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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 1 总 则 1.0.1 为使电力工程的并联电容器装置设计中,贯彻国家的技术经济政策。做到安全可靠、技术先进、经济合理和运行检修方便,制定本规范。 1.0.2 本规范适用于1000kV及以下电压等级的变电站、配电站(室)中无功补偿用三相交流高压、低压并联电容器装置的新建、扩建工程设计。 1.0.3 并联电容器装置的设计,应根据安装地点的电网条件、补偿要求、环境状况、运行检修要求和实践经验,确定补偿容量、接线方式、配套设备、保护与控制方式、布置及安装方式。 1.0.4 并联电容器装置的设备选型,应符合国家现行标准的有关规定。 1.0.5 并联电容器装置的设计,除应执行本规范外,尚应符合国家现行有关标准的规定。 2术语、符号和代号 2.1 术 语 2.1.1 电容器元件 capacitor element 由电介质和电极所构成的电容器的最小单元部件。 2.1.2 单台电容器 capacitor unit 由电容器元件组装于单个外壳中并有引出端子的组装体。 2.1.3 电容器 capacitor 本规程中,“电容器”一词是当不需要特别强调“电容器单元”或“电容器组”的不同含义时的用语。 2.1.4集合式电容器 assembling capacitor 将电容器集装于一个箱体中的组装体。 2.1.5 自愈式电容器 self-healing capacitor 具有自愈性能的电容器。 2.1.6 电容器组 capacitor bank 电气上连接在一起的多台电容器。 2.1.7 高压并联电容器装置 installation of high voltage shunt capacitors 由电容器和相应的电气一次及二次配套设备组成,并联连接于标称电压1 kV以上的交流三相电力系统中,能完成独立投运的一套设备。 2.1.8 一体化集合式电容器装置 installation of integrated style assembling capacitor 将电抗器、放电线圈、集合式电容器在箱体内完成相互之间的电气连接并集装成一个整体的设备。 2.1.9 低压并联电容器装置low-voltage shunt capacitor installation 由低压电容器和相应的电气一次及二次配套元件组成,并联连接于标称电压1 kV及以下的交流三相配电网中,能完成独立投运的一套设备。 2.1.10 电抗率 reactance ratio 并联电容器装置的串联电抗器的额定感抗与串联连接的电容器的额定容抗之比,以百分数表示。 2.1.11 放电器件discharge device 安装在电容器内部或外部,当电容器从电源脱开后能将电容器的剩余电压在规定时间内降低到规定值以下的设备或元件。 2.1.12 串联段 series section 在多台电容器连接组合中,相互并联的单台电容器群。 2.1.13剩余电压 residual voltage 电容器脱开电源一定时间后,电容器端子间残存的电压。 2.1.14 涌流 inrush transient current 电容器组投入电网时的过渡过电流。 2.1.15 负荷开关load-breaking switch 能够在正常的导电回路条件或规定的过载条件下关合、承载和开断电流,也能在异常的导电回路条件(例如短路)下按规定的时间承载电流的开关设备。按照需要,也可具有关合短路电流能力。 2.1.16外熔断器 external fuses 装于单台电容器外部并与其串联连接,当电容器发生故障时用以切除该电容器的熔断器。 2.1.17 内熔丝 internal fuses 装于单台电容器内部与元件串联连接,当元件发生故障时用以切除该元件的熔丝。 2.1.18 耐爆能量 bursting energy 电容器内部发生极间或极对壳击穿时,外部并联电容器对故障电容器放电引起故障电容器外壳或套管破裂的最小能量。 2.1.19 放电线圈最大配套电容器容量 maximum reactive power of capacitor co-ordination for a discharge coil 能满足在规定时间内将电容器的剩余电压降至规定值以下,与放电线圈并联的电容器组容量上限值。 2.1.20不平衡保护 unbalance protection 利用对电容器(组)内特定部分之间的电流差或电压差组成的保护。 2.1.21环境空气温度 ambient air temperature 电容器安装地点的空气温度(气象温度)。 2.1.22冷却空气温度 cooling air temperature 在稳定状态下,电容器组的最热区域中,两台电容器外壳最热点连线中点的空气温度。仅为一台电容器时,则指距电容器外壳最热点0.1m,距底2/3高度处测得的温度。 2.2 符 号 I*yrm——涌流峰值的标么值; K——电抗率; n——谐波次数; Q——电容器容量; Qcx——发生n次谐波谐振的电容器容量; S——电容器组每相的串联段数; Sd——并联电容器装置安装处的母线短路容量; Uc——电容器端子运行电压; Us——并联电容器装置的母线运行电压; β——涌流计算式中计及电源影响的系数。 2.3 代 号 C——电容器; 1C、2C、3C——并联电容器装置分组回路编号; C1、C2、Cn——单台电容器编号; FU——熔断器; FV——避雷器; HL——指示灯; ΔI——桥差电流; I0——中性点不平衡电流; FR——热继电器; KM——交流接触器; L——串联电抗器或限流线圈; QF——断路器; QL——负荷开关; QG——接地开关; QS——隔离开关或刀开关; TA——电流互感器; TV——放电线圈; ΔU——相不平衡电压; U0——开口三角电压。 3 接入电网基本要求 3.0.1 并联电容器装置接入电网的设计,应按全面规划、合理布局、分层分区补偿、就地平衡的原则确定最优补偿容量和分布方式。 3.0.2 变电站的电容器安装容量,应根据本地区电网无功规划和国家现行标准中有关规定经计算后确定,也可根据有关规定按变压器容量进行估算。用户的并联电容器安装容量,应满足就地平衡的要求。 3.0.3 并联电容器分组容量的确定应符合下列规定: 1 在电容器分组投切时,应满足系统无功功率和电压调控要求。 2 当分组电容器按各种容量组合运行时,应避开谐振容量,不得发生谐波的严重放大和谐振,电容器支路的接入所引起的各侧母线的任何一次谐波量均不应超过现行国家标准《电能质量公用电网谐波》GB/T 14549的有关规定。 3 发生谐振的电容器容量,可按下式计算: (3.0.3) 式中:Qcx——发生n次谐波谐振的电容器容量(MV·A); Sd——并联电容器装置安装处的母线短路容量(MV·A); n——谐波次数,即谐波频率与电网基波频率之比; K——电抗率。 3.0.4 并联电容器装置宜装设在变压器的主要负荷侧。当不具备条件时,可装设在三绕组变压器的低压侧。 3.0.5 当配电站中无高压负荷时,不宜在高压侧装设并联电容器装置。 3.0.6 低压并联电容器装置的安装地点和装设容量,应根据分散补偿和就地平衡的原则设置,并不得向电网倒送无功。 4 电气接线 4.1接线方式 4.1.1 并联电容器装置的各分组回路可采用直接接入母线,并经总回路接入变压器的接线方式(图4.1.1—1和图4.1.1—2)。当同级电压母线上有供电线路,经技术经济比较合理时,也可采用设置电容器专用母线的接线方式(图4.1.1—3)。 4.1.2 并联电容器组的接线方式应符合下列规定: 1 并联电容器组应采用星形接线。在中性点非直接接地的电网中,星形接线电容器组的中性点不应接地。 2 并联电容器组的每相或每个桥臂,由多台电容器串并联组合连接时,宜采用先并联后串联的连接方式。 3 电容器并联总容量不应超过3900kvar。 至主变压器 图4.1.1-1 同级电压母线上无供电线路时的接线方式 至主变压器 出线 图4.1.1—2 同级电压母线上有供电线路时的接线方式 至主变压器 出线 图4.1.1-3 设置电容器专用母线的接线方式 注:a——电容器专用母线。 4.1.3 低压并联电容器装置可与低压供电柜同接一条母线。低压电容器或电容器组,可采用三角形接线或星形接线方式。 4.2配套设备及其连接 4.2.1 并联电容器装置应装设下列配套设备(图4.2.1): 1 隔离开关、断路器或负荷开关; 2 串联电抗器(含阻尼式限流器); 3 操作过电压保护用避雷器; 4 接地开关; 5 放电器件; 6 继电保护、控制、信号和电测量用一次及二次设备; 7 单台电容器保护用外熔断器,应根据保护需要和单台电容器容量配置。 4.2.2 并联电容器装置分组回路投切开关应装设于电容器组的电源侧。 开关型式应根据具体工程通过经济技术性比较后确定。 图4.2.1 并联电容器组与配套设备连接方式 4.2.3 并联电容器装置的串联电抗器宜装设于电容器的电源侧,并应校验其耐受短路电流的能力。当铁心电抗器的耐受短路电流的能力不能满足装设于电源侧要求时,应装设于中性点侧。 4.2.4 电容器配置外熔断器时,每台电容器应配置一个专用熔断器。 4.2.5 电容器的外壳直接接地时,外熔断器应串接在电容器的电源侧。电容器装设于绝缘框(台)架上且串联段数为2段及以上时,应至少有一个串联段的外熔断器串接于电容器的电源侧。 4.2.6 并联电容器装置的放电线圈接线应符合下列规定: 1 放电线圈与电容器宜采用直接并联接线; 2 放电线圈一次绕组中性点不应接地。 4.2.7 并联电容器装置宜在其电源侧和中性点侧设置检修接地开关;当中性点侧装设接地开关有困难时,可采用其他检修接地措施。 4.2.8 并联电容器装置应装设抑制操作过电压的避雷器,避雷器连接方式应符合下列规定: 1 避雷器连接应采用相对地方式(图4.2.8); 图4.2.8 相对地避雷器接线 2 避雷器接入位置应紧靠电容器组的电源侧; 3 不得采用三台避雷器星形连接后经第四台避雷器接地的接线方式。 4.2.9 低压并联电容器装置宜装设下列配套元件(图4.2.9),当采用的电容器投切器件具有限制涌流功能和电容器柜有谐波超值保护时,可不装设限流线圈和过载保护器件: 1 总回路刀开关和分回路投切器件; 2 操作过电压保护用避雷器; 3 短路保护用熔断器; 4 过载保护器件; 5 限流线圈; 6 放电器件; 7 谐波含量超限保护、自动投切控制器、保护元件、信号和测量表计等配套器件。 4.2.10 低压电容器装设的外部放电器件,可采用三角形接线或星形接线,并应直接与电容器(组)并联连接。 图4.2.9 低压并联电容器装置元件配置典型接线 5 电器和导体选择 5.1一般规定 5.1.1 并联电容器装置的设备选型,应根据下列条件确定: 1 电网电压、电容器运行工况; 2 电网谐波水平; 3 母线短路电流; 4 电容器对短路电流的助增效应; 5 补偿容量和扩建规划、接线、保护及电容器组投切方式; 6 海拔高度、气温、湿度、污秽和地震烈度等环境条件; 7 布置与安装方式; 8 产品技术条件和产品标准。 5.1.2 并联电容器装置的电器和导体选择,应满足在当地环境条件下正常运行、过电压状态和短路故障的要求。 5.1.3 并联电容器装置总回路和分组回路的电器导体选择时,回路工作电流应按稳态过电流最大值确定。 5.1.4 并联电容器装置的电气设备绝缘水平,不应低于变电站、配电站(室)中同级电压的其他电气设备。 5.1.5 制造厂生产的并联电容器成套装置,其组合结构应便于运输、现场安装、运行检修和试验,并应使组装后的整体技术性能满足使用要求。 5.2 电 容 器 5.2.1 电容器选型应符合下列规定: 1 组成并联电容器装置的电容器,可选用单台电容器、集合式电容器。单组容量较大时,宜选用单台容量为500kV·A及以上的电容器。 2 在占地面积受限、高地震烈度、强台风地区宜选用一体化集合式电容器装置。 3 电容器的温度类别应根据安装地点的环境空气温度或屋内冷却空气温度选择。 4 安装在严寒、高海拔、湿热带等地区和污秽、易燃、易爆等环境中的电容器,应满足环境条件的特殊要求。 5.2.2 电容器额定电压选择,应符合下列要求: 1 宜按电容器接入电网处的运行电压进行计算。 2 应计入串联电抗器引起的电容器运行电压升高。接入串联电抗器后,电容器运行电压应按下式计算: (5.2.2) 式中:Uc——电容器的端子运行电压(kV); Us——并联电容器装置的母线运行电压(kV); S——电容器组每相的串联段数; K——电抗率。 5.2.3 电容器的绝缘水平应按电容器接入电网处的电压等级,电容器组接线方式确定的串并联组合、安装方式,环境条件要求等,根据电容器产品标准选取。不同电压等级并联电容器装置绝缘水平应符合表5.2.3规定的数值。 表5.2.3 不同电压等级并联电容器装置绝缘水平①(kV) 系统标称电压 一次电路 二次电路 工频耐受电压 (方均根值) 雷电冲击耐受电压 (峰值) 工频耐受电压 (方均根值) 10 42 75 3 20 55 125 3 35 95 185 3 续表5.2.3 系统标称电压 一次电路 二次电路 工频耐受电压 (方均根值) 雷电冲击耐受电压 (峰值) 工频耐受电压 (方均根值) 66 140 325 3 110 200 275② 450 650② 3 注:①表中所示绝缘水平仅适用于海拔1000m及以下地区,对于海拔超过1000m地区,绝缘水平应进行海拔修正;低电压等级电容器绝缘水平可参考现行国家标准《低压系统内设备的绝缘配合》GB/T 16935的相关规定。 ②适用于1000kV变电站内110kV电压等级并联电容器。 5.2.4 单台电容器额定容量选择,应根据电容器组容量和每相电容器的串联段数和并联台数确定,并宜在电容器产品额定容量系列的优先值中选取。 5.2.5 低压并联电容器装置应根据环境条件和使用技术要求选择。 5.3 投切开关 5.3.1 用于并联电容器装置的断路器选型,应采用真空断路器或SF6断路器等适合于电容器组投切的设备。对于10kV及以下并联电容器装置,宜选用真空断路器或真空接触器;对于35 kV及以上并联电容器装置,宜选用SF6断路器或负荷开关。所选用断路器/负荷开关技术性能除应符合断路器/负荷开关共用技术要求外,尚应满足下列特殊要求: 1 应具备频繁操作的性能; 2 合、分时触头弹跳不应大于限定值; 3 投切开关开合容性电流能力应满足现行国家标准《高压交流断路器》GB/T 1984中C2级断路器要求; 4 应能承受电容器组的关合涌流和工频短路电流,以及电容器高频涌流的联合作用。 5.3.2 并联电容器装置总回路中的断路器,应具有切除所连接的全部电容器组和开断总回路短路电流的能力。分组回路可采用不承担开断短路电流的开关设备。 5.3.3低压并联电容器装置中的投切开关切除电容器时,不应发生重击穿;投切开关应具有可以频繁操作的性能。宜采用具有选相功能和功耗较小的开关器件。当采用普通开关时,其接通、分断能力和短路强度等技术性能,应符合设备装设点的电网条件。 5.4 熔 断 器 5.4.1 用于单台电容器保护的外熔断器选型时,应采用电容器专用熔断器。 5.4.2 用于单台电容器保护的外熔断器的熔丝额定电流,可按电容器额定电流的1.37倍~1.50倍选择。 5.4.3 用于单台电容器保护的外熔断器的额定电压、耐受电压、开断性能、熔断性能、耐爆能量、抗涌流能力、机械强度和电气寿命等,应符合国家现行有关标准的规定。 5.5 串联电抗器 5.5.1 串联电抗器选型时,应根据工程条件经技术经济比较确定选用干式电抗器或油浸式电抗器。安装在屋内的串联电抗器,宜采用设备外漏磁场较弱的干式铁心电抗器或类似产品。 5.5.2 串联电抗器电抗率选择,应根据电网条件与电容器参数经相关计算分析确定,电抗率取值范围应符合下列规定: 1 仅用于限制涌流时,电抗率宜取0.1%~1%; 2 用于抑制谐波时,电抗率应根据并联电容器装置接入电网处的背景谐波含量的测量值选择。当谐波为5次及以上时,电抗率宜取5%;当谐波为3次及以上时,电抗率宜取12%,亦可采用5%与12%两种电抗率混装方式。 5.5.3 并联电容器装置的合闸涌流限值,宜取电容器组额定电流的20倍;当超过时,应采用装设串联电抗器予以限制。电容器组投入电网时的涌流计算,应符合本规范附录A的规定。 5.5.4 串联电抗器的额定电压和绝缘水平,应符合接入处的电网电压要求。 5.5.5 串联电抗器的额定电流应等于所连接的并联电容器组的额定电流,其允许过电流不应小于并联电容器组的最大过电流值。 5.5.6 并联电容器装置总回路装设有限流电抗器时,应计入其对电容器分组回路电抗率和母线电压的影响。 5.6放电线圈 5.6.1 放电线圈选型时,应采用电容器组专用的油浸式或干式放电线圈产品。油浸式放电线圈应为全密封结构,产品内部压力应满足使用环境温度变化的要求,在最低环境温度下不得出现负压。 5.6.2 放电线圈的额定一次电压应与所并联的电容器组的额定电压一致。 5.6.3 放电线圈的额定绝缘水平应符合下列要求: 1 安装在地面上的放电线圈,额定绝缘水平不应低于同电压等级电气设备的额定绝缘水平; 2 安装在绝缘框(台)架上的放电线圈,其额定绝缘水平应与安装在同一绝缘框(台)上的电容器的额定绝缘水平一致。 5.6.4 放电线圈的最大配套电容器容量(放电容量),不应小于与其并联的电容器组容量;放电线圈的放电性能应能满足电容器组脱开电源后,在5 s内将电容器组的剩余电压降至50 V及以下。 5.6.5 放电线圈带有二次线圈时,其额定输出、准确级,应满足保护和测量的要求。 5.6.6 低压并联电容器装置的放电器件应满足电容器断电后,在3min内将电容器的剩余电压降至50V及以下;当电容器再次投入时,电容器端子上的剩余电压不应超过额定电压的0.1倍。 5.6.7 同一装置中的放电线圈的励磁特性应一致。 5.7 避 雷 器 5.7.1 用于并联电容器装置操作过电压保护的避雷器,应采用无间隙金属氧化物避雷器。 5.7.2 用于并联电容器操作过电压保护的避雷器的参数选择,应根据电容器组参数和避雷器接线方式确定。 5.8导体及其他 5.8.1 单台电容器至母线或熔断器的连接线应采用软导线,其长期允许电流不宜小于单台电容器额定电流的1.5倍。 5.8.2 并联电容器装置的分组回路,回路导体截面应按并联电容器组额定电流的1.3倍选择,并联电容器组的汇流母线和均压线导线截面应与分组回路的导体截面相同。 5.8.3 双星形接线电容器组的中性点连接线和桥形接线电容器组的桥连接线,其长期允许电流不应小于电容器组的额定电流。 5.8.4 并联电容器装置的所有连接导体应满足长期允许电流的要求,并应满足动稳定和热稳定要求。 5.8.5 用于并联电容器装置的支柱绝缘子,应按电压等级、泄漏距离、空气净距、机械荷载等技术条件,以及运行中可能承受的最高电压选择和校验。 5.8.6 用于并联电容器组不平衡保护的电流互感器,应符合下列要求: 1 额定电压应按接入处的电网电压选择; 2 额定电流不应小于最大稳态不平衡电流; 3 电流互感器应能耐受电容器极间短路故障状态下的短路电流和高频涌放电流。不得损坏; 4 准确级应满足继电保护要求。 6 保护装置和投切装置 6.1 保护装置 6.1.1 单台电容器内部故障保护方式(内熔丝、外熔断器和继电保护),应在满足并联电容器组安全运行的条件下,根据各地的实践经验配置。 6.1.2 高压并联电容器组(内熔丝、外熔断器和无熔丝)均应设置不平衡保护。不平衡保护应满足可靠性和灵敏度要求,保护方式可根据电容器组接线在下列方式中选取: 1 单星形电容器组,可采用开口三角电压保护(图6.1.2-1)。 |
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