Resistance to Internal Faults Martin Schaak Olaf Bischur Thomas Stommel

Topics Resistance to internal faults Causes and physical effects Basic standard IEC 62271-200 Test object NXPLUS C Live test Analysis and review Open questions

Causes of Internal Faults Ageing of insulating materials under electrical stress Corrosion Overstressing Ferroresonance, overvoltages Defective installation, incorrect maintenance Maloperation Pollution, humidity, small animals penetrating in the switchgear

Electrical Accidents Reported electrical accidents in the sphere of activity of BGFE 80 % Electrical effects of high voltage 67.5 % Institute for the research of electrical accidents 60 % 1996-2000 49.3% 47.1% 2001-2005 40 % 27.4% 27.0% 20.8% 20 % 5.8% 1.5% 0 % Electric shock Arcing fault Electric shock and arcing fault Arcing fault with electro-ophthalmia and burns 1 internal arcing fault per 10,000 GIS panels and year

Physical Effects of an Internal Fault Energy balance Radiation Temperature rise and pressure rise Electric arc, plasma beam with a temperature of about 20,000 °C Thermal conduction, melting Evaporation

Possible Effects of an Internal Fault Light effect (blinding, shock) Noise development (hearing damage) Thermal load (heat, burns) Smoke development (breathing) Projection of parts (cuts) Toxic effects (intoxication) Pressure development (damage to buildings / walls and door), physiological influence on a person (shock, falling caused by defensive reaction, circulatory insufficiency)

Avoidance of Internal Faults Quality during design, production and installation Training of personnel (avoidance of maloperation) Maintenance (replacement of worn-out parts, cleaning) Active systems for fault detection Other measures for avoidance of internal arcs are described in IEC 62271-200, Table 2: “Locations, causes and examples of measures to reduce the probability of internal faults”

Comparison of the Internal Arcing Test IEC 60298 vs. IEC 62271-200 Test conditions according to IEC 60298 Test conditions according to IEC 62271-200 Application of test conditions by agreement between manufacturer and operator Test according to defined conditions of the standard Any room height, distances Defined test setup, distances Any points for arc initiation Defined points for arc initiation Defined acceptance criteria can be applied Defined acceptance criteria must be applied Feeding directions freely selectable Defined feeding direction Declaration on rating plate not necessary Internal arc classification (IAC) must be declared on the rating plate Description of test results Test passed / not passed

Comparison of the Internal Arcing Test Consequences from IEC 62271-200 Classification with IAC  Tested and passed according to standard conditions Classification without IAC  Not tested or not passed Existing switchgear assemblies tested to IEC 60298 are still allowed to operate, however they might not be comparable with other switchgear. Consequence for operators (as comparisons are hardly possible)  Request tests according to the prescribed general standard, i.e. IEC 62271‑200. This provides the quality feature of “standardized” comparability.  

Designation of the Internal Arc Classification Classification: IAC ( “Internal Arc Classified” ) Accessibility: A (F, L, R)* B (F, L, R)* C Test values: Current [ kA ] and duration [ s ] * F = Front; L = Lateral; R = Rear Example 1: IAC A FLR 25 kA 1 s Example 2: IAC B FL 25 kA 1 s

Test Procedure For switchgears with internal arc classification (IAC) according to IEC 62271‑200: Test object consists of 2 panels as a minimum Test in every compartment and at least in the end panel Completely equipped test specimen (reproductions are accepted) Test only on not pre-stressed functional compartments Defined distances (walls, ceiling) 40 % to 50 % of the surface must be covered with indicators Defined direction of power flow and points of arc initiation SF6-insulation may be replaced by air Evaluation of all five criteria Busbar compartment Circuit-breaker compartment Cable compartment

Test Arrangement Conditions (1) (a) Height of ceiling - Height of test object + 600 mm ± 100 mm - If height of test object ≤ 1.5 m > Min. height of ceiling 2 m (b) Rear wall - Non-accessible 100 mm ± 30 mm - Accessible 800 mm + 100 mm (c) Indicators - Covering 40 to 50 % (checker pattern) 800 mm 100 mm 600 mm

Test Arrangement Conditions (2) For the test object in the room mock-up For the indicators

Acceptance criteria Criteria according to IEC 62271-200 No. 1 Correctly secured doors an covers do not open Deformations are accepted with restrictions Additionally, if distance to wall after installation is smaller than tested: The permanent deformation is less than the intended distance to the wall No. 2 No fragmentation of the enclosure No projection of parts above 60 g No. 3 Arcing does not cause holes in the accessible sides up to a height of 2 m No. 4 Indicators do not ignite due to the effect of hot gases No. 5 The enclosure remains connected to its earthing point new new

Test Setup Current test object, open vessel and ignition wire

Test Parameters Type of accessibility “A” Free-standing arrangement Short-circuit current: 25 kA Short-circuit duration: 1 s Height of ceiling: 2.8 m Switch position of all devices: “CLOSED” Operating tool inserted Infeed via right-hand disconnector panel 3-phase arc initiation in gas vessel of CB-panel at cable connection bushings Direction of power flow as feeder panel  IAC A FLR 25 kA 1 s

High-Power Test Laboratory at the Location Frankfurt am Main

Test Preparations Arrangement of test object in room mock-up

Live Test Performance of internal arcing test (Changeover to high-power testing laboratory)

Flashback (Slow Motion of Live Test) Test recorded from different camera positions Camera A Camera B Camera C Switchgear front Switchgear side

Acceptance Criteria Criteria according to IEC 62271-200 No. 1 Correctly secured doors and covers did not open. No. 2 No fragmentation of the enclosure occurred and no parts with an individual mass > 60 g were projected. No. 3 Arcing did not cause holes in the accessible sides of the enclosure up to a height of 2 m. No. 4 No indicators ignited due to the effect of hot gases. No. 5 The enclosure remained connected to its earthing point.

Resulting Document As an example from previous tests

Discussion / Questions Testing Laboratory Medium Voltage Frankfurt am Main Your competent partner for tests on medium-voltage switchgear

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