PART 2 GENERAL REQUIREMENTS

Article 31. Electrical design and conditions

As stipulated in Technical Regulation.

Article 32. Specifications of Electrical Equipment

The electrical equipment and related structures shall ensure the following condition.

1)Its elevation less than 1,000m above sea level

2)Atmospheric temperatures is from - 5°C to +45°C

3)Other conditions such as abnormal level of salinity, humidity and gas

Otherwise out of above conditions, special specifications are needed to satisfy the conditions.

Article 33. Electric Mode

As stipulated in Technical Regulation.

Article 34. Civil Part

For the power projects which don’t need duty staffs, it is not necessary to build control room, auxiliary room for workers as well as repairing workshop and laboratory. Designing and selecting options for the electrical project shall be based on comparison of technical-economic criteria, application of simple and reliable diagrams, skills and experience, new technological application, optimal selection of materials.

Article 35. Security in Power Projects

Safety for power project shall be ompliedc with the obligations of the Electricity Law, in particular Decree and National Technical Safety Standard;

For the power projects there must be have appropriate measures to ensure safety as follows:

- The appropriate electrical insulators shall be used and in the exceptional case the reinforced insulators are used.

-The appropriate distances to live parts must be arranged or live parts must be enclosed.Detail descriptions are mentioned in Article 331 and 334 of Technical Regulation.

-The barriers shall be made. Detail descriptions are mentioned in Technical Regulation of Vol.1.

-The interlocks are installed for electrical instruments and barriers in order to prevent operational errors. Detail descriptions are mentioned in Article 145 of Vol.1.

-Automatic reliable and quick tripping circuits in deror to isolate faulted parts of equipment and damaged parts of power grid. Detail descriptions are mentioned in Article 417 - 435 of Vol.1

-Grounding electrical equipment enclosures and all components of power project which may be earth faulted. Detail descriptions are mentioned in Article 549 - 558 of Vol.1

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-Using isolated transformers or voltages up to 42V for leveling voltages.

-Using warning signal system, announcement signs and boards.

-Using protection tools.

Article 36. Prevention of Personal Accidents

As stipulated in Technical Regulation.

Article 37. Enclosures or Covers of Electrical Live Parts

As stipulated in Technical Regulation.

Article 38. Requirements of Barriers and Covers

The barriers and covers shall have enough mechanical strength. For equipment with voltage over 1000V, thickness of metal cover shall not be less than 1mm.The cover of conductors shall be put deeply in the electrical machines, equipment and instruments.

Detail descriptions are mentioned in Article 333 of Technical Regulation.

Article 39. Firefighting

The fire fighting equipment must be arranged in compliance with fire protection and fighting regulation. Detail descriptions are mentioned in Article 56, 315, 340, 350, 351, 360, 361 of Vol.1 and TCVN 2622.

Article 40. Compliance for Electricity Supply

As stipulated in Technical Regulation.

Article 41. Electricity Supply Plan

As stipulated in Technical Regulation.

Article 42. Electricity Supply Alternatives

As stipulated in Technical Regulation.

Article 43. General Electricity Development Plan

As stipulated in Technical Regulation.

Article 44. Power Transmission Capacity in Industrial Enterprises

It needs to ensure,

1)Transmission surplus capacity of exclusive power plant of industry to the power grid in all operation conditions.

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2)Receiving capacity, from the power grid, when the biggest power generator of exclusive power plant operation stops due to fault or for planned repairs and inspection.

Article 45. Agreement of Managing Agency of National Power Grid

As stipulated in Technical Regulation.

Article 46. Coordinate power supply for industrial enterprises and residents

As stipulated in Technical Regulation

Article 47. Categorization of Electricity Users

The power users are divided into 3 categories:

- Category I includes electricity users whose electricity supply interruption will affect national security, important organizations’ activities, endangering peopleife,l serious national economic damage, complicated technology process disorder and especially important areas of cities.

-Category II includes electricity users whose electricity supply interruption will cause damage of series of products, economic loss, machine operation stop and industrial transport stop, disorder of normal operation of large part of city.

-Category III includes electricity users who are not belonged to the above two categories.

The electricity users of the category I shall be suppliedwith electricity from at least two independent power resources and one local standbyresource. The electricity supply is allowed to be interrupted during the time when stand-by power resource is being automatically closed. The anti-asynchronous closing system must be installed.

For electricity users with small capacity, the back-up power supply resource can be fixed substation and mobile substation with generator and uninterruptible power supply (UPS) etc. mobile, battery, compression ignition engine - generator etc. or power line connected to the lower voltage substation with independent power supply resource by automatically connecting to stand-by resource.

The electricity users of the category II shall be supplied with electricity from at least one independent power resource and one local stand-by resource. The electricity supply is allowed to be interrupted in the necessary time in order to close stand-by resource are allowed to be supplied with electricity from one overhead power line with medium or higher voltage. If users are supplied with electricity by cable,

one cable line is allowed but at least two cable sections connected in parallel through separate disconnectors.

Where there is central power supply resource available, the electricity users of the categoryIIare allowed to be supplied with electricity from one transformer.

The electricity users of the category III is allowed to be interrupted in the necessary time in order duty person or repairing group to close standbyresource. For the electricity usersof the category III,

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electricity supply interruption is depending on technical, economic, social conditions there and agreement between electricity supplier and users.

enterprises and cities by power lines at voltages of 100-220kV as near as possible, construction of substation near the load center or within the enterprise, division of substations. The ring circuit should be used for supplying electricity to substation.

For supplying electricity to separate substations, direct branching from one or two power lines in parallel should be used. At branching point, disconnector should be installed.

The substation electrical simple diagram without circuit breaker at inlet and without busbar at the high voltage side or with only single busbar system is recommended to be used. The double busbar system can be used only when there is proven justification.

The electrical distribution diagram in the enterprise shall ensure the supply of electricity to production lines.

The installation of circuit breakers at the inlet shall be considered in the following cases:

1.At inlet of substation with voltage 110kV and above.

2.At inlet of up to35kV substation with power 1600kVA and above nodal and system connection substations.

Installation of circuit breakers at inlet of users’ substation which receives electricity from the national power grid must be agreed by electricity management agency.

It is recommended to use fuse disconnector combined with load disconnector and/or short circuit protection disconnector for transformers with voltage up 35kVto. And capacitors if fuses have parameters appropriate to power system (in terms of voltage, current, short circuitrent)curand selective, reliable actuation.

The sectionalizing circuit breakers are installed in busbar only standby power supply resource requires automatic closing or at big nodal substations.

In other cases, in order to sectionalize busbar, the switch can be used instead of disconnector.

In the electrical diagram of the power supply center there must be measure to limit short circuit capacity in the power system to the maximal permissible breaking capacity of circuit breakers installed in the system.

When short circuit capacity is limited by current limiting reactor installed on the outgoing power line,

the reactor is allowed to be used for many power lines provided that each power line shall be connected through separate switch. In this case, the divided reactor should be used.

Article 49. Design for Power Networks

As stipulated in Technical Regulation.

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In some cases, when substation is designed, shedding of some less important loads shall be taken into account in the fault conditions.

Article 50. Future Electricity Supply in the event of Extension of the City

As stipulated in Technical Regulation.

Article 51. Electricity Quality in the Power Network

1.Voltage

-In the normal working conditions of the electricity supply center, during the time when total load is reduced to 30% of the maximal load, the voltage at the busbar must be kept at the nominal voltage level of the power network, but during the time of maximal load, voltage must be increased by 5%.

-For voltage regulation in power system with voltage of110kV and above, the transformers with on load tap changer with voltage regulation range (10 - 15%) should be used.

Besides, use of local voltage regulation devices should be considered as follows: +Voltage compensator

+Synchronous motor

+Synchronous compensator

+Capacity compensating capacitors

+ Connection power lines with voltage up to ,000V1 between substations in order to disconnect some transformers in the minimum load conditions.

+Selection of voltage and power systems supplying electricity to motive loads and lighting in workshops using electricity at voltage up to 660kV shall be comprehensively solved.

If transformers are used to supply electricity for motors and lighting for users, the electrical diagram shall allow partially disconnecting some transformers during off working time, days-off or holidays and electricity for lighting will be supplied by small capacity transformers or power line connected to working transformers.

2. Power Factor

In case cos ϕ < 0.85 by download of households using electricity, using electricity must take measures to ensure that the power factor cos ≥ ϕ 0.85 can apply the following measures:

-Installation of reactive power compensation equipment to increase cos ϕ ≥ 0.85.

-Purchase of reactive power on the power system from the power supply.

3. Frequency

As stipulated in Technical Regulation.

4. Harmonics

As stipulated in Technical Regulation.

5. Voltage Flicker

As stipulated in Technical Regulation.

Article 52. Inspection of Voltage Fluctuation

If voltage deviation exceeds the permissible limitation, measure for voltage regulation shall be applied.

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Article 53. Increased Surface Temperature caused by Solar Radiation

As stipulated in Technical Regulation.

Article 54. SF6 Gas Leakage

In rooms with SF6 installations, which are above ground, natural cross-venting is sufficient. Inthis case, approximately half of the cross-section of the ventilation openings required shall beclose to the ground. This measure depends on the size of the room and the gas quantity. Incases of malfunction, mechanical ventilation may be required.

NOTE 1: Permanent ventilation may be omitted for chambers in installations which are not accessible. For small installations (total quantity of SF6 ≤ 1,000liter under atmospheric pressure), ventilation on one side of the room is sufficient.

In rooms with SF6 installations, which are below ground on all sides, mechanical ventilationshall be provided if gas quantities which pose an intolerable risk to the health and safety of personnel (see note 2 below) are capable of collecting due to the gas quantity and the size of the room.

Chambers, ducts, pits, shafts, etc., situated below SF6 installation rooms and connected tothem, shall be able to be ventilated.

Mechanical ventilation may be omitted provided the gas volume of the largest gas compartmentat atmospheric pressure does not exceed 10% of the volume of the room. In this case the totalvolume (calculated at the normal temperature and pressure) of SF6 gas in the cylindersconnected to the SF6 installations shall be taken into account for the purposes of calculation.

No part of equipment in contact with air may exceed a temperature of 200°C.

NOTE 2: For maximum SF6 concentration, national regulations should be considered. (Reference: Japanese maximum SF6 concentration is 1,000vol PPM.)

Article 55. Oil Leakage

The transformers and shunt reactorsshall have oil-collecting system (refer to Article 337 of Vol.1 in Technical regulation).

For indoor electrical equipment,the impermeable floor with edge high enough can be used as an oil collecting sump if the number of transformers is not exceeding 3 and oil volume in each transformer is less than 1,000liter.

For outdoor equipments, oil collectingsump might not be required if the transformer contains less than 1,000liter of oil. Such regulation shall not be applied for water collecting areas and/or the areas where the water resources are protected.

For the outdoor switchyards with the transformers are suspended on thes,poloil tanks are not necessary.

Installation of oil-collecting system shall meet stipulations provided in the article157 and 354 of Vol.1.

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Article 56. Materials for Electrical Equipment

According to the physical properties, electric engineering materials are classified into:

1.Refractory materials mean non-flammable materials or not becoming ash, and in case of being burnt, they are not able to continue burning themselves or slow burning.

2.Arc-resistant materials mean the materials whose properties are unchangednderu arc action in normal operating condition.

3.Moisture-resistant materials mean the materials whose properties are unchanged under the action of moisture.

4.Heat-resistant materials mean the materials whose properties are unchanged under action of hig or low temperatures.

5.Chemical-resistant materials mean the materials whose properties are unchanged under action of chemicals.

At the fire-resistance level (FRL), materials and building structures are classified into three groups which are specified in the following table.

Article 57. Protection against corrosion

It is important to consider the following matters at the time of construction and maintenance of paint equipment. Because it is concerned that the strength reduction and the increase of contact resistance of metal parts occur due to the corrosion of metal parts.

(1) Construction: In order to prevent the galvanic corrosionat the contact portion betweendissimilar metals, appropriate material shall be used for the bolt and the terminal,so that the difference of ionization potential between the bolt and the terminal shall become small. Inaddition, the connection

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portion shall be caulked, not to enter the moisture between the terminal and theAs boltfor. appropriate combination of dissimilar metals, refer to the article 92 of Vol.3.

(2) Maintenance: It is desirable that zincrichpaint (Cold Galvanizing Paint) containing more than 94% of metallic zinc powder in dry paint film is used for the refinish paint, in order to prolong the life of anticorrosive effect. In addition, the coating film of the above mentioned paint should be ensured about 80μm.

It is desirable to do anti-rust treatment on the metal surface of equipment by the one of the following methods for a fine view and rustproof purpose.

(1)Painting

A painting has the advantage of a fine view, because paint colors can be selected freely.

But if the coating film is damaged for some reason, the relevant part will get rusted in a short time without refinish paint. Because a painting does not have the function of sacrificial protection which a hot-dip galvanizing has.

(2)Hot-dip galvanizing

A hot-dip galvanizing is not suitable for the equipment which is installed in the place where requires a fine view, because paint colors can not be selected. But it is strong against the damage on the surface of plating and it is the most economical method for rust-proofing because it has long durable years, due to the function of protective coating and sacrificial protection.

As the following table, the thickness of plating is different based on the way of zinc galvanizing. Therefore, it should select a proper way of zinc galvanizing according to the use application.

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As for the durable year in the atmosphere, it can be calculated from the corrosion rate, th amount of deposition of zinc and the following formula:

Durable year = Amount of zinc / Corrosion rate * 0.9

Note: The durable year in the above table is calculated from the following assumptions:

-Amount of zinc : 550g/m2

-Remaining amount of plating : 10%

Metal parts of poles shall be galvanized with zinc or painted by anti-corrosion paint for protecting corrosion. (Zinc galvanization is the most effective protection method against corrosion.)

Adhesion ratio of zinc galvanization is shown in the following table as reference.

Painting shall be carefully conducted by referring the contents in article 530 in GuidelineVol.3.

Article 58. Distinction of Elements

In an electrical power project,measures are required to distinguish elements in a single part such as diagrams, equipment layout schemes, lettering, numbering, different color paints etc.

Busbar conductors, conductors must be painted as follows: according to the provisions of Section 5 of Article 2 in theVol.1 of Technical Regulation.

Article 59. Avoidance of Interference for Telecommunication Projects

In order for power projects not to interfere with and endanger telecommunication projects, existing related standards and norms as belowmust be complied with and complywith the provisions of Article 281, 282, 284, 286, 287 and 288of Vol.1 in Technical Regulation.

Article 60. Automated Equipment for unmanned substation

Substations designed with automated equipment and unstaffed. In case that a fault happens, remote control equipment and warning signals shall be used for switching toeliminate the fault from a load dispatch center remotely.

Remote control equipment and information such as state of equipment, warning signals, telemeter, etc. is used for remote control from load dispatch centerThe. example of equipment andinformation is shown in the following table.

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recommended to be used, and in urban areas and industrial zones where the planning is approved, underground cables are recommended to be used.

For building in places where power development planis approved, underground cable lines shall be used. For buildings in the places without approved power development plan, the overhead power lines are used. In cities, twisted cable and / or underground cables are used.

For low voltage power lines, the sheathed conductors are strongly recommended to be used. For power lines with voltage up to22kV in the places with narrow corridoror many trees, the sheathed conductors are recommended to be used too.

Article 63. Overload Capacity

The overload capacity of electrical equipment and standby power resources must be considered when solving reserve issues. The overload capacity of electrical equipment shall be considered with manufactures’ specifications individually.

Depending on the power demand, power network with voltage1kVofand higher should be constructed at the diagram with self-closing device for standby power supply source.

Article 64. Conditions of Fault Calculation

As stipulated in Technical Regulation.

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1. Loads of electricity users

Loads of electricity users which are connected to the power system with voltage up to 380V shall be calculated in compliance with the following:

For the initial development stage, calculated load is equal to existing load plus 10% - 20% /year. If voltage is lower than normal, the calculation results must be adjusted.

2. Coincidence coefficient for calculation (Normal users)

Coincidence coefficient for calculation of maximal load of normal users is taken as follows: For public lighting: k = 1

Residential load: k = 0.9

Commercial, services, office loads: k = 0.85 Small industry, handicraft: k = 0.4 - 0.5

3. Formula for calculation

If there is no base for calculation of coincidence coefficient due to combined loads, the following formula can be used:

Mmax = Kdt (Passh + Pcn,tcn+ Pnn) = KdtΣP Where:

Passh : Total capacity for residential lighting Pcn,tcn : Total capacity of industry, handicraft Pnn : Total capacity for agriculture

Kdt is Coincidence coefficient of loads which can be selected as follows: When Passh ≤ 0.5 ΣP, Kdt = 0.6

When Passh = 0.7 ΣP, Kdt = 0.7 When Passh = ΣP, Kdt = 0.9

For other cases, Kdt is extrapolated.

4. Coincidence coefficient for calculation (Power lines)

Coincidence coefficient for calculating loads of power lines with voltage from 6kV to 35kV: For power line with 3-5 substations, Kdt = 0.9

For power line with 6-10 substations, Kdt = 0.8 For power line with 11-20 substations, Kdt = 0.75 For power line with above 20 substations, Kdt = 0.7

Article 66. Transmitting Signal of Fault Circuit Breakers

Transmitting signal of the fault circuit breaker shall be met as specified in Article 60.

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