The difference between DC cable and AC cable

1. Compared with AC cables, DC cables have the following characteristics.

1. The system used is different. DC cables are used in rectified DC transmission systems, and AC cables are often used in power frequency (domestic 50Hz) power systems.

2. Compared with the AC cable, the power loss during the DC cable transmission is small. The power loss of the DC cable is mainly the DC resistance loss of the conductor, and the insulation loss is small (the size depends on the current fluctuation after rectification). Skin effect, the loss of insulation resistance accounts for a large proportion, mainly the impedance generated by capacitance and inductance.

3. High transmission efficiency and low line loss.

4. It is convenient to adjust the current and change the direction of power transmission.

5. Although the price of converter equipment is higher than that of transformers, the cost of using cable lines is much lower than that of AC cables. The positive and negative electrodes of the DC cable have a simple structure; the AC cable is a three-phase four-wire or five-wire system, which requires high insulation safety and a complex structure. The cost of the cable is more than three times that of the DC cable.

6. Safe use of DC cables:

 1) The inherent characteristics of DC transmission, it is not easy to generate induced current and leakage current, and will not interfere with the electric field generated by other cables.

 2) The single-core laying cable will not affect the transmission performance of the cable due to the hysteresis loss of the steel structure bridge.

 3) Compared with DC cables of the same structure, it has higher interception capability and over-cut protection.

 4) The DC electric field and the AC electric field of the same voltage are applied to the insulation, and the DC electric field is much safer than the AC electric field.

7. The installation and maintenance of the DC cable is simple and the cost is low.

2. Cable insulation requirements with the same AC and DC voltage and current

When an AC and DC electric field of the same voltage is applied to the insulation, the electric field of the DC cable is much smaller than the AC electric field. Due to the large difference in the structure of the two electric fields, the maximum electric field when the AC cable is energized is concentrated near the conductor, and the maximum electric field when the DC cable is energized is mainly concentrated on the insulating surface, which is safer (2.4 times).

Third, the mutual conversion relationship between AC and DC voltage

For the mutual conversion of AC and DC voltage, there are many different understandings. However, our company uniformly calculates according to GB12528.1, that is, the rated voltage of the DC cable of the same AC cable is 1.5 times the phase voltage of the AC cable. But our company's 1500V DC cable is designed according to DC3000V voltage and has safe electrical insulation performance.