Requirements for Grid Connection of Anti-Islanding Protection Devices and Photovoltaic Systems

Introduction

In distributed photovoltaic power stations, residential photovoltaic systems, and commercial rooftop solar projects, the islanding effect poses a significant risk to grid safety. When the grid experiences a fault and power outage, if a photovoltaic system continues to supply power to local loads, it may lead to equipment damage or accidents involving maintenance personnel. The CGS7001M anti-islanding protection device from Shanghai Changgao Relay Protection quickly disconnects the grid connection within 0.2 seconds by monitoring grid voltage, frequency, and other parameters, thus preventing unintended island operation.

Core Functions of Anti-Islanding Protection Devices

• Ensuring Grid Operation Safety: Using Active Frequency Disturbance (AFD) or passive voltage/frequency detection techniques, the device ensures that the photovoltaic system automatically disconnects from the grid following a power outage.
• Improving Power Quality: The device responds in milliseconds to abnormal conditions such as excessive harmonics and sudden voltage fluctuations, in compliance with the GB/T 19964-2012 standards for photovoltaic power station access.
• Extending Equipment Lifespan: It prevents the inverter from operating in overloaded conditions during islanding, thus reducing the failure rate of photovoltaic components and energy storage systems.

Typical Application Scenarios and Solutions

Case Studies

Case 1: Industrial Park Photovoltaic System

In an automotive manufacturing plant, a 5MW rooftop photovoltaic project experienced a power outage due to a lightning strike. The anti-islanding device successfully triggered the grid connection circuit breaker within 0.15 seconds, preventing damage to a control cabinet worth millions related to the painting production line.

Case 2: Rural Household Photovoltaic Poverty Alleviation Project

In mountainous areas with delayed grid upgrades, the device utilized its adaptive impedance measurement capability to accurately identify islanding conditions under weak grid situations, successfully preventing multiple back-feeding incidents caused by aging lines.

Key Technical Requirements for Grid Connection Acceptance

According to the NB/T 32015-2022 standard, the device must meet the following requirements:

• Frequency Protection Range: 49.5Hz – 50.5Hz (adjustable)
• Voltage Protection Threshold: ±10% Un (response time of 0.2 seconds)
• Islanding Detection Time: ≤2 seconds (as per State Grid Q/GDW 617 requirements)

It is recommended to configure protective devices with GOOSE communication capabilities at the photovoltaic grid connection points, enabling coordinated control with the station’s relay protection system to ensure selective tripping in complex multi-source scenarios.

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