Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This code is formulated on revision of GB 50227-2008 Code for Design of Installation of Shunt Capacitors by Southwest Electric Power Design Institute of China Power Engineering Consulting Group jointly with the organizations concerned according to the requirements of Notice on Printing "Formulation and Revision Plan for Engineering Construction Standards and Codes in 2014" (JIANBIAO [2013] No.169) of Ministry of Housing and Urban-Rural Development of the People's Republic of China,
Main technical contents revised in this code include:
1. Application scope of this code is expended from 750kV or below substation to 1000kV or below substation;
2. Glossaries such as "residual voltage" and "bursting energy" are modified and "load-breaking switch" is added;
3. Wiring diagram for installation of shunt capacitors is modified;
4. Wiring diagram for element configuration of low-voltage shunt capacitor installation is modified;
5. Technical specifications for integral insulation level of installation of shunt capacitors are added;
6. Technical requirements for switch of 110kV installation of shunt capacitors are added and suggestions for type selection of switch of installation of shunt capacitors with different voltage classes are provided;
7. The recommended evaluation for reactance ratio of series reactor is modified;
8. Requirements of "excitation characteristics of discharge coils in the same device shall be consistent" are added;
9. The requirements of "for polluted, flammable, explosive and other special areas, arrangement form shall be selected according to GB 50058 Code for Design of Electrical Installations in Explosive Atmospheres" are added;
10. The requirements for number of layers and rows of capacitor frame are deleted;
11. "It is strictly forbidden to directly connect or support the rigid busbar with capacitor sleeve" is revised as "capacitor sleeve shall not be directly used to connect or support the rigid busbar", and the mandatory requirements are cancelled;
12. That the fire-proofing of capacitor installation shall meet the relevant requirements of GB 50229 Code for Design of Fire Protection for Fossil Fuel Power Plants and Substations is added;
13. The requirements for permissible maximum ambient temperature of capacitor are added.
This code consists of 9 Chapters and 1 Annex, with the main contents as follows: General Provisions, Terms, Symbols and Codes, Basic Requirements for Connection into Grid, Electrical Wiring, Selection of Electrical Apparatus and Conductors, Protection Device and Switching Device, Control Circuits, Signal Circuits and Measuring Instruments, Arrangement and Installation Design, Fire Prevention and Ventilation etc.
The provisions printed in bold type in this code are mandatory ones and must be enforced strictly.
Ministry of Housing and Urban-Rural Development is in charge of the administration of this code and the explanation of the mandatory provisions, China Electricity Council is responsible for the routine management and Southwest Electric Power Design Institute of China Power Engineering Consulting Group is responsible for the explanation of specific technical contents. All relevant organizations are kindly requested to sum up experiences and accumulate information according to engineering practices during the process of implementing this code. In case of discovering any provision requiring being modified and supplemented, please feed back the opinions and suggestions to Southwest Electric Power Design Institute of China Power Engineering Consulting Group (address: No.18 Dongfeng road, Chengdu, Sichuan, postal code: 610021) for future reference in revision.
Contents
Foreword i
1 General Provisions 1
2 Terms, Symbols and Codes 1
2.1 Terms 1
2.2 Symbols 3
2.3 Codes 4
3 Basic Requirements for Connection into Grid 5
4 Electrical Wiring 6
4.1 Wiring Mode 6
4.2 Associated Equipment and its Connection 8
5 Selection of Electrical Apparatus and Conductors 12
5.1 General Requirements 12
5.2 Capacitor 13
5.3 Switch 14
5.4 Fuse 15
5.5 Series Reactor 15
5.6 Discharge Coil 16
5.7 Lightning Arrester 17
5.8 Conductor and Others 17
6 Protection Device and Switching Device 18
6.1 Protection Device 18
6.2 Switching Device 21
7 Control Circuits, Signal Circuits and Measuring Instruments 22
7.1 Control Circuits and Signal Circuits 22
7.2 Measuring Instruments 22
8 Arrangement and Installation Design 23
8.1 General Requirements 23
8.2 Arrangement and Installation Design for Shunt Capacitor Banks 25
8.3 Arrangement and Installation Design of Series Reactor 26
9 Fire Prevention and Ventilation 27
9.1 Fire Prevention 27
9.2 Ventilation 29
Annex A Calculation of Inrush Transient Current When Connecting Capacitor Banks to the Grid 30
Explanation of Wording in this Code 32
List of Quoted Standards 33
Code for Design of Installation of Shunt Capacitors
1 General Provisions
1.0.1 This code is formulated with view to implementing national technical and economic policy in the design of installation of shunt capacitors in electrical engineering, achieving safety, reliability, advanced technology, economic rationality and convenient operation and maintenance.
1.0.2 This code is applicable to the design for newly-built and extended engineering of installation of three-phase AC high/low voltage shunt capacitors for reactive compensation in substation and power distribution station (room) with voltage class of 1000kV or below.
1.0.3 For the design of installation of shunt capacitors, the compensation capacity, wiring mode, associated equipment, protection and control mode, arrangement and installation mode shall be determined according to the grid condition, compensation requirements, environmental conditions, operation and overhaul requirements and practical experience in installation site.
1.0.4 Equipment type selection of installation of shunt capacitors shall meet the relevant requirements of current national standard.
1.0.5 The design of installation of shunt capacitors shall not only meet the requirements of this code, but also comply with those specified in the current national standards.
2 Terms, Symbols and Codes
2.1 Terms
2.1.1 capacitor element
the minimum component unit of capacitor composed of dielectric medium and electric pole
2.1.2 capacitor unit
an assembly made by assembling capacitor element into an individual case and provided with leading-out terminal
2.1.3 capacitor
in this code, the word "capacitor" is used where it is unnecessary to lay special emphasis on different meanings of "capacitor unit" or "capacitor bank"
2.1.4 assembling capacitor
an assembly made by assembling capacitors into a box
2.1.5 self-healing capacitor
capacitor with self-healing performance
2.1.6 capacitor bank
multiple capacitors connected together electrically
2.1.7 installation of high voltage shunt capacitors
a set of equipment that is composed of capacitor and corresponding primary and secondary electrical associated equipment, connected in parallel to three-phase AC power system with nominal voltage above 1kV and can complete independent commissioning
2.1.8 installation of integrated style assembling capacitor
equipment integrated through electrical connection of reactor, discharge coil and assembling capacitor in box
2.1.9 low-voltage shunt capacitor installation
a set of equipment that is composed of low-voltage capacitor and corresponding primary and secondary electrical auxiliary elements, connected in parallel to three-phase AC power system with nominal voltage of 1kV or below and can complete independent commissioning
2.1.10 reactance ratio
the ratio of rated inductive reactance of series reactor to rated capacitive reactance of series capacitors in installation of shunt capacitors, expressed in %
2.1.11 discharge device
equipment or element that is installed inside or outside the capacitor and can drop the residual voltage of capacitor below specified value within specified time after the capacitor disengages from the power supply
2.1.12 series section
a group of shunt capacitor units in multiple capacitors connection combination
2.1.13 residual voltage
residual voltage between capacitor terminals after capacitor disengages from power supply for some time
2.1.14 inrush transient current
transitional overcurrent in case of connecting capacitor bank to grid
2.1.15 load-breaking switch
switchgear that can close, carry and break current under normal conduction circuit conditions or specified overload conditions and also can carry current as specified time under abnormal conduction circuit conditions (e.g. short circuit); it may also be provided with the capability of closing short-circuit currents as required
2.1.16 external fuses
fuse installed outside the capacitor unit and connected with the capacitor in series, that is used for cutting off this capacitor when this capacitor is in fault
2.1.17 internal fuses
fuse installed inside the capacitor unit and connected with element in series, that is used for cutting off this element when this element is in fault
2.1.18 bursting energy
minimum energy that causes fault capacitor case or sleeve to burst due to external shunt capacitor discharging to fault capacitor when the interpolar or pole-to-case breakdown occurs inside the capacitor
2.1.19 maximum reactive power of capacitor co-ordination for a discharge coil
the upper limit of capacity of capacitor bank that is connected in parallel with discharge coil and can drop the residual voltage of capacitor below specified value within specified time
2.1.20 unbalance protection
protection by use of the current or voltage difference between particular parts of capacitor (capacitor bank)
2.1.21 ambient air temperature
the air temperature (meteorological temperature) in installation site of capacitor
2.1.22 cooling air temperature
the air temperature at midpoint of connecting line between hottest points on the cases of two sets of capacitors in the hottest area of capacitor bank under stable state; if there is only one set of capacitor, it refers to the temperature measured at the place 0.1m away from the hottest point on capacitor case and 2/3 height away from the bottom
2.2 Symbols
I*yrm——the per-unit value of inrush transient current peak;
K——the reactance ratio;
n——the harmonic order;
Q——the capacity of capacitor;
Qcx——the capacity of capacitor generating n orders of harmonic resonance vibrations;
S——the number of series section in each phase of capacitor bank;
Sd——the busbar short circuit capacity at installation site of installation of shunt capacitors;
Uc——the terminal operating voltage of capacitor;
Us——the busbar operating voltage of installation of shunt capacitors;
β——the influence coefficient of power supply in calculation formula of inrush transient current.
2.3 Codes
C——the capacitor;
1C, 2C and 3C——the sub-bank circuit No. of installation of shunt capacitors;
C1, C2 and Cn——the No. of capacitor unit;
FU——the fuse;
FV——the lightning arrester;
HL——the indicator light;
ΔI——the bridge differential current;
I0——the unbalanced current at neutral point;
FR——the thermal relay;
KM——the AC contactor;
L——the series reactor or current-limiting coil;
QF——the circuit breaker;
QL——the load-breaking switch;
QG——the grounding switch;
QS——the disconnecting switch or knife switch;
TA——the current transformer;
TV——the discharge coil;
ΔU——the phase unbalanced voltage;
U0——the open-delta voltage;
3 Basic Requirements for Connection into Grid
3.0.1 For the design of installation of shunt capacitors connection into grid, the optimum compensation capacity and distribution mode shall be determined in the principle of overall planning, rational layout, compensation in layers and zones and local balance.
3.0.2 The installed capacity of capacitor of substation shall be determined through calculation according to the grid reactive planning in the local region and the relevant requirements in current national standard, it may also be estimated based on transformer capacity according to the relevant requirements. The installed capacity of the user's shunt capacitor shall meet the requirements of local balance.
3.0.3 The determination for sub-bank capacity of shunt capacitor shall meet the following requirements:
1 When the capacitors are switched in sub-banks, they shall meet the requirements of system reactive power and voltage regulation and control.
2 When the capacitor sub-bank operate according to the combination of various capacities, they shall be kept away from resonance vibration capacity, and severe amplification and resonance vibration of harmonic shall be avoided; any harmonic content of busbar on each side caused by connecting into branch circuit of capacitor shall not exceed the relevant requirements in current national standard GB/T 14549 Quality of Electric Energy Supply - Harmonics in Public Supply Network.
3 The capacity of capacitor generating resonance vibration may be calculated according to following formula:
(3.0.3)
Where,
Qcx——the capacity of capacitor generating n orders of harmonic resonance vibration, MV·A;
Sd——the capacity of busbar short circuit in installation site of installation of shunt capacitors, MV·A;
n——the harmonic order, namely the ratio of harmonic frequency to the fundamental frequency of grid;
K——the reactance ratio.
3.0.4 Installation of shunt capacitors should be installed at the main load side of transformer. Where impossible, it may be installed at the low-voltage side of three-winding transformer.
3.0.5 Where there is no high-voltage load in power distribution station, installation of shunt capacitors should not be installed at high-voltage side.
3.0.6 The installation site and installed capacity of low-voltage shunt capacitor installation shall be set in the principle of dispersion compensation and local balance and shall not reversely transmit reactive power to the grid.
4 Electrical Wiring
4.1 Wiring Mode
4.1.1 Each sub-bank circuit of installation of shunt capacitors may be directly connected to busbar and then connected to transformer through main circuit (Figures 4.1.1-1 and 4.1.1-2). Where there is power supply line on the same-level voltage busbar and it's reasonable through technical and economical comparison, wiring mode of setting special busbar of capacitor may also be adopted (Figure 4.1.1-3).
4.1.2 Wiring mode of shunt capacitor banks shall meet the following requirements:
1 Star wiring shall be adopted for shunt capacitor banks. In grid with neutral point not directly grounded, the neutral point of capacitor bank in star wiring shall not be grounded.
2 Where each phase or each bridge arm of shunt capacitor banks is connected through series and shunt of multiple capacitors, connection mode of "shunt before series" should be adopted.
3 The total capacity of shunt capacitors shall not exceed 3900kvar.
Figure 4.1.1-1 Wiring Mode in Which There is No Power Supply Line on the Same-level Voltage Busbar
Figure 4.1.1-2 Wiring Mode in Which There is Power Supply Line on the Same-level Voltage Busbar
Figure 4.1.1-3 Wiring Mode with Special Busbar of Capacitor Arranged
Note: a——special busbar of capacitor.
4.1.3 Low-voltage shunt capacitor installation and low-voltage power supply cabinet may be connected to the same busbar. For low-voltage capacitor or capacitor bank, delta or star wiring mode may be adopted.
4.2 Associated Equipment and its Connection
4.2.1 Installation of shunt capacitors shall be equipped with the following associated equipment (Figure 4.2.1):
1 Disconnecting switch, circuit breaker or load-breaking switch;
2 Series reactor (including damping current limiter);
3 Lightning arrester for switching overvoltage protection;
4 Grounding switch;
5 Discharge device;
6 Primary and secondary equipment for relay protection, control, signal and electrical measurement;
7 External fuses for capacitor unit protection, which shall be arranged according to protection requirements and capacitor unit capacity.
4.2.2 For installation of shunt capacitors, switching switch of its sub-bank circuit shall be arranged on power supply side of capacitor bank.
Switch type shall be determined after economic and technical comparison according to specific project.
Foreword i
1 General Provisions
2 Terms, Symbols and Codes
2.1 Terms
2.2 Symbols
2.3 Codes
3 Basic Requirements for Connection into Grid
4 Electrical Wiring
4.1 Wiring Mode
4.2 Associated Equipment and its Connection
5 Selection of Electrical Apparatus and Conductors
5.1 General Requirements
5.2 Capacitor
5.3 Switch
5.4 Fuse
5.5 Series Reactor
5.6 Discharge Coil
5.7 Lightning Arrester
5.8 Conductor and Others
6 Protection Device and Switching Device
6.1 Protection Device
6.2 Switching Device
7 Control Circuits, Signal Circuits and Measuring Instruments
7.1 Control Circuits and Signal Circuits
7.2 Measuring Instruments
8 Arrangement and Installation Design
8.1 General Requirements
8.2 Arrangement and Installation Design for Shunt Capacitor Banks
8.3 Arrangement and Installation Design of Series Reactor
9 Fire Prevention and Ventilation
9.1 Fire Prevention
9.2 Ventilation
Annex A Calculation of Inrush Transient Current When Connecting Capacitor Banks to the Grid
Explanation of Wording in this Code
List of Quoted Standards
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This code is formulated on revision of GB 50227-2008 Code for Design of Installation of Shunt Capacitors by Southwest Electric Power Design Institute of China Power Engineering Consulting Group jointly with the organizations concerned according to the requirements of Notice on Printing "Formulation and Revision Plan for Engineering Construction Standards and Codes in 2014" (JIANBIAO [2013] No.169) of Ministry of Housing and Urban-Rural Development of the People's Republic of China,
Main technical contents revised in this code include:
1. Application scope of this code is expended from 750kV or below substation to 1000kV or below substation;
2. Glossaries such as "residual voltage" and "bursting energy" are modified and "load-breaking switch" is added;
3. Wiring diagram for installation of shunt capacitors is modified;
4. Wiring diagram for element configuration of low-voltage shunt capacitor installation is modified;
5. Technical specifications for integral insulation level of installation of shunt capacitors are added;
6. Technical requirements for switch of 110kV installation of shunt capacitors are added and suggestions for type selection of switch of installation of shunt capacitors with different voltage classes are provided;
7. The recommended evaluation for reactance ratio of series reactor is modified;
8. Requirements of "excitation characteristics of discharge coils in the same device shall be consistent" are added;
9. The requirements of "for polluted, flammable, explosive and other special areas, arrangement form shall be selected according to GB 50058 Code for Design of Electrical Installations in Explosive Atmospheres" are added;
10. The requirements for number of layers and rows of capacitor frame are deleted;
11. "It is strictly forbidden to directly connect or support the rigid busbar with capacitor sleeve" is revised as "capacitor sleeve shall not be directly used to connect or support the rigid busbar", and the mandatory requirements are cancelled;
12. That the fire-proofing of capacitor installation shall meet the relevant requirements of GB 50229 Code for Design of Fire Protection for Fossil Fuel Power Plants and Substations is added;
13. The requirements for permissible maximum ambient temperature of capacitor are added.
This code consists of 9 Chapters and 1 Annex, with the main contents as follows: General Provisions, Terms, Symbols and Codes, Basic Requirements for Connection into Grid, Electrical Wiring, Selection of Electrical Apparatus and Conductors, Protection Device and Switching Device, Control Circuits, Signal Circuits and Measuring Instruments, Arrangement and Installation Design, Fire Prevention and Ventilation etc.
The provisions printed in bold type in this code are mandatory ones and must be enforced strictly.
Ministry of Housing and Urban-Rural Development is in charge of the administration of this code and the explanation of the mandatory provisions, China Electricity Council is responsible for the routine management and Southwest Electric Power Design Institute of China Power Engineering Consulting Group is responsible for the explanation of specific technical contents. All relevant organizations are kindly requested to sum up experiences and accumulate information according to engineering practices during the process of implementing this code. In case of discovering any provision requiring being modified and supplemented, please feed back the opinions and suggestions to Southwest Electric Power Design Institute of China Power Engineering Consulting Group (address: No.18 Dongfeng road, Chengdu, Sichuan, postal code: 610021) for future reference in revision.
Contents
Foreword i
1 General Provisions 1
2 Terms, Symbols and Codes 1
2.1 Terms 1
2.2 Symbols 3
2.3 Codes 4
3 Basic Requirements for Connection into Grid 5
4 Electrical Wiring 6
4.1 Wiring Mode 6
4.2 Associated Equipment and its Connection 8
5 Selection of Electrical Apparatus and Conductors 12
5.1 General Requirements 12
5.2 Capacitor 13
5.3 Switch 14
5.4 Fuse 15
5.5 Series Reactor 15
5.6 Discharge Coil 16
5.7 Lightning Arrester 17
5.8 Conductor and Others 17
6 Protection Device and Switching Device 18
6.1 Protection Device 18
6.2 Switching Device 21
7 Control Circuits, Signal Circuits and Measuring Instruments 22
7.1 Control Circuits and Signal Circuits 22
7.2 Measuring Instruments 22
8 Arrangement and Installation Design 23
8.1 General Requirements 23
8.2 Arrangement and Installation Design for Shunt Capacitor Banks 25
8.3 Arrangement and Installation Design of Series Reactor 26
9 Fire Prevention and Ventilation 27
9.1 Fire Prevention 27
9.2 Ventilation 29
Annex A Calculation of Inrush Transient Current When Connecting Capacitor Banks to the Grid 30
Explanation of Wording in this Code 32
List of Quoted Standards 33
Code for Design of Installation of Shunt Capacitors
1 General Provisions
1.0.1 This code is formulated with view to implementing national technical and economic policy in the design of installation of shunt capacitors in electrical engineering, achieving safety, reliability, advanced technology, economic rationality and convenient operation and maintenance.
1.0.2 This code is applicable to the design for newly-built and extended engineering of installation of three-phase AC high/low voltage shunt capacitors for reactive compensation in substation and power distribution station (room) with voltage class of 1000kV or below.
1.0.3 For the design of installation of shunt capacitors, the compensation capacity, wiring mode, associated equipment, protection and control mode, arrangement and installation mode shall be determined according to the grid condition, compensation requirements, environmental conditions, operation and overhaul requirements and practical experience in installation site.
1.0.4 Equipment type selection of installation of shunt capacitors shall meet the relevant requirements of current national standard.
1.0.5 The design of installation of shunt capacitors shall not only meet the requirements of this code, but also comply with those specified in the current national standards.
2 Terms, Symbols and Codes
2.1 Terms
2.1.1 capacitor element
the minimum component unit of capacitor composed of dielectric medium and electric pole
2.1.2 capacitor unit
an assembly made by assembling capacitor element into an individual case and provided with leading-out terminal
2.1.3 capacitor
in this code, the word "capacitor" is used where it is unnecessary to lay special emphasis on different meanings of "capacitor unit" or "capacitor bank"
2.1.4 assembling capacitor
an assembly made by assembling capacitors into a box
2.1.5 self-healing capacitor
capacitor with self-healing performance
2.1.6 capacitor bank
multiple capacitors connected together electrically
2.1.7 installation of high voltage shunt capacitors
a set of equipment that is composed of capacitor and corresponding primary and secondary electrical associated equipment, connected in parallel to three-phase AC power system with nominal voltage above 1kV and can complete independent commissioning
2.1.8 installation of integrated style assembling capacitor
equipment integrated through electrical connection of reactor, discharge coil and assembling capacitor in box
2.1.9 low-voltage shunt capacitor installation
a set of equipment that is composed of low-voltage capacitor and corresponding primary and secondary electrical auxiliary elements, connected in parallel to three-phase AC power system with nominal voltage of 1kV or below and can complete independent commissioning
2.1.10 reactance ratio
the ratio of rated inductive reactance of series reactor to rated capacitive reactance of series capacitors in installation of shunt capacitors, expressed in %
2.1.11 discharge device
equipment or element that is installed inside or outside the capacitor and can drop the residual voltage of capacitor below specified value within specified time after the capacitor disengages from the power supply
2.1.12 series section
a group of shunt capacitor units in multiple capacitors connection combination
2.1.13 residual voltage
residual voltage between capacitor terminals after capacitor disengages from power supply for some time
2.1.14 inrush transient current
transitional overcurrent in case of connecting capacitor bank to grid
2.1.15 load-breaking switch
switchgear that can close, carry and break current under normal conduction circuit conditions or specified overload conditions and also can carry current as specified time under abnormal conduction circuit conditions (e.g. short circuit); it may also be provided with the capability of closing short-circuit currents as required
2.1.16 external fuses
fuse installed outside the capacitor unit and connected with the capacitor in series, that is used for cutting off this capacitor when this capacitor is in fault
2.1.17 internal fuses
fuse installed inside the capacitor unit and connected with element in series, that is used for cutting off this element when this element is in fault
2.1.18 bursting energy
minimum energy that causes fault capacitor case or sleeve to burst due to external shunt capacitor discharging to fault capacitor when the interpolar or pole-to-case breakdown occurs inside the capacitor
2.1.19 maximum reactive power of capacitor co-ordination for a discharge coil
the upper limit of capacity of capacitor bank that is connected in parallel with discharge coil and can drop the residual voltage of capacitor below specified value within specified time
2.1.20 unbalance protection
protection by use of the current or voltage difference between particular parts of capacitor (capacitor bank)
2.1.21 ambient air temperature
the air temperature (meteorological temperature) in installation site of capacitor
2.1.22 cooling air temperature
the air temperature at midpoint of connecting line between hottest points on the cases of two sets of capacitors in the hottest area of capacitor bank under stable state; if there is only one set of capacitor, it refers to the temperature measured at the place 0.1m away from the hottest point on capacitor case and 2/3 height away from the bottom
2.2 Symbols
I*yrm——the per-unit value of inrush transient current peak;
K——the reactance ratio;
n——the harmonic order;
Q——the capacity of capacitor;
Qcx——the capacity of capacitor generating n orders of harmonic resonance vibrations;
S——the number of series section in each phase of capacitor bank;
Sd——the busbar short circuit capacity at installation site of installation of shunt capacitors;
Uc——the terminal operating voltage of capacitor;
Us——the busbar operating voltage of installation of shunt capacitors;
β——the influence coefficient of power supply in calculation formula of inrush transient current.
2.3 Codes
C——the capacitor;
1C, 2C and 3C——the sub-bank circuit No. of installation of shunt capacitors;
C1, C2 and Cn——the No. of capacitor unit;
FU——the fuse;
FV——the lightning arrester;
HL——the indicator light;
ΔI——the bridge differential current;
I0——the unbalanced current at neutral point;
FR——the thermal relay;
KM——the AC contactor;
L——the series reactor or current-limiting coil;
QF——the circuit breaker;
QL——the load-breaking switch;
QG——the grounding switch;
QS——the disconnecting switch or knife switch;
TA——the current transformer;
TV——the discharge coil;
ΔU——the phase unbalanced voltage;
U0——the open-delta voltage;
3 Basic Requirements for Connection into Grid
3.0.1 For the design of installation of shunt capacitors connection into grid, the optimum compensation capacity and distribution mode shall be determined in the principle of overall planning, rational layout, compensation in layers and zones and local balance.
3.0.2 The installed capacity of capacitor of substation shall be determined through calculation according to the grid reactive planning in the local region and the relevant requirements in current national standard, it may also be estimated based on transformer capacity according to the relevant requirements. The installed capacity of the user's shunt capacitor shall meet the requirements of local balance.
3.0.3 The determination for sub-bank capacity of shunt capacitor shall meet the following requirements:
1 When the capacitors are switched in sub-banks, they shall meet the requirements of system reactive power and voltage regulation and control.
2 When the capacitor sub-bank operate according to the combination of various capacities, they shall be kept away from resonance vibration capacity, and severe amplification and resonance vibration of harmonic shall be avoided; any harmonic content of busbar on each side caused by connecting into branch circuit of capacitor shall not exceed the relevant requirements in current national standard GB/T 14549 Quality of Electric Energy Supply - Harmonics in Public Supply Network.
3 The capacity of capacitor generating resonance vibration may be calculated according to following formula:
(3.0.3)
Where,
Qcx——the capacity of capacitor generating n orders of harmonic resonance vibration, MV·A;
Sd——the capacity of busbar short circuit in installation site of installation of shunt capacitors, MV·A;
n——the harmonic order, namely the ratio of harmonic frequency to the fundamental frequency of grid;
K——the reactance ratio.
3.0.4 Installation of shunt capacitors should be installed at the main load side of transformer. Where impossible, it may be installed at the low-voltage side of three-winding transformer.
3.0.5 Where there is no high-voltage load in power distribution station, installation of shunt capacitors should not be installed at high-voltage side.
3.0.6 The installation site and installed capacity of low-voltage shunt capacitor installation shall be set in the principle of dispersion compensation and local balance and shall not reversely transmit reactive power to the grid.
4 Electrical Wiring
4.1 Wiring Mode
4.1.1 Each sub-bank circuit of installation of shunt capacitors may be directly connected to busbar and then connected to transformer through main circuit (Figures 4.1.1-1 and 4.1.1-2). Where there is power supply line on the same-level voltage busbar and it's reasonable through technical and economical comparison, wiring mode of setting special busbar of capacitor may also be adopted (Figure 4.1.1-3).
4.1.2 Wiring mode of shunt capacitor banks shall meet the following requirements:
1 Star wiring shall be adopted for shunt capacitor banks. In grid with neutral point not directly grounded, the neutral point of capacitor bank in star wiring shall not be grounded.
2 Where each phase or each bridge arm of shunt capacitor banks is connected through series and shunt of multiple capacitors, connection mode of "shunt before series" should be adopted.
3 The total capacity of shunt capacitors shall not exceed 3900kvar.
Figure 4.1.1-1 Wiring Mode in Which There is No Power Supply Line on the Same-level Voltage Busbar
Figure 4.1.1-2 Wiring Mode in Which There is Power Supply Line on the Same-level Voltage Busbar
Figure 4.1.1-3 Wiring Mode with Special Busbar of Capacitor Arranged
Note: a——special busbar of capacitor.
4.1.3 Low-voltage shunt capacitor installation and low-voltage power supply cabinet may be connected to the same busbar. For low-voltage capacitor or capacitor bank, delta or star wiring mode may be adopted.
4.2 Associated Equipment and its Connection
4.2.1 Installation of shunt capacitors shall be equipped with the following associated equipment (Figure 4.2.1):
1 Disconnecting switch, circuit breaker or load-breaking switch;
2 Series reactor (including damping current limiter);
3 Lightning arrester for switching overvoltage protection;
4 Grounding switch;
5 Discharge device;
6 Primary and secondary equipment for relay protection, control, signal and electrical measurement;
7 External fuses for capacitor unit protection, which shall be arranged according to protection requirements and capacitor unit capacity.
4.2.2 For installation of shunt capacitors, switching switch of its sub-bank circuit shall be arranged on power supply side of capacitor bank.
Switch type shall be determined after economic and technical comparison according to specific project.
Contents of GB 50227-2017
Foreword i
1 General Provisions
2 Terms, Symbols and Codes
2.1 Terms
2.2 Symbols
2.3 Codes
3 Basic Requirements for Connection into Grid
4 Electrical Wiring
4.1 Wiring Mode
4.2 Associated Equipment and its Connection
5 Selection of Electrical Apparatus and Conductors
5.1 General Requirements
5.2 Capacitor
5.3 Switch
5.4 Fuse
5.5 Series Reactor
5.6 Discharge Coil
5.7 Lightning Arrester
5.8 Conductor and Others
6 Protection Device and Switching Device
6.1 Protection Device
6.2 Switching Device
7 Control Circuits, Signal Circuits and Measuring Instruments
7.1 Control Circuits and Signal Circuits
7.2 Measuring Instruments
8 Arrangement and Installation Design
8.1 General Requirements
8.2 Arrangement and Installation Design for Shunt Capacitor Banks
8.3 Arrangement and Installation Design of Series Reactor
9 Fire Prevention and Ventilation
9.1 Fire Prevention
9.2 Ventilation
Annex A Calculation of Inrush Transient Current When Connecting Capacitor Banks to the Grid
Explanation of Wording in this Code
List of Quoted Standards
