Surges transferences

The need to protect a rotating machine from switching surges, contact bouncing and surge transferences 17/576... 

Because of a surge transference from higher voltage to the lower voltage side of a power transformer, and... 

Surge transference through a transformer (from the higher voltage side to the lower voltage side)... 

A transformer has both dielectric capacitances and electromagnetic inductances. Surge transference thus depends on the electrostatic and electromagnetic transient behaviour of these parameters as noted below. 

JVote The above analysis also corroborates that surge transferences are more severe in high ratio transformers than low ratio ones (Section 18.5.2)... 

Vk = voltage of surge transference Cp = lumped capacitance between the primary and the secondary windings... 

Dampened surge transference to account for the eapa-citiince C of ctibles and icrminal equipment. 

It also covers the steepness of TRVs, their significance and methods of taming them. Reflections of travelling waves and surge transferences are also described. 

The main features in which the Radford process differs from the batch operation are in thermal dehydration and compounding. Water-wet nitrocellulose on a continuous vacuum belt filter is vacuum-dried followed by hot air transfusion (80°C) to reduce the moisture to less than 2%. After cooling, alcohol is sprayed on the nitrocellulose to a concentration of 15—20%. The alcohol-wet nitrocellulose is then transferred from a surge feeder to a compounder by a continuous weigh-belt along with the other ingredients of the composition, which are also weighed and added automatically. 

During filling, the catalyst is distributed uniformly to avoid the possibility of channeling that coiild lead to poor heat transfer, poor conversion, and harm to the catalyst because of hot spots. During startup, sudden surges of flow may disturb the bed and are to be avoided. For instance, in a study of a hydrodesulfuiizer by Murphree et al. (Ind. Eng. Chem. Proc. Des. size unit varied between 47 and 80 percent with different modes of loading and startup. 

All the tibove surges and even the transference of a lightning surge from an overhead line through inter-... 

The motor may also fail due to system overvoltages, such as during a fast bus transfer (Section 7.19) or due to voltage surges (Section 17.3). 

These are only basic guidelines. It is difficult to define exposed or shielded equipment accurately. Equipment installed indoors may never be subject to lightning strikes or their transferences, but may be exposed to severe switching surges and require surge protection as for an exposed installation. There is no readymade formula by... 

The front of the transferred surge will, however, be less steep and dampened than on the primary side due to capacitive dampening. But sometimes this may also exceed the BIL, particularly of the tertiary (if provided) and also the secondary windings of the transformer, as well as the cable and the terminal equipment connected on the lower voltage side. This is especially the case when the primary side voltage is very high compared to the secondary. Protection of the secondary windings, in all probability, will be sufficient for all the cables and terminal equipment connected on the secondary side. 

The terminal equipment connected on the secondary side of the transformer is thus automatically protected as it is subject to much less and attenuated severity of the transferred surges than the secondary windings of the transformer. Nevertheless, the BIL of the interconnec-ting cables and the terminal equipment must be properly coordinated with the BIL of the transformer secondary, particularly for larger installations, say, 50 MVA and above, to be absolutely safe. Example 18,2 will explain the procedure. 

---