About Primary and secondary fused circuit breakers

Primary and secondary fused circuit breakers, with their design integrating intelligent control units and high-voltage bodies, are becoming key equipment in power grid upgrades, playing a central role in enhancing power supply reliability and automation levels.

1. Function and core principle

Deep integration design: Integrating the circuit breaker body (primary equipment) and the FTU terminal (secondary equipment) into one unit, achieving data acquisition, fault diagnosis, and remote control ("three remote" functions), which solves the complexity of traditional equipment installation in separate parts.

Intelligent protection mechanism:

• Rapid fault isolation: It can detect anomalies such as single-phase grounding and inter-phase short circuits, supports 0-3 times of automatic reclosing, and completes fault location, isolation, and restoration of power supply in non-fault areas within seconds, significantly reducing manual handling time.
• Multiple safety guarantees: Equipped with independent zero-sequence protection, fault recording (with storage capacity of ≥60 pieces of data), and backup power supply, it ensures that data is not lost during power outages. Additionally, it adopts vacuum arc-extinguishing technology to avoid explosion risks.

Environmental adaptability: With a solid insulation design utilizing silicone rubber/epoxy resin, it supports stable operation in a plateau environment at an altitude of 3000 meters, with a mechanical lifespan of up to 10,000 cycles.

2. Practical application scenarios and effects

Power grid transformation and upgrading:

Power supply companies in Shandong, Jiangsu, Shaanxi, and other regions have installed this equipment through live-line operations to optimize the distribution network structure. For example, Weishan County in Shandong has retrofitted the lines of the fishery cooperatives in the lake area to ensure reliable power supply for enterprises; Pizhou in Jiangsu has upgraded the intelligence level of the lines during construction in muddy environments after rain.

After the renovation in Wen County, Henan Province, the power grid achieved "second-level self-healing", reducing power outage handling from hours to seconds, significantly improving power supply reliability.

Multi-scenario adaptability:

• Urban distribution network: used in old residential areas and commercial districts to minimize the scope of power outages caused by faults.
• Rural power grid: Ensure key electricity consumption for irrigation and prevent the impact of fluctuations in distributed power sources.
• New energy supporting facilities: Installing charging stations in Lintong, Shaanxi to meet the infrastructure needs for green travel.

3. Technological upgrading and industrial dynamics

Intelligentization trend:

• The Xi'an High Voltage Apparatus Research Institute has developed a deep integration technology for primary and secondary high-voltage switches, addressing the challenge of interrupting high currents.
• The patent innovation focuses on capacitor power supply circuits (to prevent lightning overvoltage), assembly process optimization (for quick disassembly and assembly), and anti-mis-touch design, enhancing safety and operation and maintenance efficiency.

Large-scale procurement and application:

• In 2025, the State Grid Corporation of China achieved a regional joint procurement volume exceeding 440,000 units, with an average price ranging from 18,600 to 19,900 yuan per unit. The demand was most robust in East China and North China. Jiangsu, Shandong, and Henan provinces accounted for nearly 50% of the bidding volume.

    •   Companies such as Heshun Electric and Jiangsu Hongda have been shortlisted as suppliers for the State Grid, promoting the                                   implementation       of product standardization.

   4. Industry chain and market focus

Core enterprise layout:

   •  Si Yuan Electric, Beijing Kerui, and other companies are focusing on the research and development of primary and secondary fusion equipment for smart distribution networks.

   •  TBEA, China XD and other UHV leaders have extended their technologies to the distribution network field.

 Policy and capital drive:

  •  The construction of new power systems is accelerating, with the State Grid Corporation of China investing 4 trillion yuan in its "15th Five-Year Plan" and increasing the proportion of intelligent distribution networks.

  •  Brokerage analysis points out that the integration of primary and secondary equipment is a key direction for power grid upgrades, but attention should be paid to the technical barriers of enterprises and the risk of bidding price fluctuations.