Seasonal variations of grounding parameters by field tests
- Georgia Power Co., Forest Park, GA (United States). Research Center
The past fifteen years have seen considerable research in the area of substation grounding design, analysis and testing. These research include the revision of the IEEE Std.-80, the development of PC based computer programs, the in depth analysis of grounding parameters and the development of new field testing methods and devices. In spite of these advances, several questions were often asked, primarily due to safety concerns. The questions were related to the seasonal variation of critical grounding parameters such as the soil and gravel resistivities and their influence on the body current in an accidental circuit. There was also a need to study the total behavior of a substation ground grid with respect to different weather conditions by performing field tests. In response to the above needs, a comprehensive field test program was developed and implemented. The field test consisted of flowing approximately 150 amperes through the Texas Valley ground grid from a remote substation. The parameters investigated in this project were the grid impedance, the grid potential rise (GPR) , the fault current distribution, the touch/step voltages, the body current on different gravel beds and the soil/gravel resistivities. The measurements were performed in the rainy, winter and summer weather conditions during 1989--1990. The field test results, overall, indicate that the rainy weather is the worst condition for the substation safety because of the substantial reduction in the protective characteristics of the gravel. Among the gravel types, the washed gravel has much superior protective characteristics compared to the crusher run type of gravel. A comparison of SGSYS computed grounding parameters with measured results indicates that the grid resistance and GPR compare well but the computed touch voltage and body current are substantially higher than the measured values.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (United States); Georgia Power Co., Forest Park, GA (United States). Research Center
- Sponsoring Organization:
- EPRI; Electric Power Research Inst., Palo Alto, CA (United States)
- OSTI ID:
- 7178516
- Report Number(s):
- EPRI-TR-100863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GRIDS
ELECTRICAL TESTING
POWER SUBSTATIONS
ELECTRIC GROUNDS
ELECTRIC POTENTIAL
FIELD TESTS
POWER TRANSMISSION
SAFETY ANALYSIS
SOIL-STRUCTURE INTERACTIONS
WEATHER
ELECTRODES
MATERIALS TESTING
NONDESTRUCTIVE TESTING
TESTING
240200* - Power System Networks
Transmission & Distribution- (1990-)