The three-level residual current protection system, also known as three-level residual current protection, is a very common safety configuration in China's low-voltage power distribution systems (especially in rural power grids, construction sites, and renovations of old residential areas). Its core principle is: tiered configuration, mutual coordination, tripping only the fault point, not the main circuit breaker.
functions of three-level residual current protection system
1️⃣ Primary Protection (Main Switch) – Fire Prevention, Prevention of Cascading Trips
Installed on transformer outgoing lines or main switchboard
High operating current (300–500mA), allows for a certain time delay
Purpose: It does not trip when there is a leakage at the end, only the downstream circuit trips; it only trips when the end circuit does not trip or the fault is very serious.
2️⃣ Secondary Protection (Branch Circuit) – Prevention of Intermittent Electric Shock, Selectivity
Installed in distribution boxes, floor distribution boxes
Medium operating current (100–300mA)
Purpose: When a branch circuit leaks current, only that branch trips, without affecting other circuits.
3️⃣ Tertiary Protection (End Circuit) – Life Protection
Installed in socket circuits, handheld power tools, temporary power supply
Operating current ≤ 30mA
Operating time ≤ 0.1s, directly prevents electric shock.
Application of three-level residual current protection system
Scenario Requirements: Rural power grid renovation, national standard GB Standard 50052–95 explicitly requires the use of three-level protection.
For temporary power supply at construction sites, JGJ 46–2005 requires the terminal voltage to be ≤30mA, with tiered configuration.
For the renovation of old residential areas, to prevent cascading tripping, three-level protection is generally adopted.
For schools, hospitals, and shopping malls, the terminal voltage should be ≤30mA, with a total incoming line voltage of 300–500mA.
Products Description
GCS low voltage withdrawable switchgear is suitable for power plants, petrochemical industry, metallurgy, textile, high-rise building power supply and other industries.
It is used in large power plants, petrochemical industry and other places with high degree of automation and requirements for computer interface, as the distribution of power in three-phase AC frequency 50Hz (60Hz), rated working voltage 380V (660V), rated current 4000A and the following power generation and power supply system,
It is a low-voltage complete power distribution device for centralized control of electric motor, current limitation of reactor and reactive power compensation.
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