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What are the measures for control cables to prevent or reduce electrical interference?

Update:22-02-2021
Summary:

The measures to prevent or reduce electrical interferen […]

The measures to prevent or reduce electrical interference mainly include the following three aspects.

1. Each spare core of the control cable is grounded
Practice has proved that when a spare core in the control cable is grounded, the amplitude of the interference voltage can be reduced to 25%~50%, and the implementation is simple, and the cost of the cable increases slightly.

2. It is not suitable to use a control cable for circuits that will have serious consequences when electrical interference
Including: (1) weak current signal control loop and strong current signal control loop; (2) low-level signal and high-level signal loop; (3) AC circuit breaker split-phase operation of each phase of the weak current control loop. The same control cable should be used. However, if each pair of back-and-forth wires of the weak current circuit belong to different control cables, they may form a loop arrangement when laying. The electric potential will be induced under the electromagnetic wires of similar power sources. The interference of flat parameters has a greater impact, so it is advisable to use a control cable for the round-trip wires.

3. The metal shield and the shield layer are grounded
Metal shielding is an important measure to reduce and prevent electrical interference, including general shielding, sub-shielding and double-layer general shielding to the core. The selection of the metal shielding type of the control cable should be based on the strength of the electrical interference that may be generated and included in the comprehensive interference suppression measures to meet the requirements of reducing interference and overvoltage. The higher the requirement for anti-interference effect, the larger the corresponding investment. When steel tape armor and steel wire braided general shielding are adopted, the price of the cable will increase by about 10% to 20%.
The control interference in the strong current circuit, due to its own strong signal, except for the ultra-high voltage power distribution device or the close and long parallel to the high voltage cable, the control cable without metal shield can be used. The control cable used in the weak current signal control loop, when it is located in an environment affected by interference and does not have effective anti-interference measures, a metal shielded control cable should be used to prevent electrical interference from causing misoperations on the low-level signal loop Or cause edge breakdown and other influences. If the control cable of the weak current loop can be separated from the power cable by a sufficient distance or laid in a steel pipe, the external electrical interference may be reduced to the allowable limit.

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