discharges occur inside and on the surface of medium and
high voltage insulation, and are the result of flaws, cracks,
voids and irregularities. These imperfections create voltage
stresses and eventually cause failure of the insulation.
Insulation failures begin and are characterized by small
detectable releases of energy or partial discharges.
Partial discharges are indications of insulation degradation
and occur in electrical systems that are 600V and higher
(2.4KV, 4.16KV, 12KV, etc). The types
of electrical equipment vulnerable to partial discharge includes, but is
not limited to, switchgear, generators, transformers,
motors, circuit breakers, cables, and cable connections.
Table 36 of the IEEE Gold Book on Electrical reliability
indicates that 84% to 95% of transformer, switchgear
bus, bus duct, cable and cable splice failures
are caused by insulation breakdown. Regular partial discharge testing can
prevent these failures from occurring.
The Insulation Quality (IQ) Program allows the insulation
quality of medium and high voltage equipment to be tested
without requiring an outage, and
is non-destructive. Valuable
information is recorded & analyzed to determine equipment condition which
allows maintenance activities to be planned and prioritized. Regular testing
allows comparison of recent tests with past records for trending analysis. Trending
identifies when a problem started and how rapidly the problem is progressing.
Partial discharge testing ensures system reliability. This method of evaluating
electrical equipment maximizes system productivity by protecting the facility
from random medium and high voltage electrical failures.