Greetings: Would be grateful for your thoughts regarding the origin of any bases used for the inrush capability of primary fuses for potential transformers. When was the last time you drove down the highway without seeing a commercial truck hauling goods? Best Of All, Transformer solved problems pdf’s Free! Eng-Tips’s functionality depends on members receiving e-mail.
By joining you are opting in to receive e-mail. Promoting, selling, recruiting, coursework and thesis posting is forbidden. 2 members like this thread! Would be grateful for your thoughts regarding the origin of any bases used for the inrush capability of primary fuses for potential transformers. 1 member likes this post! The fuses are there to protect the source and the wiring to the PTs.
PTs by nature of their duty are not liable to overloads. Any internal fault in a PT which results in a blown fuse is not going to be prevented by the fuse clearing. However, if a PT shorts internally you don’t want the PT primary conductors vaporizing, hence the use of primary fuses for PTs. A transformer may take up to 25 X FLC during the energization inrush. Many fuses rated at 12 X FLC will carry through an energization inrush due to the thermal lag, but some designers may prefer the added safety of 25 X FLC rated fuses.
Is there a trend to avoid primary fuses in MV or HV PTs? To develop a current of 12 or 25 FLC fault current from an interturn fault in PT will may take quite a bit of time and by then PT may have blasted. Railway Electrificatication with out fuses. But earlier projects they did use fuses.
Any change in fuse setting if Pts are of capacitor voltage type instead of electromagnetic? First, I am not in a part of the industry where I can comment in an informed manner as to present practice. Possibly some others will post in here. As to interturn faults, the purpose of the fuse is not to protect the transformer, it is to protect the wiring feeding the transformer. When an inter turn fault does develop into a short, the fuses will disconnect and prevent the primary conductors from vaporizing and destroying the cubicle. Interturn faults tend to be short lived.