Chapter 2-3 Transmission and Distribution Lines
Chapter 2-3-1 House and Outside Wiring Systems with Voltage up to 35kV
Article 85. Cross-Sectional Areas
-Cross-sectional areas of earthing conductors andneutral earthing conductors shall comply with requirements in Part6 in Technical RegulationVol.1 and this Guideline.
-Cross section of wires and cables gut of the electrical path indoors and outdoors inthe following table.
Table 85 |
Minimum cross-sectional area for house and outside wirings |
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Minimum cross- |
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Type of conductor or cable |
sectional area (mm2) |
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Copper |
Aluminum |
Soft conductor for connecting electrical household appliance |
0.35 |
- |
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Cable for connecting electrical mobile and movable equipment used i |
0.75 |
- |
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industries |
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Twisted-pair conductor, multi-stranded core fixed on pulleys |
1.00 |
- |
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Insulated conductor without sheath used for fixed house wiring inside |
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building: |
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• Directly placed on the floor, pulleys, wire clamps and suspendin |
1.00 |
2.50 |
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wire |
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• Placed in trough, box (except solid box) |
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+ For core with threaded connection |
1.00 |
2.00 |
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+ For core with welded connection: |
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- One core conductor |
0.50 |
- |
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- Multi-stranded conductor (soft) |
0.35 |
- |
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• Placed on insulator |
1.50 |
4.00 |
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Non-sheathed insulated conductors of outside wirings: |
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• Placed on the |
wall, insulated structures or insulators on elec |
2.50 |
4.00 |
poles and entering from overhead power line |
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• Placed on pulleys under roof overhang |
1.50 |
2.50 |
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Article 86. Installation of Conductors and Cables
Conditions for insulated conductors and cables in pipes etc. that belong to constructionsis shown as below.
1.Permissible conditions of shared installation for insulated conductors and cables in steel and other material pipes, hoses, boxes, trough and closed canals which belong to construction structures of the building (exceptional cases when they are standby for each other).
(1)All circuits of one unit.
(2)The motive and control circuits of some machines, cubicles, boards, control panels, etc. are related to each other in terms of technology process.
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(3)Complicated lighting circuits.
(4)Operative lighting or emergency lightingcircuits of the same type of some groupsand total number of conductors in one pipe not more than 8.
(5)Lighting circuits with voltage up to 42V, and lighting circuit withvoltage exceeding 42V to 1,000V that the conductors of the circuits up to 42V separatelyare installed in insulated conduits.
2.Conditions for replacement
Insulated conductors and cables which are installed in pipes, boxes, metal hoses and closed canals must be replaceable.
3.Conditions for lighting circuits etc. and spare circuits
(1)Operative lighting and emergency lighting circuits, circuit with voltage up to 42V and circuits with voltage exceeding 42V to 1000V (except the cases mentioned above 1-(5) ) are prohibited
to be installed together with spare circuitsn thei same pipe, hose, box, closed canal of construction structure or trough.These circuits are permissible to beinstalled in different compartments of a box or trough with closed walls which are separated along the whole length of box, etc. andare made of nonflammablematerials or materialshas flame withstanding ability not less than 0.25 hours.
(2)It is permitted to install operative lighting and emergency lighting circuits on different external sides of metal bars (U shaped channel bar), angle bar, etc. respectively.
4.Conditions in productive and electrical halls
(1)Insulated conductors or cablesin productive and electrical halls shall have sheaths whichare made of non-flammable or flame resistance materials.
(2)Insulated conductors and cables without sheaths in productive and electrical halls shall be installed on insulators which are made of non-flammable or flame-resistant materials.
5.Conditions for power and neutral conductors with AC or rectified current
(1)Power and neutral conductors with AC or rectified current shall be installed together either in a steel pipe or an insulated pipe with steel sheath.
(2)Power and neutral conductorswith rated current up to 25Aare permitted to beinstalled in separated steel pipe or insulated pipe with steel sheath respectively.
6.Conditions for structural elements
The structural elements for installing conductors and cables in building,works, closed canals and closed space shall be made of non-flammable materials.
7.Conditions for distance from conductors to pipe or technical equipment
The distance from conductors without protective covers (IP00) to pipes shall be not less than 1m and the distance from theconductors to technical equipment shall not be lessthan 1.5m. The distance from busbars with protective covers (IP21, 31, 65) to pipes or technical equipment is not specified.
Article 87. Provisional Length of Conductors and Cables
The provisional length of insulated conductorsand cables shall be long enough for connection works and their arrangement.
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Article 88. Installation of Connections and Branches
Connections and branches of insulated conductors and cables of house and outside wirings shall be installed as below.
1.Connections and branches shall be pressured, welded and clamped in compliance with existing instructions.
2.Connection and branch points shall not be stressed by tension of insulated conductors and cables.
3. Connection and branch points shall have theequivalent insulation to the other parts of the insulated conductors or cables.
4.Connections and branches should be arranged in connection boxes, branch boxes,insulated enclosures of clamps, special compartments of construction structuresand enclosures of electrical equipment.
Article 89. Construction and Material of Connections, Branch Boxes and Clamp Connectors
Connection and branch boxes, clamps shall be used in compliance with the instructions.
Article 90. Protection against Corrosion of House and Outside Wirings
Metal parts of house and outside wirings shall be painted orgalvanized so that corrosion by chemical materials (salt, etc.) from surrounding decelerates.
Corrosion protection shall comply with Article 57 of Vol.1 in Guideline.
Article 91. Crossing with Thermal Expansion Slots and Fracture Slots
Insulated conductors and cables shall be arranged to avoid theshift of the tension and the position by their heat extension.
Article 92. Protection against Chemical Substances
1.Places with air containing active chemical substances means places with aircontaining powder dust (magnesium, aluminum, iron, flour, manmadefabric, etc.) or flammable gas (propane, acetylene, ethanol, methanol, etc.), etc.
2.Measures to protect from active chemical substances
(1)Insulated conductors shall be installed in steel pipes or cables with metal sheath shall be installed.
(2)Anti-friction, anti-corrosion and anti-pressure packing shall be used at connection point of pipes or boxes so that active chemical substances can not intrude in pipes, etc..
(3)Pipes or boxes shall be connected without a gap by parallel screws with screw head of 5 and more or lock nuts.
Article 93. Calculation and Selection Condition of Conductors
Conductors, insulation, accessories, structures and instruments of house and outside wirings shall have mechanical strength, dielectricstrength, dimensions (cross-sectional area, size of accessories,
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etc.) and materials which can withstand voltage, current, mechanical force, weight, andtemperature calculated in the normal working conditions and in short circuit conditions.
Article 94. Symbols and Paint
Painted colors to distinguish phases of house and outside wirings shall comply with the requirements in article 25 of Vol.1 in Technical Regulation.
Article 95. Method for Preventing Conductor Proximity at Short Circuits
Conductors and insulators at bearing point shall have mechanical strength which can withstand electromagnetic force by short circuit current.
Short circuit current shall be calculated in accordance with requirements in Chapter 2-2-2.
Article 96. |
Earthing Live Parts |
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1. |
Requirement for earthing measure |
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Fixed or |
movableblades of disconnectors and |
grounding rods shall be installed in accordance |
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with requirements of article 146 in Technical RegulationVol.1 and this Guideline. |
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They shall be arranged at both terminals of |
house and outside ingswir |
as well |
as intermediate |
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points. |
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2. |
Requirements for induced voltage |
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The number of mobile ground placement shall |
be determined so that |
induced |
voltage does not |
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exceed 250V when short circuit happens at adjacent wirings
Article 97. Mechanical Load and Temperature Requirements
Mechanical safety factors for conductors, insulators and accessories shall be complied with article 324 to 328 in Technical RegulationVol.1.
Mechanical safety factors are shown in the following table as reference.
Table 97 |
(Reference) Mechanical safety factor |
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Items |
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Mechanical safety factor |
Flexible conductor |
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3 |
Rigid conductor |
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Calculated according to article81 in Technical |
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RegulationVol.1 and this Guideline |
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Suspension insulator |
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4 |
Accessories for bridging flexible conductor |
3 |
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Article 98. Combination and Configuration for Installation and Maintenance
Combinations and configurations of house and outside wirings shall be designed in accordance with the following items.
-Locations of the wirings shall bearranged with numbering, hanging labelsor paint not to be misunderstood by workers for installation and maintenance. If a large number of wirings are
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installed and the worker might misunderstand the location, signs for helping workers’ recognition shall be added.
- Wirings shall be arranged properly so that the installation and maintenance works can be conducted smoothly and safely.
-If a number of wirings are in a location, conditions for current capacity of the wirings shall be confirmed not to exceed allowable conditions.
Article 99. Protection against Lightning
1. Lightning conductor
Requirements for lightning conductors are in Chapter 3-3-1of Vol.1 in Technical Regulation and this Guideline.
2. Arrester
Arresters shall be installed at the following locations.
-The connection of cables to overhead power lines
-The connector at the position to receive the power
-Inlet branches for power user with receiving capacity of 500kW
Arresters shall be attached to earthing system satisfies the stipulations in Part 6of Vol.1 in Technical Regulation and this Guideline.
Article 100. Reduction of Electricity Loss
For house and outside wirings with symmetrical load current of 2.5kA and more, they shall satisfy the requirements in this article in Technical RegulationVol.1 and take measures (e.g. multipleconductor in a phase or phase transposition, etc.) to reduce the impedance of the wirings.
Phase transposition is recommended to be applied to extended soft house and outside wirings. The number of phase transposition shall be determined by the calculation depending on the length of the wirings.
For house and outside wirings with unsymmetrical load current, measures calculated by particular case for reducing electricity loss shall apply.
Article 101. Eliminating Dangerous Stress
1.Countermeasure against temperature change
-Conductors shall be limited to be risen the temperature of themventilationby or thermal insulation.
-Current in the electric conductors must be limitednot to exceed the permissible temperature of them in consideration of the expected temperature increase.
-Rigid conductors shall be equipped with compensators at the places of thermalexpansion and settling joints of buildings or structures.
2.Countermeasure against explosion
-Conductors shall be installed in pipes which can withstand the explosion.
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