Understanding Corona and Partial Discharge
Corona discharge is often an
indication of maintenance and safety problems that may
cause severe deterioration in maintenance especially on
insulators. Inspections with the DayCor corona camera
detects and pinpoints corona, arcing, partial discharge
and electrical flashes on high voltage (OHT) lines,
cables and insulator components. Inspection for Corona
enhances predictive maintenance procedures.
What is Partial Discharge?
Partial discharge is an electrical discharge that
does not bridge the entire space between the two
electrodes.
What is Corona?
Corona discharge is a luminous partial discharge from
conductors and insulators due to ionisation of the air,
where the electrical field exceeds a critical value.
Very little heat is created as a result of this
discharge, and it cannot therefore be detected by
infrared thermal cameras. Corona has the following damaging and environmental
disturbing effects:
-
Generation of corrosive materials, like ozone and
nitrogen oxides that yields nitric acid under conditions
of high humidity. These corrosive materials shorten the
life span of lines and substations components.
-
Corona causes damage
to insulators, especially non-ceramic (NCI)
insulators
-
 Radio interference (RI/ RFI) mainly to
AM transmissions
-
Audio noise
-
Radio interference
What can Corona detect?
-
Indication of the
effectiveness of washing of components
-
Indication of imminent
Flashover or Tripping
-
Indication
of potential fault
-
Indication of poor
installation
Corona Light Emission
The corona discharge emits radiation in the
280nm-405nm spectral range, mostly in the ultraviolet
(UV) and therefore is invisible to the human eye, though
relatively weak emission at about 400 nm might be
observed at night under conditions of absolute darkness.
The corona emission in the 280nm-405nm spectral range
cannot be detected during daytime due to the highly
disturbing background of solar radiation. The
DayCorŽ corona camera is a bi-spectral Solar Blind
UV-Visible imager, designed to detect these very faint
UV emissions in the solar blind UV band, with high
signal to background ratio.
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