Simplified conservative measurements of touch and step voltages

摘要

Protection against electric shock requires grounding systems thatmust be designed primarily to keep touch voltage (E_t) andstep voltage (E_s) to a safe value. Testing of the efficiencyof a grounding system is mandatory to verify the capability to satisfythe protection requirements at the end of the construction andperiodically in the following. With urban development and buildingsgrowth adjacent to power systems, grounds systems that are notmetallically connected may often be found. They are thus significantlyinterdependent as they are located in each other's area of influence andparticularly it is useful to consider ground potential difference (GPD).It becomes increasingly difficult to choose suitable locations for testprobes to make resistance, E_t and E_s tests of agrounding system. Accuracy of tests requires reaching remote earth andfor large grounds the spacing required may not be practical or evenpossible. Unfortunately accurate measurement is often unfeasible, owingto the additional difficulty to measure both the hazardous voltages ofthe ground system, where test ground current flows, and the hazardousvoltages of influenced ground systems. Since the rigorous measure canresult too much laborious or too much expensive, a simplifiedconservative testing method of the behavior of ground electrodes can befavorable. This paper discusses an approach to the above-simplifiedtesting method, which relies on single, or multiple auxiliary electrodesplaced at short distance from the grounding system. By means of thisapproach, a conservative test can be made of both E_t and E_s GPD