Three-stage overcurrent protection refers to instantaneous current protection Zone 1, time-limited current protection Zone 2, and overcurrent protection Zone 3.
1. Instantaneous protection Zone 1: the protection range is less than the total length of the protected line is generally set to 80% of the total length of the protected line.
2. Time-limited protection Zone 2: The protection range is the full length of the line to be protected or 15% of the next line.
3. Overcurrent protection Zone 3: The protection range is the full length of the protected line to the full length of the next line.