Ground Fault Protection with Susol Air Circuit Breakers

Ground Fault Protection with Susol Air Circuit Breakers

Ground Fault (G) protection is available on Susol Air Circuit Breakers when it is necessary to detect current leaking to ground. 
  1. Use the current setting knob (Ig) to set the desired ground fault current.
    1. Setting range: (0.2–0.3–0.4–0.5–0.6–0.7–0.8–1.0–Off) × In
    2. The Ig is set on the HMI for the P and S type trip relays (no knob exists).
  2. Use the time delay setting knob (tg) to set the desired delay time.
    1. Inverse time (I2t On): 0.1–0.2–0.3–0.4 sec
    2. Definite time (I2t Off): 0.05–0.1–0.2–0.3–0.4 sec
    3. P/S type setting range: 0.05 ~ 3.0 sec
    4. The tg is set on the HMI for the P and S type trip relays (no knob exists).
  3. The fault current is the value detected by vector sum of the input current of the R, S, T phases (3P) or the R, S, T, N (4P).
  4. When the ZSI (Zone Selective Interlocking for A, P, and S type trip relays) function is set, the protection operation will take place instantaneously when there is no ZSI input signal by downstream devices. Disabling the ZSI function on the last downstream device is advised.


When using a 3P (3-pole) breaker with a 4-wire power system (3 phase + neutral), an external, neutral CT (current transformer) is required for the calculation of the vector sum. The 4P (4-pole) breaker has a built-in CT.

Note: A Neutral CT can be purchased separately and can only be used with A, P, and S type trip relays.