EHV and VHV substations tend to have a signature hum; this is due to small electrical arcs. This is normal. Most of the time this will not be audible on VHV and EHV power lines. If you are hearing this from the power line, it could be bad and the utility may want to know. It shouldn't be a risk to you, however the hum may be resulting from arcing, which can be fairly high frequency, which can mess with electronics's signals such as cell phones and radio (won't damage them, just bad reception).
A: Hissing is because is overheating before it destroy itself. But other noises are caused by loose lamination of the core.
B: Hissing noise is produced due to this reason but here is another important point is about frequency (e.g for 50 Hz) the core lamination face attractive and repulsive forces fifty times in one
cycle because frequency is 50 Hz.
Another Answer
The original answer is unnecessarily melodramatic. Transformers are fitted with protective devices that will disconnect the transformer long before a rise in temperature will cause it to 'destroy itself'!
'Hissing', as opposed to 'humming', is usually caused by the ionisation of air in the immediate vicinity of the transformer's high-voltage bushings (hollow insulators). This also manifests itself, after dark, as a blue-coloured luminous discharge.
'Humming', on the other hand, is due to something called 'magnetostriction', a distortion to the core laminations -exactly as described in the original answer, except that the attractive/repulsive forces are twice that of the supply frequency (i.e. 100 times, in the case of 50 Hz), together with harmonics based on that frequency.
due to corona loss at high voltage on line and insulation failoure beween conductors.these is see in high voltage lines i.e, means >400 Kv.
Usually a loose iron core or saturation of the core.
there have interference between T.V. and radio waves . for stopping this resistance is used in starter.
Decrease pressure to prevent excessive velocity
An isolation transformer (or more commonly, amplifier) reduces noise in the system from the power source. This is especially necessary in medical applications where the signals that are being read are very tiny and even a small amount of noise can disrupt a signal and make it unreadable.
noise do not occurs in positive terminals noise like all signals must have a return to be seen as evidence
Skin effect is a physical effect that operates on thick conductors. In a transformer the conductors are usually too thin for any substantial skin effect to occur.
It doesn't. It exists in all electrical machines, d.c. or a.c., motor, generator, or transformer.
Madagascan hissing cockroaches make a noise by forcing air out of a special hole.
when you breath is air and force it out with your tongue it makes the hissing noise
making a hissing noise
A hole in the chest ... the hissing comes from the leaking air.
A hissing noise
Possums make a variety of hissing and snorting noises.
Yes. They make grunting-hissing noises.
Signs of your battery exploding can be swelling overheating and a hissing noise
Sheep do bleat and snake make a hissing noise.
Roaring, purring, grunting, snarling and hissing.
Decrease pressure to prevent excessive velocity
The power brake booster may be going bad.