2. Strength of guy

Strength of guys shall be determined so that the stress in guy in the event of breakingconductors and lightning conductors of overhead power lines with voltage exceeding 1kV is not more than 70% of the breaking strength of materials of guys.

Article 263. Safety for Workers Climbing on Poles

The tilt angle of tie-bars to horizontal plane on metal poles shall be lessthan 30 degrees. If the angle is bigger than 30 degrees, the stairs shall be installed. Reinforced concrete poles shall have the holes for putting tools to climb.

In calculation of brace parts of poles except horizontal braces connecting between twosections at the top of poles, the weight of person shall be considered as 70kg.

Poles which the height of the highest conductor is not less than70m shall have ladders and rest platforms with surrounding protection by lattices.

Chapter 3-3-7 Particular Requirement

Article 264. Confirming Condition of Conductors near Houses

The distance from conductors of overhead power lines with voltage up to1kV to houses, structures and architectural structures shall be determined by considering themovement of conductor due to air temperature (the sag of conductor) and wind pressure (the swing of conductor).

Article 265. Distance from the Outer Edge of Poles Foundation

The pole foundations of overhead power lines with up to1kV shall be installed to secure the safety distance stipulated in this article in Technical RegulationVol.1.

Article 266. Crossing Overhead Power Lines with Voltage up to 1kV

In the places where overhead power lines with voltage up to1kV cross other lines with voltage up to 1kV, anchor poles and support poles are permitted to be used.

When the lines cross over/under the span, the intersection shall be close to the pole with higher height and the distance between bare conductors shall not be less than 2m.

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Article 267. Twisted Cable

1. Requirement for twisted cable

-Twisted cables are prohibited to be installed underground.

-Accessories for twisted cables shall accommodate to the conductors. Tools for installation of the cables and accessories shall be used in response to the instructions.

-Twisted cables of overhead power lines with voltage up to1kV shall be used based on the specifications. If the specifications do not exist, thecables are permitted to be used based on the contents in Annex III.3.2 and III.3.3.

2.Distance for twisted conductor

The distance between twisted conductor and conductor of overhead power line with voltage up to1kV shall comply with the requirements in article 279 in Technical RegulationVol.1 and this Guideline.

The distance from the twisted conductor of overhead power lines with voltage up1kVto to the ground shall comply with the requirement in article272 and 293 in Technical RegulationVol.1 and this Guideline.

The distance from the twisted conductor of overhead power lines with voltage 1kVup to architectural structures shall not eb less than the maximum deviation (refer to AnnexI.3II.1) plus 0.1m.

The maximum deviation means the swing of twisted conductor due to wind depending on crosssectional area, span-length, tension, sag and temperature.

The distance from the twisted conductor of overhead power lines with voltage1kVup toto architectural structures or the walls conductors are installed shall not be less than 5cm.

Chapter 3-3-8 Traversing Non-Populated Areas

Article 268. Requirement for Non-Populated Areas

Cross-sectional area of conductors of overhead power lines with voltage exceeding1kV traversing non-populated areas shall satisfy the requirement in article237 in Technical RegulationVol.1 and this Guideline.

Connections of conductors of the lines traversing the areas shall satisfy the requirement in article237 in Technical RegulationVol.1 and this Guideline.

Overhead power lines with voltage exceeding 1kV traversing forests shall follow Decree “Protection of safety of high-voltage power grid works (106/2005/ND-CP&81/2009/ND-CP).

In safety corridor of overhead power lines with voltage of500kV, irrigation works by water spray equipment in cultivated area are prohibited.

Article 269. Vertical Distance for Non-Populated Areas

Vertical distance from the lowest conductor to the ground surface in npopulatednareas shall be calculated in the following conditions.

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-Maximum air temperature

-No swing of conductors due to the wind

-No heat of conductor due to electrical current

Article 270. Distance from Nearest Conductors

The distance from the outer edge conductor of overhead power lines with voltage exceeding1kV to houses or structures shall comply with the requirement in this article in Technical RegulationVol.1.

Chapter 3-3-9 Traversing Populated Areas

Article 271. Requirement in Populated Areas

1. Installation state

The angle between overhead power lines with voltage exceeding1kV traversing populated areas and roads are not stipulated.

Poles with guys are prohibited to be installed on the streets.

2. Mechanical strength

(1) Conductor and lightning conductor

Conductors and lightning conductors of overhead power lines with voltage exceeding1kV shall have cross-sectional area or mechanical strength not lessthan that of the following conductors and lightning conductors.

-Aluminum conductor with cross-sectional area of 50mm2.

-Aluminum conductor steel reinforced or aluminum alloy conductor steel reinforced with crosssectional area of 35mm2.

(2)Insulator, lock and connection

-Post-type insulators and suspension-type insulators in suspension set shall be double.

-Conductors not less than 300mm2 are permitted to be used with the slide locks.

-Conductors with cross-sectional area less than 240mm2 are prohibited to be connected in the span but conductors with cross-sectional area not less than 240mmare permitted to be connected at only one point in the span.

Article 272. Distance Safe Distance to Populated Areas

1. Conductor conditions for calculating vertical distance

Vertical distance from the lowest conductor to the ground surface in populated areas shall be determined in the following conditions.

-Maximum air temperature

-No swing of conductors due to the wind

-No heat of conductor due to electrical current

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2. Distance in fault condition

When overhead power lines with crossectionalarea less than 185mm2 cross streets, thedistance from conductor excluding the heat due to electrical current at annual mean temperature in the fault condition which the conductor in adjacent span are broken to the ground surface shall not be lessthan the values in the following table.

Article 273. Distance in Area Required High Safety Level

The distance in the area required high safety levelshould focus on safety shall comply with the requirements in this article in Technical RegulationVol.1.

Article 274. Traversing Houses and Structures in Safety Corridor

Houses and buildingsin safety corridor of the overhead power lines with voltage from1kV up to 220kV shall comply with the requirements stated in this article in Technical RegulationVol.1.

Chapter 3-3-10 Traversing Areas with Water

Article 275. Requirement in Areas with Water

1. Requirement for area with water

When overhead power lineswith voltage exceeding1kV traverse areas with water (river, channel, lake, bay, port, etc.), the cross angle between the lines and the river, etc. is not stipulated.

When support poles are used for overhead power lines cross the rivers, etc., conductors and lightning conductors of overhead power lines with voltage exceeding1kV shall be fixed to fixed support locks or dedicated locks.

2. Requirement for area with ship and boat traffic

Anchor poles shall be used at rivers, channels or lakes where ships and boats sail.

Overhead power lines with voltage exceeding 1kV and with cross-sectional area not less than 120mm2 at such places shall comply with the following requirements.

-Fixed support locks or dedicated locks shall be used for fixing conductors.

-Support crossing poles are permitted to be used in the case that they are adjacent to anchor poles.

3.Requirement for large overcrossing span

Dead end poles shall be used in large overcrossing span.

Overhead power lines with voltage exceeding 1kV and with cross-sectional area not less than 120mm2 shall comply with the following requirements.

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