35KV Prefabricated Substation Product Manual

Product Overview

A 35kV prefabricated substation (referred to as a 35kV box-type substation) is a prefabricated complete set of power distribution equipment that organically combines high-voltage power receiving, transformer voltage reduction, and low-voltage power distribution functions. This product adopts a "three-compartment" structure design, consisting of three independent functional units: a 35kV high-voltage compartment , a transformer compartment , and a low-voltage distribution compartment. It integrates high-voltage switchgear, power transformers, and low-voltage power distribution devices into one unit, and has the advantages of compact structure, convenient installation, reliable operation, and convenient maintenance.
Our products are widely used in photovoltaic power generation, wind power generation, industrial and mining enterprises, residential communities, commercial centers, municipal engineering and other fields, and are especially suitable for the step-up grid connection system of new energy power plants.

Implementation Standards and Usage Conditions

■ Implementation Standards

GB/T 17467-2020 Prefabricated High-Voltage/Low-Voltage Substations

GB 3906-2020 3.6kV～40.5kV AC Metal-Enclosed Switchgear and Controlgear

GB 7251.1-2013 Low-voltage switchgear and controlgear assemblies

NB/T 10204-2019 Technical Requirements for Low-Voltage Grid-Connected Interface Devices for Distributed Photovoltaic Power Generation

■ Normal operating conditions

Project	Technical Requirements
Ambient temperature	-25℃ to +40℃, with a 24-hour average not exceeding +35℃.
Altitude	≤2000m (reduced capacity required for applications exceeding this limit)
relative humidity	Daily average ≤95%, monthly average ≤90%
earthquake resistance	Earthquake intensity 8 degrees
Installation site	There is no risk of fire or explosion, and there is no serious pollution, chemical corrosion, or violent vibration.

Overall Structure and Layout

Three-room independent structural designThis product adopts a three-chamber layout in the shape of "目" or "品" , with each chamber completely isolated by steel plates and having an independent door to ensure operational safety.

■ Schematic diagram of floor plan

【Eye-shaped layout (recommended)】

Layout features:

The high-voltage compartment and the low-voltage compartment are located on opposite sides, with the transformer in the middle.

Each room has its own door, ensuring no interference between them.

Optimal ventilation and heat dissipation

Sufficient space for inspection and maintenance

■ Cabinet structural parameters

Project	Parameter
External dimensions (length × width × height)	5500×2500×2800mm (customizable)
Box material	2.5mm high-quality cold-rolled steel sheet/galvanized steel sheet
Surface treatment	Phosphating + electrostatic powder coating, RAL7035/Military Green
Protection level	IP54 (enclosure) / IP2X (indoor spaces)
Insulation layer	50mm thick rock wool insulation layer
ventilation system	Natural ventilation + forced cooling fan

35KV High Voltage Chamber

■ Main Functions

Receiving and distributing 35kV high-voltage electrical energy

High-voltage side overcurrent, short circuit, overvoltage, and undervoltage protection

On/off control of the high-voltage side of the transformer

Lightning overvoltage protection

Live indicator and forced interlock

■ Standard Configuration

Equipment Name	Model Specifications	Quantity
Vacuum circuit breaker	ZN63-40.5/630-31.5kA	1 unit
disconnect switch	GN22-40.5/630A	Group 1
Grounding switch	JN15-40.5/31.5kA	Group 1
Current transformer	LZZBJ9-35, transformer ratio based on capacity	3
Voltage transformer	JDZ9-35, 35/√3 : 0.1/√3	3
Zinc oxide surge arrester	HY5WZ-51/134	3
Microcomputer protection device	Integrated line/transformer protection and control system	1 set
live display	DXN-35kV, with interlocking	1 set

Technical Parameters

Rated voltage	40.5kV
Rated current	630A / 1250A
Rated short-circuit breaking current	25kA / 31.5kA
Rated short-time withstand current (4s)	25kA / 31.5kA
Rated lightning impulse withstand voltage	185kV (to ground) / 215kV (break point)
Rated power frequency withstand voltage (1 min)	95kV (to ground) / 118kV (break point)

Transformer Room

■ Main Functions

The 35kV high-voltage power is reduced to 0.4kV low-voltage power.

Power conversion and electrical isolation

Temperature monitoring and overheat protection

Forced air cooling

■ Transformer Selection (Standard Configuration)

Project	Oil-immersed transformer (S13/ S20 )	Dry-type transformer (SCB1 8 )
Rated capacity	800kVA ~ 10000kVA
Voltage combination	35 ± 2×2.5% / 0.4kV
Connection group	D,yn11
Impedance voltage	6.5% ~ 8%
Insulation class	Grade A	H-class
Cooling method	ONAN/ONAF	AN/AF
Temperature control protection	Oil surface temperature controller	Platinum resistance temperature controller

■ Auxiliary Configuration of Transformer Room

Temperature control system : Intelligent temperature controller, over-temperature alarm, over-temperature trip, automatic fan start/stop.
Cooling system : 4 axial flow fans, forced ventilation and heat dissipation
Lighting system : explosion-proof lighting fixtures, door control switches
Fire protection system : smoke detectors, heat detectors
Oil-immersed special-purpose : oil level gauge, pressure relief valve, gas relay

Low-voltage power distribution room

■ Main Functions

Distribution and control of 0.4kV low-voltage power

Low-voltage side overload, short circuit, and leakage protection

Reactive power compensation (optional)

Electricity metering and data acquisition

Grid connection interface and anti-islanding protection (dedicated to photovoltaic/wind power)

■ Standard Configuration

Functional Unit	Main Equipment	illustrate
incoming line cabinet	Intelligent frame circuit breaker ACB	Rated current is based on transformer capacity, breaking capacity 50kA
Outgoing line cabinet	Molded Case Circuit Breaker (MCCB)	4-8 rounds of play, configured as needed.
Capacitor compensation cabinet	Intelligent capacitor + reactor	Compensation capacity 30% of transformer capacity, switching accuracy ≤1kvar
Metering cabinet	0.2S-class multi-functional energy meter	Forward and reverse metering, supports 485 communication
Grid-connected cabinet (optional)	Anti-islanding protection device + grid-connected circuit breaker	Over/under voltage protection, high/low frequency protection, and reverse power protection.

■ Technical Parameters

Rated operating voltage : AC 400V
Rated frequency : 50Hz
Rated current of main busbar : 1600A ~ 4000A
Rated short-time withstand current (1s) : 50kA / 65kA / 80kA
Power factor : ≥0.95 after compensation
Protection rating : IP30

Secondary Control System

Microprocessor-based protection : The high-voltage side is equipped with a transformer/line integrated protection device, which has instantaneous overcurrent, overload, zero-sequence, overvoltage, and undervoltage protection.

Intelligent monitoring : The low-voltage side is equipped with intelligent measurement and control instruments to monitor parameters such as voltage, current, power, energy, and harmonics in real time.

Communication functions : Supports RS485/Modbus and Ethernet communication, and can be connected to SCADA systems or cloud platforms.

Temperature control linkage : The transformer temperature is linked to the cooling fan, and over-temperature automatic alarm and tripping occurs.

Access control system : Optional electronic access control system that records door opening operations.

Installation and Debugging

Foundation construction : Pour concrete foundation according to drawings, and reserve grounding electrode.

Equipment placement : hoist the entire unit to the foundation, adjusting the levelness to ≤2mm/m.

Grounding connection : The main grounding grid of the enclosure is reliably connected, and the grounding resistance is ≤4Ω.

Cable connections : High-voltage cables, low-voltage cables, and control cables should be connected according to phase sequence.

Insulation test : High voltage side ≥1000MΩ, low voltage side ≥10MΩ

Protection setting : Set the microcomputer protection parameters according to system requirements.

Power-on test : Power on in stages to verify that each function is normal.

Grid connection acceptance : Cooperate with the power supply department to complete grid connection testing and acceptance.

Maintenance and Care

Maintenance cycle	Maintenance Project
Routine inspection (daily)	Visual inspection, instrument readings, temperature monitoring, abnormal sounds
Monthly inspection	Terminal fastening, switch status, fan operation, grounding check
Quarterly maintenance	Cleaning and dust removal, insulation testing, and protection function verification.
Annual maintenance	Comprehensive inspection, oil sample testing (oil transducer), and protective transmission test.

Ordering Instructions

Specify the transformer capacity, connection group, and impedance voltage.
Define the main wiring scheme of the high-voltage switchgear and the circuit breaker parameters.
Provide the number of low-voltage outgoing circuits and the current requirements for each circuit.
Indicate whether reactive power compensation is required and the compensation capacity.
For new energy projects, please specify grid connection requirements and protection configurations.
Please specify any special environmental requirements (high altitude, extreme cold, high humidity, etc.).
Please specify any special requirements regarding the color, material, or dimensions of the enclosure.
Please provide detailed specifications for communication protocols and monitoring system requirements.
This product has passed ISO9001 quality system certification, and all components comply with the national 3C certification standard.