What is wire measurement? What is the safe current of wires and cables? - Solutions - Huaqiang Electronic Network

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Test probe P100-M3

Traverse survey refers to the operation of measuring wire length, corner and elevation, and inferring coordinates.

A method of selecting a series of points on the ground to form a line, setting up a station at the point, and then measuring the horizontal position of the points by using the edge measurement and the angle measurement method. Traverse measurement is a method of establishing a national geodetic control network and a common method for establishing control points in engineering measurements.

The line connecting the stations is called a wire, and the site is called a wire point. The distance between each adjacent two points and the angle between adjacent sides of each wire point are measured. From the coordinates and azimuth of a starting point, the horizontal position of each wire point is sequentially estimated by the measured distance and angle.

The wire measurement layout is flexible, the advancement is rapid, the terrain is limited, and the side length accuracy is evenly distributed. For example, in the areas of flat concealment, inconvenient traffic, and harsh weather, it is advantageous to use the traverse method to lay out the earth control network. However, the wire measurement control area is small, the inspection conditions are small, and the azimuth calculation error is large.

Conductor measurements, which are performed according to the accuracy requirements of the National Geodetic Network, are called precision traverse measurements. The conductors should be closed or looped between the advanced control points to increase the inspection conditions. The astronomical latitude and longitude and azimuth are measured at regular intervals on the wire to control the azimuth error.

After the appearance of the electromagnetic range finder, the traverse measurement was taken seriously. The electromagnetic wave range finder measures the distance, the operation is rapid, the accuracy is higher and higher with the improvement of the instrument, and the electromagnetic waveguide line measurement is widely used.

Closing the wire: Starting from the higher control point, it finally returns to this higher control point to form a closed polygon.

Attached wire: Another high control point is measured from the high control point.

What is the wire sag?

Wire sag refers to the vertical distance between the lowest point of the wire and the line between the two suspension points when the height of the wire on the adjacent two base poles is the same on the flat ground. If the height of the suspension point of the wire on the adjacent two poles is different, at this time, two sag will appear in one gear distance, that is, two suspension points of the wire have two vertical distances to the lowest point of the wire, which is called Maximum sag and minimum sag.

The line conductor sag measuring instrument is used, which is suitable for measuring the sag of the electric line wires of various voltage levels and the geometry of the relevant structures. Optical measuring instruments using lens technology. The main features are the setting of the objective lens, zoom lens, image plate, distance gauge, vertical adjuster and level adjuster. The real image of the measured object is taken by the objective lens and displayed on the image plate. After adjusting the instrument, the measured value is measured on the image plate by proportional principle.

A range finder can also be used for the measurement.

What is the safe current of wires and cables?

The safe current is also called safe flow or allows continuous current.

When current passes through a wire or cable, the presence of impedance causes power consumption, causing the wire seven cable to heat up and the temperature to rise. The higher the current through the wire or cable, the higher the temperature of the wire or cable. When the temperature rises to a certain value, the insulation of the seven cables of the wire may be damaged, and the external oxidation may be intensified, thereby causing leakage, disconnection, etc., and may cause fire or the like when severely punished.

In order to ensure the safe operation of electrical lines, the cross-section of the wires and cables of all lines must meet the heating conditions, that is, at any ambient temperature, when the wires and cables continuously pass the maximum load current, the line temperature is not greater than the maximum allowable temperature ( Usually about 700C), the load current at this time is called the safe current.

The safe current of wires and cables is determined by their type, specification, ambient temperature and laying method. There are special forms to check.