دانلود رایگان مقاله انگلیسی سیستم کابل زمینی AC با ولتاژ بالا مبتنی بر نظارت زمان واقعی و محاسبه نظری جریان زمینی - IEEE 2018

Abstract:

For high-voltage (HV) AC cable transmission systems, the metal sheaths of three separate single-core cables are cross-bonded at each end of the cable section, to suppress the induced voltages in sheaths. The status of HV cable grounding systems is, therefore, an important consideration for power utilities. This study presents the status evaluations of 93 cable grounding systems in Beijing, obtained using the standards established by State Grid Corporation of China. As a result, 13 of these systems were classified as abnormal or defective. Additionally, a theoretical calculation of grounding currents was proposed and these 13 systems are re-evaluated by comparing the calculated and measured values of certain parameters. Based on this work, the authors propose a modified evaluation standards. It is indicated that the absolute value of grounding current (|I|) during a given 24-hr period has no relationship with the status of grounding system, and the ratio of grounding current to load current (K) at the time of maximum load current could be used as a status indicator instead of K at some other time, in order to avoid possible incorrect evaluations due to light load conditions.

5 Conclusions

i. New criteria for evaluation of the status of the HV cables grounding systems have been proposed, based on comparison of the calculated and measured values of the grounding current/load current ratio K. Assuming that agreement between the measured and calculated values of |I| and K within 5% is accepted as a reliable indication that the status of a grounding system is normal.

ii. Based on the status evaluation criteria suggested by the Electric Power Company, the 93 HV cable grounding systems in Beijing was evaluated, and the 13 abnormal or defective grounding systems may be divided into three groups based on the numerical characteristics of |I| and K. It is indicated that |I| have no relationship with the status of grounding system, and K can be directly used to indicate whether the status of grounding system is normal or not. It is suggested that the value of K at the time of maximum load current during a given 24-hr period, could be used as a status indicator instead of K at some other time, in order to avoid possible incorrect classifications due to light load conditions.

iii. The status evaluation results based on real-time monitoring data of grounding current show that, Beijing HV cable metal sheath grounding system is smooth. For the currently operating and new HV cables, the effective technical measures to improve the cable grounding system status level include the installation of online grounding current monitoring system, and the selection of overall compound seal grounding box and cross-connect box.