Resistance to Internal Faults

1
Resistance to Internal Faults
Martin SchaakOlaf BischurThomas Stommel
2
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

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
1996-2000
49.3
47.1
2001-2005
40
27.0
27.4
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 riseand pressure rise
Evaporation
Thermal conduction, melting
Electric arc, plasma beam with a temperature of
about 20,000 C
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 62271-200, 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
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
  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.

?
?
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 sExample
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
600 mm 100 mm - If height of test object
1.5 m gt 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)
13
Test Arrangement Conditions (2)
For the test object in the room mock-up
For the indicators
14
Acceptance criteria
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
21
Acceptance Criteria
22
Resulting Document
As an example from previous tests

23
Discussion / Questions

24
Thank you very muchfor your attention!