Impacts Of Connection Mode For Secondary Circuit Of TV On Line Protection

With the rapid development of our social economy, the electric power industry are also experiencing profound changes. the continuous expansion of grid work for relay protection is put forward higher requirements. How to ensure the reliability of relay protection device, selectivity, quick acting and sensitivity increasingly become a big topic in front of scientific research personnel.Relay protection device includes measuring compared commonly components, logic components and perform output components. And the accuracy of the measuring element is the premise of the protection device can correct operation. Voltage transformer plays a very important role in the whole process. Voltage transformer using the electromagnetic induction principle to a circuit of the power system of power reflected in secondary loop. in the operation of the power grid, fault detection, condition control and relay protection But in the power system of brake operation and harsh environment, such as lightning appear larger amplitude of high voltage in the process of threat to the safe operation of power grid. How the voltage transformer can correctly reflect power system dynamic process is very important.The main functions of the voltage transformer include:supply voltage transformer relay protection device of the input signal, used for points such as closing down brake operation, the effect of different voltage transformers of different output capacity, and accurate level also each are not identical. In modern power system, the general can do four winding type voltage transformer, such a voltage transformer can be set three functions in an organic whole, in addition, the voltage transformer can be divided into electromagnetic voltage transformer and capacitor voltage transformer, including electromagnetic voltage transformer capacity is small, similar to a small capacity transformer, but compared with the transformer for safety performance requirements higher, secondary side large voltage coil impedance instrument, similar to a no-load operation of transformer. As the electric power system for output voltage level is higher and higher, electromagnetic voltage transformer takes a lot of volume to meet the requirements of its for voltage level. So got more application of capacitor voltage transformer (CVT) used in power system.In this paper, combining theory analysis and practical engineering, the main research the error voltage transformer secondary circuit grounding, the influence of the system fault on line protection main work is as follows:(1)First of all, when the secondary circuit grounded through two points or the grounding of the secondary winding and third winding is common, the qualitative analysis of the action of the relays is done through the changes of the voltage vector of the voltage changes.(2) Then, two examples are cited,which have waveforms recorded at the scene to verify the conclusion.(3)Finally, according to the findings of the study, a method was found to verify the number of the grounding point at the secondary circuits of TV in the substation.