Article 339. Clearances to Building

As stipulated in Technical Regulation.

Chapter 4-2-2 Indoor Distribution Equipment and Substations

Article 340. Flameproof level of Distribution Compartments

Distribution station/compartments and transformer's (reactor's) compartments shall be made of flameresistant materials in accordance with TCVN622. For reference, minimum requirements for the indoor transformers (reactors) provided in the IEC are given in the following table.

Table 340 Minimum requirements for the installation of indoor transformers

[IEC 61936-1 Table 4]

Note 1: REI represents bearing system (wall) whereas EI represents non-load bearing system (wall) where R is the load bearing capacity, E is the fire integrity, I is the thermal insulation and 60/90 refers to time in minutes.

Note 2: Enhanced protection means

-Tank rupture strength;

-Tank pressure relief;

-Low current fault protection;

-High current fault protection. Note 3 Fire behavior class

-F0: No special risk of fire to be considered

-F1: Risk of fire exists, limited flammability is acceptable. Self extinguishing of the fire must occur within 60 minutes.

-F2: Class F1 requirements must be fulfilled. Inddition,a the transformer must be capable of operating for a defined time* when subjected to an external fire.

(* To be agreed between the manufacturer and the buyer.)

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Doors shall have a fire resistance of at least 60 min. Doors which open to the outside earadequate if they are of fire-retardant material and construction.Ventilation openings necessary for the operation of the transformers are permitted. When designing the openings, the possible escape of hot gases shall be considered.

Article 341. Distance from Independent Distribution Stations

The clearances from independent distribution station tomanufacturing halls and other premises in an industrial enterprise, to residential housing and public structuresshall meet the value for transportation and fire fighting stipulated in the TCVN 2622.

In case of narrow space, the above-mentioned fire fighting clearance can be reduced provided that the distribution building has solid wall, no doors directed towards neighboring houses or works, and upon agreement with local fire prevention and fire fighting authority.

There is no requirement on clearance between the adjacent substations and or inside house, or along industrial house area.

Special requirements for adjacent substations or inside public house or civil house are thosespecified in the existing construction standards, norms.

For substation adjacent to existing house, if wall of that house is used as wall of substation, thereshall be agreement and special measure applied in order to avoid damage of common wall.

Article 342. Separated Distribution Compartments

As stipulated in Technical Regulation.

Article 343. Condition of Installation Place

As stipulated in Technical Regulation.

Article 344. Selection of Insulators

Insulators at the input point and insulators subject to outdoor open conductors of generators with pole voltages of 6 and10kV shall be handled based onthe specification of 20kV; pole voltages from 13.8 to 24kV shall be handled based onthe specification of 35kV. When the above mentioned insulators are installed in the polluted area, the creepage distance for Insulator shall be decided in accordance with the pollution level. (see the article 330)

Article 345. Minimum Air Clearance of Indoor Substation Facilities

As stipulated in Technical Regulation.

Article 346. Withstand voltage test of indoor substation equipment

Withstand voltage test of indoor substation equipmentshall satisfy the requirements stipulated in article 332.

Article 347. Offset distance from live components with barrier

As stipulated in Technical Regulation.

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Article 348. Distance between live components without compartment

As stipulated in Technical Regulation.

Article 349. Operation control corridor

(1)Passageway width of operating area

As for easy maintenance of equipment and easy transportaion of them, the passageway width for operating area between protective barriers shall be not less than:

-1m: if equipment are installed on one side of passageway

-2m: if equipment are installed on both sides of passageway

In case that the mechanical section of circuit breakers, disconnectorat opened position are installed in the passageway of operating area, the above mentioned value shall be increased to 1.5m and 2m respectively(to ensure the same width). If the relevant passageway is 7m long and equipment are installed along both sides, it is allowed to reduce the passage width to 1.8m.

The passageway width for fire-exit shall be not less than 1.2m.

In the passageway of operating area and fire-exit, the protruding part of equipment shall be within 0.2m.

(2) Exit of explosion-exit corridor

Distribution equipment compartment shall have exit of passage ways in compliance with the following requirements:

-If the length of passage ways for compartment is up to 7m, one exit should be placed.

-If a relevant length is from 7m to 60m, two exits should be placed at opposite ends of the compartment. It is allowed to place exit in distance up to 7m from the end of compartment.

-If a relevant length is over 60m, in addition to two main exits placed at opposite ends,-side doors should be arranged so that the distance from any point in operation controlcorridor ways

or explosion-exit corridor for fire and explosion to the nearest exit shall not exceed 30m.

Doors of the exits can open to the outside; into the stairs led to other production rooms in which

walls and ceiling are fireproof, and there are no inflammable or explosive equipment and materials; or into other distribution equipment compartments.

Doors shall be made of fireproof or non-flammable materials with fire resistance capacity not less than 0.6 hour.

In the multi-floor distribution equipment installation compartment, the one of two main exits and the side doors can open into the balconies where there is fire-fighting ladder available.

Article 350. Fire Prevention Measures for Indoor Substations

(1) Division of compartments

If the explosion-exit corridor is too long, it shall be divided into compartments with length shorter

than 60m. Partitions between compartments shall be made of flameproof materials with fire resistance capacity not less than 1 hour. Compartments shall have doors which meet requirements

in the article 349 and 351. The explosion-exit corridor shall have doors which open to the outside or to the stairs.

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(2) Floor and wall of distribution equipment compartment

The floor level ofthe distribution equipment compartments should besame. The surface of floors shall be dust-resistant finish. It is not basicallyallowed to place sill at the doors between compartments and in the corridors.

In addition, plates covering ditches shall be tight, made of fireproof, anti-slipping, anti-stumbling materials, and placed at the same floor level. The weight of each plate shall be not less than 50kg. Holes that are bored through floors, walls or partitions (including cable holes)shall be sealed with non-flammable materials with fire resistance capacity for duration not less than 0.75 hour.

To prevent the compartments against the entering of animals, all the holes led to the outside must be protected with meshwork sized 10x10mm.

Article 351. Doorway of Indoor Substation

Doors of the distribution equipment compartments shall be ofhe tswing-out type, opening to the outside or into other compartments. Doors shall also be equipped with auto-locked latches so that they can be opened from the inside with no key required.

Doors (gates) of the compartments where oil-filled equipment with oil content more than 60kg are installed shall be made of non-flammable materials with fire resistance capacity which is not less than

0.75 hour, if doors which open to other compartments that are out of substations area, or their locations are in the midway between explosion-exit corridor and distribution equipment compartment.

For other cases, doors can be made of materials with lower fire resistance capacity.

If the width of doors (gates) is larger than 1.5m, a side entry gate shall be built for peoplessingpa through.

Distribution equipment compartment should not have windows. In the area without guarding, window shall not be allowed. In case natural illumination is required, it is permissible to use glass bricks or steel-cored glass.

Window of distribution equipment compartment shall be non-open type.

If the window is protected withwire mesh/screen with size not larger than 25*25mm/mesh hole from the outside, it can be opened but swung into the inside.

Placing window on the roof for getting illumination is forbidden.

Article 352. Oil-immersed transformer installed indoor

In the compartment installed distribution equipment at voltage level of 1kV and above, it is allowed to place one oil-filled transformer with capacity up to 630kVA or two oil-filled transformer with capacity of each up to 400kVA, provided that they are separated with the remaining space of the compartment by flameproof partition with fire resistance capacity rated 1 hour.

Live parts without insulation with voltage level above 1kV shall be protected by protective barriers in accordance with requirements in the article 347.

The equipment related to starting electrical motors or synchronous compensators, etc. (such as: circuit breaker, start-up reactor, transformer, etc) are permitted to be installed hein samet compartment without partitions.

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In the distribution equipment compartmentwith doors that open to het explosion-exit corridor, it is allowed to place oil-filled transformer with oil content up to 600kg.

Regardless of the amount of oil, it is allowed to place instrument transformers in the open compartment. But the weir of oil outflow prevention or sloping the floor area of the equipment to

keep the entire quantity of oil is necessary.

Oil circuit breaker with oil content more than 60kg shall be placed in separated explosion-prone compartments with doors that open to the outside or to the explosion-exit corridor.

Oil circuit breaker with oil content from 25kg to 60kg can be placed in open compartments or explosion-prone compartments. The circuit breaker thatinstalled in open compartments or in compartments with doors that open to explosion-exit corridor shall reserve the 20% of the rated breaking capacity.

Oil circuit breaker with oil content up to 25kg, low oil content circuit breaker and oil lessrcuitci breaker can be placed in open compartments.

As for the compartment where to put low oil content circuit breaker with oil content 60kg or more in a phase, the weir of oil outflow prevention shall be installed to keep entire oil volume.

Circuit breaker placed in open compartments shall be separated by fireproof partitions shall be also separated from drive device by partitions or protection boards made of fireproof materials. The top edge of partition or protection board shall be at less 1.9m high above the floor.

It is not required to use partition for air circuit breaker.

It is not allowed to install the equipment with live parts without insulations in the explos- iton corridor.

Article 353. Oil collection sump

As for the oil-collecting system for indoor substations located in separated house, adjacent to or inside manufacture house, it is not required to constructcatchment tank in compartments where there are installed transformers, oil circuit breakers and other oil-filled equipment with oil content in each tank up to 600kg, provided that these compartments are in the first floor and have doors open to the outside. If the oil content of a tank is more than 600kg,catchment tank or weir of oil outflow preventionshall be built using fireproof materials, with capacity equivalent to 20% of the entire quantity of oil of the

largest transformer. Besides, appropriate measures should be applied to prevent waste oil from flowing into cable ditches.

The example of oil-collecting sump and catchment tank, etc is shown in the article 157.

Article 354. Installation of oil collecting sump

As for the compartments placed on basement or on the 2nd floor and upper with doorsthat open to explosion-exit corridor, in such cases,catchment tank shall be built under transformers, oil circuit breakers and other oil-filled equipment in compliance with the following requirements:

1.If the oil amount in transformer or in each tank of oilfilledequipment is less than 60kgweir of oil outflow prevention or sloping the floor area of the equipment to keep the entire quantity of oil.

2.If the oil content in one tank is from 60 to 600kg:

a.Build catchment tank to collect the entire quantity of oil.

b.Build border or make the floor slope down inside in order to keep the entire quantity of oil.

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3.If the oil content in a tank is more than 600kg:

a.Build catchment tank that is capable of containing at least 20% of the entire quantity of oil of the largest transformer or the oil-filled equipment with drain pipe led to the common catchment tank for several equipment.

Oil drain pipe from the oil collectingsump under transformer shall have diameter of at least 10cm.

Oil drain pipe shall be covered with meshwork at the end connected to the oil collecting sump.

b.In the case catchment tank is built without drain pipe to the common catchment tank, it shall be installed with a grating on which a layer of ballasting with thickness of 25cm is laid. The catchment tank shall be capable to contain the entire quantity of oil with the maximum oil level

5cm lower than the grating. Topmost surface of the layer of ballasting shall be 7.5cm lower than ventilation hole. Bottom of catchment tankshall have a slope of 2 degrees downwards to its sunken point. Catchment tank shall have surface area larger than groundwork of the transformer or the equipment.

Examples of oil-collecting sump and catchment tank, etc. are shown in the Article 157.

Article 355. Ventilation System in Transformer Compartment

(1) Amount of required ventilation from the amount of generated heat

In case that the heating elements such as transformers, etc. are installed in the room, the amount of required ventilation from the amount of generated heat can be calculated by the following formula. It is preferable to use natural ventilation for transformer rooms to coolroomthe temperature within the permissible temperature. If room temperature is not ablebe tocooled within the permissible temperature by natural ventilation, it is necessary to introduce a forced ventilationor air conditioning.

Ventilation openings shall be designed so as to prevent any dangerous proximity to live parts and any dangerous ingress of foreign objects.

H

Amount of ventilation [m3/h] =

d * Cp * (t2-t1)

Where:

H: Amount of generated heat [J/h] d: Specific gravity of air [1.2kg/m3]

Cp: Specific heat of air [1006J/(kg*k)] t2: Permissible room temperature [°C] t1: Intake air temperature [°C]

And furthermore, emperature in compartments where control panel-board and distribution equipment is placedshall be ensured in accordance with requirements set by the equipment manufacturers. And temperature in compartments where on-duty person is present for 6 hours and more must be kept at temperature not lower than 18°C and not higher than 28°C.

(2) Emergency ventilation system

Explosion-exit corridor and management corridor of open compartments or complete cubicles containing equipment which are filled with oil or other synthetic fluid shall be equipped with

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