1.Grid-connected Cabinet Functional Modules and Core Components
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Function Module |
Core Function |
Core Component |
Component Function |
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Incoming Line & Power Distribution Module |
Receive AC power output by the inverter, realize power collection and distribution, and construct the main grid-connection circuit channel |
Incoming Line Circuit Breaker |
Incoming Line Circuit Breaker: Break the main circuit + overload / short-circuit protection |
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Isolating Switch |
Isolating Switch: Provide obvious break points for maintenance |
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Busbar / Copper Bar |
Busbar: Bear large current and collect multi-channel electric energy |
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Outgoing Terminal Block |
Outgoing Terminal Block: Standardize the connection between grid-connection cabinet and grid-side cables, reduce the risk of wiring faults, and facilitate later maintenance |
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Grid-connection Protection Module (Core Safety Unit) |
Ensure the two-way safety of power generation system and power grid, prevent equipment damage caused by grid faults / islanding effect / surges |
Anti-islanding Protection Device |
Anti-islanding Device: Core component, detect islanding effect and cut off the circuit |
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Overvoltage / Undervoltage / Overfrequency / Underfrequency Relay |
SPD: Suppress transient overvoltage and protect components |
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Surge Protective Device (SPD) |
Relay: Monitor grid parameters and trigger abnormal protection |
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Ground Fault Protection Device |
Ground Fault Protection Device: Real-time monitor ground fault current, quickly cut off the circuit in case of fault, and prevent personal or equipment accidents caused by electric leakage |
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Power Metering & Monitoring Module |
Accurately measure grid-connected electric energy, monitor the operating parameters of power grid / power generation system, and provide data for settlement / diagnosis |
Three-phase Multifunctional Electric Meter |
CT/VT: Convert large current / high voltage into small signals to adapt to meter measurement |
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Current Transformer (CT) / Voltage Transformer (VT) |
Electric Meter: Measure active / reactive electric energy, monitor voltage / current / frequency |
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Measurement & Control Terminal |
Measurement & Control Terminal: Collect data and support local / remote display |
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Status Indicator Light / Display Screen |
Status Indicator Light: Intuitively display the status of grid-connection closing, fault alarm, power on, etc.; Display Screen: View electric energy data, grid parameters and fault codes locally without external equipment |
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Grid-connection Control & Communication Module |
Realize intelligent switching of grid-connection circuit, exchange information with grid dispatching / photovoltaic monitoring system, and meet dispatching requirements |
Grid-connection Contactor |
Contactor: Receive signals and automatically switch the grid-connection circuit |
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Controller / PLC |
Controller: Coordinate the actions of each module and execute preset logic |
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Communication Module (4G / Ethernet / RS485) |
Communication Module: Realize remote monitoring and data transmission |
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Manual / Automatic Changeover Switch |
Manual / Automatic Changeover Switch: Switch the control mode, receive remote / PLC instructions in automatic mode; Realize local operation in manual mode to meet the needs of maintenance or emergency |
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Cabinet & Auxiliary Module |
Provide installation carrier and protective environment to ensure the stable operation of internal components in outdoor / industrial environments |
Metal Cabinet (IP54 and above) |
Cabinet: Dustproof, waterproof and prevent the intrusion of foreign objects |
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Cooling Fan / Thermostat |
Cooling Fan: Start and stop according to temperature to prevent high-temperature aging of components |
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Maintenance Lighting |
Maintenance Lighting: Provide light source for in-cabinet maintenance |
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Cable Tray / Trunking |
Cable Tray / Trunking: Arrange wiring neatly and facilitate maintenance |
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Sealing Strip |
Sealing Strip: Enhance the sealing performance of the cabinet, prevent dust and rainwater from entering the cabinet, and ensure the reliable operation of components in harsh environments |
Based on the descriptions of the functional modules and core components of the grid-connected cabinet in the table above, it is possible to quickly select and match any grid-connected cabinet solution. Here are two examples.
2.400KW Four-Channel Grid-Connected Cabinet
The component selection for the 400kW grid-connected cabinet is based on a comprehensive calculation involving system rated voltage, total current, input current per inverter channel, protection coordination, metering accuracy requirements, and environmental adaptability. Below is the detailed selection justification for the key components in this solution:
Incoming Line and Main Circuit Components
Frame Circuit Breaker (TGW1N-1600/4P-800A)
Calculation Basis:
Total system power: 400kW
Rated voltage: 380V (Three-phase)
Power factor: Conservatively estimated at 0.8
Current calculation formula:
Considering a 1.1x redundancy and harmonic effects, 800A is selected as the standard rating.
PV-Specific Function: Equipped with undervoltage delay tripping to prevent sudden grid-connection impacts when the grid recovers.
Input Circuit Breaker (NM1-250S/4300 250A)
Estimated Power per Inverter Channel:
4 input channels, each approximately 100kW
Current per channel:
Selection of 250A provides a 1.3x overload capacity, ensuring no nuisance tripping during short-term inverter overloads.
Rotary Isolating Switch (HD13BX-1000A/41 4P)
Selection Justification:
Used to provide visible break points to ensure maintenance safety.
Rated at 1000A > main breaker's 800A, meeting isolation requirements.
Busbar (Copper Bar, 800A)
Selection Basis:
Current-carrying capacity of copper busbars is estimated at 2A per mm². An 800A requirement necessitates at least 400mm² cross-sectional area.
Typically, TMY-80×10 (800mm²) or equivalent specification is used to ensure temperature rise ≤40K.
Protection Module Components
Surge Protective Device (LYY1-40kA)
Selection Basis:
Photovoltaic systems are often exposed to outdoor environments with high lightning-induced surge risks.
40kA discharge capacity meets Class II test requirements, suitable for lightning protection in low-voltage distribution systems.
SPD Protection Circuit Breaker (NXB-63AC63 4P)
Selection Justification:
Used for front-end protection of the SPD to prevent the SPD from affecting the main circuit in case of a short circuit.
63A rating matches the SPD, ensuring it doesn't trip during normal SPD conduction.
Metering Module Components
Current Transformer (BH-0.66 800/5 Class 0.5)
Selection Basis:
Main circuit current is approx. 760A. Selecting an 800/5 CT results in a 5A secondary current, suitable for metering instruments.
Accuracy Class 0.5 meets grid-connection metering requirements.
Multifunctional Electric Meter (AMC96L-E4)
Selection Justification:
Supports RS485 communication, enabling data upload for voltage, current, power, energy, etc.
Complies with grid requirements for data acquisition and monitoring at photovoltaic grid-connection points.
Control and Auxiliary Module Components
Fuse (RT14-400V 6A)
Selection Justification:
Used for protection of secondary circuits, such as control power supplies, communication modules, instrument power, etc.
6A fuses can withstand short-duration inrush currents and disconnect quickly during short circuits to protect control components.
Current/Voltage Terminals (45 / 90 pcs)
Selection Basis:
Each CT requires connection to current terminals; each voltage signal requires connection to voltage terminals.
Considering the need for 3 CTs, three-phase voltage, multifunctional meter, anti-theft box, etc., 45/90 terminals provide reasonable redundancy.
Enclosure (GGD 800×800×2200)
Selection Justification:
The GGD cabinet is a standard low-voltage distribution cabinet, suitable for high current and multi-circuit layouts.
Dimensions accommodate the space required for arranging the breaker, busbars, CTs, meter, anti-theft box, etc.
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No. |
Component Name (with Model & Specification) |
Unit |
Quantity |
Function Module |
Corresponding Core Function of Module |
Component Function Description |
Picture |
|
1 |
Frame Circuit Breaker (TGW1N-1600/4P-800A, with PV-specific undervoltage delay tripping) |
Piece |
1 |
Incoming Line & Power Distribution Module |
Receive AC power output by the inverter, realize power collection and distribution, and construct the main grid-connection circuit channel |
With undervoltage delay tripping function, undertake main circuit breaking, overload/short-circuit protection and PV-specific grid-connection control |
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2 |
Input Circuit Breaker (NM1-250S/4300 250A) |
Piece |
4 |
4-channel incoming line circuit breaker, responsible for breaking and short-circuit/overload protection of incoming lines of each inverter |
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3 |
Rotary Isolating Knife Switch (HD13BX-1000A/41 4P) |
Piece |
1 |
Provide obvious break points during maintenance to ensure the personal safety of operation and maintenance personnel |
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4 |
Miniature Circuit Breaker (NXB-16AC63 2P) |
Piece |
1 |
Provide independent power supply circuit protection for auxiliary equipment (such as metering terminals, control circuits) |
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5 |
Bus Bar Support |
Set |
2 |
Fix and support the bus bar copper row, ensure firm installation and reliable insulation of the copper row, and avoid short-circuit risks |
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6 |
Copper Connector |
Piece |
18 |
Used for the connection of copper rows with cables and components, ensure stable current transmission and reduce contact resistance |
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7 |
Copper Core Wire, Copper Row (800A) |
KG |
60 |
Bear 800A large current, collect 4-channel input electric energy and transmit it to the main switch and grid side, which is the core carrier of electric energy transmission |
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8 |
Lightning Protection Circuit Breaker (NXB-63AC63 4P) |
Piece |
1 |
Grid-connection Protection Module |
Ensure the two-way safety of power generation system and power grid, prevent equipment damage caused by grid faults/islanding effect/surges |
Control the on-off of the surge protector circuit, assist the realization of lightning protection function, and avoid the abnormal lightning protection circuit affecting the main circuit |
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9 |
Surge Protective Device (LYY1-40KA) |
Piece |
1 |
Suppress transient overvoltage caused by lightning strikes and grid fluctuations, and protect the electrical components in the cabinet |
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10 |
Current Transformer (BH-0.66 800/5 Class 0.5) |
Piece |
3 |
Power Metering & Monitoring Module |
Accurately measure grid-connected electric energy, monitor the operating parameters of power grid/power generation system, and provide data for settlement/diagnosis |
Convert 800A large current into 5A small signal, adapt to the measurement of multifunctional electric meter, and ensure metering accuracy and equipment safety |
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11 |
Multifunctional Electric Meter (AMC96L-E4, with communication) |
Piece |
1 |
Measure grid-connected electric energy, monitor parameters such as voltage, current and power, and support communication function to realize data transmission |
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12 |
Signal Light (AD11-22/41) |
Piece |
3 |
Intuitively display the equipment operating status (such as power on, grid-connection closing, fault alarm, etc.) for local viewing |
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13 |
Claw Fixed Bracket (TMH) |
Piece |
2 |
Fix metering-related components, cooperate with anti-electricity-theft box to realize anti-electricity-theft function and ensure the safety of metering data |
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14 |
Anti-electricity-theft Box (TMH) |
Piece |
1 |
Special for anti-electricity-theft, protect the wiring of metering circuit and ensure the authenticity and accuracy of electric energy metering data |
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15 |
Cabinet (GGD, W800×D800×H2200) |
Piece |
1 |
Cabinet & Auxiliary Module |
Provide installation carrier and protective environment to ensure the stable operation of internal components |
Provide installation space for all components, have basic dustproof and protective functions, and adapt to indoor use environment |
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16 |
Fuse (RT14-400V 6A) |
Set |
5 |
Protect the secondary power circuit and control circuit to avoid damage to control components and communication modules due to overload or short circuit |
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17 |
Current Terminal |
Piece |
45 |
Standardize the connection of current signal lines for convenient wiring arrangement and later maintenance |
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18 |
Voltage Terminal |
Piece |
90 |
Standardize the connection of voltage signal lines, ensure reliable signal transmission, and facilitate wiring arrangement and later maintenance |
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19 |
Accessories such as Copper Lug, Cable Tie, Positioning Clip, Plastic Cover |
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- |
Assist in wiring, fixing components and insulation protection, ensure neat internal wiring and firm component installation, and improve operation reliability |
750KW 7-Channel Grid-Tied Cabinet
Incoming Line and Main Circuit Components
Main Grid-Connection Switch (NXA16N16-MF4 1250A, 4P 65kA)
Calculation Basis:
Total system power: 750kW
Rated voltage: 380V (Three-phase)
Power factor: Conservatively estimated at 0.8
Total current calculation:
Normal operating current range of approximately 1200-1300A
Intelligent Functions: Equipped with electrical opening/closing, undervoltage release, voltage-check closing, and delay functions, ensuring safe and controlled grid-connection operations.
Input Circuit Breaker (NM1-250L/4300B 50kA)
Estimated Power per Inverter Channel:
7 input channels, each approximately 107kW
Current per channel:
Selection Justification:
250A rating provides 1.23x overload capacity, ensuring no nuisance tripping during short-term inverter overloads.
50kA breaking capacity meets the short-circuit current withstand requirements at the grid-connection point.
The 4300B model (with auxiliary contacts) facilitates remote status monitoring.
Isolating Switch (1500A/4P HD12)
Selection Basis:
Rated current: 1500A > main switch's 1250A, meeting isolation requirements.
Provides visible break points to ensure absolute safety for maintenance personnel.
4-pole design ensures complete isolation of all live conductors.
Busbar (80×10mm Copper Bar)
Selection Basis:
Current-carrying capacity of copper busbars: TMY-80×10 (800mm²) can carry approximately 1600-1800A under standard conditions.
Temperature rise control: ≤40K at 1250A operating current.
Sufficient cross-sectional area ensures low impedance and minimal power loss.
Multiple busbar supports ensure mechanical stability under short-circuit electromagnetic forces.
Input Miniature Circuit Breaker (NXB-32A/4P)
Selection Justification:
Dedicated power supply protection for the metering collection terminal of the power supply bureau.
32A rating ensures selectivity with upstream protection devices.
4-pole design ensures complete isolation of the metering power supply.
Protection Module Components
1.AC Surge Arrester (NXUII-C40/40kA)
Selection Basis:
40kA (8/20μs) discharge capacity meets Class II test requirements for low-voltage distribution systems.
Maximum continuous operating voltage Uc~385V AC, suitable for 380V systems.
Protection level Up ≤ 1.8kV, effectively protecting downstream equipment.
Surge Arrester Protection Circuit Breaker (NXB-63/63A/4P)
Selection Justification:
Front-end protection for the surge arrester to prevent it from affecting the main circuit in case of short circuit failure.
63A rating coordinates with the surge arrester's nominal discharge current.
Metering Module Components
1.Measurement Current Transformer (1200/5A Class 0.5)
Selection Basis:
Main circuit current is approximately 1200-1300A under full load.
1200/5A ratio results in a 5A secondary current at nominal load, suitable for standard metering instruments.
At 1250A main current, secondary current = (1250/1200)×5 ≈ 5.21A, within the meter's measuring range.
Accuracy Class 0.5 meets grid-connection metering requirements for commercial applications.
Rated burden matches the multifunctional meter's input impedance.
2.380V Multifunctional Meter (with RS485 Communication)
Selection Justification:
Displays power, voltage, current, frequency, power factor, and energy.
RS485 communication enables data upload to monitoring systems.
Complies with grid requirements for data acquisition and monitoring at photovoltaic grid-connection points.
Supports both local display and remote data transmission.
3.Power Indicator Lights (Yellow/Green/Red)
Selection Justification:
Provides intuitive visual indication of equipment status:
Red: Power on / Grid-connected
Green: Standby / Ready
4.Lead Sealing Junction Box and Horn Bracket (2 sets)
Selection Justification:
Anti-electricity-theft function to protect metering circuit wiring.
Ensures authenticity and accuracy of energy metering data.
Complies with power supply bureau requirements for metering security.
Control and Communication Module Components
1.Time Relay
Selection Justification:
Provides delay control functions for coordinated operation.
Works with the main grid-connection switch to implement delayed closing/opening logic.
Prevents simultaneous switching operations that could cause system disturbances.
2.Intermediate Relays (4 units)
Selection Justification:
Amplify control signals from the controller or manual switches.
Convert control logic to drive high-current contactors and breakers.
4 units allocated for:
Closing command (1)
Opening command (1)
Status feedback (1)
Interlock logic (1)
Ensures reliable execution of closing/opening control commands.
Closing/Opening Buttons and Transfer Switch
Selection Justification:
Manual control buttons: Allow local operation of grid-connection circuit during maintenance or emergencies.
Transfer switch: Enables switching between manual and automatic control modes.
Auto mode: Receives remote/PLC commands
Manual mode: Local operation for maintenance or emergency needs
Cabinet and Auxiliary Module Components
1.GGD Standard Cabinet (W1000×D800×H2200mm)
Selection Justification:
GGD cabinet is a standard low-voltage distribution cabinet, suitable for high current and multi-circuit layouts.
Dimensions accommodate:
Main switch (1250A frame size)
7 input breakers (250A each)
Busbar system
CTs, meter, control devices, and auxiliary components
Cold-rolled steel plate with spray coating provides basic corrosion protection.
Indoor use rating with adequate ventilation for heat dissipation.
2.Secondary Power Fuses (RT28-32/6A, 6 units)
Selection Justification:
Protect secondary power circuits (control power, communication module power, instrument power).
6A rating can withstand short-duration inrush currents while providing quick disconnection during short circuits.
6 units allocated for:
Control circuit power (2)
Metering circuit power (2)
Communication module power (1)
Spare (1)
3.Secondary Wiring Cables, Terminals, and Accessories
Selection Justification:
Signal transmission and power supply connections for all control and monitoring components.
Standardized terminals ensure reliable connections and facilitate maintenance.
Proper wire sizing for current-carrying capacity and voltage drop requirements.
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No. |
Component Name (with Model & Specification) |
Unit |
Quantity |
Function Module |
Corresponding Core Function of Module |
Component Function Description |
Picture |
|
1 |
Main Grid-Connection Switch (NXA16N16-MF4 1250A, 4P 65kA) |
Piece |
1 |
Incoming Line & Power Distribution Module |
Receive AC power output by the inverter, realize power collection and distribution, and construct the main grid-connection circuit channel |
Fixed intelligent main switch with electrical opening/closing, undervoltage release, voltage-check closing, and delay functions. Undertakes main circuit breaking + overload/short-circuit protection |
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2 |
Input Circuit Breaker (NM1-250L/4300B 50kA) |
Piece |
7 |
250A input circuit breaker, responsible for breaking and short-circuit/overload protection of each inverter incoming line |
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3 |
Input Miniature Circuit Breaker (NXB-32A/4P) |
Piece |
1 |
Power supply switch for utility metering collection terminal, providing independent power supply circuit protection for the metering terminal |
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4 |
Busbar (80×10mm Copper Bar) |
Set |
Several |
Carry large current, collect power from 7 input circuit breakers, and transmit it to the main grid-connection switch and grid side |
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5 |
Isolating Switch (1500A/4P HD12) |
Piece |
1 |
Provide obvious break points during maintenance to ensure the personal safety of operation and maintenance personnel |
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6 |
AC Surge Arrester (NXUII-C40/40kA) |
Set |
1 |
Grid-connection Protection Module |
Ensure the two-way safety of power generation system and power grid, prevent equipment damage caused by grid faults/surges |
AC lightning protection, suppress transient overvoltage, protect electrical components in the cabinet from lightning strikes or grid fluctuations |
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7 |
Surge Arrester Protection Circuit Breaker (NXB-63/63A/4P) |
Set |
1 |
Surge protection input control, control the on-off of the surge arrester circuit, assist in realizing lightning protection function |
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8 |
380V Multifunctional Meter (with RS485 Communication) |
Piece |
1 |
Power Metering & Monitoring Module |
Accurately measure grid-connected electric energy, monitor the operating parameters of power grid/power generation system, and provide data for settlement/diagnosis |
Display power, voltage, current, support RS485 communication, realize electric energy metering and data transmission |
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9 |
Measurement Current Transformer (1200/5A Class 0.5) |
Piece |
3 |
Convert 1200A large current into 5A small signal, adapt to multifunctional meter measurement, ensure metering accuracy and equipment safety |
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10 |
Power Indicator Light (Yellow/Green/Red) |
Piece |
5 |
Intuitively display the equipment operating status (such as power on, grid-connection closing, fault alarm, etc.) for local viewing |
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11 |
Lead Sealing Junction Box, Horn Bracket |
Set |
2 |
Anti-electricity-theft use, ensure the authenticity and security of electric energy metering data |
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12 |
Time Relay |
Piece |
1 |
Grid-connection Control & Communication Module |
Realize intelligent switching of grid-connection circuit, exchange information with grid dispatching/photovoltaic monitoring system, and meet dispatching requirements |
Provide delay control function, cooperate with the main grid-connection switch to realize delayed closing/opening logic |
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13 |
Intermediate Relay |
Piece |
4 |
Amplify control signals, convert control logic, ensure reliable execution of closing/opening and other control commands |
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14 |
Closing/Opening Button, Transfer Switch |
Piece |
3 |
Locally manually control the closing and opening of the grid-connection circuit, switch control modes (such as manual/automatic) |
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15 |
GGD Standard Cabinet (W1000×D800×H2200mm) |
Piece |
1 |
Cabinet & Auxiliary Module |
Provide installation carrier and protective environment to ensure the stable operation of internal components |
Indoor cabinet, cold-rolled plate spray painting, provide installation space and basic protection for all components |
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16 |
Secondary Power Fuse (RT28-32/6A) |
Piece |
6 |
Protect secondary power circuits, avoid damage to control components due to overload or short circuit of secondary lines |
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17 |
Secondary Wiring Cables, Terminals, and Accessories |
Lot |
Several |
Standardize the connection of secondary lines, realize signal transmission and power supply connection of various control and monitoring components, facilitate maintenance |
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