1. Main Sources of Interference From the perspective of the working site of the hydropower station computer monitoring system, the main sources of interference are three aspects: power supply interference, input/output interface channel interference, and electromagnetic field interference. Interference usually enters the computer in the form of pulses. 1.1 Power Supply Interference Because the power supply for small hydropower stations comes from the power grid and the generator terminals, with the development of industrial production, some high-power equipment causes significant interference to the power grid during start-up and shutdown, generating relatively high voltage spikes that, when superimposed on the AC sinusoidal voltage, sometimes exceed 1000V. These spikes are very harmful to the normal operation of the computer. According to statistics, more than 90% of computer failures are caused by power supply problems. 1.2 Input/Output Interface Channel Interference The hydropower station computer monitoring system has a large number of connections to the power station equipment, resulting in a large number of interface channels. These interface channels become pathways for interference to the computer monitoring system. Signals and data will experience delays, distortions, and attenuation during transmission, which constitutes interference. In addition, due to the influence of external electromagnetic fields, induced interference signals will be coupled into the transmission lines of the input/output interface channels, which can severely malfunction the computer. 1.3 Electromagnetic Interference Electromagnetic interference originates from both external and internal sources within the computer monitoring system. In strong electromagnetic field environments, the casing, input/output interfaces, and channels of a computer monitoring system will induce voltage, forming interference sources. Internally, because computers are composed of large-scale integrated circuit components, the wiring is typically very dense, making electromagnetic interference between these components and lines significant. Furthermore, noise and vibration interference are also significant interference signals in hydropower stations. Noise is related to DC output, increasing with increasing DC output. 2. Measures to Enhance Anti-Interference Capability 2.1 Improving the Power Supply's Anti-Interference Capability To avoid direct interference to the computer caused by unstable grid voltage, AC voltage regulators and low-pass filters are mainly used to filter out high-order harmonics in the power supply system and reduce voltage spikes. Isolation transformers use shielding between their primary and secondary windings to reduce distributed capacitance and improve common-mode immunity. This is typically achieved with an uninterruptible power supply (UPS), which combines an AC voltage regulator, low-pass filter, and isolation transformer. When selecting the capacity of an uninterruptible power supply (UPS), the UPS capacity should be greater than 30% of the total power supply capacity, and the power supply time should be greater than 2 hours. Using distributed independent power supplies, employing multiple independent power sources, can prevent a single power supply failure from affecting the entire monitoring system. It also reduces the coupling of various interferences in the power system, thus greatly improving power supply reliability. 2.2 Improving the anti-interference capability of input/output interface channels: Using opto-isolation components on the digital input/output interface channels can isolate the electrical connection between the computer's internal and external systems, effectively preventing spike voltage interference and other types of interference, and improving the signal-to-noise ratio on the input/output channels. Furthermore, the input and output of the opto-isolation device are sealed in a single chip, making it unaffected by external light. Back-calibration technology is used on the digital output channels. Back-calibration improves the reliability of control outputs, especially for the control of some important circuit breakers, preventing failure to operate or malfunction. Filters are used on the analog input channels. This is a compensation measure taken when interference signals mix with valid signals, and it is also an important means of noise suppression. To prevent interference between magnetic fields and connecting lines, all external leads to input/output interfaces are double-wired. This ensures that electromagnetic induction interference in each small loop cancels out, which is also the most economical and convenient method. Additionally, RC circuits can absorb the interference from electrical sparks generated when contacts in various components operate. 2.3 Improving Electromagnetic Interference Resistance Eliminating or suppressing electromagnetic interference can be done by addressing its three elements. Necessary measures can be taken within the system to eliminate it, primarily utilizing shielding, isolation, wiring, and grounding techniques. Shielding and Isolation: Electromagnetic interference is a form of spatial interference and can be mitigated using shielding techniques. Shielded cables are used for connecting cables outside the shielding cabinet of the hydropower station computer monitoring system to prevent electromagnetic interference to the input/output interfaces. For some equipment, metal casings can be used for shielding, and the shielding layer must be securely grounded to prevent high-frequency signals from entering the corresponding components of the computer monitoring system through distributed capacitance. Wiring Requirements: Isolation should be considered during loop wiring to reduce mutual inductive coupling and prevent interference from entering through mutual inductive coupling. When wiring inside the cabinet, AC power lines, DC power lines, switch input/output signal lines, analog input signal lines, and inductive load control lines such as relays should be separated as much as possible to minimize electromagnetic interference between lines. When wiring outside the cabinet, cables related to the computer monitoring system should avoid high-rise cables, busbars, and power cables. Strong and weak signal cables should not share the same cable. Signal cables should avoid power cables as much as possible, maximizing the distance between them and minimizing their parallel length. Grounding: The grounding of shielded cables connecting the computer monitoring system cabinet to the outside is usually required to be single-point grounding. When multiple circuits share a grounding wire, its impedance should be minimized. In systems composed of multiple electronic components, the working grounds of each electronic component should be connected together and connected to the safety grounding network through a single point. The potential of each point on the working grounding network should be kept as consistent as possible. In areas prone to lightning strikes, lightning protection for computers cannot be ignored. This includes using dual electromagnetic and electrostatic shielding and installing lightning rods 1.2 meters above overhead computer lines. Secondly, proper equipment placement can reduce the impact of interference, sometimes even eliminating it without additional technical measures. For example, the location and orientation of the host industrial control computer affect electromagnetic interference differently, and in some cases, it can even eliminate the interference. Furthermore, strengthening anti-interference capabilities in the software can also improve the reliability of the monitoring system.