Busbar Protection Based On Transient Component Digital Test And Analysis

Bus protection is critical in power system. Therefore, the bus protection with high reliability, good selectivity and high sensitivity is necessary.Traditional bus protection is mostly based on industrial frequency component. The anti-TA saturation ability is poor and the action speed is low. Then new ultra high speed bus protection algorithm based on fault transient component is proposed.Bus protection based on transient component uses the transient traveling wave within a few milliseconds after fault. It could avoid the impact of TA saturation, so it has practical research significance.Based on the study of transient traveling wave signal, different high speed transient component bus protection principles are found by comparing singularity or high frequency component between bus internal fault and external fault. The use of amplitude and polarity of traveling wave head can constitute a series of traveling wave based bus protection, such as current traveling wave differential bus protection. The use of high frequency transient component of fault can constitute transient based bus protection like transient high energy bus protection.With the substantial increase of hardware level and the emergence of DSP, as well as the rapid development of new digital signal processing tools and artificial intelligence technology, this new rapid bus protection principle is achieved. Wavelet transform can analyze the component of signal, and its good feature of time-frequency localization makes it more exactly and reliably to detect singular characteristics of signal, so wavelet transform is used in this paper.An integral protective device is consisted by starting element and fault decision element. The bus internal fault is identified after the starting element act. There are many starting elements, but starting element based on wavelet transform modulus maxima (WTMM) or wavelet transform modulus sum (WTMS) has good reliability and high speed.This paper will present starting element and variety of bus protections based on fault transient component, and discuss the protection operating characteristics under factors such as fault characteristics, bus structure, bus capacitance, un-synchronization closing of three-phase breakers, lightning arrester operation, substation lightning invading wave, transfer characteristics of transformer, sampling rate and the wavelet scale. Simulation is carried out with the electromagnetic transient simulation software PSCAD/EMTDC.However, the ultra high speed bus protection faces many challenges which can't be resolved entirely. One of the main problems is the contradiction between speed and reliability. The fault transient signal is large random component contained, easy influenced, fast disappeared, not repeated, and difficult to measure and capture accurately, these all lead to the low protection reliability. So the next study step is to optimize the performance of protection and make use of them.