Table 128-6 Coefficient of oscillation of conductors K

Chapter 2-4 Distribution Equipment up to 1kV

Article 129. The Selection of Appropriate Devices in Distribution Equipment and Substations

As stipulated in Technical Regulation.

Article 130. Instructions Provided at Each Facility

As stipulated in Technical Regulation.

Article 131. Identification of the Circuit

There are a lot of circuits which have a different use, such as a control circuit, a power circuit, AC and DC circuits, etc. in a switching board and a cubicle. And a lot of insulated cables are used in those circuits. Therefore, t i is desirable touse color-coding of insulated cables(conductors) for identification of circuits according to the following table, to avoid the accident derived from the false recognition of workers.

Article 132. Arrangement of Phases and Electrodes

The arrangement of phase shall comply with the Article 104 of Volume 3.

Article 133. Coating with an Anti-corrosive Layer

Corrosion protection shall comply with the Article 57.

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Article 134. Grounding

The grounding shall be carried out in accordance with the regulations and guideline stated in Part 6.

Chapter 2-5 Substations above 1kV

Article 135. Electric Equipment Installation Condition

As for the minimum clearance between live parts or between live parts and earth, this clearance is shown in the Article 331 in Technical Regulation.

As for the safe clearance about arc, the following items should be taken into consideration.

- The clearance between equipment that generates arc during a breaking operation, such as disconnector, and combustibles, should retain the clearance shown in the Article 136.

- The safety clearance during a breaking operation, for circuit-breakers with an external exhaust for ionized gas of flame (for MCCB), should consider the contents of the Article 305.

Article 136. No-load disconnector switching

The minimum clearance of disconnectors between live partsor between live parts and earthis shown in the Article 331 in Technical Regulation. In addition, it should be checked that the disconnector is isolated from combustibles at a safe enoughclearance, because the disconnector generates arc during operation. The minimum clearance is shown in the following table.

Table 136 Minimum clearance between the equipment which generates arc and combustibles

Nominal voltage

7kV and less

More than 7kV

In case that the direction and length of arc are restricted so that there is no fear of fire and the nominal voltage is 35kV and less.

* Note: The above clearance shall not be applied, when fireproof materials are installed between the equipment which generates arc and combustibles.

Article 137. Conditions of Kinetic Stability and Heat Stability

As for breaking capacity of circuit breakers, the rated short-circuit breaking current showsthe actual performance of breaking capacity. The rated short-circuit breaking current is the highest short circuit current which the circuit breaker shall be capable of breaking under the conditions of use.

The following are the outline of the determination of the rated short circuit breaking current. The rated short-circuit breaking current is characterized by two values: (see the figure 137-1)

-The value of its AC component (RMS)

-The DC time constant of the rated short-circuit breaking current which results in a percentage of DC component at contact separation. The percentage DC component varies with time from the

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incidence of the short circuit and with the corresponding DC time constant of the rated short circuit breaking current.

Note: If the percentage of DC component at contact separation doesn't exceed 20%, the rated shortcircuit breaking current is characterized only by the AC component.

ID0

AA' : Envelope of current-wave

BB' : ditto

BX : Normal zero line

CC' : Displacement of current-wave zero-line at any instant

DD' :The value (RMS;root-mean-square) of the AC component of current at any instant,

: Percentage value of the DC component

IDC = ID0 ×ε −LRt (L/R is the time constant of the circuit) ID0 : The initial value of the DC component

cos φ : Short circuit power factor ( Phase Angle φ = arctan (ω L / R))

Figure 137-1 Determination of short-circuit breaking currents and of percentage D.C. component

The standard DC time constant is 45ms. The following are special case DC time constants, related to the rated voltage of the circuit breaker:

-120ms for nominal voltage of system up to and including 35kV

-60ms for nominal voltage of system 110kV and 220kV

-75ms for nominal voltage of system 500kV

These special case time constants recognize that the standard value may be inadequate in some systems. They are provided as unified values for such special system needs, taking into accountthe characteristics of the different ranges of rated voltage, for example their particular system structures, design of lines, etc.

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When the location of the installation is sufficiently remote electrically from rotating machines, the decrement of the AC component is negligible and it is only necessary to verifythat the short circuit power factor is not less than 0.071 in case of the standard time constant.

As stated above, the rated short circuit current shall correspond to the rated voltage and is related to the DC time constant of the system. For DC time constant τ = 45ms, it shall be 2.5 times (i.e. approximately 1.8 *√2 times) the AC component of the rated short circuit breaking current of the circuit breaker. If one of the special case DC time constant (60ms, 75ms or 120ms), the rated short circuit current shall be 2.7 times the AC component of the rated short circuit breaking current of the circuit breaker.

Figure 137-2 Percentage DC component in relation to the time interval from the initiation of the short circuit for the standard time constant and for the special case time constants

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Article 138. Ability to Withstand Gravity Force

The short circuit electromagnetic force which acts on structure shall be calculated based on the requirements regulated in article 81.

The increased temperature which is accessible part ofthe structure located in close to a live part shall be within 50°C, and in case of inaccessible position, increased temperature shall be within 70°C. It is not necessary to test the increased temperature of the structure which is close to a live part of ominal AC current at 1,000A or lower.

Article 139. Installation of Disconnect Switches

In the circuits of distribution equipment, disconnecting devices shall be installed in the place where their disconnecting position of each circuit can be checked by visual.

This requirement is not applicable to fully equipped distribution system such as (including GIS), highfrequency reactor and communication capacitors arranged at busbars and terminals of outgoing power lines, lightning arrester installed at the outlet of transformer and at the transformer connected by cable.

In particular case, depending on design of structure or diagram, it is permissible to install voltage transformer before disconnectors in order to disconnect the remained equipment of this circuit from power supply source.

Article 140. Close or Open Indicators for Circuit Breakers

The provisions of this article shall refer to the Article 294 of Volume 4.

Article 141. Insulation in Dirty Air Condition (Prevention of Dust, Harmful Gases, and Steam)

In case distribution system and substation are located in the polluted environmental area, appropriate measures shall be applied in order to ensure reliable and safe operation of equipment, such as:

-Use of reinforced insulators.

-Use of conducting bars made of materials that are resistant to environmental impacts or covered with protection paint.

-Avoiding wind direction that may cause damage.

-Use of simple electrical diagrams.

-Use of distribution equipment and substations of close type or GIS.

-Preventing dust, harmful gases and steam from invading the distribution equipment compartment.

In case outdoor distribution equipment and substation are located at the place less than 5 km away from the seacoast or a chemical plant, it shall use the anticorrosive aluminum conductor or the copper conductor. Because experience shows that polluted air make aluminum conductor corrosive at such a place.

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Article 142. Installation at Higher Elevation at a height of 1000m

For equipment mounted at a height of 1000m above sea level:

Minimum clearance for themaximum working voltage must be increased as compared with the largest number of Table 254 of Technical Regulation every about 100m up 1.4% from a height of 1,000m above sea level.

For installation at an altitude higher than 1,000mthe insulation level of external insulation shall be determined by multiplyingthe insulation withstand voltages(see the article331 of the technical regulation) required at the service location by a factor Ka in accordance with the following figure.

Figure 142 Altitude correction factor

These factors can be calculated from the following equation:

Ka = em (H−1 000)/8150

where

H is the altitude in meter

m is taken as fixed value in each case for simplification as follows:

m = 1 for power-frequency, lightning impulse and phase-to-phase switching impulse voltages m = 0.9 for longitudinal switching impulse voltage

m = 0.75 for phase-to-earth switching impulse voltage.

Article 143. Materials of Distribution System Conductors

As stipulated in Technical Regulation.

Article 144. Phase Symbols/Signs

The provisions of this article shall refer to the Article 104 of Volume 3.

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Regarding the external fences/walls and protective barriers, minimum clearance and etc. shall meet the criteria provided in the Article 333 and 334 in Technical Regulation.

The mesh size of protective barrier and external fence is provided in the Article333 in Technical Regulation f(The mesh size shall meet IP1XB or IP2X.) However, thesmallest mesh size shall be 10 x 10mm (corresponding to IP2X) and maximum size shall be 25 x 25mm (corresponding to IP1XB).

It is allowed to install barrier-rods at entries of the compartments of circuit breaker, transformer or other electrical equipment so that the operator can stand outside of the barrier-rods to observe live parts.

Barrier-rods shall be removable and be arranged at a minimum height of 1.2m and a maximum height

of 1.4m. In case that the floor of the compartment is 0.3m higher above the ground, the distance between the door and barrier-rod shall be not less than 0.5m or the space in front of the door shall be secured for operators to observe the equipment.

Article 148. Prevention of Damage from Temperature or Vibration

When an earthquake occurs, a tensile force of lead wires connecting equipment may occur. Because the lead wire is pulled by the vibration of equipment due to the earthquake. At this time, if an extra length of the lead wire is too short, the tensile force will get large. And so the insulator of pulled equipment by the tensile force may break.

Therefore lead wires should have a minimum extra length regulated below. In addition, if lead wires can't have a sufficient extra length, flexible wires should be used instead of rigid wires to absorbthe tensile force (vibration).

[Policy of an extra length of lead wires (Example of Japanese design)]

-Earthquake-resistant design condition: Keeping a sufficient extra length of the lead wire at the time of vibrating the connected equipment at the 0G.3resonant three cycle sine wave (G is

gravitational acceleration).

Keeping the extra length which is more than the maximum value of the following three items, in order to meet the above design condition.

(1)Keeping the extra length which is more than thetop displacement at the time of vibrating the equipment at the 0.3G resonant three cycle sine wave

(2)Keeping the extra length which is more than 5% of the span length

(3)Minimum value: 70mm Required extra length (Le) =

maximum value of the above items + 10 / 3 tan-1 (H/S) * (S2 + H2)/ S

where S: Span length

H: Difference in level

The calculation example according to the above formula under the below condition is given as follows.

1.Calculation condition

-Span length: 1,000mm

-Difference in level: 20mm

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Article 151. Color of Transformers, Reactors, Capacitors

For the paint for outdoor equipment, a bright color and a gloss paint have an advantage in the heat barrier, because reflectance of solar radiation is high. In addition a gloss paint have an advantage in cleaning the paintwork easily and improving the weatherproof performance. But in case of high gloss

Therefore, local environment as same as the paint performance should be taken into consideration at the time of deciding the paint for outdoor equipment.

Article 152. Lighting System in Substation

A lighting facility for supervising, operating and maintaining for equipment shall be installed in a distribution system and a substation, etc.. In practical installation, it is desirable to set the illumination range of installation site according to the following table.

In addition, an emergency light shall be installed there for a safe evacuation, in consideration of the loss of AC powersupply due to the power outage or the fire disaster of substations, etc..Regarding the specification of this light, it is turned on by DC power supply, and the illumination intensity shall be maintain 1lux and more on the floor surface after lighting during 30 minutes.

As stipulated in Technical Regulation.

Article 154. Transportation Accessibility

Within closed electrical operating areas, transport routes should be constructed for assembling, repairing and testing equipment using heavy machines, etc. Minimum protective clearance between vehicles and live parts shall be ensured at the time of designing the transport routes. As for concrete clearance, refer to the article 320.

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Article 155. Noise Regulations

As stipulated in the item 4 of article 1 of Vol.1 in Technical Regulation.

Noise abatement measures:

-Technical measures: industrial design, separation, isolation ofnoise resources, using technologies with low noise level, electrical equipment with low sound power.

-Acoustic measures in construction: sound-damping materials or sound deadening materials will be used.

-Application of remote control and automation.

Article 156. Corrosion Regulation

Corrosion protection shall comply with Article 57.

Article 157. Oil Collecting Systems

The quantity of insulating oil in equipment, the volume of water from rain and fire protection systems, the proximity to water courses and soil conditions shallconsideredbe in the selection of a containment system.

Containments and holding-tanks, where provided, may be designed and arranged as follows:

-tanks;

-sump with integrated catchment tank for the entire quantity of insulating oil (figure 157-1);

-sump with separate catchment tank. Where there are several sumps, the drain pipes may lead to a common catchment tank; this common catchment tank should then be capable of holding the insulating oil of the largest transformer (figure 157-2 ;

-sump with integrated common catchment tank for several transformers, capable of holding the insulating oil of the largest transformer (figure 157-3).

The walls and the associated pipings of sumps and catchment tanks shall be impermeable to liquid.

The capacity of the sumps/catchment tanks for insulating and cooling oil shall not be unduly reduced by water flowing in. It shall be possible to drain or to draw off the water.

The entire layout example of including the oil sumps, catchment tank, weir of oil outflow prevention and etc. is shown in the Article 162 of Vol. 3.

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