5、Casing flashover
The incrusting
transformer bushing form the pollution flashover under the conditon of fog or light rain, and thus cause the
transformer HV side single phase earthing or phase to phase short-circuit.
transformer bushing breaks by the external force, mechanical stress, thermal stress are also the reasons for the flashover. The foreign body on the tank cover such as the tree branches will also cause the bushing discharge of phase to phase short circuit.
The above analysis of the
transformer fault from the noise, temperature, oil level, and apperance and other phenomenons is the initial judgement of the site. The internal fault of the
transformer is not only the single direct reflect, it also involves many factors, and some times it even shows the false phenomenons, sometimes there is a need to do the
transformer test and comprehensive analysis to find the cause, and therefore promote the rational approach.
The common fault and abnormal phenomenons of distribution
transformer in the process of power transmission and operation：
(1)The
transformer is always abnormal when the
transformer tranmiss the power after stop or commissioning transmission, for example, two phase high one phase low or the the value is zero; or the voltage of three phase of some commissioning
transformers are all very high and thus some elctrical equipment are burned down for the over high voltage；
(2)The HV fuse burn down and therefore can not transmiss the power；
(3)the
transformer can not tranmiss the power after thunderstrom；
(4)
transformer noise is abnormal, for example,the "zizi" or "pipi" sound, or the frog sound during the operation；
(5)The HV post heat burnt down, and there are serious damage or flashover signs in the HV bushing；
(6)the oil temperature continuously rise under the normal cooling condition；
(7)great change of the oil color, it maybe that there is carbon in the oil；
(8)There is abnormal sound, and the oil injects from the pressure-relief vent, oil conservator, the oil tank and the radiating collar distort, leak oil and penetrate and so on.
6.2.1judgement of the transformer failure by sound
（1）the sound of lack phase
When the transformer lack phase, and if the second phase does not connect, it remains silent when electrified, and only when submitted to the third phase that can have the sound; if the third phase does not connect, there is no change about the sound just the same as the second phase. There are about three reasons about the lack of phase: ① the lack of elctrical power; ② transformer HV fuse burns down the first phase; ③the uncareful transport and the thin HV lead result in the vibration break (not shell).
（2）voltage regulation tap changer is not in the right place or bad connected
When the transformer comes into service, and if the tap chager is not in the right place, there is a big chirps sound, and even will cause the HV fuse burns down; and if the tap changer is bad connected, it will squeal of the spark discharge sound, and if to increase the load, it will be burn the contact of the tap changer. If the aboved situation happens, it should promptly stop the power for repair.
（3）there are foreign bodies or the screw with tang is loose
When the screw with tang of the transformer core taptite is loose, there are screw cap component remain on the core or small metal parts fall into the transformer, then the transformer will give the wind sound and the sound like the magnet suck the gasket, while the voltage, current and temperature of the transformer is normal, and the treatment can be after the power cut.
（4）transformer HV bushing is dirt or cracking
When the transformer HV bushing is dirt or the surface enamel loss or crack, there will the flashover phenomenon or the sound of hiss will be heard, and if it was in evening, the spark can be seen.
（5）transformer core earthing breaks
Location: >> news >> FAQ >> Article
