1. Resistance to Internal Faults
Martin Schaak Olaf Bischur Thomas Stommel

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

3. 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

4. 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 %
49.3%
47.1%
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

5. 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

6. 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)

7. 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 , Table 2: “Locations, causes and examples of measures to reduce the probability of internal faults”

8. Comparison of the Internal Arcing Test IEC 60298 vs. IEC 62271-200
Test conditions according to IEC 60298
Test conditions according to IEC
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

9. 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 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.  

10. 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

11. 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

12. Test Arrangement Conditions (1)
(a) Height of ceiling - Height of test object 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 mm
(c) Indicators - Covering 40 to 50 % (checker pattern)
800 mm
100 mm
600 mm

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

14. 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

15. Test Setup
Current test object, open vessel and ignition wire

16. 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

17. High-Power Test Laboratory at the Location Frankfurt am Main

18. Test Preparations
Arrangement of test object in room mock-up

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

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

21. 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.

22. Resulting Document
As an example from previous tests

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

24. Thank you very much for your attention!