Circular No. 30/2019/TT-BCT dated November 18, 2019 of the Ministry of Industry and Trade on amending and supplementing a number of articles of the Circular No. 25/2016/TT-BCT dated November 30, 2016 of the Ministry of Industry and Trade on regulations on electricity transmission system and the Circular No. 39/2015/TT-BCT dated November 18, 2015 of the Minister of Industry and Trade on regulations on electricity distribution system

CIRCULARS
Amending and supplementing a number of articles oftheCircular No. 25/2016/TT-BCT dated November 30, 2016 of the Ministry of Industry and Trade on regulations on electricity transmission system and Circular No. 39/2015/TT-BCT dated November 18, 2015 of the Minister of Industry and Trade on regulations on electricity distribution system
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Pursuant to the Law on Electricity dated December 3, 2004 and the Law dated November 20, 2012 amending and supplementing a number of articles of the Law Electricity;

Pursuant to the Government s Decree No. 98/2017/ND-CP dated August 18, 2017 defining the functions, tasks, powers and organizational structure of the Ministry of Industry and Trade;

Pursuant to the Government s Decree No. 137/2013/ND-CP dated October 21, 2013 detailing the implementation of a number of articles of the Law on Electricity and the Law amending and supplementing a number of articles of the Law on Electricity;

At the request of the Director of Electricity Regulatory Authority;

The Minister of Industry and Trade promulgatesatheCircular amending and supplementing a number of articles of Circular No. 25/2016/TT-BCT dated November 30, 2016 of the Ministry of Industry and Trade on regulations on electricity transmission system and Circular No. 39/2015/TT-BCT dated November 18, 2015 of the Minister of Industry and Trade on regulations on electricity distribution system

Article 1. Amending and supplementing a number of articles of Circular No. 25/2016/TT-BCT dated November 30, 2016 of the Ministry of Industry and Trade on regulations on electricity transmission system

11. Adding Clause 5a following Clause 5, Clause 6a following Clause 6 of Article 3 as follows:

“5a.Rated capacity of a power plantis the total rated capacity of the generating sets in such power plant in stable and normal operation mode and declared by the manufacturer in the design description of the generating sets. For solar power plants, the rated capacity of a solar power plant is the maximum alternating electric power of such plant that can be calculated and announced in line with the planned DC capacity of such solar power plant.

6a.DIM(Dispatch Instruction Management) is the information management system of dispatch instruction between the dispatching level with control authority and the power plant or the Control Center of power plants.”

2. Amending Clauses 10, 35, 49 and 53 of Article 3 as follows:

“10.Frequency adjustment in an electricity system(hereinafter referred to as frequency adjustment) is an adjustment process in an electricity system to maintain the stable operation of such system, including primary frequency adjustment, secondary frequency adjustment, and tertiary frequency adjustment:

a) Primary frequency adjustment is the process of adjusting electricity system frequency immediately by a large number of generating sets equipped with a governor.

b) Secondary frequency adjustment is the adjustment process following the primary frequency adjustment carried out through the impact of AGC system to keep thefrequencywithin the permissible long-term working band.

c) Tertiary frequency adjustment is the adjustment process following the secondary frequency adjustment carried out by a dispatch instruction to keep the electricity system frequency operating stably according to current regulations and ensure economical distribution of generating capacity among generating sets.

35.Short-termflicker perceptibility(P_st) and long-term flicker perceptibility (P_lt)are values calculated according to current National Standards. In case the P_stand P_ltvalues ​​are not included in the National Standards, they shall be calculated according to the current IEC Standards published by the International Electrotechnical Commission.

49.PSS (Power System Stabilizer)is a device that injects additional signals into the automatic voltage regulator (AVR) to decrease voltage fluctuation in the electricity system.

53.Automatic load sheddingis the act of automatically cutting loads by relays in accordance with the signals of frequency, voltage or transmission power of the electricity system when such frequency, voltage or transmission power level drops below the permissible limits calculated by the electricity system and market operator.”.

3. Amending Article 7 as follows:

“Article 7. Phase balance

1. In normal operation mode, negative sequence voltage components are not allowed to exceed 3% of nominal voltage in case of nominal voltage levels on transmission grid.

2. The negative sequence voltage components on the transmission grid at some points of time are allowed to exceed the value specified in Clause 1 of this Article, but 95% of the values​​which is calculated within at least 01 week long with samples taken frequency of every 10 minutes shall not exceed the prescribed limitshall be calculated within at least 01 week longand samples shall be taken every 10 minutes without exceeding the prescribed limit.”.

4. Amending Clauses 1, 2 and adding Clause 6 to Article 8 as follows:

“1. Voltage harmonics

a) The total harmonic distortion shall be calculated as the ratio of the root mean square (RMS) value of the voltage harmonics to the RMS value of the voltage at fundamental frequency in the following formula:

Where:

- THD: Total harmonic distortion;

- V_i: is the RMS voltage ofi^thharmonic and N is the highest order of harmonics to be assessed;

- V_l: is the RMS value of the voltage at fundamental frequency (50 Hz).

b) Permissible maximum value of total harmonic distortion caused by high-level harmonic components to the voltage level of 220 kV and 500 kV is not allowed to exceed 3%.

2. Current harmonics

a) The total demand distortion shall be calculated as the ratio of the RMS value of the current harmonics to the RMS value of the maximum demand load current at fundamental frequency in the following formula:

Where:

- TDD: Total demand distortion;

- I_i: is the RMS current ofi^thharmonic and N is the highest order of harmonics to be assessed;

- I_L: is the RMS value of the maximum demand load current at fundamental frequency (50 Hz) (the maximum demand and load is the average of the 12 maximum monthly demands and loads over the previous 12 months respectively; in case of new connections or inability to recording the maximum monthly demands and loads over the previous 12 months, the maximum demand and load shall be equal to the maximum demand and load during the time of calculation).

b) Permissible maximum value of total demand distortion caused by high-level harmonic components to the voltage level of 220 kV and 500 kV is not allowed to exceed 3%.

6. Unusually harmonic sharp peaks on the transmission grid are allowed to exceed the total harmonic distortion as specified in Clauses 1 and 2 of this Article, but95% of the voltage and current harmonic values which is calculated within at least 01 week long with samples taken frequency of every 10 minutes shall not exceed the prescribed limit95% of the voltage and current harmonic values ​​shall be calculated within at least 01 week long and samples shall be taken every 10 minutes without exceeding the prescribed limit.”.

5. Amending Article 12 as follows:

“Article 12. Short-circuit current and fault clearing time

1. Permissible maximum short-circuit current

a)Permissible maximum value of short-circuit current and fault clearing time by main protection on the electricity transmission system are stipulated in Table 6 below:

Table 6

Permissible maximum value of short-circuit current and fault clearing time by main protection

b) Main protection of an electrical equipment is a key element of protection which is installed and set to make initial impacts, ensuring selectivity and reliability of impacts and time of impacts of the protection system in case of a fault within the scope of protection;

c) For 110 kV busbars of 500 kV or 220 kV transformers in the transmission grid, permissible maximum short-circuit current is 40 kA.

2. The switchgears on the electricity transmission grid shall be able to de-energize maximum short-circuit current through the switchgears at least for the next 10 years from the expected time of putting the switchgears into operation and enduring this short-circuit current for at least 01 second.

3. For hydroelectric and thermoelectric generating sets with the capacity of more than 30 MW, total value of unsaturated sub transient reactance of a generating set (X_d’’-%) and short-circuit reactance of a terminal transformer (U_k-%) according to the per-unit systempu(puunits shall refer to the rated apparent power of the generating set) is not allowed to be less than 40%.

If the aforesaid requirements cannot be met, the investor shall be responsible for installing further reactance so that total value of X_d’’, U_kand electrical reactance according to the per-unit systempu(puunits shall refer to the rated apparent power of the generating set) is not less than 40%.

4. If value of short-circuit current at connection point of any electrical works to an electricity transmission system is greater than permissible maximum short-circuit as stipulated in Table 6, the investor shall take measures to restrict the short-circuit current at connection points to a level lower or equal to permissible maximum short-circuit current as stipulated in Table 6.

5. The transmission network operator shall be responsible for informing the customer using transmission grid about the maximum value of short-circuit current at connection point at the present time and the calculations for at least the next 10 years for coordination during the investment and installation of equipment, ensuring that the switchgears are able to de-energize maximum short-circuit current at connection point at least for the next 10 years.”.

6. Amending Clause 3 of Article 28 as follows:

“3. If any connection proposed by a customer is in opposition to the approved electricity development planning, the transmission network operator shall be responsible for making notification to the such customer for adjustments and supplements to the planning according to the related regulations.”

7. Amending Clause 1 of Article 31 as follows:

“1. The customer using transmission grid shall be responsible for investing, installing and managing the information system under his/her scope of management and ensuring it is connected to the information system belonging to the transmission network operator and the dispatch level as well as  the telecommunication and data transmission (including data of SCADA system, PMU and fault recording management) are sufficient, reliable and uninterrupted for electricity system and market operation. Means of communications serving dispatching and operation, including at least direct communication channel, telephone, facsimile and DIM, shall be ensured operating reliably and uninterruptedly.”.

8. Amending Clauses 1 and 2 of Article 32 as follows:

“1. Transformers from 220 kV and on, power plants with installed capacity greater than 30 MW and power plants connected to the transmission grid which is not yet connected to the Control Center shall be equipped with a Gateway or RTU with two ports physically connecting independently to the SCADA system of the dispatch level.

2. Transformers from 220 kV and on, power plants with installed capacity greater than 30 MW and power plants connecting to the transmission grid which is connected to and controlled by the Control Center must be equipped with a Gateway or RTU with one port connecting to the SCADA system of the dispatch level and two ports connecting to the controlling system at the Control Center.”.

9. Amending Article 36 as follows:

“Article 36. Automatic frequency load shedding system

1. The customer using transmission grid shall be responsible for cooperating with relevant units in unifying the installation of the automatic frequency load shedding system in his/hẻ electricity system and ensuring that it operates in accordance with calculations and requirements of the dispatch level.

2. The system shall be designed and set to meet following requirements:

a) Reliability shall not be less than 99%;

b) Any unsuccessful load shedding of any load shall not affect the operation of the entire electricity system.

c) Load shedding procedures and amount of shed power shall be in compliance with level of distribution by the dispatch level and shall not be changed in any case without consent of the dispatch level.

3. Load recovery procedures shall be in compliance with dispatch instruction of the dispatch level.”.

10. Amending Clause 2 of Article 37 as follows:

“2. Requirements for connection of Control Center

a) Requirements for connection to information system

- There is one data transmission line to be connected to the information system of the dispatch level. If multiple dispatching levels with control authority exist, an information sharing method must be agreed by all the dispatching levels;

- There are two data transmission lines (one operating and one backup) to be connected to the control and information system of power plants, substations remotely controlled by the Control Center;

- Means of communications serving dispatching and operation, including at least direct communication channel, telephone, facsimile, DIM and computer network, shall be ensured well operating.

b) Requirements for connection to SCADA system

- There is one port connecting to SCADA system of the dispatch level. If multiple dispatching levels with control authority exist, all the dispatching levels shall share information;

- There are two ports connecting to RTU/Gateway, control system of power plants, substations and switchgears on the electrical grid remotely controlled by the Control Center.

c) The Control Center must install a monitoring screen connected to the surveillance camera system at power plants, substations and switchgears on the electrical grid, which sends information back to the Control Center.”.

11. Amending Clause 3 of Article 38 as follows:

“3. Generating sets of a power plant shall be capable of adjusting the primary frequency as the frequency drops out of the governor dead-band as well as meeting all the primary frequency adjusting capacity of the generating sets in 15 seconds and maintaining such capacity at least 15 seconds. The primary frequency adjusting capacity of the set shall be calculated according to the actual frequency deviation and settings required by the electricity system and market operator.”

12. Amending Article 42 as follows:

“Article 42. Technical requirements of wind and solar power plants

1. Wind and solar power plants shall be capable of maintaining generation of active power in following modes:

a) Free generation mode: Generation of possible maximum powerin accordance with change of primary sources(wind or solar)

b) Generating capacity control mode:

Wind and solar power plants shall be capable of adjusting generating power according to dispatch instruction as follows:

-Generation of possible maximum powerin case primary sources are lower than limited valueof dispatch instruction;

- Generation of power in accordance with dispatch instructionwithin ± 01 % of rated powerin case primary sources are equal or greater than value than limited valueof dispatch instruction.

2. Wind and solar power plants at every time of connection to the grid shall be capable of maintaining generation of power for a minimum period of time in proportion to working frequency band prescribed in Table 8 below:

Table 8

Minimum time to maintain power generation in proportion to frequency band of electricity system of wind or solar power plants

3. When the electricity system’s frequency is greater than 50.5 Hz, wind and solar power plants shall reduce active power with thedroop characteristics ranging from 2% to 10%. The setting value ofdroop characteristicsshall be calculated and determined by dispatch level.

4. Wind and solar power plants shall be capable of adjusting reactive power as described by the graph below and at Point a, b of this Clause:

a) If a power plant generates an active power greater or equal to 20% of rated active power and voltageat connection point varying beyond ± 10 % of nominal voltage, such power plant shall be capable of adjusting reactive power continuously in a power factor from0.95[CNT1] (corresponding to reactive power generation mode) to 0.95 (corresponding to reactive power receiving mode) at connection point in proportion to the rated power;

b) If a power plant generates an active power less than 20% of rated power, such power plant shall reduce the ability to receive or generate reactive power in accordance with its characteristics.

5. Control mode of voltage and reactive power:

a) Wind and solar power plants shall be capable of adjusting voltage and reactive power in the following modes:

- Voltage control mode according to voltage adjustment droop characteristics (voltage/reactive power characteristics);

- Control mode according to the value of reactive power setting;

- Control mode according to the power factor.

b) If voltage at connection point varies beyond ± 10 % of rated voltage, the power plant shall be capable of adjusting the voltage at the lower side of the booster transformer with deviation no more than ± 0.,5 % of rated voltage (compared to the voltage setting) whenever the reactive power of the generating set is still within the permissible working band and completed in no more than 05 seconds.

6.Wind and solar power plants at every time of connection to the gridshall be capable of maintaining generation of power in proportion to voltage at the connection in the time as follows:

a)Voltage less than 0.3 pu, minimum time is 0.15 seconds;

b) Voltage from 0.3 pu to under 0.9 pu, minimum time is calculated in following formula:

T_min= 4 x U – 0.6

Where:

- T_min(second): Minimum time to maintain power generation:

- U (pu): Actual voltage at connectionpoint (pu).

c) Voltage from 0.9 pu to under 1.1 pu, wind and solar power plants shall maintain continuous generation;

d) Voltage from 1.1 pu to under 1.15 pu, wind and solar power plants shall maintain generation for 03 seconds;

dd) Voltage from 1.15 pu to under1.152[CNT2] pu[l3] , wind and solarpower[l4] plants shall maintain generation for 0.5 seconds.

7. Phase unbalance, total harmonic distortion  and flicker perceptibility caused by wind and solar power plants at connection point shall not be allowed to exceed the values prescribed in Articles 7, 8 and 9 herein.

8. Wind and solar power plants shall invest in equipment and adjusting systems which automatically ensure a stable, reliable and secured connection to theAutomatic Generation Control(AGC) system of the electricity system and market operator for remotely adjusting the capacity of such plants through the dispatch instruction by such electricity system and market operator”.

13. Amending Point a, Clause 2 of Article 59 as follows:

“a) Frequency regulation reserve and quick-start reserve levels are lower than required in normal operation mode”.

14. Amending Point b, Clause 3 of Article 64 as follows:

“b) Carry out load shedding on each line through an automatic load shedding relay or carry out load shedding under dispatch instruction.”

15. Adding Clause 2a following Clause 2 to Article 69 as follows:

"2a. Provide information on primary sources (hydrological information for hydroelectric plants, information about coal/oil/fuel for thermal power plants, meteorological observation information for wind and solar power plants), forecast the capacity and output of the plants and transmit such data to the electricity system and market operator.”.

16. Amending Article 72 as follows:

“Article 72. Types of ancillary services

Types of ancillary services used for the electricity transmission system:

1. Secondary frequency regulation (secondary regulation).

2. Quick-start.

3. Voltage adjustment.

4. Must-run operation reserves to ensure electricity system security

5. Black start.”

17. Amending Article 73 as follows:

“Article 73. Technical requirements of ancillary services

1. Secondary regulation: Generating sets providing secondary regulation service shall be capable of starting to provide frequency regulation power within 20 seconds after receiving an AGC signal from the electricity system and market operator and fully provide secondary regulation power as registered within 10 minutes and maintaining such power for a minimum of 15 minutes.

2. Quick-start: Generating sets providing quick-start reserve shall be capable of increasing to the rated power within 25 minutes and maintaining such rated power for a minimum of 08 hours

3. Voltage adjustment: Generating sets providing voltage adjustment shall be capable of changing reactive power outside the adjustment band as prescribed in Clause 2, Article 38 herein, meeting requirements of the electricity system and market operator.

4. Must-run operation reserves to ensure electricity system security: Generating sets providing must-run operation to ensure electricity system security shall be capable of increasing to a rated power within one hour and maintaining such rated power for a minimum of 08 hours (excluding the time of starting).

5. Black start: Generating sets providing black start shall be capable of self-starting in a cold state without power supply from the national electricity system and capable of supplying electricity to transmission grids, distribution grids after successfully started.”

18. Amending Article 74 as follows:

“Article 74. Determining demand for and operating ancillary services

1. General principles of determining demand for ancillary services:

a) Maintain electrical energy and capacity reserves of the electricity system in order to meet electricity system operation and security standards;

b) Ensure minimum expenses in accordance with conditions and obligations of the national electricity system.

2. The electricity system and market operator shall be responsible for calculating and reporting to Vietnam Electricity the demand for ancillary services of the national electricity system according to the Procedures for determining demand for and operating ancillary services issued by the Electricity Regulatory Authority.

3. Before November 01 annually, the Vietnam Electricity shall be responsible for reporting to the Electricity Regulatory Authority for approval of the demand for ancillary services of the national electricity system in the coming year, serving as a basis for planning the procurement and/or mobilization of ancillary services in the plan of national electricity system operation for the coming year.

19. Amending Point b, Clause 1 of Article 85 as follows:

“b) When an unbalance occurs on the electricity system, the electricity system and market operator shall mobilize generating sets to provide ancillary services and adjust generation capacity of the generating sets based on the mobilization order of generating sets in the electricity system to keep the system back in equilibrium and maintain the reserves in accordance with regulations.”

20. Adding Clause 4 to Article 90 as follows:

“4. The transmission network operator shall be responsible for making a written report as prescribed by Clauses 1, 2 and 3 of this Article and sending it through documentation process or via email.”.

21. Adding Clause 5 to Article 91 as follows:

“5. The electricity system and market operator shall be responsible for making a written report as prescribed by Clauses 1, 2, 3 and 4 of this Article and sending it through documentation process or via email.”.

Article 2. Amending and supplementing a number of articles of Circular No. 39/2015/TT-BCT dated November 18, 2015 of the Minister of Industry and Trade on regulations on electricity distribution system

1. Adding Clause 3a following Clause 3 to Article 3 as follows:

“3a.Rated capacity of a power plantis the total rated capacity of the generating sets in such power plant in stable and normal operation mode and declared by the manufacturer in the design description of the generating sets. For solar power plants, the rated capacity of a solar power plant is the maximum alternating electric power of such plant that can be calculated and announced in the approved technical design in line with the planned DC capacity of such solar power plant.”.

2. Amending and supplementing Article 5 as follows:

“Article 5. Voltage

1. Nominal voltage levels in the electricity distribution system are110 kV, 35 kV, 22 kV, 15 kV, 10 kV, 06 kV and 0.38 kV.

2. Permissible working voltage fluctuations on the distribution grid in normal operation mode:

a) Permissible working voltage fluctuations at busbars on the distribution grid of the electricity distributor are + 10% and - 05% of the nominal voltage;

b) Permissible working voltage fluctuations at the connection point compared with the rated voltage:

- At the connection point of electricity customers: ± 05%;

- At the connection point of the power plant: + 10% and - 05%;

- If the power plant and the electricity customers connect to the same busbar or line on the distribution grid, the voltage at the connection point shall be decided by the electricity distributor operating the regional grid, which shall ensure the compliance with technical requirements of electricity distribution grid operation and the voltage quality for the electricity customer according to regulations.

3. For the unstable grid after encountering a fault, the voltage fluctuations at the connection point with the customers directly affected by such fault are + 5% and - 10% of the nominal voltage.

4. In an emergency operation mode or electricity system restoration mode,permissible voltage fluctuationon the distribution grid is ± 10% of the nominal voltage.

5. During the fault, voltage at the place where the fault occurs and its surrounding areas shall drop to 0 at phases with fault or increase over 110% of the nominal voltage at phases without fault until the fault is cleared.

6. The voltage fluctuation at the connection point on the distribution grid caused by the fluctuations in the loads of electricity customers or the operation of switchgears within the power plant shall not exceed 2.5% of the nominal voltage and among the permissible working voltages as specified in Clause 2 of this Article.

7. In case customers using distribution grid require higher voltage quality than those specified in Clause 2 of this Article, such customers shall negotiate with the electricity distributor or electricity retailers. The electricity distributor or electricity retailers shall be responsible for asking for consultancy from the dispatch level before negotiating with the customers.”.

3. Amending Article 6 as follows:

“Article 6. Phase balance

1. In normal operation mode, negative sequence components of the phase voltage shall not exceed 03% of the nominal voltage at 110 kV or 05% of the nominal voltage at medium and low voltage levels.

2. Negative sequence components of the phase voltage on the distribution grid at some points of time are allowed to exceed the values as specified in Clause 1 of this Article, butt95% of the voltage and current harmonic values which is calculated within at least 01 week long with samples taken frequency of every 10 minutes shall not exceed the prescribed limit95% of the voltage and current harmonic values ​​shall be calculated within at least 01 week long and samples shall be taken every 10 minutes without exceeding the prescribed limit.”.

4. Amending and supplementing Article 7 as follows:

“Article 7. Harmonics

1. Voltage harmonics:

a) The total harmonic distortion shall be calculated as the ratio of the root mean square (RMS) value of the voltage harmonics to the RMS value of the voltage at fundamental frequency in the following formula:

Where:

- THD: Total harmonic distortion;

- V_i: is the RMS voltage ofi^thharmonic and N is the highest order of harmonics to be assessed;

- V₁: is the RMS value of the voltage at fundamental frequency (50 Hz).

b) Permissible maximum harmonic distortions on the distribution grid is specified in Table 1a below:

Table1a

Permissible maximum harmonic distortions

2. Current harmonics

a) The total demand distortion shall be calculated as the ratio of the RMS value of the current harmonics to the RMS value of the maximum demand load current at fundamental frequency in the following formula:

Where:

- TDD: Total demand distortion;

- I_i: is the RMS current ofi^thharmonic and N is the highest order of harmonics to be assessed;

- I_L: is the RMS value of the maximum demand load current at fundamental frequency (50 Hz) (the maximum demand and load is the average of the 12 maximum monthly demands and loads over the previous 12 months respectively; in case of new connections or inability to recording the maximum monthly demands and loads over the previous 12 months, the maximum demand and load shall be equal to the maximum demand and load during the time of calculation).

b) Power plants connected to the distribution grid shall not cause demand distortions to exceed the values specified in Table 1b below:

Table 1b

Permissible maximum demand distortion for power plants

c) The electrical loads connected to the distribution grid shall not cause the demand distortions to exceed the values specified in Table 1c below:

Table 1c

Permissible maximum demand distortion for electrical loads

3. Unusually harmonic sharp peaks on the distribution grid are allowed to exceed the total harmonic distortion as specified in Clauses 1 and 2 of this Article, but95% of the voltage and current harmonic values which is calculated within at least 01 week long with samples taken frequency of every 10 minutes shall not exceed the prescribed limit95% of the voltage and current harmonic values shall be calculated within at least 01 week long and samples shall be taken every 10 minutes without exceeding the prescribed limit.”.

5. Amending Article 8 as follows:

“Article 8. Flicker perceptibility

1. In normal operational conditions, flicker perceptibility at any connection point shall not exceed the limits as prescribed in Table 2 below:

Table 2

Flicker perceptibility

2.Short-term flicker perceptibility (P_st) and long-term flicker perceptibility (P_lt) are values calculated according to current National Standards. In case the Pst and Plt values are not included in the National Standards, they shall be calculated according to the current IEC Standards published by the International Electrotechnical Commission.”.

6. Amending Article 9 as follows:

“Article 9. Short-circuit current and fault clearing time

1. Permissible maximum short-circuit current on the distribution grid and fault clearing time by main protection are stipulated in Table 3 below:

Table 3

Permissible maximum short-circuit current and fault clearing time by main protection

2. The switchgears on the electricity distribution grid shall be able to de-energize maximum short-circuit current through the switchgears at least for the next 10 years from the expected time of putting the switchgears into operation and enduring this short-circuit current for at least 01 second.

3. For medium-voltage lines with many segments, which cause difficulties for switchgears in coordinating protection on the grid, permissible fault clearing time by main protection at some switching positions is allowed to be greater than the values specified in Clause 1 of this Article less than 01 second while ensuring the safety of the switchgears and the grid.

4. If value of short-circuit current at connection point of any electrical works to an electricity distribution system is greater than permissible maximum values of short-circuit current as stipulated in Table 3, the investor of such electrical works shall take measures to restrict the short-circuit current at connection points to a level lower or equal to permissible maximum short-circuit current as stipulated in Table 3.

5. The electricity distributor shall inform the customer using electricity distribution grid about the maximum value of short-circuit current at connection point at the time of connection for coordination during the investment and installation of equipment, ensuring that the switchgears are able to de-energize maximum short-circuit current at connection point at least for the next 10 years from the expected time of putting the switchgears into operation.”.

7. Adding Article 17a following Article 17:

“Article 17a. Disclosure of information on electricity supply reliability, power loss and customer service quality.

1. Before the 10^thday of every month, the electricity distributor shall publish information on electricity supply reliability, power loss and customer service quality of the previous month on its website.

2. Before January 31 annually, the electricity distributor shall publish information on electricity supply reliability, power loss and customer service quality of the previous year on its website.”.

8. Amending Clause 2 of Article 28 as follows:

“2. If any connection proposed by a customer is in opposition to the approved electricity development planning, the electricity distributor or electricity retailers shall be responsible for making notification to the such customer for adjustments and supplements to the planning according to the related regulations.”

9. Amending Article 32 as follows:

“Article 32. Requirements for harmonic distortion

The permissible harmonic distortion at the connection point to the distribution grid shall meet the requirements specified in Article 7 herein.”.

10. Amending Clauses 1 and 2 of Article 38 as follows:

“1. Power plants connected to the distribution grid with the capacity of at least 10 MW (regardless of the voltages at connection point) and 110kV transformers which is not yet connected to the Control Center shall be equipped with a Gateway or RTU with two ports physically connecting independently to the SCADA system of the dispatch level. If multiple dispatching levels with control authority exist in the power plants or transformers, all the dispatching levels shall share information for coordination in operating the electricity system.

2. Power plants connected to the distribution grid with the capacity of at least 10 MW and 110kV transformers which is connected to the Control Center shall be equipped with a Gateway or RTU with one port connecting to the SCADA system of the dispatch level and two ports connecting to the controlling system at the Control Center.”.

11. Amending and supplementing Article 40 as follows:

“Article 40. Technical requirements of wind and solar power plantsconnected to power distribution grids at the medium voltage and on

1. Wind and solar power plants shall be capable of maintaining generation of active power in following modes:

a) Free generation mode: Generation of possible maximum powerin accordance with change of primary sources(wind or solar)

b) Generating capacity control mode:

Wind and solar power plants shall be capable of adjusting generating power according to dispatch instruction as follows:

- Generation of possible maximum power in case primary sources are lower than limited valueof dispatch instruction;

- Generation of power in accordance with dispatch instructionwithin ± 01 % of rated powerin case primary sources are equal or greater than value than limited valueof dispatch instruction.

2. Wind and solar power plants at every time of connection to the grid shall be capable of maintaining generation of power for a minimum period of time in proportion to working frequency band prescribed in Table 8 below:

Table 8

Minimum time to maintain power generation in proportion to frequency band of electricity system of wind or solar power plants

3. When the electricity system’s frequency is greater than 50.5 Hz, wind and solar power plants shall reduce active power with thedroop characteristics ranging from 2% to 10%. The setting value ofdroop characteristicsshall be calculated and determined by dispatch level.

4. Wind and solar power plants shall be capable of adjusting reactive power as described by the graph below and at Point a, b of this Clause:

a) If a power plant generates an active power greater or equal to 20% of rated active power and voltageat connection point varying beyond ± 10 % of nominal voltage, such power plant shall be capable of adjusting reactive power continuously in a power factor from0.95[CNT5] (corresponding to reactive power generation mode) to 0.95 (corresponding to reactive power receiving mode) at connection point in proportion to the rated power;

b) If a power plant generates an active power less than 20% of rated power, such power plant shall reduce the ability to receive or generate reactive power in accordance with its characteristics.

5. Control mode of voltage and reactive power:

a) Wind and solar power plants shall be capable of adjusting voltage and reactive power in the following modes:

- Voltage control mode according to voltage adjustment droop characteristics (voltage/reactive power characteristics);

- Control mode according to the value of reactive power setting;

- Control mode according to the power factor.

b) If voltage at connection point varies beyond ± 10 % of rated voltage, the power plant shall be capable of adjusting the voltage at the lower side of the booster transformer with deviation no more than ± 0,.5 % of rated voltage (compared to the voltage setting) whenever the reactive power of the generating set is still within the permissible working band and completed in no more than 05 seconds.

6. Wind and solar power plants at every time of connection to the grid shall be capable of maintaining generation of power in proportion to voltage at the connection in the time as follows:

a)Voltage less than 0.3 pu, minimum time is 0.15 seconds;

b) Voltage from 0.3 pu to under 0.9 pu, minimum time is calculated in following formula:

T_min= 4 x U – 0.6

Where:

- T_min(second): Minimum time to maintain power generation:

- U (pu): Actual voltage at connectionpoint (pu).

c) Voltage from 0.9 pu to under 1.1 pu, wind and solar power plants shall maintain continuous generation;

d) Voltage from 1.1 pu to under 1.15 pu, wind and solar power plants shall maintain generation for 03 seconds;

dd) Voltage from 1.15 pu to under 1.2 pu, wind and solar power plants shall maintain generation for 0.5 seconds.

7. Phase unbalance, total harmonic distortion and flicker perceptibility caused by wind and solar power plants at connection point shall not be allowed to exceed the values prescribed in Articles 6, 7 and 8 herein.

8. Wind and solar power plants shall invest in equipment and adjusting systems which automatically ensure a stable, reliable and secured connection to theAutomatic Generation Control(AGC) system of the electricity system and market operator for remotely adjusting the capacity of such plants through the dispatch instruction by such electricity system and market operator”.

12. Amending and supplementing Article 41 as follows:

“Article 41. Requirements for solar power systems connected to the low-voltage electricity distribution grid

Solar power systems are allowed to connect to low-voltage grid when meeting the following requirements:

1. Connection capacity

a) The total installed capacity of the solar power systems connected to the low-voltage transformers shall not exceed the installed capacity of such transformers;

b) Solar power systems with the capacity of less than 20 kWp shall be connected to a single-phase or 03-phase grid upon agreement with the electricity distributor and electricity retailers;

c) Solar power systems with the capacity of more than 20 kWp shall be connected to 03-phase grid.

2. At every time of connection to the grid, solar power systems allowed to be connected with low-voltage grid shall be capable of maintaining generation of power for a minimum period of time in proportion to working frequency band prescribed in Table 5a below:

Table 5a

Minimum time to maintain power generation in proportion to frequency band of electricity system

3. When the electricity system’s frequency is greater than 50.5 Hz, solar power systems with the capacity of more than 20 kWp shall reduce active power determined in the following formula:

Where:

- ΔP: Level of active power reduction (MW);

- P_m: Active power in proportion to the point of time prior to power reduction (MW);

- f_n: Electricity system frequency prior to power reduction (Hz).

4. Solar power systems shall be capable of maintaining continuous generation of power within the voltage ranges at connection points as prescribed in Table 5b below:

Table 5b

Minimum time to maintain power generation in proportion to voltage ranges at connection points

5. Solar power systems connected to the low-voltage grid shall not generate reactive power into the grid and operate in reactive power consumption mode in a power factor (cosφ) greater than 0.98.

6. Solar power systems shall not cause direct current-electrical penetration into the distribution grid to exceed 0.5% of the rated current at the connection point.

7. Solar power systems connected to the low-voltage grid shall comply with the regulations on voltage, phase balance, harmonics, flicker perceptibility and grounding as prescribed in Articles 5, 6, 7, 8 and 10 herein.

8. Solar power systems shall be equipped with protective equipment meeting the following requirements:

a) Disconnect itself from the distribution grid when there is a fault within the solar power system;

b) Disconnect itself when power failure occurs in the distribution grid and not generate power when the distribution grid is out of power;

c) Not automatically reconnect to the grid if the following conditions are satisfied:

- The frequency of the grid shall be maintained from 48Hz to 51Hz in at least 60 seconds;

- Voltage of all phases at connection point shall be maintained from 85% to 110% of rated voltage in at least 60 seconds.

d) For solar power systems connected to 03-phase low-voltage grid, customers who request connection shall negotiate and agree on the protection system requirements with the electricity distributor, in which at least protections specified at Points a, b, c of this Clause, overvoltage protection, undervoltage protection and frequency protection shall be included.”.

13. Amending Clause 2 of Article 42 as follows:

“2. Requirements for connection of Control Center

a) Requirements for connection to information system

- There is one data transmission line to be connected to the information system of the dispatch level. If multiple dispatching levels with control authority exist, an information sharing method must be agreed by all the dispatching levels;

- There are two data transmission lines (one operating and one backup) to be connected to the control and information system of power plants, substations remotely controlled by the Control Center;

- Means of communications serving dispatching and operation, including at least direct communication channel, telephone, facsimile and computer network, shall be ensured well operating.

b) Requirements for connection to SCADA system

- There is one port connecting to SCADA system of the dispatch level. If multiple dispatching levels with control authority exist, all the dispatching levels shall share information;

- There are two ports connecting to RTU/Gateway, control system of power plants, substations and switchgears on the electrical grid remotely controlled by the Control Center.

c) The Control Center must install a monitoring screen connected to the surveillance camera system at power plants, substations and switchgears on the electrical grid, which sends information back to the Control Center.”.

14. Adding Clause 3 to Article 43 as follows:

“3. At the time of making the application for connection to the medium and 110 kV voltage class, if the information and documents as specified in Clause 2 of this Article are not sufficient, the customer using the distribution grid shall negotiate with the electricity distributor about the supply of information and documents and clearly state in the connection agreement.".

15. Renaming Article 44 as follows:

“Article 44. Connection agreement negotiation order for customers using distribution grid who have proposed connection at 110 kV and customers who own generating sets and propose connection to the medium-voltage grid”

16. Amending Point c, Clause 2 of Article 44 as follows:

“c) Collecting opinions of the dispatch level and related entities about the effect of connection on the regional electricity system and grid, the requests for connection to the information system and SCADA system of the dispatch level, requirements of protective relays, automation and contents related to technical requirements of equipment at connection points;”.

17. Amending Clause 2 of Article 45 as follows:

“2. For electricity customers with separate power stations connected to the medium-voltage grid: Within 02 working days after receiving complete and valid applications from the customers, the electricity distributor or electricity retailers shall be responsible for carrying out practical investigation, then negotiating and signing the grid connection agreement with the electricity customers who have their own power stations connected to the medium-voltage grid.”

18. Amending Clause 2 of Article 51 as follows:

“2. For electricity customers with separate power stations connected to the medium-voltage grid: Within 05 working days after receiving complete and valid applications for energizing the connection points from the customers with separate power stations connected to the medium-voltage grid as prescribed in Article 48 herein, the electricity distributor shall coordinate with customers in testing, acceptance and officially energizing the connections at the request of the customers.”.

19. Amending Clauses 2 and 6 of Article 52 as follows:

“2. In case the two parties do not agree on the inspection results and the causes of the violations, the two parties shall negotiate and agree on the scope of inspection scope so that customer can hire an independent testing unit to conduct the testing and reinspection. If the testing results of the independent testing unit show that the violations are caused by the equipment of the customer, but the customer does not accept the consequence improvement measures or fails to complete the consequence improvement in time as committed to the electricity distributor, the electricity distributor shall disconnect customers’ equipment from the distribution grid. The time for consequence improvement shall be agreed upon by the two parties,in whichif the two parties fail to agree on the time for consequence improvement, the parties shall resolve their disputes according to the Regulations on inspection of electricity activities and use,electricitysettlement of disputes related to electricity trading contracts issued by the Ministry of Industry and Trade.”.

6. During operation, if there emerge risks against operational safety of the electricity system caused by equipment of the customers, the electricity distributor shall notify without delay the dispatching levels with control authority and the customers using distribution grid with separate power stations for solving the risks. If the technical problems cannot be solved or the equipment of the customers is suspected to  adversely affect the distribution grid, the electricity distributor shall request the customers to conduct inspection and revision of the equipment under their scope of management according to Clauses 1 and 2 of this Article.”.

20. Adding Point d to Clause 2 of Article 64 as follows:

“d) The generating units shall be responsible for providing information on primary sources (hydrological information for hydroelectric plants, information about coal/oil/fuel for thermal power plants, meteorological observation information for wind and solar power plants), forecast the capacity and output of the plants and transmit such data to the dispatch level according to the Procedures for planning the operation of national electricity system issued by the Electricity Regulatory Authority.”.

21. Amending Article 79 as follows:

“Article 79. Load regulation

1. Load regulation in the electricity system includes the following measures:

a) Stopping or reducing power supply;

b) Load shedding;

c) Adjusting the electrical loads of electricity customers when they participate in power demand management programs.

2. The dispatching level with control authority and the electricity distributor shall carry out load regulation according to the Procedures for dispatching national electricity system and the Regulations on contents and implementation order of load regulation programs issued by the Ministry of Industry and Trade.”.

22. Amending Clause 1 of Article 82 as follows:

“1. Automatic load shedding is the act of selectively cutting loads with impacts of frequency relays, voltage or transmission power level to keep the electricity system operating within the permissible limits, avoiding widespread power outages.”.

23. Adding Clause 4 to Article 99 as follows:

“4. The Vietnam Electricity Corporation and the electricity distributor shall make written reports as prescribed by Clauses 1, 2 and 3 of this Article and sending it through documentation process or via email.”.

Article 3. Annulling a number of clause and articles in Circular No. 25/2016/TT-BCT dated November 30, 2016 of theMinistryMinisterof Industry and Trade on regulations on electricity transmission system and Circular No. 39/2015/TT-BCT dated November 18, 2015 of the Minister of Industry and Trade on regulations on electricity distribution system

1. Annulling Clauses 8, 9 and 36 of Article 3 and Chapter IV of Circular No. 25/2016/TT-BCT dated November 30, 2016 of the Minister of Industry and Trade on electricity transmission system.

2. Annulling Chapter IV and Article 101 of Circular No. 39/2015/TT-BCT dated November 18, 2015 of the Minister of Industry and Trade on electricity distribution system.

Article 4. Effect

1. This Circular takes effect from January 3, 2020.

2. In the course of implementation, if any problem arises, relevant units shall report them to the Electricity Regulatory Authority for consideration and settlement according to its competence or for submission to the Ministry of Industry and Trade for settlement./.