CIRCULAR

Article 24specifies the operating procedures in the national power system

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Pursuant to Decree No. 95/2012/NĐ-CP dated November 12, 2012, of the Government, detailing the functions, tasks, powers, and organizational structure of the Ministry of Industry and Trade;

Based on the Electricity Law dated December 3, 2004, and the Law Amending and Supplementing Certain Provisions of the Electricity Law dated November 20, 2012;

Based on Decree No. 137/2013/NĐ-CP dated October 21, 2013, issued by the Government, detailing the implementation of certain provisions of the Electricity Law and the Law Amending and Supplementing Certain Provisions of the Electricity Law;

At the proposal of the Director of the Electricity Regulatory Authority,

The Minister of Industry and Trade issues the Circular stipulating the operating procedures in the national power system.

PART I

GENERAL PROVISIONS

Article 1. Scope of Regulation

1. This Circular stipulates the sequence of performing operations; basic operations of electrical equipment of power plants, substations, transmission networks with voltage of 01 kV or higher under normal operation conditions of the national power system; and regulations on numbering electrical equipment of power plants, substations, transmission networks with voltage of 01 kV or higher.

2. Operations of electrical equipment of power plants, substations, transmission networks during emergency situations shall be carried out according to the Procedures for Handling Emergencies in the National Power System issued by the Ministry of Industry and Trade.

3. In cases of cross-border electricity trading, the operations of connecting lines' equipment shall be performed according to the dispatching agreements signed between the parties.

Article 2. Applicability

1. National Power System Dispatching Unit.

2. Power Generation Unit.

3. Transmission Unit.

4. Distribution Unit.

5. Distribution and Retail Unit.

6. Customers directly receiving electricity from the transmission network, customers using distribution networks with their own substations.

7. Operation staff of units.

8. Other related organizations and individuals.

Article 3. Explanation of Terms

Strategic multi-purpose hydropower plant

1. Dispatch level is the dispatch level having the authority to command and dispatch the national power system according to the分级调度权限的规定由工业和贸易部发布的《国家电力系统调度规程》。

2. Dispatcher is the person directly commanding and dispatching the national power system under the control authority as stipulated in the Procedures for Dispatching the National Power System issued by the Ministry of Industry and Trade.

3. Operating Management Unit is the organization or individual managing and operating power lines or electrical equipment connected to the national power system, including:

a) Power generation unit;

b) Transmission unit;

c) Distribution unit;

d) Distribution and retail unit;

đ) Customers directly receiving electricity from the transmission network;

e) Customers using distribution networks with their own substations.

4. Regional Power System is the power system up to 220 kV voltage level and divided by regions such as North, Central, and South.

5. Operation Order is the request to change the operational status of electrical equipment.

6. Order Issuer is the person authorized to issue operation orders, including:

a) Dispatchers at all dispatch levels;

b) Shift leaders of power plants;

c) Crew leaders of substations;

d) Shift leaders or crew leaders of power plant control centers.

7. Order Receiver is the lower-level operation staff directly subordinate to the order issuer.

8. Supervisor is the operation staff assigned the task of supervising operations, including:

a) Shift supervisors or dispatchers assigned tasks at all dispatch levels;

b) Shift leaders, crew leaders, or main operators at power plants;

c) Crew leaders or main operators at substations;

d) Shift leaders, crew leaders, main operators, or persons assigned tasks at control centers;

đ) Operators assigned tasks at distribution networks.

9. Operator is the person responsible for operating electrical equipment, including:

a) Dispatchers at all dispatch levels;

b) Staff assigned tasks at substations;

c) On-duty staff assigned tasks at power plants;

d) Staff assigned tasks at control centers;

đ) Operators assigned tasks at distribution networks.

10. Operation Staff is the person directly involved in controlling the power generation, transmission, and distribution processes, working in shifts, including:

a) Dispatchers at all dispatch levels;

b) Shift leaders, crew leaders, main operators, and deputy operators at power plants or power plant cluster control centers;

c) Crew leaders, main operators, and deputy operators at substations or substation group control centers;

d) Operators on duty at distribution networks.

11. Hot Work is maintenance and upkeep work on power lines, substations, and elements within the national power system while they are energized.

12. Substation is a transformer station, switchgear station, or compensation station.

13. Operation is the activity of changing the status of one or more devices in the power system with the aim of altering the operational mode of that device.

14. Remote Operation is an operation conducted by operation staff at dispatch levels or Control Centers sending remote control signals through the control and communication systems to change the status or operational parameters of electrical equipment on power lines, substations, and power plants.

15. Control Center is a center equipped with information technology and telecommunications infrastructure capable of monitoring and remotely controlling a group of power plants, a group of substations, or switching devices on the grid.

Chapter II

SEQUENCE OF PERFORMING OPERATIONS

      Section 1        

ORGANIZATION OF OPERATIONS

Article 4. General requirements for operating electrical equipment in the national power system

1. The operation management unit shall be responsible for:

a) Issuing operating procedures for electrical equipment within its management scope in accordance with the manufacturer's requirements, wiring diagrams, and provisions set forth in this Circular;

b) Regularly inspecting, maintaining, and repairing circuit breakers and control systems within its management scope in accordance with regulations to ensure that these devices operate well during operations;

c) Conducting remote control tests on circuit breakers, isolating switches, and transformer tap changers if the period without operation exceeds 12 months and does not cause power supply interruptions to customers;

d) Organizing training, testing, and drills for operational skills for staff at least once annually.

2. All operations must be documented in an operation ticket and approved before proceeding, except in cases stipulated in Clause 3 of this Article. It is strictly prohibited to perform operations from memory.

3. Operation staff may not need to prepare an operation ticket but must record all steps of the operation in the operation log before performing the operation in the following cases:

a) Handling incidents;

b) Simple operations involving no more than three steps and performed at dispatch levels, control centers, or remotely.

4. The operation management unit is responsible for writing, approving, and implementing operation tickets within the scope of one substation, power plant, or control center. Prior to executing the operation ticket, permission from the authorized dispatch level must be obtained.

5. The authorized dispatch level is responsible for writing, approving, and directing the implementation of operation tickets when coordinating operations of electrical equipment across multiple substations, power plants, or control centers, or when operations are conducted remotely from the authorized dispatch level.

Article 5. Verbal operation orders

1. Verbal operation orders shall comply with the requirements for verbal dispatch orders as specified in the National Power System Dispatch Procedures Regulation issued by the Ministry of Industry and Trade.

In case of direct communication loss with the recipient, it is permissible to relay operation orders through intermediate shift operation staff at other units. Intermediate shift operation staff must record the full order in their logbook and have the responsibility to immediately convey the operation order to the correct recipient. If the intermediate shift operation staff cannot contact the recipient, they must immediately inform the issuer.

2. When conveying orders, the issuer must clearly state their name and must identify the name and position of the recipient. Operation orders must be recorded in full in the operation logbooks at each unit.

3. Operation orders must be concise, clear, accurate, and specify the purpose of the operation. Operational staff must understand the sequence of all planned operation steps, the conditions allowing execution based on actual wiring diagrams, and the operational mode of the equipment.

4. In cases where communication with mobile operation staff is anticipated to be lost, simultaneous issuance of multiple operation tasks is allowed, and a synchronized time for operation must be agreed upon with mobile operation staff. When issuing orders, the issuer must request the recipient to verify and adjust the time according to the issuer's clock. Unauthorized deviation from the scheduled operation time is prohibited.

5. The recipient of the operation order must repeat the order, fully record the operation order, the name of the issuer, and the time requested for the operation. Only when the issuer confirms the accuracy and permits the operation can the recipient proceed. Upon completion, the end time must be recorded and reported back to the issuer.

6. If the recipient does not fully understand the operation order, the recipient has the right to request clarification from the issuer and may only proceed with the operation after understanding the order.

7. An operation order is considered completed when the recipient reports the results to the issuer.

7. An instruction operation shall be considered completed when the recipient reports to the issuer regarding the results of the completion.

Article 6. Operation Ticket

1. The model of the operation ticket is prescribed in Appendix 2 attached to this Circular.

2. The operation ticket must be clear, not subject to correction, erasure, and must clearly indicate for which wiring diagram it was written. Before performing the operation, the operator must check the correspondence between the actual wiring diagram and the wiring diagram in the operation ticket. If the wiring diagram in the operation ticket does not match the actual wiring diagram, a new operation ticket must be written that corresponds to the actual wiring diagram according to Article 8 of this Circular.

Any changes to the content of the operation ticket to align with the actual wiring diagram must be agreed upon by the person approving the ticket and recorded in the "Abnormal Events During Operation" section of the operation ticket and the operational logbook.

3. All issued operation tickets must be numbered. Completed operation tickets must be stored for at least three months. Operation tickets must be kept in the investigation file if an incident or accident occurs during the operation.

4. Units are permitted to issue standard operation tickets prepared and approved in advance for certain operations based on basic wiring diagrams, including the following operations:

a) Operations to disconnect or put into operation a busbar;

b) Operations to substitute a circuit breaker with a bypass circuit breaker and vice versa;

c) Operations to disconnect or put into operation a transformer;

d) Operations to disconnect or put into operation reactive power compensation devices;

e) Operations to disconnect or put into operation transmission lines.

Standard operation tickets shall be written and approved in accordance with Article 7 of this Circular. Prior to performing operations according to a standard operation ticket, the operator must verify the consistency of the actual wiring diagram with the wiring diagram in the standard operation ticket.

Article 7. Writing and Approving Operation Tickets According to Plans

1. Operation tickets within the scope of one substation, power plant, or under the control of one control center, managed and operated by the unit, shall be written and approved and specified as follows:

a) At substations

- The writer of the ticket is an operating staff member or a staff member assigned to write operation tickets;

- The approver of the ticket is the Head or Deputy Head of the substation or a person authorized.

b) At power plants

- The writer of the ticket is an operating staff member or a staff member assigned to write operation tickets;

- The approver of the ticket is the Director or Deputy Director of the power plant; the Workshop Manager or Deputy Workshop Manager of the power plant's operating department or a person authorized.

c) At control centers

- The writer of the ticket is an operating staff member or a staff member assigned to write operation tickets;

- The approver of the ticket is the Head or Deputy Head of the control center or a person authorized.

2. Operation tickets involving multiple substations, power plants, or remote operations from dispatching levels must be written and approved by the dispatching level with authority to control and specified as follows:

a) The writer of the ticket is a method officer of the dispatching level with authority to control, assigned to write operation tickets;

b) The approver of the ticket is the Head or Deputy Head of the dispatching unit; the Head or Deputy Head of the dispatching department or a person authorized.

3. Operation tickets at district or county electricity companies or district or county electricity departments are specified as follows:

a) The writer of the ticket is a staff member assigned to write operation tickets;

b) The approver of the ticket is the Unit Leader or a person authorized.

Article 8. Writing and Approving Emergency Operation Tickets

1. Emergency operation tickets shall be implemented within the scope of one power substation, power plant, or within the control range of one control center managed by the operating unit, which shall be written and approved as follows:

a) At substations

- The person writing the ticket is the power station operator;

- The person approving the ticket is the Head or Deputy Head of the power station; Shift Leader or Chief Duty Officer.

b) At power plants

- The person writing the ticket is the electrical equipment operator;

- The person approving the ticket is the Director or Deputy Director of the power plant; Workshop Manager or Deputy Manager of the power plant's operating workshop; Shift Leader or Team Leader.

c) At control centers

- The person writing the ticket is the control center operator;

- The person approving the ticket is the Head or Deputy Head of the control center; Shift Leader or Team Leader.

2. Coordinated emergency operations involving multiple power substations, power plants, or remote operations from dispatch levels shall be written and approved by the dispatch level with authority to control, as follows:

a) The person writing the ticket is the dispatcher;

b) The person approving the ticket is the Head or Deputy Head of the dispatch unit; Head or Deputy Head of the dispatch department; Shift dispatcher responsible for duty.

3. Emergency operation tickets at district or county electricity companies shall be specified as follows:

a) The person writing the ticket is the operation duty staff assigned the task of writing operation tickets;

b) The person approving the ticket is the Unit Leader or operation duty staff assigned the task of approving operation tickets.

Article 9. Time and Method of Transferring Operation Tickets

1. Planned operation tickets must be transferred to the direct operation personnel at least 45 minutes before the scheduled start time of the operation.

2. The operating management unit is responsible for specifying the method of transferring operation tickets within the unit.

3. The method of transferring operation tickets between participating units during operations shall be carried out according to one of the following methods:

a) Reading over the phone;

b) Transmitting via fax;

c) Transmitting via email or other network methods;

d) Direct delivery.

Participating units in operations must notify in advance the telephone number, fax number, email address, and website used for transmitting operation tickets.

Article 10. Work Relationships During Execution of Operations

1. Work relationships during operations between dispatchers at various dispatch levels and operators at power plants, substations, and control centers must comply with the National Power System Dispatching Procedures issued by the Ministry of Industry and Trade.

2. Work relationships during operations among operators within one operating management unit shall follow the provisions of the Equipment Operation Procedures issued by the operating management unit, but shall not contravene the provisions of this Circular.

Section 2

EXECUTION OF OPERATIONS

Article 11. Requirements for the Person Issuing Operation Orders

1. Before issuing operation orders, the issuer must be familiar with the following contents:

a) Name of the operation and purpose of the operation;

b) Scheduled start and end times of the operation;

c) Current wiring diagram of the power system, regional grid, power plant, and substation to be operated;

d) Operating status and operational principles of circuit breakers; protective relays, automatic devices; arc suppression coils, neutral grounding points; measuring, controlling, and remote signaling devices;

đ) Grounded elements;

e) Trends in load changes, system power, and voltage before and after the operation, and appropriate measures must be taken to avoid overload, low voltage, or high voltage according to the voltage regulation regulations;

g) Communication system diagram serving dispatch, especially in cases where operations affect the operation mode of the communication system;

h) Switching of self-use power supply if necessary;

i) Safety measures for personnel and equipment, other relevant considerations related to the operation.

2. The issuer is responsible for issuing operation orders and must understand the operation clearly, identify unreasonable points before issuing the order.

Article 12. Requirements for supervisors and operators

When implementing the operation ticket, the supervisor and operator must perform the following contents:

1. Carefully read the operation ticket and check that the operation ticket is consistent with the purpose of the operation.

2. If there are unreasonable or unclear items in the operation ticket, they must request the person issuing the operation command or the person approving the ticket to explain, and only proceed with the operation after fully understanding each step.

3. Must sign and clearly write their full name on the operation ticket before performing the operation.

4. Before conducting the operation, check the correspondence and consistency between the actual wiring diagram and the diagram in the operation ticket.

5. Must perform all operations strictly according to the sequence in the operation ticket. No changes to the sequence may be made without permission from the person issuing the operation command.

6. After completing each step of the operation, mark each operation on the ticket to avoid confusion and omissions of items.

7. During the operation, if warnings appear or equipment malfunctions and abnormal phenomena occur, stop the operation to inspect and find the cause before continuing with subsequent operations.

8. Must implement safety measures according to technical electrical safety regulations.

Article 13. Performing primary equipment operations

1. All primary equipment operations must be carried out by two people: one supervisor and one direct operator. In all cases, both individuals share equal responsibility for the operation.

2. At power plants or substations, the two individuals performing the operation must be familiar with the diagrams and positions of the primary equipment at the site, have been trained and certified for operational duties, and be assigned to perform the operation. The direct operator must have a safety level of three or higher, while the supervisor must have a safety level of four or higher.

3. The procedure for carrying out operations according to the operation ticket is as follows:

a) At the operation or control position, the operator must verify that the names of the equipment correspond to those listed in the operation ticket;

b) Once it is confirmed that the equipment to be operated is correct, the supervisor reads the command, the direct operator repeats the command and performs each step of the operation according to the operation ticket.

4. For complex operations such as energizing or testing new equipment, they must be conducted according to the approved method, with coordination among related units and the corresponding dispatch authority. This includes specifying the person responsible for the entire process of the operation and the tasks recorded in the program.

5. After completing the operation, the operator must carry out handover procedures for the equipment, recording the following details in the operation log:

a) Name of the operation ticket;

b) Changes in the relay protection and automatic device diagrams, installation or removal of portable grounding devices (specify the location of installation or removal);

c) Wiring changes on the operation diagram, work teams currently working or completed.

6. Primary equipment or transmission lines can only be put back into operation after maintenance when the operating management unit confirms that the following contents have been completed:

a) All work units (personnel and tools) have been withdrawn;

b) All portable grounding devices have been removed;

c) Details of the work ticket have been recorded in the operation log;

d) Handover of the equipment has been verbally confirmed over the phone with recording.

Article 14. Performing operations related to the second circuit

1. During the operation of primary equipment, the operator must carry out necessary operations on protective relays and automatic devices in accordance with the unit's procedures for operating such equipment.

2. The operator must take necessary measures to prevent protective relays from incorrectly tripping when electrical equipment is taken out for repair.

3. It is prohibited to perform switching-on operations on power lines or electrical equipment if all main protective relays are not functioning.

4. Automatic reclosing circuits for power lines must be locked (switched to non-operational position) during hot-line maintenance work.

5. Interlocking circuits (logic circuits) are provided to prevent incorrect operations by operators. In case one switchgear operation cannot be performed, the operator must stop the operation to check:

a) Whether the operation was correct or not;

b) Whether the positions of the relevant equipment involved in the ongoing operations match the interlocking circuit;

c) Whether the interlocking circuit is functioning properly. If the inspection reveals any faults in the interlocking circuit, they must be immediately reported to the person who issued the operation command;

d) Operators may not arbitrarily disconnect or isolate interlocking circuits. Any changes to interlocking circuits must be approved by the direct unit leader or a higher-level operator.

Article 15. Operations during peak electricity demand hours and shift changeovers

1. Limit operations during peak electricity demand hours and shift changeover times, except in the following cases:

b) Simple operations involving no more than three steps and performed at dispatch levels, control centers, or remotely.

b) Threats to personnel or equipment safety;

c) Need to reduce load to stabilize the power system.

2. When operations initiated before the shift change continue into the changeover period, the outgoing shift operator must select appropriate operation items to stop reasonably and hand over to the incoming shift operator to continue the operations. For complex operations, the outgoing shift operator must remain until all operation items are completed, only permitted to change shifts if the incoming shift operator has fully understood the subsequent steps and agrees to take over. The incoming shift operator is responsible for continuing the operations to ensure that the outgoing shift operator does not exceed the overtime limit stipulated by labor laws.

Article 16. Operations under adverse weather conditions

1. Outdoor operations at locations where electrical equipment is installed shall not be carried out under adverse weather conditions (rain causing water flow on electrical equipment, thunderstorms, flooding, winds of force 6 or above).

2. Operations under adverse weather conditions are allowed if they are conducted from the control room and immediate on-site checks of the switchgear status are not required.

Article 17. Temporary suspension of operations

Temporary suspension of operations is allowed in the following cases:

1. Continuous operation time exceeding four hours for operators directly at substations or power plants. The duration of the temporary suspension shall not exceed one hour. During the suspension, the operator must ensure safety conditions according to electrical safety regulations.

2. Operations must be conducted outdoors under adverse weather conditions.

3. Temporarily suspend operations until abnormal conditions or incidents are resolved if they occur during ongoing operations at substations, power plants, or on the power system.

Section 3

REMOTE OPERATIONS

Article 18. General Provisions on Remote Operations

1. The System Dispatching Unit, the Operation Management Unit shall be responsible for issuing Operating Procedures and Fault Handling Procedures for remote monitoring and control systems that are appropriate to technological equipment, relevant regulations, and instructing operational staff to implement them.

2. Operational staff must strictly follow the Operating Procedures and Fault Handling Procedures for remote monitoring and control systems issued by the System Dispatching Unit and the Operation Management Unit.

3. All remote operations must be carried out based on operation tickets, except for cases specified in Clause 3, Article 4 of this Circular.

4. Remote monitoring and control systems at dispatch centers and control centers must store all remote operation events, with storage duration determined by the unit but not less than three months.

5. For planned remote operations related to equipment handover, the Operation Management Unit must assign operational staff to be present at substations or power plants during the execution of remote operations to ensure safety measures and equipment handover.

6. In case of loss of remote control, the Operation Management Unit must immediately assign operational staff to perform remote operations at substations or power plants.

Article 19. Conditions for Implementing Remote Operations

1. Monitoring, control, telecommunications, and signal acquisition systems at dispatch centers and control centers must be regularly tested and inspected to ensure reliable and accurate remote operations, in compliance with the Transmission System Regulations and Distribution System Regulations issued by the Ministry of Industry and Trade.

2. Data transmission and control signal communication systems linking dispatch centers and control centers with substations or power plants must ensure accurate and reliable operation.

3. Control systems (DCS) and gateway (Gateway) or terminal devices (RTU) at substations or power plants must operate properly.Gateway) or terminal device (RTU) at the power station or generating plant is operating properly.

4. Control lock status at the device control panel must be set for remote control position.

5. Control lock status at substations or power plants must be set for remote operation position (from the dispatch center or control center).

6. Control systems at dispatch centers and control centers must operate properly.

Chapter III

PROVISIONS FOR BASIC OPERATIONS

Section 1

OPERATIONS OF BREAKER EQUIPMENT

Article 20. General Provisions on Breaker Operations

1. Breakers are permitted to close and open loads and short circuits within their rated capacity. Closing and opening breaker operations must be conducted according to the manufacturer's specifications or the Electrical Equipment Operating Procedures issued by the Operation Management Unit.

2. Breakers must be checked and found to meet the closing and opening standards before operations.

3. Breakers need to be inspected and maintained (according to the breaker operating procedures or the manufacturer's instructions) under the following circumstances:

a) When the total short-circuit current has reached the specified level;

b) When the number of short-circuit interruptions has reached the specified level;

c) When the number of closing and opening operations has reached the specified level;

d) When the operating time has reached the specified level;

đ) When the operating parameters do not meet the manufacturer's standards or prescribed standards.

4. Breaker operations are only allowed when the control circuit is in good condition and not grounded. In the event of a grounded control circuit, breaker operations can only proceed after fault handling.

5. After breaker operations, if there are subsequent local operations on both sides of the isolating switches of the breaker, operational staff must check the local status indicators and control circuit locks of the breaker.

6. Before moving a breaker set from the operating position to the test position or vice versa, operational staff must check the open status of the breaker set.

7. Test breaker operations may be performed when one of the following requirements is met:

a) Both sides of the isolating switches of the breaker have been fully opened, and only grounding switches or mobile grounding switches are closed on one side of the breaker;

b) If one side of the isolating switch of the breaker is closed, all grounding switches of the breaker compartment must be opened, and attention must be paid to any interlocking and automatic devices installed.

8. It is permissible to check the status of the breaker based on signals and measurement parameters in the control room without checking the local status indicators in the following situations:

a) After breaker operations, no operations are performed on both sides of the isolating switches of the breaker;

b) After breaker operations, operations on both sides of the isolating switches of the breaker are performed remotely (from the central control room);

c) Performing remote operations or operations under adverse weather conditions.

9. In necessary cases, additional fault interruptions may be allowed for breakers that have already cut the total short-circuit current or reached the specified number of short-circuit interruptions, provided they have been checked to meet operational standards and received approval from the Director or Deputy Director of Technical Affairs of the Operation Management Unit.

Article 21. Isolator Switch Operations

1. Isolator switches may be operated without electricity or with electricity when the operating current is less than the allowable operating current according to the Isolator Switch Operating Procedures issued by the Operating Management Unit. Isolator switches may be used to perform live operations in the following cases:

a) Closing and opening the neutral point of transformers and reactors;

b) Closing and opening arc suppression coils when there is no ground fault in the power grid;

c) Closing and opening transfer bars when circuit breakers or isolator switches connecting the busbar have been closed;

d) Closing and opening unloaded busbars or conductor sections;

đ) Closing and opening bypass isolator switches;

e) Closing and opening unloaded voltage transformers and current transformers;

g) Unloaded operations of power transformers, overhead lines, and cables must be approved by the Operating Management Unit according to the regulations for each type of isolator switch;

h) Mechanical or automatic drive mechanisms of isolator switches used to interrupt magnetic currents, charging currents, load currents, and balancing currents must ensure rapid travel and decisive operation.

2. Before performing on-site isolator switch operations, all conditions must be checked to ensure that dangerous arcs will not occur during the operation. The conditions for on-site isolator switch operations are specified in the Isolator Switch Operating Procedures issued by the Operating Management Unit but must not contravene the provisions of this Circular.

3. The sequence of two-side isolator switch operations with circuit breakers is as follows:

a) In the case where one side has voltage and the other side does not have voltage

- When opening the isolator switch: Open the isolator switch on the side without voltage first, then open the isolator switch on the side with voltage;

- When closing the isolator switch: Close the isolator switch on the side with voltage first, then close the isolator switch on the side without voltage.

b) In the case where both sides have voltage

- When opening the isolator switch: Open the isolator switch on the side where a fault would have less impact on the power system's operation first, then open the other isolator switch;

- When closing the isolator switch: Close the isolator switch on the side where a fault would have a greater impact on the power system's operation first, then close the other isolator switch.

4. On-site isolator switch operations must be performed quickly and decisively, but must not damage the isolator switch. It is strictly prohibited to re-close (or re-open) the blade if an arc appears during the closing (or opening) process of the isolator switch.

5. Immediately after completing the operation, the position of the isolator switch blades must be checked to ensure they have fully traveled their stroke or made good contact, except in remote operations at unattended substations or power plants.

Article 22. Grounding Switch Operations

1. Before performing grounding switch closing operations, the power line or electrical equipment must be verified as de-energized (based on voltage readings or dedicated testing equipment) and the related circuit breaker and isolator switch must be confirmed to be fully opened.

2. Prior to energizing power lines or electrical equipment, the status of the grounding switches must be checked to ensure they are fully open.

Section 2

OPERATIONS OF TRANSFORMERS

Article 23. Transformer disconnection operation

The procedure for disconnecting transformers for maintenance is as follows:

1. Check power flow, mobilize power sources or adjust grid connections appropriately to avoid overloading other transformers or related transmission lines.

2. Switch to self-use power source if the self-use power source is taken from that transformer.

3. Lock out the automatic voltage regulator under load (if it is set to automatic).

4. Disconnect the circuit breakers on the low-voltage, medium-voltage, and high-voltage sides of the transformer according to the principle of ensuring safety for the transformer (avoiding overvoltage) and the power grid (avoiding low voltage).

5. Verify that the transformer has no residual voltage.

6. Disconnect the necessary isolating switches on the low-voltage, medium-voltage, and high-voltage sides of the transformer in a convenient sequence for the operation.

7. Close the fixed grounding switches on the low-voltage, medium-voltage, and high-voltage sides of the transformer.

8. Disconnect the voltage regulators of the transformer's voltage transformers (if present).

9. The operating management unit implements safety measures, hangs warning signs as prescribed by electrical safety regulations.

10. Hand over the transformer to the operating management unit and the work unit while reminding them of additional safety measures.

Article 24. Transformer energization operation

The procedure for energizing a transformer after maintenance is as follows:

1. The operating management unit and the work unit are responsible for confirming that the transformer meets operational standards in the handover notice returned to the units that had handed over the transformer. The handover content is as follows: "Work on the transformer has been completed, all personnel and equipment have been withdrawn, all portable grounding devices have been removed from the transformer, the transformer meets operational standards and is ready for energization."

2. Close the voltage regulators of the transformer's voltage transformers (if present).

3. Disconnect all fixed grounding switches on both sides of the transformer.

4. Inspect the protection relays, cooling systems, and fire suppression systems (if present) of the transformer being put into operation.

5. Set the tap changer to an appropriate position to avoid overvoltage when energizing the transformer.

6. Close the isolating switches on the low-voltage, medium-voltage, and high-voltage sides of the transformer.

7. Close the circuit breaker on the side with power to energize the transformer, check the transformer's voltage; subsequently close the circuit breakers on the remaining sides, paying attention to loop closure or synchronization conditions if the remaining sides have power.

8. Switch the self-use power source (if necessary).

9. After putting the transformer into operation, the operator must inspect its operational status. Based on the operational mode, the automatic tap changer control mode of the transformer can be activated.

Section 3

LINE OPERATIONS

Article 25. Line de-energization operation

The procedure for de-energizing a line is as follows:

1. Check power flow and voltage of the system before the operation. Adjust power and voltage, transfer loads at substations receiving power from this line.

2. Sequentially disconnect all circuit breakers at both ends of the line or branches starting from the end farthest from the power source and then the end closest to the power source.

3. Sequentially disconnect the isolating switches at both ends of the line and branches.

4. Close the grounding switches at both ends of the line and branches.

5. Disconnect the voltage regulators of the line's voltage transformers (if present).

6. The dispatching unit hands over the line to the operating management unit. The operating management unit independently implements safety measures and hangs warning signs as prescribed by electrical safety regulations.

Article 26. Closing Operations on Power Lines

Closing operations on power lines shall be carried out in the following sequence:

1. The operating management unit shall notify the control authority with the right to control about confirming the status and handing over the line for operation. The handover content shall be as follows: "Work on the line has been completed, all personnel and equipment have been withdrawn, all mobile grounding devices on the line have been removed, the line meets operational standards and is ready for closing."

2. Close the circuit breakers of the voltage transformers on the line (if applicable).

3. Open all grounding switches at both ends and branches of the line.

4. Sequentially close the isolating switches at both ends and branches of the line.

5. Sequentially close the circuit breakers at both ends and branches of the line according to the following sequence:

a) For a single-ended line with one end energized: Close the energized end first;

b) For a looped line where all ends are energized: Close the end far from the power plant first, then close the loop or synchronize the end near the power plant. If there is a risk of overvoltage at the end of the line, close the end with lower voltage first, then close the other end.

6. Check and adjust the power, voltage, and transfer loads appropriately after putting the line into operation.

Article 27. Safety Measures for Power Lines

1. Overhead lines operating in unloaded energized mode from one source or in standby mode must have the isolating switches on the line side of the circuit breakers in the open state.

2. Only after the line has been de-energized and safety measures completed can it be handed over to the work registration unit. When handing over the line to the repair unit, the handover content must include:

a) The line has been de-energized (specify name and circuit), positions where grounding devices have been closed (specify substation, power plant, grounding position). Allow safety measures to be taken so that the work unit can start working;

b) The time when the work must be completed;

c) If the line has two circuits, specify whether the other circuit is energized and take necessary measures to prevent induced current;

d) Other relevant notes related to the work.

3. Strictly prohibit operating staff from cutting grounded devices or removing warning signs without an order from the person issuing the operation command.

4. If due to work conditions, it is necessary to cut fixed grounding devices on the line while there are still workers on the line, another grounding device or a mobile grounding device must be installed before cutting these fixed grounding devices. After completing the work, the fixed grounding devices must be reclosed before removing the mobile grounding devices.

5. Except in cases where the status display diagram is shown on the control screen, operating staff, after performing the de-energization operation on the line and related equipment at the substation or power plant for maintenance, must perform the steps of the operation diagram as recorded in the work ticket and hang warning signs and grounding symbols fully. Record the operation time and permission to work in the operation logbook. In the work ticket and operation logbook, clearly record the number of grounding devices closed, the number of participating maintenance units, and other important characteristics.

6. After completing the maintenance work on the line and related equipment at the substation or power plant, the operating management unit must confirm that all personnel and equipment have been withdrawn, and all mobile grounding devices have been removed. The operating management unit shall return the line and the blocking equipment of the substation or power plant to the control authority with the right to issue the closing command. The content of the handover report shall include:

a) Work on the line (record the name of the line and circuit), equipment (record the name of the equipment in the outgoing circuit breaker section of the substation or power plant) according to the work ticket (number) has been completed;

b) All mobile grounding devices at the site have been removed;

c) Personnel from the work units have been withdrawn;

d) The line and equipment meet operational standards and are ready to receive electricity, requesting to return the line and equipment for closing.

7. If during the de-energization of the line, measures such as primary rewiring and secondary rewiring were implemented, when re-energizing this line, the operating staff must check and rewire the primary and secondary rewiring appropriately.

Section 4

OPERATIONS FOR REMOVAL OF GROUNDING DEVICES

Article 28. Operation of Spare Busbar

1. Before performing the operation to put the spare busbar into service, the following actions must be carried out:

a) Check that the spare busbar has no mobile grounding, and all fixed grounding switches have been fully disconnected;

b) Use the busbar circuit breaker with protective relays to test energize the spare busbar. In case there is no busbar circuit breaker, select the appropriate circuit breaker at the connection point to energize the spare busbar.

2. Before performing the busbar switching operation, the following actions must be carried out:

a) Check the differential protection relay of the busbar, isolate the differential protection relay of the busbar (if necessary) according to the regulations of the Operating Management Unit (after completing the operation, the differential protection relay of the busbar must be returned to service);

b) Check the circuit breaker or isolating switch interconnection between two busbars that are closed. The control circuit must be de-energized or the circuit breaker interconnection locked during the time of isolating switch operation to change the connection point;

c) Monitor changes in power flow and current through the circuit breaker interconnection. Select a reasonable step for the switching operation to change the connection point from one busbar to another to avoid overloading the circuit breaker interconnection.

3. The Operating Management Unit must prepare a model operation ticket applicable for the busbar switching operation. This model operation ticket clearly records the sequence of primary and secondary operation steps suitable for the primary and secondary diagrams of the substation.

Article 29. Operation of Ring Circuit Breaker

1. At substations equipped with ring circuit breakers, the Operating Management Unit must prepare a model operation ticket applicable for the operation using a ring circuit breaker instead of another circuit breaker and vice versa.

2. The model operation ticket for using a ring circuit breaker instead of another circuit breaker and vice versa must clearly record the sequence of primary and secondary operation steps suitable for the primary and secondary diagrams of the substation or power plant.

Section 5

CLOSING THE GRID, CLOSING OR OPENING RING CIRCUIT

Article 30. Synchronization Operation

The synchronization operation (on-site or remote) must be performed on a circuit breaker equipped with synchronous devices under the following conditions:

1. Conditions for synchronization on a system with 500 kV voltage level include:

a) Phase angle difference of voltage between both sides of the synchronization point: d £ 150;

b) Frequency difference between both sides of the synchronization point: Df £ 0.05 Hz;

c) Voltage difference between both sides of the synchronization point: DU £ 5%.

2. Conditions for synchronization on a system with voltage level £ 220 kV include:

a) Phase angle difference of voltage between both sides of the synchronization point: d £ 300;

b) Frequency difference between both sides of the synchronization point: Df £ 0.25 Hz;

c) Voltage difference between both sides of the synchronization point: DU £ 10%.

Article 31. Ring Circuit Closing Operation

1. Only one ring circuit may be closed in the system when the phase angle and phase sequence are confirmed to be identical at the ring circuit closing point.

2. Conditions for closing a ring circuit in the system

a) Phase angle difference of voltage between both sides of the ring circuit closing point: d £ 300;

b) Voltage difference between both sides of the ring circuit closing point: DU £ 10%.

3. The ring circuit closing operation must check the phase angle difference and voltage difference conditions as stipulated in Clause 2 of this Article. If the phase angle difference cannot be checked, it must be calculated beforehand to check the phase angle difference.

4. Pay attention to the operation of protective relays and automatic devices, changes in power flow and voltage in the system when closing the ring circuit.

Article 32. Loop Breaking Operation

1. Prior to performing the loop breaking operation, the power or current through the circuit breaker must be reduced to the minimum level, and calculations must be conducted to ensure that the circuit breaker will not experience excessive recovery voltage before executing this loop breaking operation.

2. When separating electrical systems for independent operation, all levels of dispatch must coordinate to adjust the power between power plants or balance the power among electrical systems so as to maintain normal operation of the systems after the loop connection system is broken.

Chapter 6

 OPERATIONS OF OTHER ELECTRICAL EQUIPMENT AND COMMISSIONING OF NEW PROJECTS

AND COMMISSIONING OF NEW PROJECTS

Article 33. Operations of Other Electrical Equipment

1. The operations of disconnecting or connecting generators and compensators to the grid; switching on and off reactors and capacitors; changing tap positions of transformers and related operations must be carried out according to the operational procedures of each power plant or substation.

2. All levels of dispatch and operating management units must recheck the operational mode of the electrical system, power plant, and substation before and after disconnecting or connecting generators to the grid, switching on and off reactors or capacitors, and changing tap positions of transformers.

Article 34. Conditions for Commissioning New Projects

1. The conditions for commissioning new equipment and new transmission lines shall be implemented in accordance with the provisions of the Transmission System Regulations and Distribution System Regulations issued by the Ministry of Industry and Trade.

2. The project investor is responsible for negotiating with the dispatch level having control authority to establish and implement the method of energizing the new project into operation.

Article 35. Commissioning Circuit Breaker Energization

1. Establish a method using a circuit breaker equipped with a protective relay that has been set up to serve the initial energization of the circuit breaker.

2. In cases where it is impossible to create a method using a circuit breaker for the initial energization of the circuit breaker, only isolating switches controlled from the control room or remote operation and ready protective relays may be allowed to energize the new circuit breaker.

3. Commissioning circuit breaker energization shall be carried out according to the approved operation ticket.

Article 36. Commissioning Transformer Energization

1. Establish a method using a circuit breaker equipped with a protective relay that has been set up to serve the initial energization of the transformer. For distribution transformers below 35 kV without direct circuit breakers, they must be equipped with protection devices in accordance with standards and regulations issued by the Ministry of Industry and Trade, allowing these devices to be used for the initial energization of the transformer but the nearest sectional circuit breaker towards the power supply side must be set up to serve the initial energization of the transformer.

2. The transformer tap position must be appropriate for the grid voltage, ensuring no overvoltage during energization.

3. Select an appropriate voltage level for the initial energization of the transformer.

4. After energizing unloaded from one side, the phase sequence and phase angle of the remaining sides must be checked correctly. If closing the loop, sufficient conditions for closing the loop must be verified.

5. Commissioning transformer energization shall be carried out according to the approved operation ticket.

Article 37. Commissioning Line and Cable Energization

1. Create a method using circuit breakers and backup protective relays that have been set up to serve the initial energization of the line.

2. Lockout the automatic reclosing function of the line before the initial energization.

3. After energizing unloaded from one end, the line must be checked for correct phase sequence and phase angle at the remaining ends before closing the loop or connecting two systems.

4. Commissioning line energization shall be carried out according to the approved operation ticket.

Article 38. Initial Grid Synchronization of Generator Units

1. The automatic synchronization equipment has been tested and meets operational standards.

2. The initial grid synchronization test program for generator units must be approved by competent authorities.

3. Automatic synchronization must be carried out according to the generator unit operation procedures issued by the power generation entity.

Article 39. Commissioning Switching of Reactive Power Compensation Equipment

1. A method involving circuit breakers and protective relays (if available) must be set up to facilitate the first commissioning switching of reactive power compensation equipment.

2. Voltage must be adjusted appropriately to ensure that voltage fluctuations do not exceed permissible limits during switching.

Chapter IV

NUMBERING OF EQUIPMENT IN THE NATIONAL ELECTRIC POWER SYSTEM

Section 1

GENERAL PRINCIPLES

Article 40. Classification and Naming of Primary Equipment

1. All primary equipment put into operation in the national electric power system must be named and numbered.

2. Primary equipment within the national electric power system under the control of a particular entity shall be numbered, approved, and the approved numbering diagram sent to the higher-level dispatch authority by that entity, except for power plants specified in Clause 3 of this Article.

3. Power plants connected to the transmission network at voltages above 35 kV to 220 kV shall be numbered and approved by the regional dispatch authority with control rights based on the agreement of the national dispatch authority.

4. Naming new substations or power plants shall be based on the project name. In cases where the project name duplicates the name of an existing substation or power plant in operation, the dispatch authority with control rights shall issue diagrams after agreeing to change the name with the operating management unit to avoid confusion.

5. Naming and numbering of primary equipment of power plants or substations shall follow the provisions of Section 2 of this Chapter. If the primary equipment named and numbered according to the provisions of Section 2 of this Chapter have duplicate names or numbers, the last character shall be added with letters from the Vietnamese alphabet or digits from 0 to 9 to distinguish them.

6. The operating management unit may propose changes to the numbering of new facilities for reasonable reasons. Any changes to the numbering diagram must be agreed upon by the dispatch authority with control rights and a decision issued to replace the previous numbering diagram.

7. The operating management unit is responsible for clearly installing and maintaining signs, names, and numbers of its equipment without causing confusion.

8. For equipment in the national electric power system that was numbered according to the decisions of dispatch authorities before the effective date of this Circular, it is permitted to retain the original number or renumber according to the proposal of the operating management unit.

Article 41. Numbering and Naming of Main or Auxiliary Equipment

1. At power plants or substations, main equipment or auxiliary equipment must be named and numbered.

2. Main equipment must be numbered according to the entity's regulations, while auxiliary equipment must be numbered sequentially according to the main equipment and additional characters added to differentiate them.

3. For protection relay and automatic equipment cabinets, panels, and control desks, names must be marked on both the front and back sides according to the dispatch name; all installations within the panel or behind the control desk on both sides must be labeled or marked in accordance with the diagram. On the protection relay and automatic equipment cabinet, the names of the installed equipment must be marked to prevent operational errors by operators.

Section 2

PRIMARY EQUIPMENT NUMBERING

Article 42. Voltage Level Numbering

1. For 500 kV voltage: Use the digit 5.

2. For 220 kV voltage: Use the digit 2.

3. For 110 kV voltage: Use the digit 1.

4. For 66 kV voltage: Use the digit 7.

5. For 35 kV voltage: Use the digit 3.

6. For 22 kV voltage: Use the digit 4.

7. For 15 kV voltage: Use the digit 8.

8. For 10 kV voltage: Use the digit 9.

9. For 6 kV voltage: Use the digit 6.

10. In the case of generator terminal voltage or synchronous compensator terminal voltage, it shall be specified as follows:

a) If the terminal voltage is greater than or equal to 10 kV, use the digit 9;

b) If the terminal voltage is less than 10 kV, use the digit 6.

11. Other voltage levels shall be defined by the dispatch level authority.

Article 43. Naming of Busbars

1. The first character shall be the letter C.

2. The second character shall indicate the voltage level.

3. The third character shall indicate the busbar sequence number, with the number 9 representing a ring busbar.

Example:

- C12: Represents the second busbar at 110 kV voltage level.

- C21: Represents the first busbar at 220 kV voltage level.

- C29: Represents the ring busbar at 220 kV voltage level.

Article 44. Naming of Generators and Synchronous Compensators

1. The initial character shall be designated as follows:

a) For steam thermal power plants: The symbol is the letter S;

b) For hydroelectric power plants: The symbol is the letter H;

c) For gas turbines: The symbol is the letter GT;

d) For exhaust steam of gas turbines: The symbol is the letter ST;

đ) For diesel engines: The symbol is the letter D;

e) For wind power: The symbol is the letter WT;

g) For pumped storage hydroelectric power plants: The symbol is the letter PH;

h) For tidal power: The symbol is the letter TH;

i) For nuclear power: The symbol is the letter N;

k) For solar power: The symbol is the letter SS;

l) For geothermal power: The symbol is the letter GS;

m) For synchronous compensators: The symbol is the letter B.

2. The subsequent character shall be the generator's serial number.

Example:

- S1: Represents the first steam thermal power plant unit.

- GT2: Represents the second gas turbine unit.

Article 45. Naming of Transformers

1. The initial character shall be designated as follows:

a) For two-winding or three-winding transformers: The symbol is the letter T;

b) For autotransformers: The symbol is the letter AT;

c) For self-used transformers: The symbol is the letter TD;

d) For excitation transformers for generators: The symbol is the letter TE;

đ) For neutral grounding transformers: The symbol is the letter TT.

2. The subsequent character shall be the transformer's serial number. For self-used transformers, the subsequent character shall be the voltage level and the serial number within that voltage level.

Example:

- T1: Represents the first transformer.

- T2: Represents the second transformer.

- TD31: Represents the first self-used transformer at 35 kV voltage level.

- AT1: Represents the first autotransformer.

Article 46. Naming of Neutral Resistors and Neutral Reactors of Transformers

1. The first two characters are RT for neutral resistors and KT for neutral reactors.

2. The third character shall be based on the winding voltage level of multi-winding transformers.

3. The subsequent character shall be the name of the transformer to which the RT or KT is connected.

Example:

- RT3T1: Represents the neutral resistor of the 35 kV winding of transformer T1.

- KT5AT2: Represents the neutral reactor of the 500 kV autotransformer AT2.

Article 47. Naming of Shunt Reactors

1. The first two characters are KH.

2. The third character shall represent the voltage level.

3. The fourth character shall be the number 0 (or number 9 if the diagram is complex).

4. The fifth character shall be the shunt reactor circuit number.

Example: KH504 represents the 500 kV shunt reactor installed in circuit number 4.

Article 48. Naming of Neutral Reactors and Neutral Resistors of Shunt Reactors

1. The first two characters are KT for neutral reactors and RT for neutral resistors of shunt reactors.

2. Subsequent characters shall follow the last three characters of the reactor.

Example:

- KT504: Represents the neutral reactor of reactor KH504.

- RT504: Represents the neutral resistor of reactor KH504.

Article 49. Naming of Short Circuit Current Limiting Reactors

1. The first two characters are the letters "KI".

2. The third character shall represent the voltage level.

3. Subsequent characters are assigned according to the serial number of the cable or busbar.

Example:

- KI212 indicates the short circuit current limiting reactor for the 220 kV voltage level connecting busbar number 1 with busbar number 2.

- KI171 indicates the short circuit current limiting reactor for cable 171.

Article 50. Naming of Shunt Reactors

1. The first character is the letter "L".

2. The second character is the name of the section of the transmission line.

Example: L171 indicates the shunt reactor of the 110 kV line 171.

Article 51. Naming of Shunt Capacitors

1. The first three characters: For series capacitors, use the letters "TBD", for parallel capacitors, use the letters "TBN".

2. The fourth character represents the voltage level.

3. The fifth character is the number 0 (or 9 if the diagram is complex).

4. The sixth character is the serial number of the capacitor circuit for series capacitors, and the serial number of the capacitor bank for parallel capacitors.

Example:

- TBD501 indicates the series capacitor at the 500 kV voltage level connected to circuit number 1.

- TBN302 indicates the parallel capacitor at the 35 kV voltage level in capacitor bank number 2.

Article 52. Naming of Static Var Compensators

1. The initial characters are taken from the abbreviated English name.

2. Subsequent characters represent the voltage level and serial number similar to those specified for shunt capacitors in Article 51 of this Circular.

Example:

- SVC302 indicates the SVC (Static Var Compensator) at the 35 kV voltage level in SVC unit number 2.

- TSSC501 indicates the TSSC (Thyristor Switched Series Capacitor) at the 500 kV voltage level connected to circuit number 1.

Article 53. Naming of Overvoltage Arresters

1. The first character is the letter "C".

2. The subsequent character takes the name of the equipment being protected against overvoltage. For equipment where the name does not clearly indicate the voltage level, after the first character will be a character representing the voltage level, followed by the name of the equipment.

Example: C9H1 indicates the overvoltage arrester connected to the high side of generator H1.

Article 54. Naming of Voltage Transformers

1. The first character is "TU".

2. Subsequent characters take the name of the equipment to which the voltage transformer is connected. For equipment where the name does not clearly indicate the voltage level, after the first two characters will be a character representing the voltage level, followed by the name of the equipment.

Example:

- TU171 indicates the voltage transformer on the 110 kV line 171.

- TUC22 indicates the voltage transformer for busbar number 2 at the 220 kV voltage level.

- TU5T2 indicates the voltage transformer for the 500 kV side of transformer T2.

Article 55. Naming of Current Transformers

1. The first two characters are "TI".

2. Subsequent characters take the name of the equipment to which the current transformer is connected. For equipment where the name does not clearly indicate the voltage level, after the first two characters will be a character representing the voltage level, followed by the name of the equipment.

Example:

- TI171 indicates the current transformer for the 110 kV line 171.

- TI5AT2 indicates the current transformer for the 500 kV side of the bushing in transformer AT2.

Article 56. Naming of Lightning Arresters

1. The first two characters are the letters "CS".

2. The subsequent character takes the name of the equipment being protected. For equipment where the name does not clearly indicate the voltage level, after the first two characters will be a character representing the voltage level, followed by the name of the equipment. For lightning arresters connected to the neutral of a transformer, use the number 0.

Example:

- CS1T1 indicates the lightning arrester for transformer T1 on the 110 kV side.

- CS0T1 indicates the lightning arrester connected to the neutral of transformer T1.

- CS271 indicates the lightning arrester for line 271.

Article 57. Naming circuit breakers

1. Initial characters: For general circuit breakers, use the letters CC, and for automatic circuit breakers, use the letters FCO.

2. The next character is a hyphen (-) followed by the name of the protected device.

Example: CC-TUC31 represents the circuit breaker for the primary winding C31 transformer.

Article 58. Numbering of switches

1. The first character indicates the voltage level. For capacitor switches, the first character is T, and for reactor switches, it is K; the second character indicates the voltage level.

2. The second character (third character for reactor and capacitor switches) indicates the position of the switch, as follows:

a) Transformer switch: Use number 3;

b) Line switch: Use numbers 7 and 8 (or from 5 to 8 if the diagram is complex);

c) Self-use transformer switch: Use number 4;

d) Generator end switch: Use number 0;

đ) Reactive power compensation machine switch: Use number 0;

e) Shunt capacitor bank switch: Use number 0;

g) Series capacitor bank switch: Use number 0 (or 9 if the diagram is complex);

h) Reactor switch: Use number 0 (or 9 if the diagram is complex).

3. The third character (fourth character for reactor and capacitor switches) is represented by a digit from 0 to 9.

4. For switches on the busbar loop, the two characters following the first character are: 00.

5. For switches connecting two busbars, the two characters following the first character are the numbers of the two busbars.

6. For a single busbar with sections, even-numbered switches on even-numbered busbars are numbered with even numbers, and odd-numbered switches on odd-numbered busbars are numbered with odd numbers.

7. For polygonal diagrams, number the switches according to the line switches.

8. For 3/2 (one and a half) and 4/3 diagrams, numbering can be done as follows depending on the diagram:

a) Number the switches according to the line switches;

b) Number the second character of the middle switch (not connected to the busbar) as 5 or 6; Number the third character according to the bay sequence.

Example:

- 131: Represents the switch of transformer number 1 at 110 kV voltage level.

- 903: Represents the switch of generator number 3 at 10 kV voltage level.

- K504: Represents the switch of reactor number 4 at 500 kV voltage level.

- 100: Represents the loop switch at 110 kV voltage level.

- 212: Represents the interconnection switch between busbars at 220 kV voltage level.

Article 59. Numbering of disconnectors

1. The initial characters are the name of the switch or directly connected equipment (for disconnector of TU: the first characters are the name of TU, followed by the name of the directly connected equipment), followed by a hyphen (-).

2. The subsequent character is defined as follows:

a) Busbar disconnector takes the serial number of the busbar connected to the disconnector;

b) Line disconnector (line-side disconnector) uses number 7;

c) Disconnector connected to the transformer uses number 3;

d) Disconnector connected to the loop busbar uses number 9;

đ) Disconnector connected to a single piece of equipment uses number 0 or 9;

e) Disconnector connected to a section (section side) uses the serial number of that section busbar (or busbar);

g) Disconnector connected to neutral resistance or neutral reactor uses number 0;

h) Disconnector connected to the generator uses number 0 or 9.

Example:

- 131-3: Represents the disconnector of transformer T1 at 110 kV voltage level.

- KH501-1: Represents the disconnector of capacitor number 1 at 500 kV voltage level connected to busbar number 1.

- TUC22-2: Represents the disconnector of transformer TUC22 at 220 kV voltage level connected to busbar number 2.

- 171-7: Represents the line-side disconnector of switch 171 at 110 kV voltage level.

- 272-9: Represents the disconnector of switch 272 connected to the loop busbar.

- 275-0: Represents the disconnector bypassing switch 275.

- KT101-0: Represents the neutral disconnector of transformer T1 at 110 kV voltage level connected to neutral reactor KT101.

Article 60. Numbering of Grounding Switches

1. The initial characters shall be the name of the disconnector or directly related equipment.

2. The subsequent character shall denote the grounding switch, specified as follows:

a) Grounding switches for transmission lines and capacitors shall be numbered with 6.

b) Grounding switches for transformers, reactors, and voltage regulators shall be numbered with 8.

c) Grounding switches for circuit breakers shall be numbered with 5.

d) Grounding switches for busbars shall be numbered with 4.

e) Grounding switches for the neutral point of transformers or reactors shall be numbered with 08.

f) Grounding switches for generators shall be numbered with 5.

Example:

- 271-76: indicates the external grounding switch for transmission line 271.

- 171-15: indicates the grounding switch for circuit breaker 171 adjacent to disconnector 171-1.

- 131-08: indicates the neutral point grounding switch for the 110 kV winding of transformer number 1.

Article 61. Numbering of Circuit Breakers and Disconnectors at Branch Lines and Segments of Transmission Lines

1. For sectionalizing circuit breakers on transmission lines, they shall be numbered like circuit breakers on transmission lines; for branch circuit breakers leading to transformers, they shall be numbered like circuit breakers on transformers.

2. For sectionalizing disconnectors or branch disconnectors, the initial characters shall be numbered according to Article 59 of this Circular (the numbering of disconnectors shall be assumed as if there were circuit breakers).

3. The final characters shall be a separator (/) followed by the pole number of the sectionalizing or branching point.

Example:

- 371/XX: indicates circuit breaker 371 for sectionalizing the 35 kV transmission line at pole number XX.

- 171-7/XX: indicates the disconnector for sectionalizing the 110 kV transmission line at pole number XX.

- 171-76/XX: indicates the grounding disconnector for the 110 kV transmission line at pole number XX.

Chapter V

IMPLEMENTATION

Article 62. Implementation Organization

1. The Electricity Regulatory Authority shall be responsible for disseminating and guiding the implementation of this Circular.

2. The Vietnam Electricity Corporation shall be responsible for directing subordinate units to implement this Circular.

Article 63. Effective Date

1. This Circular takes effect from January 23, 2015. Decision No. 16/2007/QĐ-BCN dated March 28, 2007, issued by the Minister of Industry regarding the National Power System Operation Procedures, shall cease to be effective from the date this Circular takes effect.

2. During the implementation of this Circular, if there are any difficulties or new issues arising, relevant units shall have the responsibility to report to the Electricity Regulatory Authority for research, proposal, and submission to the Minister of Industry and Trade for amendments and supplements to this Circular as appropriate../.