Why must the communication cables of the PCS in an energy storage system be shielded at both ends?

Communication cables for PCS (such as CAN, Ethernet, RS485) must be double-shielded, primarily to ensure effective shielding at high frequencies. Single-ended shielding is only effective against low-frequency electric and constant magnetic fields. As the frequency increases (typically >1MHz), the shielding effect relies mainly on the cancellation of interfering magnetic fields by induced eddy currents, requiring a continuous low-impedance loop in the shielding layer. Double-ended grounding provides this loop, enabling the shielding layer to effectively suppress interference from high-frequency electromagnetic fields (including radiation and induction). In high-frequency noise-rich environments like PCS, double-ended shielding prevents external strong electromagnetic noise from interfering with communication signals and also prevents the communication signals themselves from radiating outwards. However, it's important to note that double-ended grounding can create a ground loop. Therefore, the potential difference between the two grounding points should be as small as possible, and the grounding impedance should be low, or common-mode chokes should be used at both ends of the cable to suppress low-frequency interference introduced by the ground loop.