High Voltage Switchgear Internal Arc Fault

IEC 62271-200 Clause 8.104 states that if the switchgear is installed, operated and maintained according to the instructions of the manufacturer, there should be less probability that internal arc occurs. Failure within the switchgear due to a defect or an exceptional service condition or maloperation may cause an internal arc, which is a hazard if persons are present.

Faults are more likely to occur inside a switchgear enclosure than in other locations. IEC 62271-200 Table 102 provides a list of locations where faults are most likely to occur, the causes of failure and possible measures to decrease the possibility of internal arc faults, most of which are applicable to installation, commissioning, operation and maintenance.

Table 102 - Locations, causes and examples of measures to decrease the probability of internal arc faults
Locations where internal arc faults are most likely to occur
(1)
Possible causes of internal arc faults
(2)
Examples of possible preventive measures
(3)
Connection compartments Inadequate design Selection of adequate dimensions
Use of appropriate materials
Faulty installation Avoidance of crossed cables connections. Checking of workmanship on site. Correct torque
Failure of solid or liquid insulation
(defective or missing)
Checking of workmanship and/or dielectric test on site.
Disconnectors
Switches
Earthing switches
Maloperation Interlocks. Delayed reopening.
Independent manual operation. Making capacity for switches and earthing switches. Instructions to personnel
Bolted connections and contacts Corrosion Use of corrosion inhibiting coating and/or greases. Use of plating. Encapsulation, where possible
Supplemental heating to prevent condensation.
Faulty assembly Checking of workmanship by suitable means. Correct torque. Adequate locking means
During racking-in or rackingout of withdrawable parts.
E.g. due to dielectric change of state in combination with damage or distortion of the plugging contacts and/or shutters
Checking of workmanship at site.
Instrument transformers Ferro-resonance Avoidance of these electrical influences by suitable design of the circuit
Short circuit on low-voltage side for VTs Avoid short circuit by proper means for example, protection cover, low-voltage fuses
Circuit-breakers Insufficient maintenance Regular programmed maintenance
Instructions to personnel
All locations Error by personnel Limitation of access by compartmentalisation.
Insulation embedded live parts. Instructions to personnel
Ageing under electric stresses Partial discharge routine tests
Pollution, moisture ingress of dust, vermin, etc. Measures to ensure that the specified service
conditions are achieved (refer to clause 2). Use of gas-filled compartments
Overvoltages Surge protection. Adequate insulation co-ordination.
Dielectric tests on site

Reference: IEC 62271-200 (2011)

About the Author

Ver Pangonilo
A Filipino Engineer, Registered Professional Engineer of Queensland (RPEQ) - Australia and Professional Electrical Engineer (PEE) - Philippines with extensive experience in concept select, front-end engineering, HV & LV detail design, construction and commissioning of Hazardous and Non-Hazardous Area electrical installations in water and waste water pipeline and pumping facilities, offshore platforms, hydrocarbon process plants and pipelines including related facilities. Hazardous area classification and design certification (UEENEEM015B, UEENEEM016B, UEENEEM017B).
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