Follow us for fresh information

News

What is the measured value of insulation resistance between low-voltage cables and wires, and between wires and ground?

Release time:

2023-07-27 11:14

What is the measured value of insulation resistance between low-voltage cables and wires, and between wires and ground?

The standard is not less than 0.5M, but the actual measured data is very uneven. The insulation resistance is directly related to the material, cross-sectional area and length, as well as the number of line connectors and the temperature of insulation recovery! Take the house as an example: in the absence of lighting equipment, it is generally 9~15M, air conditioning socket 30~150, kitchen and toilet 30~200M ordinary socket is the smallest, because the extra power cord needs to be connected, hot tin, to restore insulation, insulation resistance is the smallest, generally not more than 1.5m. This is the insulation resistance of the whole line and the ground two lines. In the case of cable line, the main influencing factors are length, temperature, humidity, construction quality, etc! Usually 100-400 is no problem!

1. Select the cable section according to the long-term load and short-term load, K * Ixu>Ig can start calculation; Ixu is the load flow allowed by the cable, Ig is the long-term allowable working current, and can also be selected according to the load according to the capacity selection.

First of all, according to the transformer capacity and connection method, generally 0.4kV is Y connection, and according to the 630 and 400 capacity, the rated current of low voltage output is 909A and 577A; According to this current, it can be used as long-term working current. Of course, Ig ==== Igt K * Idt (see the contents selected in chapter 7 of the power design manual for details) can also be used, I .e. selected according to long-term load and short-term load; Cable cross section, K * Ixu = Ig;Ixu is the allowable current carrying capacity of the cable, Ig is the long-term allowable working current, which can be selected according to the capacity or the load. Therefore, the selection according to the rated capacity is only large or not. K is the correction coefficient under different cable laying conditions. It is divided into single cable in the air and low voltage working current in the air. It can also be selected according to the capacity or load, only large or not small; according to the different capacity of the transformer, it is generally Y wiring, and in the air, according to the capacity selection can also be selected according to the load. In addition, the temperature of 400kVA is 35 degrees, allowing the working temperature of the cable to be 65 degrees, single 577/0.865A = 667A, which does not meet the requirements of the 300 section!

3, cable (electriccable;powercable): usually consists of several or several groups of wires.

4, the cable is usually a kind of several or several groups of wires [each at least two] twisted into a rope-like cable, each group of wires insulated from each other, and often around a center twisted into a whole, the entire outer cover has a high insulation layer. Multiple erection for telecommunications or power transmission is underground, underwater. In 1832, Xu Lingge, a retired officer of Tsarist Russia, buried the telegraph line underground. After six wires were insulated with rubber, they were installed in glass tubes together, which was called the earliest underground cable in the world.

An insulated wire consisting of one or more electrically conductive cores insulated from each other within a gland. A protective layer can be added to the outside of it to transmit electrical energy or send telecommunications signals. It is different from the general wire, mainly wire size, complex structure.