Circular No. 28/2022/TT-BCT dated October 31, 2022 promulgates National Technical Regulation No. QCVN 17:2022/BCT on safety for 6 kV explosion-proof distribution panels used in underground mines.

 CIRCULAR

ISSUING NATIONAL TECHNICAL REGULATION ON SAFETY FOR DISTRIBUTION CABINETS WITH EXPLOSION-PROOF USE IN UNDERGROUND MINES AT 6KV

____________

THE MINISTER OF INDUSTRY AND TRADE

 

Pursuant to the Law on Standards and Technical Regulations dated June 29, 2006;

Pursuant to the Law on Product and Goods Quality dated November 21, 2007; lượng sn lproducts, goods on November 21, 2007;

Camendbased on Decree No. 98/2017/NĐ-CP dated August 18, 2017 of the Government stipulating the functions, tasks, powers, and organizational structure of the Ministry of Industry and Trade;"b) In addition to the lists of public services issued according to the provisions of Clause 2, Article 4 of this Decree, specialized agencies under provincial People's Committees shall report to the provincial People's Committee for decision-making on amending, supplementing, or issuing the list of public services funded by the state budget within their jurisdiction and consistent with the local budget capacity within the approved budget by the Provincial People's Assembly, and send it to the Ministry of Finance and relevant ministries and sectors for supervision during implementation."hereinafter referred to as the DecreeDeputy ministers of ministerial-level agencies, 27/2007/NĐ-CP dated

Decree No. 1August 27, 2007 of the Government detailing the implementation of certain provisions of the Law on Standards and Technical Regulations; Decree No. 78/2018/NĐ-CP dated May 16, 2018 of the Government amending 01 supplementing certain articles of Decree No. 127/2007/NĐ-CP dated August 1, 2007 of the Government detailing the implementation of certain provisions of the Law on Standards and Technical Regulations;đổamending and supplementing certain articles of the Civil Servants Law and the Civil Servants Law dated November 25, 2019;, amended and supplemented by Decree No. 109/2025/NĐ-CP and Decree No. 193/2025/NĐ-CPm, amended and supplemented by Decree No. 109/2025/NĐ-CP and Decree No. 193/2025/NĐ-CP Article of the Law on Military Service; number some provisions of the Law on StandardsNo. Technical Standards;Article 3. Functions, duties, powers of Management Boards and duties, powers of the Chairperson, Vice Chairperson (if any), Secretary, and Members of Management Boardsto Technical regulations;

Decree No. 132/2008/NĐ-CP dated December 31,amendyear 2008 of the Government detailing the implementation of certain provisions of the Law on Product Quality and Goods;"b) In addition to the lists of public services issued according to the provisions of Clause 2, Article 4 of this Decree, specialized agencies under provincial People's Committees shall report to the provincial People's Committee for decision-making on amending, supplementing, or issuing the list of public services funded by the state budget within their jurisdiction and consistent with the local budget capacity within the approved budget by the Provincial People's Assembly, and send it to the Ministry of Finance and relevant ministries and sectors for supervision during implementation."hereinafter referred to as the DecreeDeputy ministers of ministerial-level agencies, Decree No. 74/2018/NĐ-CP dated May 15, 2018 of the Government amending, supplementing certain articles of 132/2008/NĐ-CP dated December 31, 2008 of the Government detailing the implementation of certain provisions of the Law on Product Quality and Goods;

At the proposal of the Director of the Department of Safety Technology and Environmentỹ IndustrialngTrade promulgates the National Technical Regulation on Safety for Distribution Cabinets with Explosion-Proof at 6kV used in underground mines.;

Bộ trưởng Bộ Công anngIssued along with this Circular is the National Technical Regulation on Safety for Distribution Cabinets with Explosion-Proof at 6kV used in underground mines.Deputy ministers of ministerial-level agencies, roadân phNo.Code: QCVN 17: 2022/BCT., amended and supplemented by Decree No. 109/2025/NĐ-CP and Decree No. 193/2025/NĐ-CP CLASS MONOCOTYLEDONđổ OF NATIONAL trThis Circular takes effect from July 1, 2023.ỏ hầNATIONAL TECHNICAL REGULATION ON SAFETY FOR DISTRIBUTION CABINETS WITH EXPLOSION-PROOF AT 6KV USED IN UNDERGROUND MINES

 

Article 1. National technical regulation on safety for high voltage 6kV distribution equipment explosion-proof used in underground mine

QCVN 17:2022/BCT was drafted by the Drafting Group of the National Technical Regulation on Safety for Distribution Cabinets with Explosion-Proof at 6kV used in underground mines, reviewed by the Department of Safety Technology and Environment - Ministry of Industry and Trade, examined by the Ministry of Science and Technology, and issued by the Minister of Industry and Trade pursuant to Circular No. 28/2022/TT-BCT dated October 31, 2022.

Article 2. Effective Date

I. SCOPE

Article 3. Implementation Organization

The Head of the Ministry's Office, the Director of the Department of Safety and Environmental Technology; Heads of relevant agencies, organizations, and individuals are responsible for implementing this Circular./.

 

QCVN 17:2022/BCT

This technical regulation specifies technical safety requirements and management for distribution cabinets with explosion-proof at 6kV in three-phase high-voltage AC networks with isolated neutral used in underground mines with flammable gases and dust explosions

(hereinafter referred to as explosion-proof 6kV distribution cabinets)

 

PREAMBLE

 

with HS code 8537.20.90.

 

This technical regulation specifies technical safety requirements and management for distribution cabinets with explosion-proof at 6kV in three-phase high-voltage AC networks with isolated neutral used in underground mines with flammable gases and dust explosions

(hereinafter referred to as explosion-proof 6kV distribution cabinets)

 

This technical regulation applies to organizations and individuals producing, importing, testing, inspecting, certifying, appraising, using, and other individuals related to explosion-proof 6kV distribution cabinets in underground mines within the territory of Vietnam. GENERAL PROVISIONS

Thông tư này quy định chi tiết khoản 4 Điều 38 Luật Thủy sản số 18/2017/QH14 đã được sửa đổi, bổ sung tại điểm c khoản 21 Điều 14 Luật số 146/2025/QH15.

3. Definitions 3.1. Flammablemixture

Thông tư này áp dụng đối với tổ chức, cá nhân có liên quan đến hoạt động kinh doanh đối tượng thủy sản nuôi chủ lực trên lãnh thổ Việt Nam.

is a mixture of flammable substances in the form of gas, vapor, dust, fiber, or flying material with air, under atmospheric conditions that allow flame propagation after ignition.

3.2. 6kV distribution cabinet12. Leather shoes

is a switching device capable of closing and opening circuits under normal conditions, as well as automatically disconnecting power under abnormal conditions and faults in high-voltage networks."b) In addition to the lists of public services issued according to the provisions of Clause 2, Article 4 of this Decree, specialized agencies under provincial People's Committees shall report to the provincial People's Committee for decision-making on amending, supplementing, or issuing the list of public services funded by the state budget within their jurisdiction and consistent with the local budget capacity within the approved budget by the Provincial People's Assembly, and send it to the Ministry of Finance and relevant ministries and sectors for supervision during implementation." NO.development3.3. Main circuit of the explosion-proof 6kV distribution cabinet is the entire electrical part of the circuit used to transmit electrical energy to the load.

3.4. Auxiliary circuit of the explosion-proof 6kV distribution cabinet is the entire electrical part (not the main circuit) in control, protection, measurement, and signal circuits.

3.5. Explosion-proof 6kV distribution cabinet is a 6kV distribution cabinet manufactured for use in environments with flammable gases and dust explosions.

3.6. Cable entry and exitâis a part used to receive and protect cable ends, seal the conductors and insulating materials of the cable with a filling compound or sealing ring attached to the equipment housing by threads or bolts. 3.7. Non-explosion-proof enclosure type "d"

is a construction containing parts that can ignite the explosive gas mixture and can withstand the pressure generated inside the explosive gas mixture and prevent the spread of the explosion to the surrounding explosive atmosphere. Flameproof protection type

"i" is a type of protection where the electrical energy of the equipment and its connecting components when placed in an explosive atmosphere is limited below the level that could ignite the explosive mixture by spark effects or thermal effects.

II. TECHNICAL SAFETY REQUIREMENTSỏ 4. Reference documents 4.1. QCVN QTĐ-5:2009/BCT National Technical Regulation on Electrical Engineering - Volume 5 Testing of Electrical Equipment.

3.8. 4.2. QCVN 01:2011/BCT National Technical Regulation on Safety in Underground Coal Mining. 4.3. QCVN 04:2017/BCT National Technical Regulation on Safety in Underground Metal Mining." 4.4. TCVN 4255:2008 (IEC 60529:2001) Protection by Enclosures (IP Code).

4.5. TCVN 6099-1-2007 (IEC 60060-1:1989) High Voltage Testing Techniques - Part 1: General Definitions and Test Requirements.

4.6. TCVN 6592-1:2009 (IEC 60947-1:2007) Low Voltage Switchgear and Controlgear - Part 1: General Rules.FUNCTIONS, DUTIES, POWERS, ORGANIZATIONAL STRUCTURE, OPERATIONAL REGULATIONS, AND RELATIONSHIPS OF MANAGEMENT BOARDS; DUTIES, POWERS OF THE CHAIRPERSON, VICE CHAIRPERSON (IF ANY), SECRETARY, AND MEMBERS OF MANAGEMENT BOARDSn

4.7. TCVN 8096-200-2010 (IEC 62271-200:2003) High Voltage Switchgear and Controlgear - Part 200: Metal-Enclosed Switchgear and Controlgear for Alternating Current up to 52kV.

4.8. TCVN 10888-0:2015 (IEC 60079-0:2011) Explosive Atmospheres - Part 0: Equipment - General Requirements.

4.9. TCVN 10888-1:2015 (IEC 60079-1:2014) Explosive Atmospheres - Part 1: Protection of Equipment by Non-Explosion-Proof Enclosure Type "d".

4.10. TCVN 7079-7:2002 Equipment for Underground Mines - Part 7: Enhanced Safety - Type "e" Protection.

4.11. TCVN 7079-11:2002 Electrical Equipment for Underground Mines - Part 11: Intrinsically Safe Protection - Type "i".

4.12. TCVN 7079-17:2003 Electrical Equipment for Underground Mines - Part 17: Inspection and Maintenance of Equipment.

4.13. IEC 60079-7:2015 Explosive Atmospheres - Part 7: Protection of Equipment by Enhanced Safety "e".

4.14. IEC 60079-11:2011 Explosive Atmospheres - Part 11: Protection of Equipment by Intrinsic Safety "i".

4.15. IEC 60079-17:2013 Explosive Atmospheres - Part 17: Inspection and Maintenance of Electrical Installations.

4.10. TCVN 7079-7:2002 Equipment used in underground mines - Part 7: Increased safety protection type "e".

4.11. TCVN 7079-11:2002 Electrical equipment used in underground mines - Part 11: Spark-proof protection type "i".

4.12. TCVN 7079-17:2003 Electrical equipment used in underground mines - Part 17: Inspection and maintenance of equipment.

4.13. IEC 60079-7:2015 Explosive atmospheres - Part 7: Equipment protection by increased safety "e".

4.14. IEC 60079-11:2011 Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i".

4.15. IEC 60079-17:2013 Explosive atmospheres - Part 17: Electrical installation inspection and maintenance.

4.16. IEC 62271-1:2017 and Amendment 1:2021 High-voltage switchgear and controlgear - Part 1: Common specifications (High-voltage switching and control equipment - Part 1: General technical characteristics)

5. General Requirements

5.1. Explosion-proof distribution cabinets at 6 kV used in underground mines must meet the technical safety requirements for general 6 kV distribution cabinets used in environments without flammable gases and explosive dust.

5.2. Explosion-proof distribution cabinets at 6 kV used in underground mines must have one of the following explosion-proof types: Ex d I Mb, Ex d [ia] I Mb, Ex d [ib] I Mb as marked in Clause 29.4 TCVN 10888-0:2015.

5.3. Classification of explosion-proof distribution cabinets at 6 kV

5.3.1. Classification according to the opening-closing mechanism:

5.3.1.1. Spring-operated opening-closing cabinets;

5.3.1.2. Electromagnetic opening-closing cabinets.

5.3.2. Classification according to function:

5.3.2.1. Input cabinets;

5.3.2.2. Sectionalizing cabinets;

5.3.2.3. Output cabinets;

5.3.2.4. Isolation cabinets.

5.4. Operating Conditions Requirements

5.4.1. Rated frequency: 50 Hz.

5.4.2. Operating mode: Continuous operation, stable within the range from 85 to 115 percent of rated voltage.

5.4.3. Ambient temperature:

5.4.3.1. Ambient temperature from -20 °C to +40 °C; relative humidity value up to (98 ± 2) percent at 35 °C;

5.4.3.2. Hazardous environment with flammable gases and explosive dust, dust content not exceeding 1200 mg/m³.³.

5.5. Installation Position Requirements

5.5.1. Tilt angle not exceeding ±15 ° in all directions relative to the vertical axis and in chambers, stations, and tunnels with structures ensuring safety.

5.5.2. Dry and properly ventilated as specified in Article 42 QCVN 01:2011/BCT for coal mines, Article 43 QCVN 04:2017/BCT for ore mines.

5.5.3. Free from corrosive or damaging vapors or gases.

5.5 4 Maximum altitude not exceeding 1000 m above sea level.

5.6. Structural Requirements

5.6.1. Grounding Requirements

5.6.1.1. Grounding requirements must comply with those stipulated in Article 5.3 TCVN 8096-200:2010 (IEC 62271-200:2003), Clause 20 Article 102 QCVN 01:2011/BCT, and Articles 5.1, 5.2, 5.4, and 5.5 TCVN 10888-0:2015 (IEC 60079-0:2011).

5.6.1.2. In cable head compartments, there must be mechanisms to secure grounding wires and weld them to the casing; cable heads must have mechanisms to secure grounding wires.

5.6.2. Explosion-proof distribution cabinets at 6 kV used in underground mines must have mounting brackets under the casing and upper hooks for ease of installation, movement, and operation.

5.6.3. The interlocking mechanism of the cabinet must comply with the provisions of Article 5.11 TCVN 8096-200:2010 (IEC 62271-200:2003) and Article 10 TCVN 10888-0:2015 (IEC 60079-0:2011).

5.6.4. All slow-opening covers must be securely fastened with screws or bolts and have a warning sign "Do Not Open When Energized."

5.6.5. Operation buttons, control mechanisms, and operations of explosion-proof distribution cabinets at 6 kV must have clear, non-erasable operation markings.

5.6.6. Electrical components frequently adjusted during operation must be placed in compartments with quick-opening covers; cable connectors and busbar connections of inputs and outputs must be placed in compartments with slow-opening covers.

5.6.7. Mechanical interlocking mechanisms must comply with the provisions of Clause 5.6.3 of this Technical Standard and must meet the following requirements:

5.6.7.1. Quick-opening covers can only be opened when:

5.6.7.1.1. The opening-closing mechanism is in the open position;

5.6.7.1.2. The main circuit disconnector contacts are open;

5.6.7.1.3. The interlocking mechanism lock is released;

5.6.7.1.4. The capacitor discharge device is reliably grounded.

5.6.7.2. When the quick-opening cover is in the open position, the main circuit disconnector contacts cannot be closed.

5.6.7.3. When the circuit breaker is in the closed position, the main circuit disconnector contacts cannot be operated.

5.6.7.4. When the circuit breaker is in the closed position, the spring energy storage mechanism cannot store energy to perform closing operations.

5.6.8. Explosion-proof distribution cabinets at 6 kV must be equipped with transparent doors to observe operational parameters; mechanical position indicators for the opening-closing mechanism; positions of the main circuit disconnector contacts.

5.6.9. Circuit diagrams and electrical connection diagrams must be securely attached to the cabinet and in easily observable positions.

5.6.10. Remote control circuits of explosion-proof distribution cabinets at 6 kV must be intrinsically safe "i" type circuits with safety levels ia or ib as stipulated in Articles 3.7 and 3.8 TCVN 7079-11:2002.

5.6.11. Control and protection functional blocks must prevent incorrect installation.

5.6.12. Low-voltage internal connections and high-voltage main circuit input and output connections of explosion-proof distribution cabinets at 6 kV must comply with the provisions of Clause 5.4.5.2 IEC 62271-1:2017 and Amendment 1:2021.

5.6.12.1. Wire terminals must maintain necessary contact pressure and have anti-loosening details corresponding to the current and short-circuit current ratings of the circuit.

5.6.13. The external protection level of remote control devices, electrical interlocks, and integrated protections in explosion-proof distribution cabinets at 6 kV must be manufactured with a protection level no lower than IP54 as directed in Article 5.2 TCVN 4255:2008.

5.6.14. The casing of explosion-proof distribution cabinets at 6 kV must have high-voltage input and output mounting structures to allow independent operation or coupling to form high-voltage distribution substations with technical features and explosion-proof capabilities.

6. Requirements for Explosion-Proof Structures of Explosion-Proof Distribution Cabinets at 6 kV

Explosion-proof distribution cabinets at 6 kV used in underground mines with flammable gases and explosive dust must be designed, manufactured, and tested in accordance with standards TCVN 10888-0:2015 (IEC 60079-0:2011), TCVN 10888-1:2015 (IEC 60079-1:2014); standard TCVN 7079-7 (IEC 60079-7), TCVN 7079-11 (IEC 60079-11) corresponding to explosion-proof types and provisions of this Technical Standard.

6.1. Main parts of the non-penetrating explosion-proof enclosure type "d" include:

6.1.1. Cable connection compartments;

6.1.2. Cable heads and cable bushings;

6.1.3. Porcelain insulators through the walls of the explosion-proof enclosure;

6.1.4. Transparent elements;

6.1.5. Control buttons and switch locks;

6.1.6. Mechanisms for transmitting rotary or linear motion;

6.1.7. Locks, related holes, and empty elements;

6.1.8. Special securing mechanisms;

6.1.9. Interlocking mechanisms;

6.1.10. Quick-opening covers;

6.1.11. Compartments containing electrical equipment.

6.2. Requirements for non-explosive-proof "d" type enclosures

6.2.1. Types of explosive-proof joints

Explosive-proof joints must comply with Articles 5, 6, 7, and 8 of TCVN 10888-1:2015 (IEC 60079-1:2014) and the provisions of this technical standard.

6.2.1.1. Explosive-proof pipe joint without bolt holes as shown in Figure 1.

Note:

of - Width of the flat part of the explosive-proof joint, mm.

For coal-fired thermal power plants where the enterprise holds 100% of the registered capital and uses 100% of its own capital to invest in the project approved by the competent authority, E is determined as 100%; - Width of the cylindrical part of the explosive-proof joint, mm.

F - Clearance of the beveled edge, mm.

L - Minimum width of the explosive-proof joint, mm; L = c + d with the condition: c ≥ 3,0 mm, f ≤ 1,0 mm.

T - Inside surface of the equipment enclosure.

Figure 1. Explosive-proof pipe joint without bolt holes, amended and supplemented by Decree No. 109/2025/NĐ-CP and Decree No. 193/2025/NĐ-CP cylindrical shape without bolt holes

6.2.1.2. Explosive-proof pipe joint with bolt holes as shown in Figure 2.

Note:

a - Width of the cylindrical part of the joint, mm.

The Standing Office of the Council for International Cooperation on Non-Governmental Organizations (Vietnam Friendship Association) is the agency responsible for receiving registration dossiers, leading, and coordinating with member agencies of the Council to examine dossiers and return results of reviews of registration dossiers of foreign non-governmental organizations in Vietnam. - Width of the flat part of the joint to the bolt hole, mm.

international - Clearance of the cylindrical part of the joint, mm.

l – Minimum distance from inside the equipment to the bolt hole, mm; I = a + b if international ≤ 0,2 mm.

L - Minimum width of the explosive-proof joint, mm.

T - Inside surface of the equipment enclosure.

HìFigure 2. Explosive-proof pipe joint with bolt holes

6.2.1.3. Explosive-proof flange joint as shown in Figure 3.

Note:

l - Minimum distance from inside the equipment to the bolt hole, mm.

L - Minimum width of the explosive-proof joint, mm.

T - Inside surface of the equipment enclosure.

Figure 3. Explosive-proof flange joint

6.2.1.4. The minimum distance from inside the equipment to the bolt hole must comply with the provisions of Table 1 of this technical standard.

Table 1. Minimum distance from inside the equipment to the bolt hole.of the Government stipulating functions, tasks, powers, and organizational structure of the Ministry of Home Affairsorganize credit institutions, foreign bank branches are responsible for organizing the implementation of this Circular. from inside the equipment to the bolt hole.

6.2.1.5. Explosive-proof flange joint with a gasket as shown in Figure 4.

Note:

G - Gasket.

L - Minimum width of the explosive-proof flange, mm.

d.1. Amount of taxable income in Vietnam: - Inside surface of the equipment enclosure.

Figure 4. Explosive-proof flange joint with a gasket

6.2.1.6. Explosive-proof rotary or linear slide joint as shown in Figure 5.

Note:

L - Minimum width of the explosive-proof joint, mm.

In cases where it is necessary to operate through the wall of a non-penetrating enclosure, the width of the joint must comply with Article 7 of TCVN 10888-1:2015 (IEC 60079-1:2014).

Figure 5. Explosive-proof rotary jointexport, explosion-proof rotary joint

6.2.1.7. Explosive-proof rotary joint with a bearing liner as shown in Figure 6.

Note:

L - Minimum width of the explosive-proof joint, mm.

Figure 6. Explosive-proof rotary joint with a bearing linerexport, explosion-proof rotary joint with bearing

6.2.1.8. Explosive-proof threaded joint must comply with Articles 5.2.8 and 5.3 of TCVN 10888-1:2015 (IEC 60079-1), as shown in Figure 7.

Note:

d.1. Amount of taxable income in Vietnam: - Thread pitch.

Y - Thread engagement length, mm.

α- Thread apex angle, degrees,

Figure 7. Explosive-proof threaded joint

6.2.2. Minimum width and clearance of explosive-proof joints:

6.2.2.1. For joints of types: Pipe, cylinder, flange, rotary shaft, as specified in Table 2 of this technical standard, the surface roughness (Ra) must not exceed 63 µm._a shall not exceed 63 µm.

Table 2. Minimum width and clearance of explosive-proof joints

6.2.2.2. For threaded joints, the following requirements must be met:

6.2.2.2.1. At least five threads must engage each other.

6.2.2.2.2. Thread pitch ≥ 0,7 mm.

6.2.2.2.3. Thread apex angle equal to 60° (± 5°).

6.2.2.2.4. Thread engagement length ≥ 5 mm with V ≤ 100 cm³.

6.2.2.2.5. Thread engagement length ≥ 8 mm with V > 100 cm³.

6.2.3. Special fastening devices

6.2.3.1. Fastening devices must comply with Article 9 of TCVN 10888-0:2015 (IEC 60079-0:2011).

6.2.3.2. For special fastening devices of non-penetrating enclosure protection type "d", they must comply with the provisions of Clause 2.3.1 of this Article and Article 11 of TCVN 10888-1:2015 (IEC 64079-1:2014).

6.2.3.3. All explosive-proof joints using bolts must have anti-loosening washers and can only be opened with tools.

6.2.4. Quick-opening covers must have interlocking locking mechanisms: can only be opened after power has been cut off and the interlocking mechanism has been released.

6.2.5. Cable entry into the equipment

Cable entries leading to the cable junction box of the 6 kV explosion-proof distribution cabinet must comply with Article 16 and Appendix A of TCVN 10888-0:2015 (IEC 60079-0:2011), Article 13 of TCVN 10888-1:2015 (IEC 60079-1:2014), and the following requirements:

6.2.5.1. Must be securely attached to the equipment enclosure and have all necessary parts to seal and clamp cables, one of the types of cable glands as shown in Figure 8.

Note:

1- Rubber sealing ring for cable.

2- Rubber cable.

3- Cable clamping detail.

4- Detail for cable entry to compress rubber gasket.

5- Equipment enclosure.

d- Outer diameter of rubber cable, mm.

D1 - Inner diameter of cable gland, mm.

D2, D3 - Outer, inner diameters of rubber gasket, mm.

Figure 8. Cable gland when connected

6.2.5.2. Distance between the cable gland, gasket, and rubber cable as specified in Table 3 of this technical standard.

Table 3. Distance between cable gland, gasket, and rubber cable điện cao su

6.2.5.3. The cable coupling components must be tightened to ensure sealing performance.

6.2.5.3. Cable gland details must be tightened to ensure sealing performance.

6.2.5.4. Rubber sealing rings must ensure no cracking, good elasticity, and that the cable is not stretched or bent during assembly and operation.

6.2.5.5. In high-voltage cable glands using insulating filler material, the solidified filler must ensure no cracks.

Note:

6.2.6. Unconnected cable glands must be sealed as shown in Figure 9 or another similar sealing method.

1 - Sealing plug.

2 - Rubber sealing ring.

3 - Detail for cable entry and exit to seal.

4 - Cable clamping detail.of the Government stipulating functions, tasks, powers, and organizational structure of the Ministry of Home AffairsFigure 9. Unconnected cable gland

6.3. Light-transmitting elements

The translucent parts must comply with Article 9 TCVN 10888-1:2015 (IEC 60079-1:2014) and Article 26 TCVN 10888-0:2015 (IEC 60079-0:2011).

6.4. Materials for the enclosure

6.4.1. Non-metallic materials

Non-metallic materials used to manufacture components, parts, and sections of the enclosure of explosion-proof distribution cabinets at 6 kV must comply with the provisions of Article 7 TCVN 10888-0:2015 (IEC 60079-0:2011).

6.4.2. Metallic materials

Metallic materials used to manufacture components and parts of the enclosure of explosion-proof distribution cabinets at 6 kV must comply with the provisions of Article 8 TCVN 10888-0:2015 (IEC 60079-0).

6.5. Insulating bushings (porcelain inserts), cable glands passing through the walls of the cabinet must comply with the provisions of Article 11 TCVN 10888-0:2015 (IEC 60079-0:2011) and ensure that they are not damaged during the connection of electrical conductors.

6.6. Connection means and cable compartments must comply with the provisions of Articles 14 and 15 TCVN 10888-0:2015 (IEC 60079-0:2011).

6.7. The relative dielectric discharge index of solid insulating materials used in explosion-proof distribution cabinets at 6 kV must comply with the provisions of Article 4.1 IEC 60079-7:2015, and the relative dielectric discharge index of solid insulating materials (CTl) according to Table 4 of this technical standard.

Table 4. Relative discharge index of solid insulating materials无效 CLASS MONOCOTYLEDONNo. relative flashover voltage of solid insulating materials

Solid insulating materials used in circuits operating at voltages exceeding 250 V or carrying currents greater than 16 A must have a CTI value not less than 400.

6.8. Requirements for clearance and creepage distance

The requirements for clearance in air between two live parts and the creepage distance along the surface of the insulating material between two conductive parts must comply with the provisions of Articles 4.3 and 4.4 IEC 60079-7:2015 and Table 5 of this technical standard.

Table 5. Clearance and Creepage Distance

6.9.2. The parameters R, L & C of the circuit must ensure that when tested, it does not ignite the test gas mixture due to sparks.

6.9.3. Any thermal effects generated in the flameproof safety circuits under any circumstances must ensure that they do not ignite the gas mixture due to surface heating.

6.9.4. Flameproof safety circuits must be isolated from each other and from non-flameproof safety circuits.

7. Technical requirements for explosion-proof distribution cabinets at 6 kV used in underground mines

7.1. Basic parameters

7.1.1. Rated voltage (Uđổ ): 6 kV.

7.1.2. Rated current (

) is a value in the following range: 50 A, 100 A, 200 A, 315 A, 400 A, 500 A, 630 A, 800 A, 1 000 A, 1 250 A._F7.1.3. Rated short-circuit breaking capacity (/I

) is a value in the following range: 6,3 kA, 8 kA, 12,5 kA, 16 kA, 20 kA, 25 kA, 31,5 kA.I_F7.1.4. Maximum rated short-circuit making capacity

(Ip)_kis 2.5 times the effective value of the alternating current component of the rated short-circuit breaking capacity.

7.1.5. Rated short-circuit duration ( ): 2 s. 7.1.6. Operating voltage range of auxiliary equipment (control, protection, monitoring, signaling, and electronic communication) is 75% to 120%. The rated supply voltage of the switching mechanism and auxiliary circuits (

7.1.6.1. For DC voltage: 24 Vdc, 48 Vdc, 60 Vdc, 110 Vdc, 220 V, and not more than 250 Vdc;organize credit institutions, foreign bank branches are responsible for organizing the implementation of this Circular._k7.1.6.2. For AC voltage: 120 Vac, 230 Vac.

7.2. Requirements for structure and electrical diagramsThe decision to switch the issuance of coats, overcoats, windbreakers, and down jackets to other uniforms for civil servants working at the National Market Management and Development Agency is decided by the Minister of Industry and Trade._a).

7.2.1. Requirements for function and protection:

7.2.1.1. Normal operation when grid voltage fluctuates within the range (from 85 to 115) % of the rated voltage;

7.2.1.2. Overcurrent protection;

7.2.1.3. Overcurrent protection with delayed action;

7.2.1.4. Overcurrent protection with inverse time-delay action (overload protection);

7.2.1.5. Short-circuit protection;

7.2.1.6. Earth fault (ground fault) protection;

7.2.1.7. Low voltage protection;

7.2.1.8. Overvoltage protection.

7.2.2. Display operational parameters during operation, status signals of the cabinet: closing-opening; actions of various protections and interlocks.

7.2.3. Have a testing mode for the operation of protective devices and reporting faults.

7.3. Insulation requirements

7.3.1. Insulation resistance value

7.3.1.1. The main circuit at 6 kV must be tested according to the manufacturer's documentation or according to Table 2-24-1 Article 28 QTĐ 05:2009/BCT, and must not be less than 200 MΩ at 30 °C.

7.3.1.2. Auxiliary circuits (control, protection, measurement, and signaling) must be tested and must not be lower than 2 MΩ according to Article 32 QTĐ-05:2009/BCT.

7.3.2. Withstand insulation level

The insulation of explosion-proof distribution cabinets at 6 kV must withstand an AC test voltage of 50 Hz for 1 minute without surface discharge or insulation breakdown according to Article 4.2 IEC 62271-1:2017 and Amendment 1:2021.

7.3.2.1. For the main circuit

The test voltage for the insulation endurance of the main circuit according to Table 6 of this technical standard.

Table 6. Test voltage for insulation endurance of the main circuit

Rated voltage (maximum voltage) kV

Test voltage (useful value) kV

Bn lSurge voltage (value) kV

7.3.2.2. For auxiliary circuits

7.3.2.2.1. The insulation withstand level of auxiliary circuits must comply with the provisions of Article 7.2.3 of TCVN 6592-1:2009 (IEC 60947-1:2007). The test voltage for the insulation endurance of auxiliary circuits is specified in Table 7 of this technical regulation.

Table 7. Test voltage for insulation endurance of auxiliary circuits

7.3.2.2.2. For spark-safe circuits, they must comply with the provisions of Article 7.3.2.2.1 of this Technical Standard and Article 6.3.13 IEC 60079-11:2015.

7.4. Requirements for protective characteristics

7.4.1. Rated supply voltage for protection systems

The rated supply voltage for relay protection lies within the following ranges: 24 Vdc, 48 Vdc, 60 Vdc, 110 Vdc, 120 Vdc. Frequency 50 Hz, power consumption not exceeding 30 VA and reliable operation within the range from 75 % to 120 % of the rated voltage.

7.4.2. Inverse-time overcurrent protection settings are set according to a scale with values of 20 %, 30 %, 40 %, 50 %, 60 %, 70 %, 80 %, 90 %, 100 % of the secondary rated current (I_{Average loan repayment period is 10 years;} = 5 A) of the current transformer. The characteristics of inverse-time overcurrent protection are specified in Table 8 of this Technical Standard.

Table 8. Characteristics of inverse-time overcurrent protection

7.4.3. Short-circuit protection

7.4.3.1. The short-circuit protection current setting is established on a scale from 1 to 9 times the secondary rated current of the current transformer (I_{Average loan repayment period is 10 years;}) and the error of the set value does not exceed ±10 %. When the short-circuit current value is 1.2 times the set current value, the short-circuit protection is activated with an action time less than 0.1 s.

7.4.3.2. When a short circuit occurs at the end of the source in the high-voltage distribution system with a current exceeding 4 times the rated current (Il_F) of the current transformer, the current supply for short-circuit protection must meet the following requirements:

7.4.3.3. The secondary winding of the current transformer (CT) must generate a power of 25 VA with a load resistance of 25 Ω and reliably trip the circuit breaker.

7.4.3.4. Protective equipment must maintain normal operating time of at least 5 s to ensure reliable opening and closing of the circuit breaker and guarantee the storage and transmission of operational information of the 6 kV explosion-proof distribution cabinet.

7.4.4. Voltage protection

7.4.4.1. Low voltage protection

The low voltage release mechanism must operate to open the switching device when the voltage at the terminals of the release mechanism drops below 35 % of the rated voltage. The delayed action time is within the range (from 0 to 5) s.

7.4.4.2. Overvoltage protection

When the grid voltage exceeds the rated value by 115 %, the protective device must act. The delayed action time is within the range (from 0 to 5) s.

7.4.5. Insulation monitoring protection

Explosion-proof 6 kV distribution cabinets must have insulation monitoring protection for cable outputs to loads, with operating parameters as specified in Table 9 of this Technical Standard.

Table 9. Operating parameters of insulation monitoring protection

7.4.6. Ground fault protection

7.4.6.1. Directional ground fault protection (where the neutral current does not act according to 3I₀ and voltage 3U₀) as specified in Table 10 of this Technical Standard.

Table 10. Operating parameters of directional ground fault protection

7.4.6.2. Non-directional ground fault protection (acts according to 3I₀), the neutral current primary setting is divided into scales of 0.5 A, 1.0 A, 2.0 A, 4.0 A, 6.0 A, with an action time of 0.1 s and an error value not greater than 10%.

7.4.7. Overvoltage protection during operation

The output of the explosion-proof 6 kV distribution cabinet must have overvoltage surge protection during operation using Varistor elements suitable for high-voltage grid operation.

7.5. For exposed cabinets with leakage current lockout protection, the value of the lockout protection resistance must not be less than 360 kΩ.

7.6. Self-test circuit

Protection devices using digital technology must have a self-test circuit for the relay protection device and display the working status of the device.

7.7. Main circuit contact resistance

Main circuit contact resistance includes: Contact resistance of the main circuit contacts of the circuit breaker, contact resistance of the high-voltage isolating switch contacts. The contact resistances are specified by the manufacturer in technical documentation.

7.8. Capacitor discharge characteristic

For explosion-proof 6 kV distribution cabinets with integrated capacitors in auxiliary circuits, the capacitor discharge time must comply with the provisions of Article 6.3 TCVN 10888-0:2015 (IEC 60079-0:2011).

7.9. Temperature rise

When the ambient air temperature does not exceed 40 °C, the temperature rise of any part of the explosion-proof 6 kV distribution cabinet must not exceed the maximum allowable temperature rise specified in Table 11 of this Technical Standard.

Table 11. Maximum allowable temperature rise for components

7.10. Maximum surface temperature of the explosion-proof 6 kV distribution cabinet complies with Articles 5.3, 26.5 TCVN 10888-0:2015 and does not exceed the following provisions:

7.10.1. For surfaces with adhered explosive dust: 150 °C;

7.10.2. For surfaces without adhered explosive dust: 450 °C.

8. Requirements and testing methods

8.1. Environmental requirements:

8.1.1. Ambient temperature from -20 °C to +40 °C;

8.1.2. Relative humidity value up to (98 ± 2) % at 35 °C;

8.1.3. Oxygen content is 21 % by volume;

8.1.4. No air flow, toxic gases, or corrosive vapors.

8.2. Testing equipment must have an appropriate accuracy level for measuring the values of the parameters to be tested.

8.3. Inspection and testing of explosion-proof structures

8.3.1. The enclosure of the 6 kV explosion-proof distribution cabinet must have an explosion-proof protection type "d".

8.3.1.1. Inspect the explosion-proof structure of the enclosure including:

8.3.1.1.1. All assembled parts on the explosion-proof enclosure must be inspected to comply with the explosion-proof requirements of TCVN 10888-0:2015 (IEC 60079-0:2011), TCVN 10888-1:2015 (IEC 60079-1:2014), and Article 6 of this Technical Regulation.

8.3.1.1.2. The construction of the flameproof joint surface and its roughness must be checked sequentially using a feeler gauge, caliper, micrometer, surface roughness tester, or other testing instruments, the results must meet the provisions of Article 6.2.2 of this Technical Regulation.

8.3.1.1.3. The clearance between isolated gaps and the length of leakage paths between conductors must be measured using suitable measuring tools, the results must comply with the provisions of Article 6.8 of this Technical Regulation.

8.3.1.1.4. Interlocking mechanisms must be intact, reliable, and prevent the quick opening of the cover when the distribution cabinet is energized.

8.3.1.1.5. Inspect mechanical indicators for position status, switch-on/off positions of the sand machine, and isolator contacts through observation windows, these indicators must be accurate and clear.

8.3.1.1.6. Inspect display functions.

When the electrical distribution equipment is energized, it must display working voltage and current, as well as the status of on/off, and must correspond to the actual status of the electrical distribution equipment. Upon detecting fault signals, the screen must display them.

8.3.1.2. Test the explosion-proof structure of the enclosure including:

8.3.1.2.1. Determine the maximum surface temperature test

The operational temperature and maximum surface temperature tests must comply with the provisions of Articles 26.5.1.2 and 26.5.1.3 of TCVN 10888-0:2015 (IEC 60079-0:2011), the maximum temperature must be less than 150 °C.

8.3.1.2.2. Determine the relative arc resistance index (CTI)

The CTI of solid insulating materials used in the 6 kV explosion-proof distribution cabinet must be tested according to standard IEC 60112:2009, the results must meet the provisions of Article 6.7 of this Technical Regulation.

8.3.1.2.3. Pressure resistance test of the explosion-proof enclosure

8.3.1.2.3.1. The test to determine the maximum standard internal explosion pressure is carried out according to the provisions of Article 15.2.2 of TCVN 10888-1:2015 (IEC 60079-1:2014);

8.3.1.2.3.2. The overpressure test (enclosure strength) is carried out according to the provisions of Article 15.2.3 of TCVN 10888-1:2015 (IEC 60079-1:2014).

8.3.1.2.4. Non-propagation of fire from inside test

The test to determine non-propagation of fire from the internal explosion within the explosion-proof enclosure to the surrounding explosive atmosphere is carried out according to the provisions of Article 15.3 of TCVN 10888-1:2015 (IEC 60079-1:2014).

8.3.1.2.5. Cable gland performance test including:

8.3.1.2.5.1. Determining clamping force, impact resistance of cable glands performed according to the provisions of Appendix A, Article A3 of TCVN 10888-0:2015 (IEC 60079-0:2011).

8.3.1.2.5.2. Sealing ring tightness, mechanical strength of cable glands performed according to the provisions of Appendix C, Article C3 of TCVN 10888-1:2015 (IEC 60079-1:2014).

8.3.1.2.5.3. Thermal endurance of rubber seals and sealing rings performed according to the provisions of Articles 26.8, 26.9, and 26.16 of TCVN 10888-0:2015 (IEC 60079-0:2011).

8.3.1.2.6. Tests for installed transparent elements on the explosion-proof enclosure including:

8.3.1.2.6.1. Impact test of transparent elements performed according to the provisions of Article 26.4.3 of TCVN 10888-0:2015 (IEC 60079-0:2011), the sample must not be damaged, cracked, or broken.

8.3.1.2.6.2. Heat shock test performed according to the provisions of Article 26.5.2 of TCVN 10888-0:2015 (IEC 60079-0:2011), the sample must not crack, break, or be damaged.

8.3.1.2.7. Torque test of cable conduits and terminal connections performed according to the provisions of Article 26.6 of TCVN 10888-0:2015 (IEC 60079-0:2011).

8.3.2. Inspect components with spark-proof protection including:

8.3.2.1. Cross-sectional area of internal conductors and printed circuit boards of the spark-proof circuit, the results must comply with the provisions of Article 5.6.4 of IEC 60079-11:2011.

8.3.2.2. Isolation of the spark-proof circuit performed according to the provisions of Article 6.3 of IEC 60079-11:2011, the distance between the terminals of the spark-proof circuit and non-spark-proof circuit must comply with the provisions of Article 6.2.1 of IEC 60079-11:2011 and must be greater than 50 mm.

8.3.2.3. Spark-proof circuits must be tested for ignition by sparks according to the provisions of Article 10.1 of IEC 60079-11:2015, the result must not ignite the explosive gas mixture during testing.

8.4. Inspection and testing of technical features

8.4.1. Inspect and test insulation.

8.4.1.1. Inspect insulation resistance

Insulation resistance is tested between phases and ground for the main circuit and auxiliary circuits, the results must comply with the provisions of Article 7.3.1 of this Technical Regulation.

8.4.1.2. High-frequency industrial voltage withstand test

The insulation withstand test using high-frequency industrial voltage is conducted according to TCVN 6099-1-2007 (IEC 60060-1-1989), the test values are specified in Table 6 for the main circuit and Table 7 for auxiliary circuits, the results must comply with the provisions of Article 7.3.2 of this Technical Regulation.

8.4.2. Operation test for closing and opening

8.4.2.1. Manual operation test for closing and opening

Perform three manual operations or button presses on-site, ensuring that there are no abnormalities in the 6 kV explosion-proof distribution cabinet.

8.4.2.2. Electrical operation test for closing and opening

Perform three operations at rated voltage via remote control, ensuring that there are no abnormalities in the 6 kV explosion-proof distribution cabinet.

8.4.2.3. Automatic disconnection mechanism test

Execute the cut command on the circuit breaker to ensure that the 6 kV explosion-proof distribution panel is immediately disconnected and not reconnected.

8.4.3. Testing to determine the closing and opening parameters

8.4.3.1. Determining the contact resistance of the main circuit contacts

The contact resistance of the main circuit contacts is measured using the Volt-Ampere method with a direct current or using contact resistance bridges with a scale up to µΩ, the measurement results must meet the technical specifications of the manufacturer.

8.4.3.2. Determining the time for contact closure and opening

The time for contact closure and opening must be measured and checked to ensure compliance with the technical specifications of the manufacturer.

8.4.3.3. Checking simultaneous three-phase contact

The time for non-simultaneous three-phase closure and opening must be measured and checked to ensure compliance with the design of the manufacturer or not exceeding 0.006 seconds.

8.4.4. Testing the minimum operating voltage of the closing and opening mechanism

Do not apply voltage to the main circuit of the cabinet, remove the potential transformer (PT) from the test circuit, supply power corresponding to the cabinet diagram to the auxiliary circuits (control, protection, signal), and determine the smallest closing and opening voltage when the 6 kV explosion-proof distribution panel completes the closing and opening process. The minimum allowable value is specified in Table 12 of this Technical Standard.

Table 12. Minimum operating voltage values of the circuit breaker

8.4.5. Testing the voltage and current transformers

8.4.5.1. Testing the voltage transformer (PT)

The inspection and testing of the voltage transformer shall be carried out in accordance with Article 28 of QCVN QTĐ-05:2009/MIC.

8.4.5.2. Testing the current transformer (CT)

The inspection and testing of the current transformer shall be carried out in accordance with Article 29 of QCVN QTĐ-05:2009/MIC.

8.4.6. Testing low voltage protection

Inspection and testing of low voltage protection must comply with Clause 7.4.4.1 of this Technical Standard.

8.4.7. Testing overcurrent protection

Inspection and testing of overcurrent protection must comply with Clause 7.4.2 of this Technical Standard.

8.4.8. Testing short-circuit protection

Inspection and testing of short-circuit protection must comply with Clause 7.4.3 of this Technical Standard.

8.4.9. Testing the insulation monitoring protection circuit

Inspection and testing of the insulation monitoring protection circuit must comply with Clause 7.4.5 of this Technical Standard.

8.4.10. Testing the ground fault lockout circuit on the load side

Inspection and testing of the ground fault lockout circuit on the load side must comply with Clause 7.5 of this Technical Standard.

III. PROVISIONS ON MANAGEMENTOpinion

9. Labeling provisions

The information recorded on the label of the 6 kV explosion-proof distribution panel used in underground mines must comply with the provisions of Government Decree No. 43/2017/ND-CP dated April 14, 2017, which stipulates labeling requirements for goods, amended and supplemented by Government Decree No. 111/2021/ND-CP dated December 9, 2021, amending and supplementing certain articles of Government Decree No. 43/2017/ND-CP dated April 14, 2017, on labeling requirements for goods and parts of the 6 kV explosion-proof distribution panel must include the following contents:

9.1.1. Type, model;

9.1.2. Rated voltage, V;

9.1.3. Rated current, A;

9.1.4. Circuit-breaking current limit, kA;

9.1.5. Rated frequency, Hz;

9.1.6. Explosion-proof protection type;

9.1.7. Enclosure protection rating (IP code);

9.1.8. Explosion-proof certificate number;

9.1.9. Factory serial number;

9.1.10. Safe spark circuit parameters (if applicable);

9.1.11. Year of manufacture;

9.1.12. Weight, kg.

9.2. Material and location of the label

The label must be made of white steel or brass with a thickness of 1.5 mm, the information in the table must be engraved with a depth of at least 0.5 mm, and must be arranged in a place that is easy to see and read, securely fastened to the casing by riveting or screwing.

9.3. Electrical schematic plate

The electrical schematic diagram describing the operation principle and wiring of the 6 kV explosion-proof distribution panel must be attached inside the casing wall.

10. Provisions on declaration

p regulationsnational10.1. The 6 kV explosion-proof distribution panels within the scope of this Standard must declare conformity in accordance with the technical safety regulations in Part II of this Technical Standard, affix the conformity mark (CR mark) before entering the market.

10.2. Imported 6 kV explosion-proof distribution panels must comply with the national quality inspection registration procedures for imported goods as stipulated in Circular No. 36/2019/TT-BCT dated November 29, 2019, issued by the Ministry of Industry and Trade, regulating the management of product and commodity quality group 2 under the responsibility of the Ministry of Industry and Trade.

10.3. Declaration of conformity

10.3.1. The declaration of conformity for 6 kV explosion-proof distribution panels must be based on the certification results of organizations certified to operate in the field according to the provisions of Government Decree No. 107/2016/ND-CP dated July 1, 2016, stipulating business activities of conformity assessment services, amended and supplemented by Government Decree No. 154/2018/ND-CP dated November 9, 2018, amending and supplementing, abolishing some provisions on investment and business conditions in the field of state management of the Ministry of Science and Technology and some provisions on specialized inspections (hereinafter referred to as Government Decree No. 107/2016/ND-CP) or recognized according to the provisions of Circular No. 27/2007/TT-BKHCN dated October 31, 2007, issued by the Minister of Science and Technology guiding the signing and implementation of Mutual Recognition Agreements and Mutual Recognition Arrangements on Conformity Assessment Results (hereinafter referred to as Circular No. 27/2007/TT-BKHCN).

10.3.2. Conformity certification

Conformity certification for domestically produced and imported 6 kV explosion-proof distribution panels shall be carried out according to Method 5 "Typical sample testing and production process evaluation; monitoring through sampling testing at the production site or on the market or import consignment combined with production process evaluation" or Method 7 "Testing and evaluating batches of products and goods" at the production facility in accordance with Clause 1 of Article 5 of Circular No. 28/2012/TT-BKHCN.

10.3.3. Testing for certification purposes must be conducted by one of the following organizations:

10.3.3. Certification testing must be carried out by one of the following organizations:

10.3.3.1. Testing for domestic-made explosion-proof distribution cabinets at 6 kV: Testing shall be conducted in accordance with the provisions of Decree No. 107/2016/ND-CP or by testing organizations designated by the Ministry of Industry and Trade pursuant to Circular No. 36/2019/TT-BCT or organizations recognized under the provisions of Circular No. 27/2007/TT-BKHCN.

10.3.3.2. Testing for imported explosion-proof distribution cabinets at 6 kV: Testing shall be conducted by organizations designated by the Ministry of Industry and Trade pursuant to Circular No. 36/2019/TT-BCT and Decree No. 154/2018/NĐ-CP dated September 11, 2018 of the Government or organizations recognized under the provisions of Circular No. 27/2007/TT-BKHCN.

10.3.4. The conformity mark must comply with the provisions set forth in Clause 2, Article 4 on certification of compliance with standards, certification of conformity, and announcement of compliance with standards and conformity, as stipulated in Circular No. 28/2012/TT-BKHCN.

10.3.5. Procedures, formalities, and documentation for announcing conformity

Procedures, formalities, and documentation for announcing conformity for domestically-produced and imported explosion-proof distribution cabinets at 6 kV shall be carried out in accordance with Circular No. 36/2019/TT-BCT dated November 29, 2019 issued by the Minister of Industry and Trade regarding quality management of products and goods under the responsibility of the Ministry of Industry and Trade.

11. Requirements for management fileDeputy ministers of ministerial-level agencies, of explosion-proof distribution cabinets at 6 kV used in underground mines

11.1. Must have complete technical documents from the manufacturer, including: Transportation, usage, maintenance, and storage instructions. In cases where technical documents are in a foreign language, they must be translated into Vietnamese.

11.2. Organizations and individuals using explosion-proof distribution cabinets at 6 kV must establish a management file from the time of initial use, including:

11.2.1. Design or construction/installation methods of explosion-proof distribution cabinets at 6 kV approved.

11.2.2. Post-installation acceptance documents.

11.2.3. Completion installation documents.

11.2.4. Inspection and testing/calibration documents.

11.2.5. Operating procedures.

11.2.6. Record book of technical safety inspection results and monitoring the operational status of explosion-proof distribution cabinets at 6 kV used in underground mines.

11.2.7. Safety regulations, procedures for transportation, installation, inspection, operation, maintenance, repair, and storage of explosion-proof distribution cabinets at 6 kV used in underground mines.

12. Requirements for inspection during operation

12.1. Explosion-proof distribution cabinets at 6 kV used in underground mines must be inspected during operation in accordance with the provisions of this Technical Regulation.

12.2. Visual inspection: Inspection that does not require the use of equipment or tools.

12.3. Direct inspection: Inspection of external parts through visual means and determination of defects using tools and equipment. Direct inspection shall not involve opening the casing or disconnecting power to the device.

12.4. Detailed inspection: Inspection which includes the contents of direct inspection and determination of defects using tools and equipment. Detailed inspection must involve disconnecting power and opening the device's casing.

13. Inspection period and content

13.1. Responsibility and frequency of inspection:

13.1.1. Operators or electricians on duty must inspect each shift at the beginning of work shifts.

13.1.2. Deputy Workshop Mechanical and Electrical Director or authorized person must inspect weekly.

13.1.3. Mechanical and Electrical Department Head or authorized person must inspect quarterly.

13.1.4. Deputy Mine Mechanical and Electrical Director or designated persons must inspect annually.

13.2. Inspection content shall be implemented in accordance with the provisions of Appendix A of this Technical Regulation.

13.3. Inspection results must be:

13.3.1. Recorded in the inspection logbook in accordance with the provisions of Appendix C of this Technical Regulation.

13.3.2. Concluded on the technical safety condition of explosion-proof distribution cabinets at 6 kV used in underground mines and only allowed to be put into use or continue operation when ensuring technical safety.

13.4. When discovering unsafe equipment, the operator or monitor must stop the operation and report to responsible persons for handling.

14. Requirements for testing and inspection

14.1. According to types of inspection, tests and inspections must be carried out according to technical guidelines, test methods, testing procedures, and testing equipment in Standards TCVN 4255:2008 (IEC 60529:2001), TCVN 6592-1:2009 (IEC 60947-1:2007), TCVN 8096-200:2010 (IEC 62271-200:2003), TCVN 10888-0:2015 (IEC 60079-0:2011), TCVN 10888-1:2015 (IEC 60079-1:2014), TCVN 7079-7:2002, TCVN 7079-11:2002, TCVN 7079-17:2003, IEC 60079-7:2015, (IEC 60079-11:2011, IEC 60079-17:2013, IEC 62271-1-2011 and requirements in this standard.

14.1.1. Specific items and parameters of inspection and testing steps shall be carried out according to the guidance of applied technical standards and the manufacturer's instruction documents.

14.1.2. Measuring instruments (voltage, current, frequency meters, insulation resistance testers, temperature, humidity, methane gas detectors) used in testing, inspection, and calibration in this Technical Regulation must be calibrated, tested, and verified in accordance with legal metrology regulations.

14.2. Reporting and evaluating test and inspection results

Reporting and evaluating test and inspection results must clearly indicate whether the test and inspection results meet or fail to meet the technical requirements in the applicable standards and technical regulations.

14.2.1. Test and inspection pass when: Meeting the technical requirements of the applicable standards and technical regulations listed in Table B of Appendix B of this Technical Regulation.

14.2.2. Test and inspection fail when: Not meeting one of the technical requirements of the applicable standards and technical regulations listed in Table B of Appendix B of this Technical Regulation.

IV. RESPONSIBILITIES OF ORGANIZATIONS AND INDIVIDUALS

15. Responsibilities of organizations and individuals

15.1. Organizations and individuals related to production, import, testing, inspection, certification, appraisal, use, and other individuals related to explosion-proof distribution cabinets at 6 kV in underground mines must comply with the provisions of this Technical Regulation.

15.2. Organizations and individuals using explosion-proof distribution cabinets at 6 kV in underground mines must:

15.2.1. Regularly inspect explosion-proof distribution cabinets at 6 kV in accordance with regulations, promptly report and handle incidents or signs of safety issues during operation.

15.2.2. Repair, maintenance, testing, and inspection of 6 kV explosion-proof distribution panels shall be carried out in accordance with the technical regulations set forth herein and other relevant legal documents.

15.2.3. Establish and maintain records for the safe management and use of 6 kV explosion-proof distribution panels used in underground mines in compliance with Article 11 of these technical regulations.

15.3. Testing and inspection organizations

Testing and inspection organizations must comply with the provisions of these technical regulations and bear responsibility for the results of their tests and inspections as stipulated by current regulations.

V. IMPLEMENTATION

16. Implementation

16.1. The Department of Safety Technology and Industrial Environment under the Ministry of Industry and Trade is responsible for:

16.1.1. Providing guidance and organizing the implementation of the provisions of these technical regulations.

16.1.2. Conducting inspections and checks on the implementation of the contents specified in these technical regulations by organizations related to the use of 6 kV explosion-proof distribution panels in underground mines.

16.2. Provincial Departments of Industry and Trade shall organize inspections and checks on the implementation of the contents specified in these technical regulations within their jurisdictional functions and powers.

17. Effective Date

17.1. These technical regulations shall take effect from July 1, 2023.

17.2. In case the legal documents, standards, and technical regulations referred to in these technical regulations are amended, supplemented, or replaced, they shall be implemented according to the new regulations.

17.3. Organizations and individuals implementing these technical regulations are advised to report any difficulties or issues encountered during implementation to the Ministry of Industry and Trade for consideration and resolution./.