After the control cable is put into operation, there is a problem of electrical interference between different cores of the same cable and between adjacent parallel cables. The main causes of electrical interference are:
(1) Due to the electrostatic interference generated by the coupling of capacitors between cores caused by external voltage;
(2) Due to electromagnetic induction interference caused by the current passing through. Overall, when there are high voltage and high current interference sources nearby, electrical interference is more severe. Due to the smaller distance between the cores of the same cable, the degree of interference is much greater than that of adjacent cables laid in parallel. For example, in the control circuit of a phase separated operation circuit breaker in a certain ultra-high voltage substation, the three phases share one cable. Such an accident once occurred, where the pulse of the phase separated operation triggered the thyristors of other phases, resulting in three-phase linkage. Later, separate independent cables were used, and no further misoperation accidents occurred. For example, in the computer monitoring system of a certain power plant, the use of a four core cable to share the low-level analog signal line with the power line of the transmitter caused interference voltage of 70V on the signal line, which obviously affected the normal operation of the low-level signal circuit measured in millivolts.