Control Cable and Its Metal Shielding Standards
Release date:
2022-12-27 11:42
Source:
Control cable Suitable for industrial and mining enterprises, as well as the energy and transportation sectors, these cables are designed for control and protection circuits with rated AC voltages of 450/750V and below. Control cables feature moisture-proof, corrosion-resistant, and damage-preventive properties, making them ideal for installation in tunnels or cable trenches. Power cables are used to transmit and distribute high-power electrical energy along the main lines of power systems, while control cables serve to deliver electricity directly from distribution points within the power system to the power supply connections of various electrical equipment and appliances. Typically, power cables have a rated voltage of 0.6/1kV and above, whereas control cables primarily operate at 450/750V.
Control cables shall use copper conductors with a rated voltage no lower than the operating voltage of the connected circuit, and 450/750V cables are recommended. The selection of insulation and sheath types for control cables must meet the requirements of the installation environment and environmental protection standards, as well as comply with relevant regulations.
The number of control cables should meet the following requirements: 1. Multi-core cables are recommended for control and signal applications. When the cross-sectional area of the conductor is 1.5 mm² or 2.5 mm², the number of cable cores should not exceed 24. For conductors with a cross-sectional area of 4 mm² or 6 mm², the number of cores should be limited to no more than 10. 2. Control cables must include spare cores, which should be selected based on a comprehensive consideration of factors such as cable length, conductor cross-section, and installation conditions. 3. Circuits under any of the following conditions must not share the same control cable: AC current and voltage circuits, AC and DC circuits, high-power and low-power circuits; low-level signal circuits and high-level signal loops; the control circuits for two sets of trip coils in an AC circuit breaker, as well as the low-voltage control circuits for each phase during phase-specific operation; and the star-connected and open-delta-connected circuits of the same voltage transformer running from the switchgear to the relay room. 4. Each pair of return conductors in low-voltage circuits must be routed within the same control cable. 5. The three-phase conductors and the neutral conductor from the secondary winding of the same current transformer must be placed within the same control cable.
The selection of the metal shielding layer for control cables should meet the following requirements: 1. For control cables in high-voltage circuits, if they are located within high-voltage switchgear or remain in close proximity to, or run parallel with, high-voltage cables for extended periods—provided that interference is effectively suppressed—metal shielding may not be necessary. 2. For control cables carrying weak electrical signals and used in control loops, metal shielding must be employed when these cables are situated in environments prone to interference and no effective anti-interference measures are available. 3. Secondary circuit cables for microcomputer-based relay protection systems and computer monitoring systems must use shielded cables. 4. DC power cables for control and protection equipment should also utilize shielded cables.
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