Electronic trip unit with user-adjustable sensitivity to current spikes

A circuit breaker trip unit with user-adjustable sensitivity to current spikes (22) includes a user-adjustable switch (30), a current sensor (32), an analog-to-digital (A/D) converter (34), a microprocessor (36), and a power supply (37). The current sensor (32) is electrically connected to the distribution circuit (10) and provides analog signals indicative of current measurements in the distribution circuit (10) to the A/D converter (34). The A/D converter (34) converts the analog signal to a digital line signal and presents the digital line signal, via a bus (38), to the microprocessor (36). The user-adjustable switch (30) is arranged to provide a signal indicative of a limit value, via a bus (40), to the microprocessor (36). The microprocessor (36) comprises a plurality of registers (42-48) and ROM (50) internal thereto. The ROM (50) includes trip unit application code, e.g., main functionality firmware, including initializing parameters, boot code, and a short circuit protection algorithm. The short circuit protection algorithm compares the line signal stored in the threshold register (48) to a predetermined threshold value stored in the ROM (50). If the line signal exceeds the threshold value, the microprocessor increments a peak count value stored in the peak count register (42). When the peak count reaches the limit value stored in the peak count register (42), a trip signal is generated by the microprocessor (36).