IEEE Std 2720:2021 pdf download.IEEE Guide for Rail Potential Management for DC Electrification Systems.
This guide provides a description of the concepts, applicable standards, and methods used for the calculation and management of rail potential on dc-electrified rail transit systems.
1.2 Purpose
This guide describes existing methods, tenninology. and additional references for the management of rail potential on dc-electrified rail transit systems.
1.3 Word usage
The word shall indicates mandatory requirements strictly to be followed in order to conform to the standard and from which no deviation is permitted (shall equals is required to).
The word shouki indicates that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others: or that a certain course of action is preferred but not necessarily required (should equals is recommended that).
The word may is used to indicate a course of action permissible within the limits of the standard (may equals is permitted to).
The word can is used for statements of possibility and capability, whether material, physical, or causal (can equals is able to).
2. Normative references
The following referenced documents are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relationship to this document is explained). For dated references, only the cdition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies.
IEEE Std 80. IEEE Guide for Safety in ac Substation Grounding’
BS EN 50122-1, Railway applications—Fixed installations—Electrical safety, earthing and the return circuit, Part 1: Protective provisions against electric shock
IEC 62 128-I, Railway applications—Fixed installations—Part 1: Protective provisions relating to electrical safety and earthing
IEC 60479-I, Effects of current on human being and livestock—Part I: General aspects
IEC/TR 60479-5, Effects of current on human being and livestock—Part 5: Touch voltage threshold values for physiological effects
3. Definitions, acronyms, and abbreviations
3.1 Definitions
For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary Online should he consulted for terms not defined in this clause.4
body voltage: The product of the current through the body and the body impedance.
earth: The conductive mass of the earth, whose electric potential at any point is conventionally taken as equal to zero (also referred to as bremote earth”).
earth electrode: A conductor or a group of conductors in intimate contact with, and providing an electrical connection to, earth (also referred to as a 4bgrounding electrode”).
NOTE—”Earth” will be used in place ofground” in this guide to avoid potential confusion with other IEEE definitions of ground.
negative grounding device (NGD): a device that connects the substation negative bus to the substation grounding grid when the voltage between them exceeds a setpoint. The voltage setpoint can be a voltage magnitude with or without a time delay, or a voltage versus time curve. Also referred to as an automatic grounding switch, floating negative automatic grounding switch, or grounding contactor.IEEE Std 2720 pdf download.