frankfurt (germany), 6-9 june 2011 session 1 – roundtable c – internal arc session 1 –...

Frankfurt (Germany), 6-9 June 2011

Session 1 – Roundtable C – Internal Arc

Session 1 – Roundtable C:

Internal Arc Classification –How to convert test results into Personal

Safety on SiteConvenor: Uwe KALTENBORN Schneider Electric, Germany

Panelists: Jean-Marc Biasse IEC SC 17C, FranceHarm Bannink KEMA, The NetherlandsPeter Beer PEHLA, GermanyJose-Manuel Inchausti Ormazabal, SpainGerard Schoonenberg Eaton, The NetherlandsCarlo Gemme ABB, ItalyThomas Reiher Siemens, Germany


Structure of Roundtable


1. Introduction of key topics 5 min

2. Overview of relevant papers in Session 1 4 min

3. Introduction of all panelist with their key topic 7x5 min

4. Discussion 45 min


Introduction of Key Topics


1. Jean Marc Biasse: Evolutions of IEC 62271-200 on internal fault topic

2. Harm Bannink: Definition of correct test circuits for IEC 62271-200

3. Peter Beer: Test Execution according 62271-200

4. Jose Inchausti:Design of Gas Insulated Switchgear in accordance with 62271-200

5. Gerard Schoonenberg:Solid Insulated Switchgear and their interaction with internal arc

6. Carlo Gemme:Active Internal Arc fault protection

7. Thomas Reiher: Utilisation of Test-Results for the Simulation of the Internal Arc Behaviour of Switchgear in Buildings


Introduction of Session 1 papers


1170: DEVELOPMENTS FOR MAXIMUM SAFETY IN MEDIUM VOLTAGE SUBSTATIONS REGARDING INTERNAL ARCS

Paper 1170 provides a good review of the internal arc protection topic in MV switchgear and substations. The evolution of IEC standards in this respect is presented. Some test results are also given for testing according to conditions newly defined in the next edition of IEC 62271-200 (single phase to earth fault) and also in conditions not covered by the standards (e.g. open compartment).

1137: SOLUTIONS FOR INTERNAL ARC PROTECTION ACC. IEC 62271-200 WITH PRESSURE RELIEF INTO THE SWITCHGEAR ROOM FOR AIS and GISPaper 1137 presents solutions developed for reducing overpressure inside the switchgear room in case of internal arc, when exhaust ducts to the outside of the room are not possible. Suitable arc energy absorbers have been found effective in reducing the temperature of the exhaust gases and the pressure rise in the room: their adaptation to two types of MV switchgear (air insulated and gas insulated) is described.


Introduction of Session 1 papers


0385: SOLUTION FOR INTERNAL ARC FLASH HAZARDS IN AISAnother, and possibly complementary, approach is presented in paper 385 which describes an active arc protection system. It consists in arc sensors (light and current), in a specific arc protection relay with a short operating time of 2.5 ms, and a fast acting earthing switch driven by a Thomson coil mechanism (closing time 3.5 ms). It is thus possible to short-circuit the arc in less than 10 ms, and in this way to reduce a lot the dangerous effects of the arc fault, compared to a fast acting protection by a 3-cycles (50 ms at 60 Hz) circuit-breaker.

1326: SIMPLIFIED INTERNAL ARC-STRUCTURAL SIMULATIONIn paper 1326 are reported some advances in internal arc simulation for pressure rise and structural response in the compartments subjected to an internal arc. Although simplified, the proposed method does not need to use an empiric energy transfer factor (that can vary from one configuration to another) as an adjustable parameter, and shows good agreement between calculations and test results.


Among safety aspects, optional performance to withstand internal has been introduced in IEC 60298

It was a first step but not sufficient « Test procedure to be agreed between manufacturer

and user » may lead to endless discussion Annex AA already normative but not precise enough Approach more adapted to specific projects than to

repetitive MV products

JM Biasse – France – RT Internal arc

IEC standards were developed in the past years to provide more safety


First protection is to prevent internal fault occurrence by proper design

Among other methods, IAC contributes to internal arc protection

Internal Arc classification defined and optionnal Internal arc test becomes a type test (optionnal) Tests have to be done in every MV compartment

to claim for internal arc withstand.


IEC 62271-200 Ed 1.0 2003 brought a breakthrough


Internal arc performance still optional Still focused on safety for individuals Criteria to pass the test will be in the main text Annex is now only relevant for test labs Test procedure better defined on several points


Future IEC 62271-200 Ed 2.0 (2011) will be more precise


Performing between 80 – 100 internal arc tests per year Requests for testing is rising Approx. 20% of all internal arc test objects do not pass, mostly

because of ignition of indicators Certification now considered in

STL (Short-circuit Testing Liaison)

Replacing SF6 insulation by air in testing is still under discussion

CIGRE is working on TechnicalBrochure on modelling of internal arc effects

Internal Arc Testing

H. Bannink – Netherlands – RT S1c

0%

20%

40%

60%

80%

100%

1 2 3 4 5 total resultcriterium as specified in IEC 62271-200 A6

not fulfilled fulfilled


IEC states lab grounding of enclosure is the most severe situation IEEE states extended neutral is most severe situation

Dedicated tests show that in balanced three phase test circuits there is almost no current in the extended neutral

Pressure rise in both neutral situations is almost identical

H. Bannink – Netherlands – RT S1c

Neutral treatment during IA testing

260 280 300 320 340 360 380

0

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0.8

1

1.2

1.4

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time (ms)

pres

sure

(b)

, cu

rren

t (1

00 k

A)

current

enclosure to lab ground only

extended neutral


Tests should be performed with sufficient supply voltage (close to rated voltage) in order to create stresses equal to the service situation.

At supply voltage much lower than rated, the effect of arc voltage on current asymmetry becomes too strong

Internal pressure rise with low supply voltage is too low, even though RMS current is identical

Importance of proper supply voltage

H. Bannink – Netherlands – RT S1c260 280 300 320 340 360 380

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00 k

A)

24 kV supply voltage

6 kV supply voltage

300 350 400 450 500 550 600

-20

-10

0

10

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40 24 kV supply voltage6 kV supply voltage


Peter Beer – Germany – RT1c – Paper ID

Test Execution according IEC 62271-200/FDIS-Ed2

Strengthening of the normative Character by integration of the IAC tests in the main text (§6.106)

Appendix AA contains directives for performing the tests, as room simulation, indicators, calibration of the test values

Optional: IAC-classification “IACe” for single pole compartment

Ignition only conductor to earth with smaller current IAe

if neighbour conductor is damaged => repetition of 3 phase test with IA

Criteria 2 Parts > 60g between panels and indicator frame are allowed to fall

down (e.g. a plugged operating lever)



Minimum distance to ceiling according manufacturer instruction

Test result is than also valid for larger distances of the ceiling

Distances to the ceiling < 20cm indicate a separate testing*Test for accessible rear side is valid also for installation directly to the wall with distance 30 cm / 10 cm distance to the wall, which means distance to indicator frame (30cm/10cm = accessibility A/B)

Manufacturer instruction

supply

10 cm10 cm or80* cm

Operating side




as a basic principle no new requirements or higher test values

test results according edition 1, IEC 62271-200 keep valid correction of formal or editorial inconsistencies IAC qualification more significantly integrated into the Type

Tests test requirement more related to practice

Time Schedule: FDIS “12/2010” Edition 2 middle of 2011



Standardised characteristics and tests are oriented to reduce to a minimum the probability of arc fault on GIS.

Metallic envelope offers protection to the people, among others against internal arc fault; when declared by the manufacturer.

Standardised way of declaration of internal arc fault protection is IAC classification.

Currently one value of arc current and one arc duration can be declared per switchgear.

Elements that may be outside the metallic envelope like busbars or cables are not considered by IAC classification.

J.M.Inchausti – Spain – RT S1c

Arc protection design on IEC 62271-200


LSC classification is not related with IAC classification, but more compartments are present on a GIS, less parts are affected by the arc fault and more type tests have to be performed to obtain IAC classification (one test per compartment).

Use of short-circuit current limiters (fuses or circuit-breakers) may reduce arc current value and/or arc duration for the IAC declaration.

Active protection systems based on internal short-circuiting devices to reduce the duration of the arc fault and its consequences are not free to be at the origin of an arc fault and therefore IAC classification only considers the tested actual duration of the arc.




Solid insulation on GIS may reduce the number of parts affected by an arc fault or limit this to a phase-to-earth or two-phases arc fault. This situation is not correctly addressed by current standard.

Internal arc protection design should consider geometry, materials involved and evolution of an eventual arc inside each compartment. Proper design will lead the arc to a place protected against the thermal action of the arc.

Hot gases produced by decomposition of insulating solid, liquid or gas by the action of the arc shall be driven and or cooled to avoid any damage on the people in close proximity to the switchgear when an arc fault is produced. Therefore evacuation of these gases is considered by the standard.




Will you drive a car without airbag and servobrakes?

Carlo Gemme – Italy – RT1c

Active Internal Arc fault protection – measures recommended by IEC62271-200

Active protection

Passive protection


Ultra Fast Earthingprevention of thermal damagereduced pressure rise

Fast protection relay Limited consequences

for equipment and personnel

Conventional protection relay Dramatic consequences Fire/Explosion hazard

(heavy injuries of personnel)

Cable fire

Copper fire

Steel fire



Ultra Fast Earthing Switch Fast fault detection by Arc protection relay

(<1ms), light & current rise detection Ultra-fast extinction of the internal arc by

diverting it to metallic short circuit (<4 ms), Final clearing of the fault current by the

upstream circuit-breaker

Metal particles

Cable floor

deformation



Preliminary considerations

• arc fault because of short-circuit in a switchgear• high energy explosion in some milliseconds• power peaks up to 100 MW• the result is a conducting insulating distance• free burning high alternating current arc fault

REIHER – DE – RT-S1c– Paper ID

Arc Fault Pressure Simulation for Switchgear Buildings by CFD

Example:

Switchgear 12 kV / 50 kA

Arc fault energy 7,83 MWs = 2,2 kWh

Power 200 MW at 9 ms

Pressure Peak 1,1 bar at 8,8 ms

Face pressure 10 t / m² of panel parts

copyright: TÜV Rheinland / Berlin-Brandenburg Schutzseminar 2002


Average pressure Pigler (1976)

Following criteria missing:• no switch gear corpus/absorber• no flow blockages in the room• location of pressure relief openings• geometry of the room• dynamic processes as reflection,

diffraction, interference neglected• pulsing arc fault power assumed constant

• This approach is only a rough estimation of the pressure rise

• For closed rooms and if the room is filled with pressure permanent (small rooms), this approach is a good estimation




3D-Finite Elemente Approach

• The 3-D finite element CFD method solves in spatial variables the pressure on all room walls and the fluid flow

• The pressure relief openings are considered at their locations and have the correct dimensions

• The room can be evaluated by the calculated pressureaccording to the given pressure relief opening

• In the case of too high pressure the pressure mustbe reevaluated for a bigger relief opening

• In the openings the velocity can be evaluated and the volume flowover time can be determined




Key Topics for Discussion









frankfurt (germany), 6-9 june 2011 session 1 – roundtable c – internal arc session 1 –...

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