**a) The Concept of Wire and Cable and the Difference Between Wires and Cables:**
Wire and cable refer to materials used for transmitting power, communication signals, and other related functions. While the terms "wire" and "cable" are often used interchangeably, there is no strict boundary between them. Generally, a product with fewer cores, smaller diameter, and simpler structure is referred to as a wire. A wire without insulation is called a bare wire, while those with insulation are known as cables. Conductors with a cross-sectional area greater than 6 mm² are considered large wires, whereas those smaller than or equal to 6 mm² are called small wires. Insulated wires are sometimes referred to as cloth wires.
Wires and cables include various types such as bare wires, electromagnetic wires, insulated wires for electrical appliances, power cables, communication cables, and optical fibers. Although the full name of a wire or cable can be quite complex, people often use a simplified name combined with the model and specifications to describe it. For example, "low voltage cable" may represent all plastic-insulated power cables rated at 0.6/1 kV. The range of wire and cable products is extensive, and once the standard model and specifications are defined, specific products can be identified. However, knowing the full name might still be unclear without proper context.
**The following principles apply when naming wire and cable products:**
1. **Content in the Product Name:**
- The application or size category name.
- The material or type of the structure.
- Significant or additional features of the product. These are typically named in that order, but sometimes important features are placed at the front or integrated into the structural description.
2. **Order of Structural Description:**
- The structure is described from the inside out: conductor → insulation → inner sheath → outer sheath → armored layer.
3. **Simplification:**
- In cases where confusion is unlikely, some parts of the structure may be omitted or abbreviated. For instance, if aluminum conductors are not used in automotive wiring, their material may not be specified.
**Examples:**
A cable named “Rated Voltage 8.7/15kV Flame-Retardant Copper Core XLPE Insulated Steel Tape Armored PVC Sheathed Power Cable†includes the following elements:
- “Rated Voltage 8.7/15kV†– indicates the application and voltage rating.
- “Flame-Retardant†– emphasizes a special feature.
- “Copper Core†– specifies the conductor material.
- “Crosslinked Polyethylene Insulation†– identifies the insulating material.
- “Steel Tape Armored†– describes the armored layer.
- “PVC Sheath†– refers to the outer sheath material.
- “Power Cable†– the overall product category.
In model notation, such as ZR-YJV22-8.7/15, the structure is as follows:
- [1: Category, Use]
- [2: Conductor]
- [3: Insulation]
- [4: Inner Sheath]
- [5: Structural Features]
- [6: Outer Sheath or Derivative]
- [7: Usage Characteristics]
Items 1–5 and 7 are usually represented by pinyin letters, while polymer materials are indicated by English letters. Each section may consist of 1–2 letters, and item 6 may have 1–3 digits. The copper core is typically denoted by “T,†unless specified otherwise. Bare wires, power cables, and magnet wires do not require major code indicators.
**5. What is a cable intermediate connector?**
Answer: A device used to connect the conductor, insulation shield, and protective layer of two cables to form a continuous cable line is called a cable intermediate connector.
**6. What is the main electrical connection?**
Answer: The main electrical connection refers to the way key electrical equipment and busbars are connected in power plants and substations, including the main busbar and plant power systems, based on functional requirements.
**7. What rules should be followed when selecting the cross-section of a power cable?**
Answer: When choosing the cross-section of a power cable, the following principles should be followed:
- The cable’s rated voltage must be equal to or higher than the system voltage at the installation point.
- The continuous allowable current of the cable must be equal to or greater than the maximum continuous load current.
- The core cross-section must meet short-circuit stability requirements.
- Verify that the voltage drop is within acceptable limits based on the cable length.
- The minimum short-circuit current at the end of the line should ensure reliable operation of the protection device.
**8. What are the advantages of cross-linked polyethylene (XLPE) cables compared to oil-paper cables?**
Answer:
- Easy to install due to a small bending radius and lightweight design.
- Not limited by line drop constraints.
- Excellent thermal performance, allowing higher working temperatures and greater transmission capacity.
- Simple and dry-type accessories.
- Low maintenance, with no oil leakage issues.
- Lower cost.
- High reliability and low failure rate.
- Fewer manufacturing steps, simpler processes, and better economic benefits.
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