Correct and uninterrupted operation of on-board radio-electronic equipment (REE) operating in extreme space conditions is an important requirement in spacecraft (SC) development and operation, since its violation can cause irreparable damage. Ensuring interference immunity of power supply bus (PSB) of on-board REE of SC. When designing the PSB, the task of ensuring the integrity of the power supply was solved by developing a protection device against conductive interference, including protection against ultra-short pulses (USP). The duration of such interference is in the nanosecond and subnanosecond range. Due to their wide range, such interference overcomes traditional means of protection. To protect against USP, devices called modal filters (MF) have been proposed. MFs are designed to be integrated into PSBs and provide effective protection against USP. Meanwhile, in order to obtain a complex protection effect of a spacecraft against radiated and conductive large-amplitude USP, a joint use of MF and an electromagnetic interference (EMI) filter on elements with concentrated parameters is proposed. For the first time, recommendations on step-by-step development of an PSB protection device against USP, which is a hybrid consisting of MF and EMI-filter, are presented. Experimental studies have shown that such a hybrid attenuates common and differential interference in the frequency range up to 5 GHz by 5.81 and 11.9 times, respectively. In addition, the device is small and lightweight, which is important for space applications.