Dry type transformers find use in locations where it is not possible to use oil-filled transformers such as shopping malls. Hospitals, residential complexes, etc due to the risk of fire. In dry type transformers air is used as the cooling medium instead of oil. 

The insulation used in dry type transformers is designed to withstand higher temperatures. Dry type transformers are thus more expensive than conventional transformers Vacuum Pressure Impregnation, Epoxy Resin cast are some of the methods of Insulation adopted in dry-type transformer construction. 

The downside of the dry type transformers is that the efficiency of these transformers is lower than that of conventional transformers. Dry type transformers cannot be designed for very high voltages and are designed only upto the MV range.

Transformer explosions can be catastrophic.  They can cause loss of lives and severe damage to the substation and surrounding area and long interruption to the power supply.

Transformer explosion occur due to low impedance faults within the transformer.  Such low impedance faults result in extremely high currents.  The arcs created during the faults result in very high temperatures which vaporizes the oil.  This heated and vaporised oil results in a sharp spike in pressure within the transformer.

Improper contact between the terminals of the online tape changer has also resulted in Transformer explosions. Hence, it is necessary that all Power Transformers be equipped with a reliable Explosion Protection System.

This pressure waves bounce off the transformer walls and this results in multiple waves due to reflection.  The superimposition of these reflected waves can result in extremely high pressures which result in the explosion.

Conventional methods of pressure relief such as the safety valve and devices such as the Buccholz relay take too long to respond and may not be sufficient to relieve the pressure or to activate a shutdown.  Relay Protection such as Differential Relays will not be adequate to protect the transfer as they take more than 60ms to operate including the time taken for the breaker to trip. 

Transformer Explosion prevention systems work by quickly depressurizing the transformer by activating a valve.   A sensor detects the initial pressure wave and opens a valve leading to a separate chamber to facilitate depressurization.  Thus the pressure is relieved quickly before it can build up.

The explosive gases which are produced by the arc need to be expelled into a separate chamber by pumping inert gas into the system.  This is usually taken care of by the Transformer Explosion Protection System. Failure to do this can result in a severe explosion when the transformer  is opened by technicians resulting in death or injury.

Below is a video on a transformer explosion captured on video

AAAC or All Aluminium Alloy Conductors are increasingly used in transmission linesinstead of ACSR Conductors. AAAC conductors have better mechanical properties and improved resistance to Corrosion as compared to ACSR conductor. 

AAAC Conductors are made from an alloy of Aluminium, Magnesium  and Silicon.  The absence of the steel core which is prone to corrosion makes AAAC conductors as ideal for use in coastal and industrial area. 

AAAC conductors have increased current carrying capacity, lower power loss and higher thermal stability limit.   Besides, AAAC conductors have higher strength-to-weight ratio Which reduce the cost of supports. 

In areas which have poor security, ACSR Conductors are prone to theft, particularly low voltage lines. AAAC conductors are not attractive to thieves as there are no alternative applications for the alloy which is made of aluminium, magnesium and silicon.      

This conductor is manufactured from Aluminium-Magnesium-Silicon alloy of high electrical conductivity containing enough magnesium silicate to give it better mechanical properties. AAAC conductors have better corrosion resistance and better strength to weight ratio and improved electrical conductivity than ACSR Conductors on equal Diameter basis.