What causes generator
voltage transformer failure?
1.Winding turn to turn
short circuit
Fault phenomenon: During
operation, the temperature rises, there is discharge sound, the high-voltage
fuse is blown, the secondary side voltmeter indication is unstable.
Reason: System
over-voltage, long-term overload operation, aging insulation, poor
manufacturing process.
2.Insulation damage
between iron chips
Fault phenomenon:
temperature rise during operation.
Reason: Poor insulation
between iron chips; Poor service environment; Long term operation at high
temperature promotes aging of insulation between iron chips.
3.Poor contact between
grounding lug and iron core of diesel engine
Fault phenomenon: There
is discharge sound between iron core and oil tank during operation.
Reason: The grounding
plate is not inserted tightly, and the mounting screw is not tightened.
4.Core loosening
Fault phenomenon: There
is abnormal vibration or noise during operation.
Reason: The iron core
clamp is not clamped, and the iron chip is loose.
5.Winding break.
Fault phenomenon: During
operation, there may be arc and discharge noise at the disconnection. The
voltmeter indication of the broken phase is reduced or zero.
Reason:The winding leads
are broken due to poor welding process, insufficient mechanical strength or
unqualified outgoing wires.
6.Winding to ground
insulation breakdown
Fault phenomenon: The
fuse on the high voltage side of the diesel engine is continuously blown, which
may cause discharge noise.
Reason: The winding
insulation is aging or there are conductive sundries in the winding, the
insulating oil is damped, over-voltage breakdown, serious oil shortage, etc.
7.Short circuit between
winding
Fault phenomenon: the
fuse on the high-voltage side is blown, the oil temperature is increased
sharply, and even the fuel injection is smoking.
Reason: the winding
insulation is aging, the insulating oil is damped, and there is serious oil shortage.
8.Discharge flashover
between casings
Fault phenomenon: fuse
on high voltage side is fused and bushing flashover is discharged.
Reason: mechanical
damage of casing due to external force. There are foreign matters or small
animals entering between casings, the casings are seriously polluted and the
insulation is poor.
When
using voltage transformer, what should we pay attention to?
1.We should operate with
a suitable transformation ratio, rated capacity, accuracy level. And consider
that the voltage drop caused by the secondary wiring will affect the
measurement results, so the length can not be too long.
2.The primary winding of
the voltage transformer is connected to the line, and the secondary winding is
connected to the measuring instrument and relay. When wiring, pay attention to
polarity group and phase, and do not connect them wrong.
3.The primary and
secondary sides of the voltage transformer shall be equipped with fuses to
prevent short circuit accidents. When working on the secondary circuit, pay
attention not to short circuit the secondary side of the voltage transformer,
otherwise it will cause overheating and burn the transformer.
4.One end of secondary
side of voltage transformer shall be grounded for the same reason as current
transformer.
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