BS EN 61472:2013:2016 Edition
$189.07
Live working. Minimum approach distances for a.c systems in the voltage range 72,5 kV to 800 kV. A method of calculation
| Published By | Publication Date | Number of Pages |
| BSI | 2016 | 48 |
This International Standard describes a method for calculating the minimum approach distances for live working, at maximum voltages between 72,5 kV and 800 kV. This standard addresses system overvoltages and the working air distances or tool insulation between parts and/or workers at different electric potentials.
The required withstand voltage and minimum approach distances calculated by the method described in this standard are evaluated taking into consideration the following:
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workers are trained for, and skilled in, working in the live working zone;
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the anticipated overvoltages do not exceed the value selected for the determination of the required minimum approach distance;
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transient overvoltages are the determining overvoltages;
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tool insulation has no continuous film of moisture or measurable contamination present on the surface;
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no lightning is seen or heard within 10 km of the work site;
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allowance is made for the effect of conducting components of tools;
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the effect of altitude, insulators in the gap, etc, on the electric strength is taken into consideration.
For conditions other than the above, the evaluation of the minimum approach distances may require specific data, derived by other calculation or obtained from additional laboratory investigations on the actual situation.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 5 | English CONTENTS |
| 7 | 1 Scope 2 Terms, definitions and symbols 2.1 Terms and definitions |
| 9 | 2.2 Symbols used in the normative part of the document |
| 10 | 3 Methodology |
| 11 | 4 Factors influencing calculations 4.1 Statistical overvoltage 4.2 Gap strength |
| 12 | 4.3 Calculation of electrical distance DU 4.3.1 General equation 4.3.2 Factors affecting gap strength |
| 13 | Table 1 – Average ka values |
| 14 | Figure 1 – Illustration of two floating conductive objects of different dimensions and at different distances from the axis of the gap |
| 15 | Table 2 – Floating conductive object factor kf |
| 16 | Figure 2 – Typical live working tasks |
| 17 | 5 Evaluation of risks |
| 18 | 6 Calculation of minimum approach distance DA Annexes |
| 19 | Annex A (informative)Ergonomic distance |
| 21 | Annex B (informative)Overvoltages Table B.1 – Classification of overvoltages according to IEC 60071-1 |
| 23 | Figure B.1 – Ranges of ue2 at the open ended line due to closing and reclosing according to the type of network (meshed or antenna) with and without closing resistors and shunt reactors |
| 25 | Annex C (informative)Dielectric strength of air |
| 27 | Annex D (informative)Gap factor kg |
| 28 | Table D.1 – Gap factors for some actual phase to earth configurations |
| 29 | Annex E (informative)Allowing for atmospheric conditions |
| 31 | Table E.1 – Atmospheric factor ka for different reference altitudes and values of U90 |
| 33 | Annex F (informative)Influence of floating conductive objects on the dielectric strength |
| 36 | Figure F.1 – Influence of the length of the floating conductive objects – phase to earth rod-rod configuration – 250 µs /2 500 µs impulse |
| 37 | Figure F.2 – Influence of the length of the floating conductive objects – phase to phase conductor-conductor configuration – 250 µs /2 500 µs impulse |
| 38 | Figure F.3 – Reduction of the dielectric strength as a function of the length D for constant values of β – Phase to earth rod-rod configuration Figure F.4 – Reduction of the dielectric strength as a function of the length P for constant values of β – Phase to phase conductor-conductor configuration |
| 41 | Annex G (informative)Live working near contaminated, damaged or moist insulation |
| 42 | Table G.1 – Example of maximum number of damaged insulators calculation(gap factor 1,4) |
| 43 | Table G.2 – Example of maximum number of damaged insulators calculation(gap factor 1,2) |
| 44 | Figure G.1 – Strength of composite insulators affected by simulated conductive and semi-conductive defects |
| 46 | Bibliography Figures Tables |
