265 / 2022-03-14 22:48:18

Stray Current Measurement and Analysis of a 500kV Substation

Stray currents; field measurements; DC bias; transformer neutrals; vibration

IEEE ICHVE 2022 / 1-PAGE ABSTRACT

Stray Current Measurement and Analysis of a 500kV Substation

XIAO Li, LI Shuyu, SHE Chuyun, LAI Zhenyu,WANG Yan,PAN Zhuohong

Southern Power Grid Shenzhen Power Supply Bureau Co

43634380@qq.com,185795980@qq.com,108685084@qq.com,85379795@qq.com,1853715694@qq.com,panzhuohong@ncepu.edu.cn

Purpose/Aim

Stray currents leaking from railways may invade the power supply system of urban power grids and cause DC bias hazards in transformers. In order to study the dynamic stray currents causing DC bias of transformers, it is necessary to conduct on-site stray current measurements and data analysis. The analysis of stray current data can effectively determine the effective spectral components of stray currents, which can provide reproducible basic data for transformer DC bias tests.

Experimental/Modeling methods

For a 500kV substation, a specially designed open coil type stray current sensor and an 8-channel vibration acceleration synchronization monitoring system were used to perform on-site measurements of stray current and transformer case vibration acceleration. A laptop computer is used to transmit real-time data between the mainframe stray current sensor and the PC software through a wireless receiver unit. The vibration acceleration synchronization monitoring system also realized the measurement of 8k sampling rate through USB connection.

Results/discussion

The stray current measurements show that although the stray current waveforms show alternating positive and negative characteristics, they show an overall flow from earth to the grid throughout the day. The non-zero net value of stray current throughout the day is the cause of the transformer DC bias. Fourier analysis of the stray current measurement data shows that the main spectrum of the stray current is concentrated in the frequency band of 0Hz~0.6Hz.

Conclusions

Field measurements of stray currents and transformer case vibration acceleration at the neutral point of a 500 kV substation were carried out using a specially designed open coil type stray current sensor. The results showed that the stray current waveform showed an overall unidirectional excursion, although it alternated positive and negative. The non-zero net stray currents resulted in a DC bias of the transformer. The Fourier analysis results of the stray current measurement data show that the main spectrum of stray current is concentrated within the frequency band of 0Hz~0.6Hz.