

Capacitive load switching

Unloaded cable and line

Capacitor banks

Load remains charged after interruption

Release of energy at “re-strike” results in risk to

switching device and system

Inductive load switching

Capacitor banks

Shunt reactor

Current may be trapped in shunt reactor

Release of energy at “re-ignition” results in risk to

switching device and system

Why is it critical?

Low current enables short arc duration

High TRV promotes re-strike / re-ignition

Release of high-energy in breakdown

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Load current switching is a major cause of breaker failure

CIGRE 2012

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Overh

ead lin

e

Tra

nsfo

rmer

Cable

Shunt

reacto

r

Capacitor

Bus c

ouple

r

Oth

er

Tota

l 0

1

2

3

4

5

6

7

MaF fre

quency [

per

100 C

B-y

ears

]

Live tank

Dead tank

GIS

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Re-ignitions at inductive switching 245 kV circuit breaker

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suppression peak

first re-ignition

voltage across load reactor

551 kV

hor.: 0.5 ms-div; vert.: 200 kV/div

steep fronts distribute voltage unevenly (trafos!)

DNV GL © 2014

Internal arc tests

Internal arcs happen when there is a fault in

the switchgear

Switchgear assembly needs pressure relief

venting in case of an internal (fault) arc in

the installation

These vents must be designed based on

maximum pressure

Exhausts must be inaccessible to people

Installation rooms are becoming smaller

More installed power

Schematic diagram of a MV circuit breaker

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Carrying out the test

Cotton indicators mimic worker’s clothing

exhaust

room simulation

front indicators

lateral indicators

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Deflector plate Arc absorber Diversion channel

Mitigating internal arc effects

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Testing circuit breakers and switchgear

Tests for full voltage or current

Insulation:

– Gas, air…

Many internal connections

– Can cause hot spots

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Source: siemens.com

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Testing circuit breakers and switchgear

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Temperature-rise tests on circuit breakers and switchgear is also

important

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What is a standard?

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What is a standard?

A standard is:

An agreed set of rules that establishes uniform behaviour, criteria, methods, processes and /

or practices

Usually voluntary, but may be cited in legal regulations, contracts & tenders

A technical standard can be:

A formal document that establishes uniform engineering and/or technical criteria, methods,

processes and practices

A reference standard

– Realizations of SI units held in national laboratories

– Used for calibration

– e.g. quality, purity, strength and consistency of medicines

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Why standards?

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Why standards?

Standards benefit business, industry, government and consumers

Increase product safety & quality

Protect environmental resources

Permit inter-changeability, interoperability and compatibility

Simplify product development, reduce costs & duplication

Improve efficiency in design, marketing and acquisition

Increase competition & open global markets

Support scientific discovery & innovation

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Standards can have various goals

Safety

Primarily low voltage equipment

Definitions

Exact descriptions; representation

of languages

Quality

e.g. ISO 9000 series

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Functionality

Definition, (Type) test programs

Extreme testing

Wind, water, current, voltage

Scope or field of play

DNV GL © 2014

Technical standards come in various formats

Standard specification

Set of requirements for a type of item,

material, component, system or service

Standard test method

Definitive procedure which produces

a test result

– From personal observation to highly

technical measurement

Standard practice

A set of instructions for performing

operations or functions

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Standard guide

General information or options

Standard practice

Instructions typically used for performing

operations or functions

Recommendation

Non-mandatory agreement e.g. from

industry body or group of companies

Technical document:

Content provides recommendations only

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Certification

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What is certification & who provides it?

Certification

“the provision by an independent body of written assurance (a certificate)

that the product, service or system in question meets specific requirements”

Based on testing

Product, service or system must pass test successfully to receive a certificate

Certification bodies

Global and local companies

Independent from manufacturers

Accredited nationally or internationally

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Why does certification matter?

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Why does certification matter?

Certification

Provides evidence of reliability, safety, quality

Supports open markets & international procurement

Mitigates risk

– Proof of due diligence in choosing products, services or systems

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How is certification carried out?

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Certification for T&D

No internationally recognized standard way of testing for HV T&D equipment

Certification companies have own rules governing Type Test certification for HV components

DNV GL rules draw on existing ISO / IEC standards for low, medium and high voltage

equipment and for Short-Circuit Testing on STL documents

STL industry body

– “Focused on harmonized application of IEC and Regional Standards for the type testing

of electrical power equipment”

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DNV GL approach

Responsible for:

Validity and contents of certificate

Identification of the apparatus tested

Interpretation of the standard

Repeating tests and their influence

on the certificate

Ensures:

All critical tests are performed in its own

laboratories

Complete series of tests is performed

All applicable requirements of the standard are met

Right ratings and specific characteristics are used

Right (number of) samples are tested

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Certificates and reports; a vital distinction

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Certificates and reports: a vital distinction

Type Test Certificates

Complete peace of mind

– Independent evidence of compliance with specified requirements / standards

– Proof that the component tested has fulfilled all the requirements of a recognized

standard and the relevant ratings assigned by the manufacturer are endorsed

by the certification body

Test reports

Must be read carefully

– Records tests which have been carried out strictly in accordance with a recognized

international standard

– Beware!

– A series of tests in a report does not necessarily fulfill the requirements for a Certificate

– Tests will be documented whether the component passed or failed

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Different kinds of Type Test

Complete

Partial

– Dielectric…

– Temperature rise

– Short-circuit

– Switching performance

– Internal arc performance

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Different kinds of Test Reports

Report of performance

– Strictly, Based on

Clients instructions

Calibration certificate

Inspection

On site testing

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Standards, Testing, Certification

Standards

Define components’ characteristics and how they

should perform

Testing

Is how you assess whether standards / specifications

are met

Certification

Provides documentary evidence that standards

are met

Type Test Certificates (of Complete Type Test)

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Complete testing

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Documents

Type test certificates

Test reports

Calibration certificates

Inspection reports

Investigation reports

We do it all

Medium, high & very high voltages

Testing methods

Laboratory testing

Onsite testing

Witness testing

Remote testing

Tests

Certification tests

Acceptance tests

Type tests

Power electronics tests

Calibration of systems

Diagnostics

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Conclusions

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Conclusions

Demand for electricity is growing

Awareness of environmental impact of energy is also increasing

Consequently, electricity networks are getting larger, more interconnected

and smarter

Grids and the equipment in them need to do more

Increasing the chances and scale of power outages

Power outages cause economic and social problems

TSO / DSOs increasing being held (financially) liable for outages on their networks

Most avoidable outages are caused by equipment faults

Equipment reliability is critical to avoiding large blackouts

Certification is the key to equipment reliability

Testing is the cornerstone of certification

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