The 9 Core Roles of Huihai Electric Prefabricated Substations in Photovoltaic Power Generation Systems

In photovoltaic power generation systems, every link, from distributed power generation by photovoltaic modules to safe grid connection and efficient operation and maintenance, relies on the support of core power distribution equipment. Huihai Electric's prefabricated substations, acting as the "power hub" of a photovoltaic power station, utilize integrated design, comprehensive safety protection, and efficient power processing capabilities to span the entire process of photovoltaic power generation, collection, voltage regulation, and grid connection. They bear the crucial mission of ensuring stable system operation, optimizing power quality, and reducing operation and maintenance costs. Their nine core roles solidify the foundation for safe and efficient power generation in photovoltaic power stations.

1. Low-voltage boost and regulation for grid connection adaptation

1.1. Low-voltage input (inverter side)

• Rated low voltage: 400V / 540V / 690V / 800V (three-phase AC).
• Commonly used standard configurations: 0.4kV (400V), 0.8kV (800V).
• Voltage fluctuation tolerance range: ±10% (wide inverter output fluctuation, transformer substation can operate normally).
• Frequency: 50Hz ±0.5Hz.

1.2. High-voltage output (grid connection side)

• Rated high voltage: 10kV / 20kV / 35kV (domestic photovoltaic mainstream is 10kV, 35kV).
• Commonly used standard configurations: 10.5kV (corresponding to 10kV grid), 37kV (corresponding to 35kV grid).
• Voltage regulation levels: ±2×2.5% (5 adjustable levels).
• For example: 10.5kV → 11.025kV / 10.7625kV / 10.5kV / 10.2375kV / 9.975kV.
• Grid connection voltage accuracy: Controlled within ±5% of the grid rated voltage, meeting GB/T 19964 requirements.

1.3. Step-up transformer efficiency and losses (key data)

• Rated conversion efficiency: ≥98.7% (50%–100% load).
• No-load loss: ≤0.3% (lower for amorphous alloy cores, approximately 0.25%).
• Short-circuit impedance: 4%–6% (dedicated for photovoltaic systems, suppressing harmonics and resisting impact).

1.4. Capacity matching (commonly used in photovoltaic power plants)

• Single transformer capacity: 800kVA～3150kVA.
• Typical configuration: 1MW photovoltaic → 1000kVA prefabricated substation (0.4kV→10kV), 2MW photovoltaic → 2000kVA prefabricated substation (0.8kV→10.5kV), 5MW photovoltaic → 2500kVA～3150kVA (0.8kV→35kV).

Huihai Electric photovoltaic prefabricated substations step up the inverter's 0.4kV/0.8kV low-voltage AC power to a 10kV/35kV grid-connected voltage with an efficiency of ≥98.7%. It features ±5% high-precision voltage regulation, 5 adjustable levels, and compatibility with grid standards, enabling low-loss power transmission over long distances.

2. Multi-channel Power Aggregation, Integrating Array Power

Multi-channel power aggregation, integrating array power with precise industry-tested data (compatible with Huihai Electric PV transformer substations)

2.1. Number of Low-Voltage Incoming Line Aggregation Circuits

• Standard Low-Voltage Cabinet Incoming Line Circuits: 6-12 circuits.
• Conventional PV Configuration: 8-channel standard aggregation.
• Large MW Customized Model: 16-channel multi-channel aggregation.

2.2. Single Circuit Capacity

• Single-Channel Inverter Power Capacity: 500kW-1250kW.
• Single-Channel Rated Current: 361A-902A (compatible with 0.8kV mainstream PV voltage).

2.3. Maximum PV Aggregation Capacity of a Single Transformer

• 8-channel aggregation configuration: Based on 630kW per channel: can aggregate 5.04MW PV array.
• 12-channel aggregation: can aggregate 7.56MW PV array.
• 16-channel aggregation: Capable of aggregating power from a 10.08MW photovoltaic array

2.4. Line Loss Optimization Data

• Direct grid connection of distributed single arrays: Line loss 2.5%～3.5%.
• After centralized aggregation via box-type substation: Overall line loss reduced to 0.8%～1.2%.
• Annual power saving benefits: Compared to distributed wiring, annual power loss is reduced by approximately 12,000～18,000 kWh per MW.

2.5. Wiring and Cost Data

• After centralized aggregation: On-site cable usage reduced by 35%～45%.
• Overall cost reduction of over 30% for cable trays, auxiliary materials, and construction labor

Huihai Electric box-type substations are standardly equipped with 6～12 low-voltage incoming line aggregations, with customization up to 16 channels. A single unit can integrate power from a 10.08MW photovoltaic array; centralized aggregation and standardized transmission reduces on-site line losses from 2.5%～3.5% to 0.8%～1.2%, and simultaneously reduces cable consumption and construction costs by over 30%.

3. Comprehensive Electrical Protection to Prevent Fault Propagation

Specific data for comprehensive electrical protection to prevent fault propagation (Huihai Electric PV transformer standard parameters)

3.1. Overload Protection Parameters

• Overload setting range: 0.5～1.25 times rated current.
• Inverse time overload protection, precise tripping within 10～120s after timeout.
• Slight overload within 15%: Maintains normal operation; beyond 15%, immediate current limiting protection.

3.2. Short Circuit Protection Data

• Instantaneous short circuit action time: ≤0.04s (40ms).
• Short circuit breaking capacity: 20kA/25kA/31.5kA on the high-voltage side, 40kA/50kA on the low-voltage side.
• Withstands short-term 1s thermal stability current: 20～31.5kA.

3.3. Overvoltage/Undervoltage Protection Settings

• Overvoltage protection action value: 1.15Un, tripping after a 0.5s delay.
• Undervoltage protection action value: 0.75Un, tripping after a 1.0s delay.
• Zero-sequence overvoltage: 0.15Un activates insulation monitoring to prevent single-phase grounding hazards.

3.4. Lightning protection parameters

• High-voltage surge arrester: Rated voltage 17kV/42kV, lightning impulse residual voltage ≤45kV/105kV.
• Low-voltage side lightning protection: Class II lightning protection, withstands surge current 20kA.
• Overall enclosure grounding resistance: ≤4Ω, ≤1Ω in mountainous and saline-alkali areas

3.5. Over-temperature and oil temperature protection data

• Transformer oil temperature alarm: 85^oC.
• Oil temperature tripping: 95^oC.
• Winding high temperature protection: 110^oC warning, 120^oC tripping.
• Built-in fan start/stop: 65^oC start, 55^oC stop.

3.6. Anti-islanding and anti-reverse power transmission protection (PV dedicated)

• Anti-islanding detection response time: ≤0.2s.
• Reverse power protection: Immediately locks out when reverse power exceeds 5% of rated capacity.
• Bidirectional electrical interlocking, completely blocking reverse power transmission from the grid.

3.7. Fault Isolation and Propagation Blocking

• Fault zone isolation time: ≤0.04s.
• Individual branch faults are isolated separately, without affecting the normal power generation of other PV arrays.
• Equipped with fault memory and event recording, capable of storing ≥500 fault records.

Huihai Electric PV transformer substation is equipped with comprehensive electrical protection against overload, short circuit, over/under voltage, lightning, oil temperature, and anti-islanding. It features instantaneous short circuit interruption within 40ms, high and low voltage breaking capacity up to 31.5kA/50kA; grounding resistance ≤4Ω; oil temperature alarm at 85^oC and tripping at 95^oC; rapid isolation of single branch faults, preventing propagation and ensuring the safe operation of the entire PV power generation system.

4. Optimized Power Quality, Stable Grid Connection Performance

Built-in reactive power compensation and harmonic mitigation modules correct power factor, suppress harmonic distortion, stabilize voltage fluctuations, and strictly comply with grid-connected photovoltaic power quality specifications.

5. Intelligent Power Flow Management, Stable Grid Interaction

Precisely manages photovoltaic power flow, enabling self-consumption, surplus power grid connection, peak shaving and valley filling, adapting to grid dispatch, and ensuring complementary photovoltaic and energy storage operation and stable grid connection.

6. Integrated Power Distribution, Simplified Power Station Architecture

High-voltage switches, transformers, low-voltage cabinets, and protection and control systems are integrated into a pre-installed enclosure, eliminating the need for a civil engineering substation. Compact footprint and simple layout simplify the entire photovoltaic power station's electrical system.

7. All-Weather Environmental Adaptability, Stable Operation in Harsh Conditions

High-standard corrosion resistance, dustproofing, waterproofing, and high/low temperature tolerance make it suitable for complex photovoltaic scenarios such as mountains, deserts, rooftops, and saline-alkali land. Stable long-term operation from -40^oC to +50^oC.

8. Intelligent Monitoring and Maintenance, Remote Control and Early Warning

Real-time collection of voltage, current, oil temperature, load, and switch status; cloud-based remote monitoring, fault alarms, and data traceability significantly reduce the inspection and maintenance costs of photovoltaic power plants.

9. Compliant Metering and Settlement, Guaranteed Electricity Revenue

Built-in high-precision electricity metering device accurately counts grid-connected electricity and self-generated electricity consumption, meeting the compliance requirements for electricity settlement, tax reporting, and photovoltaic revenue accounting.

In summary, the nine core functions of Huihai Electric's prefabricated substation cover the entire chain of photovoltaic power generation from power collection to grid connection and settlement. It solves the integration challenges of decentralized photovoltaic power generation, the optimization of power quality, and the challenges of stable operation under complex conditions and efficient operation and maintenance management. Relying on precise parameter configuration, reliable protection performance, and convenient integrated design, Huihai Electric's prefabricated substation not only provides comprehensive protection for the safe and stable operation of photovoltaic power plants but also helps photovoltaic projects achieve cost reduction and efficiency improvement, compliant grid connection, and injects strong momentum into the high-quality development of the new energy industry.

Written by

Huihai Electric Co., Ltd.

Editor Xu

www.huihai-electric.com

WhatsApp:+86 139 1136 0187

Email:13705388456@163.com