Fuses for high voltage measuring transformers – method of fuse selection, use
We measure high voltage for you
using instrument transformers for both outdoor and indoor applications, special transformers, sensors and power transformers
Fuses for high voltage measuring transformers
KPB Intra s.r.o.
Ing. Josef Stejskal
Use of fuses for voltage transformers is a long-term custom supported by rich experience. A fuse is a protective element that ensures transformer disconnection from network circuits by switching off the currents exceeding the rated value. Switching off a current usually results from a defect of the insulation system of the transformer; however, transient phenomena and ferro-resonance currents also cannot be excluded in many cases. The fuse usually switches off upon bursting of the transformer and development of an electric arc. It means that the function of fuses consists in protection of the surroundings against destructive effects.
High voltage current protections are the new protective component. In KPB Intra they are produced in two-type dimensions into electric system up to 22kV and also for 35kV (picture 5). Rated current protections are 32,50 and 80mA. High voltage will be switched off and disconnected at their exceed. Current protections position predetermines their higher sensitivity for overcurrents than at current fuses. Their contribution is faster frequent disconnection often before its explosion.
The company offers application of fuses in transformers in several modifications, e.g. Fig. 1 shows a fuse in the horizontal position with an outlet in its axis. A fuse in the horizontal position with an outlet in the vertical axis of the transformer is another variant, see Fig. 2. The third method is represented by a vertical fuse in the axis of instrument high voltage with the outlet on a cable, see Fig. 3. Fuse carriers are located in epoxy casing. Connection to the transformer high voltage terminal is made by means of a screw; lug type thread is illustrated in Fig. 2.
| Fig. 1 | Fig. 2 | Fig. 3 | Fig. 4 |
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| Fig. 5 | |||
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VTS38 transformers for 35 kV networks illustrated in Fig. 4 can be fitted with fuse 3.15A supplied by BRUSH. This concept is identical to the case illustrated in Fig. 3. Individual methods of design arrangements have resulted from requirements of the customers. Specific dimensions form a part of company documentation and can be sent upon request.
In conclusion it is possible to say that we definitely recommend fuse preselection and transformators protection.