1.Air effects on the operation of transient lines 2.Types of damage to cable lines Done by: Aman A.B., Ergasheva Zh.B. ENSe Checked by: Baimakhanov. - презентация

1 1.Air effects on the operation of transient lines 2.Types of damage to cable lines Done by: Aman A.B., Ergasheva Zh.B. ENSe Checked by: Baimakhanov O.D.

2 Operating conditions of transient lines are largely dependent on climatic conditions: Air temperature Icing and frost formations Wind Lightning

3 Impact of air temperature For safety purpose, the ground clearance of the conductors at maximum temperature and minimum loading condition should be maintained. Analysis of the sag and tension is important in the transmission line for the continuity and quality of electrical services. If the tension of the conductor is increased beyond the limit, it may get broken, and the power transmission of the system get erupt. The dip of the conductor between the two level supports is called sag. In other words, the vertical distance between the highest point of the electrical pole or tower (where the conductor is connected) and the lowest point of the conductor between the two adjacent level supports is known as sag shown in the figure below. The horizontal distance between two electrical supports is called the span.

4 Icing and frost formations Ice formation occurs in frosty weather when the air temperature in the surface layer is from -0.5 to -5 ° C, less often at -10 ° C. The reason for the occurrence of ice is the intention of supercooled water droplets falling out of drizzle and rain. Ice crust adheres tightly to the overhead wire. In the case of asymmetric formation of ice causes a twisting of the wire, and with a large thickness of the wall of ice, its weight can many times exceed the weight of the wire itself.

5 Impact of the wind Transient lines are terrestrial structures, so for them the main disturbance is the horizontal component of the wind. It is the direction and speed of the horizontal component that are recorded and subsequently taken as input data when determining the calculated horizontal loads. The direct influence of wind on the operation of the transient line is its pressure on the wires, cables and supports. This pressure can cause breakage and the fall of the supports with the tearing of the foundations not firmly fixed in the ground. Support fall in hurricane winds

6 Lightning Lightning is a type of gas discharge with a very long spark. The total length of the lightning channel reaches several kilometers, with a significant part of this channel located inside a thundercloud. Overvoltage can reach hundreds of thousands of volts and cause a breakdown of the insulation of wires and electrical equipment and fires. They are dangerous to the lives of people who are in buildings and structures that are powered by electricity over the air line. To protect against lightning surges, overhead lines in populated areas with one- and two-storey buildings, not shielded by boiler chimneys, tall trees, buildings, etc., should have grounding devices. Grounding resistance - no more than 30 Ohms. The distances between the grounds for areas with an average number of hours of thunderstorms up to 40 take 200 m.

7 Types of damage to cable lines Damage occurs as a result of factors such as: - seasonal movements of soil, which usually occur in spring when thawing; - violations of operating conditions of cable lines (overcurrent); - passage of external (transit) short-circuit currents along the cable line; - execution of works near the cable line; - violation of technology with the installation of cable couplings.

8 Types of damage to cable lines - The nature of the damage depends on the choice of the method of finding its location. Here are the main ones: - A complete cable break. The main cause of occurrence: earthworks using excavators, short circuits in cable couplings. - Short-circuit of the cable phase core to the ground (for cables with voltage above 1000 V). - The short circuit between the veins. - Low insulation or breakdown during routine high voltage tests. It is characterized by the fact that the cable line can remain in operation, but guarantee that it will not short circuit at any time. - Phase-phase-ground closure combinations.

9 How to define cable route? The result of the search for the place of damage is an accurate indication of the terrain of the site with the damage. And since the cable line is hidden in the ground, then first specify the track on which it passes. You need to know the route with maximum accuracy. To determine it, a device called a tracer is used.

10 A locating device capable of operating in several modes: - determination of the location of the cable line under voltage. The greater the load (current) of the line, the better it is tapped; - define the alignment of the disconnected line. To do this, the set to the locator includes a sound signal generator. It connects between two veins of the line at one end of it, at the other end these veins are shorted. The signal supplied to the line is a sequence of modulated sound pulses with a low repetition rate. - determination of the place of closure of two conductors. To do this, a signal is sent from one end of the line to these cores. The cable radiates it to the point of damage, behind it the signal disappears.

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