Unexpected primary fuse blown on instrument VT's
Unexpected primary fuse blown on instrument VT's
(OP)
Repetitive and aleatory faults due to primary fuse blown without apparent cause on instrument voltage transformers, open delta connection. No secondary faults has been reported. Usually, events occur in A and C phases and rarely in B phase. VT's are 4200/120 V, 60 Hz, protected by current limiting fuses E rated. Some voltage sags and distortioned voltage waveforms has been registered.
Thanks to anyone for comments.
Jose Barrios
Thanks to anyone for comments.
Jose Barrios






RE: Unexpected primary fuse blown on instrument VT's
If they are failing under perceived steady-state conditions, you may have some ferroresonance on your system. Do you have any secondary voltage traces from the VT's at the time of the fuse failure?
RE: Unexpected primary fuse blown on instrument VT's
Long Shot — See pages 10-14 on VT-primary fusing. For open-delta PTs, there is some discussion of fusing “…those connections in which each fuse carries the exciting current of only one transformer.” The text referes to this as a “Class-1” connection.
www.geindustrial.com/products/buyersguide/GEP-9186-6.pdf
Although the “four-fuse” recommendation seems a bit unusual, it may be applicable to the subject installation for lack of other solutions.
RE: Unexpected primary fuse blown on instrument VT's
Fuses failed only under steady-state conditions.
Secondary traces from the VT´s at the time of the fuse failure shown a distorted waveform and undervoltage (only one phase)
RE: Unexpected primary fuse blown on instrument VT's