Relay protection as the first line of defense of the power system, in order to protect the UHV AC-DC interconnected power grid and smart grid security and stable operation has played an important role. If you want to ensure that the power system to normal operation, it must ensure the safety of transformer equipment. Due to external factors, the voltage in the operation or failure, so to take measures to solve these problems and deal with, but also to take the way to prevent common faults in the transformer, if the fault is not timely, it will affect Operation safety of power system.
The relay protection device has four performance:
First, sensitivity, refers to the use of sensitive coefficients that reflect the ability to fault.
Second, reliability, that does not occur to refuse action.
Third, fast, in the event of failure and abnormal, can be quickly resolved.
Four is selective, cut off the fault, so that failure in the smallest interval, the maximum part of the failure to continue to supply power.
Cause of Relay Protection of Power Transformer
Based on past operating experience, it can be concluded that the failure of the power transformer is generally divided into two kinds, one is the internal fault and the other is the external fault.
Internal fault is mainly in the transformer failure, such as a short circuit between the windings, lead wire or winding through the shell and the ground fault occurred.
The external fault is due to the external lead-out of the transformer tank and the insulation casing failure, such as the insulation casing broken lead to ground short circuit, because the lead line has failed to lead to deformation and so on.
Transformer internal fault according to the nature can be divided into electrical failure and thermal failure.
Thermal failure, usually manifested in the transformer temperature rise or local overheating. Under normal circumstances, the thermal failure generally has four kinds of fault conditions, when the temperature is less than 150 degrees Celsius, for the mild overheating; when the temperature of one hundred and fifty to three hundred degrees Celsius, for the low temperature overheating; when the temperature in the three 100 to 100 degrees Celsius, is the temperature overheating; when the temperature is higher than seven hundred degrees Celsius, for high temperature overheating.
Electrical fault mainly refers to the transformer internal because of high electric field strength caused by deterioration of the insulation performance or decline. Electrical fault according to the discharge energy density is not the same, divided into spark discharge, partial discharge and high-energy arc discharge.
Recent advances in relay protection technology: With the continuous improvement of the level of manufacturing equipment, the State Grid Corporation of China organized a technical research on a new generation of protection devices characterized by localization, miniaturization, plug and play, and relay protection Into a new stage of development. In order to fully verify the performance of the first localized plug-and-play protection devices, the China Electric Power Research Institute organized a harsh test. After a comprehensive, harsh test, through the test device will be in the cold, high altitude, high temperature, high humidity, strong sunshine, salt spray and other representative areas for hanging test operation.
When the power system is working abnormally or fails, the faulty device can be removed from the system in the shortest possible time and in the smallest area, or the power system can be signaled to allow the operator to service the fault of the power system. To ensure that users can use electricity properly, reducing the impact on people's lives and work.