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 Site Convenor:Uwe KALTENBORNSchneider Electric, Germany Panelists:Jean-Marc BiasseIEC SC 17C, France Harm BanninkKEMA, The Netherlands Peter BeerPEHLA, Germany Jose-Manuel InchaustiOrmazabal, Spain Gerard SchoonenbergEaton, The Netherlands Carlo GemmeABB, Italy Thomas ReiherSiemens, Germany

Frankfurt (Germany), 6-9 June 2011 Structure of Roundtable Session 1 – Roundtable C – Internal Arc 1.Introduction of key topics5 min 2.Overview of relevant papers in Session 14 min 3.Introduction of all panelist with their key topic7x5 min 4.Discussion45 min

Frankfurt (Germany), 6-9 June 2011 Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 2011 Introduction of Session 1 papers Session 1 – Roundtable C – Internal Arc 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 (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 WITH PRESSURE RELIEF INTO THE SWITCHGEAR ROOM FOR AIS and GIS Paper 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.

Frankfurt (Germany), 6-9 June 2011 Introduction of Session 1 papers Session 1 – Roundtable C – Internal Arc 0385: SOLUTION FOR INTERNAL ARC FLASH HAZARDS IN AIS Another, 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 SIMULATION In 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.

Frankfurt (Germany), 6-9 June 2011 Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 2011  Among safety aspects, optional performance to withstand internal has been introduced in IEC  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

Frankfurt (Germany), 6-9 June 2011  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. JM Biasse – France – RT Internal arc IEC Ed brought a breakthrough

Frankfurt (Germany), 6-9 June 2011  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 JM Biasse – France – RT Internal arc Future IEC Ed 2.0 (2011) will be more precise

Frankfurt (Germany), 6-9 June 2011 Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 2011  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 Technical Brochure on modelling of internal arc effects Internal Arc Testing H. Bannink – Netherlands – RT S1c

Frankfurt (Germany), 6-9 June 2011  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

Frankfurt (Germany), 6-9 June 2011  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 S1c

Frankfurt (Germany), 6-9 June 2011 Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 2011 Peter Beer – Germany – RT1c – Paper ID Test Execution according IEC /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 “IAC e ” for single pole compartment Ignition only conductor to earth with smaller current I Ae if neighbour conductor is damaged => repetition of 3 phase test with I A  Criteria 2 Parts > 60g between panels and indicator frame are allowed to fall down (e.g. a plugged operating lever)

Frankfurt (Germany), 6-9 June 2011 Peter Beer – Germany – RT1c – Paper ID  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 cm or 80* cm Operating side Test Execution according IEC /FDIS-Ed2

Frankfurt (Germany), 6-9 June 2011 Peter Beer – Germany – RT1c – Paper ID  as a basic principle no new requirements or higher test values  test results according edition 1, IEC 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 Test Execution according IEC /FDIS-Ed2

Frankfurt (Germany), 6-9 June 2011 Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 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

Frankfurt (Germany), 6-9 June 2011  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. J.M.Inchausti – Spain – RT S1c Arc protection design on IEC

Frankfurt (Germany), 6-9 June 2011  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. J.M.Inchausti – Spain – RT S1c Arc protection design on IEC

Frankfurt (Germany), 6-9 June 2011 Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 2011

Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 2011  Will you drive a car without airbag and servobrakes? Carlo Gemme – Italy – RT1c Active Internal Arc fault protection – measures recommended by IEC  Active protection  Passive protection

Frankfurt (Germany), 6-9 June 2011 Ultra Fast Earthing prevention of thermal damage reduced 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 Carlo Gemme – Italy – RT1c

Frankfurt (Germany), 6-9 June 2011 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 Carlo Gemme – Italy – RT1c

Frankfurt (Germany), 6-9 June 2011 Introduction of Key Topics Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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

Frankfurt (Germany), 6-9 June 2011 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: Switchgear12 kV / 50 kA Arc fault energy7,83 MWs = 2,2 kWh Power200 MW at 9 ms Pressure Peak1,1 bar at 8,8 ms Face pressure  10 t / m² of panel parts copyright: TÜV Rheinland / Berlin-Brandenburg Schutzseminar 2002

Frankfurt (Germany), 6-9 June 2011 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 REIHER – DE – RT-S1c– Paper ID Arc Fault Pressure Simulation for Switchgear Buildings by CFD

Frankfurt (Germany), 6-9 June D-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 pressure according to the given pressure relief opening In the case of too high pressure the pressure must be reevaluated for a bigger relief opening In the openings the velocity can be evaluated and the volume flow over time can be determined REIHER – DE – RT-S1c– Paper ID Arc Fault Pressure Simulation for Switchgear Buildings by CFD

Frankfurt (Germany), 6-9 June 2011 Key Topics for Discussion Session 1 – Roundtable C – Internal Arc 1.Jean Marc Biasse: Evolutions of IEC on internal fault topic 2.Harm Bannink: Definition of correct test circuits for IEC Peter Beer: Test Execution according Jose Inchausti: Design of Gas Insulated Switchgear in accordance with 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