Ferroresonance protection of voltage transformers against ferroresonance
We measure high voltage for you
using instrument transformers for both outdoor and indoor applications, special transformers, sensors and power transformers
Protection of voltage transformers against ferroresonance
KPB Intra s.r.o.
Ing. Josef Stejskal
The phenomenon of „ferroresonnance “ can occur in single –pole voltage transformers in HV inadequately earthed cable networks. The impedance of transformer and the earthing capacity of the cable create a potentially oscillating RLC circuit. When an overvoltage come by the case of earth connection or some switching, the phenomenon of ferroresonnance can appear. The consequences are overheating of magnetic core and coil, damage of insulation and burst.
To prevent HV equipment we recommend to use connection of dump resistor in open delta of additional secondary windings (see picture 12 below). Mounting dimensions are in the picture 13. The value of resistance is 68 Ohm/ 200W (type of TR305 producer is „ Tesla Blatná“). Resistor is available to order in our firm and we can deliver it single or with other transformers.
We recommed to use it in new installations as prevention
We hope to contribute to understanding of issues and prevention of consequent potential damages by giving the explanation above.