When the power transformer is working under a relatively dangerous circumstance, the self-protection measures will take effect in general, while the abnormal working status may include overload, over-current resulted by an external short-circuit and the overvoltage at the neutral point caused by external earth short circuit, etc.. Besides, for the large-capacity transformer, since the rated working magnetic flux density is high and the working magnetic flux density is proportional to the voltage and frequency ratio, thus when working under overvoltage or low frequency circumstances, the fault of over-excitation may occur to the transformer.

For the circumstances above mentioned, the following protections are applicable for the large-scale power transformer and the overload protection system will take effect when faults occurred to protect symmetric overload, which may only be used as the signal. Protection against fuel gas, to protect the transformer from the internal short or oil level reduction faults. Over-excitation protection, to prevent the excitation from surpassing the permissible limit. Zero sequence current protection, to protect against the external phase-to-earth fault of large-scale earth current system. Over-current protection, to protect against the external phase fault and act as the standby protection system to the fuel gas protection and differential protection system (or current quick-break protection system). The differential protection and current quick-break protection system, to protect against all inter-phase short circuits of the transformer winding or the outgoing line, earth short circuit of the earth current system and winding inter-turn short circuit.

Among the protection systems above, the fuel gas protection system is applicable for various faults occurred in the fuel tank of the reactor transformer and oil level reduction cases. The oil immersed transformer of 0.8MVA or above and the workshop internal oil immersed transformer of 0.4MVA or above shall equip the fuel gas protection system. The above is the description shared on the self-protection measures against power transformer, and I wish it may be helpful for you guys. If you are interested in our products, please make contact and talk with us, no matter who you are and where you are from, you are always warmly welcomed by us and we are looking forward to creating a beautiful future together with you.