What is guarding in overhead lines? A guarding is provided for the safety of life, installation, and communication circuits. The guarding for 11 KV lines is provided at road crossings, canal crossings, railway crossing, crossing over lt lines, or communication lines.
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What is purpose of guard wire?
A grounded conductor placed beneath an overhead transmission line in order to ground the line, in case it breaks, before reaching the ground.
Why guard ring is used in transmission line?
The purpose of guard ring in transmission lines is to Reduce the earth capacitance of the lowest unit.
What is guarding in electrical?
Guarding involves locating or enclosing electric equipment to make sure people do not. accidentally contact live parts. Effective guarding requires equipment with exposed parts. operating at 50 volts or more to be placed where it is accessible only to authorized people. qualified to work with it.
Why insulators are used in overhead lines?
The insulators in overhead transmission lines are required to withstand both mechanical and electrical stresses. The mechanical stress is due to the conductor load, wind load, etc. while the electrical stress is mainly due to line voltage and it may cause the breakdown of the insulator.
What is Shield angle?
The Shielding Angle is defined as the angle between an imaginary vertical line extending downward from the overhead ground wire and an imaginary line connecting the ground wire and phase conductor, as shown in figure below.
What happens if earth wire is not provided in overhead?
If the resistance between them is not low and the earth wire or tower will be struck by the lighting, then the lighting will be raised to the very high potential, which will cause a flash over from the tower to one or more phase conductors. Such a flashover is known as back flashover.
Why are the guard ring used in high tension line?
Grading Ring or Guard Ring equalizes the potential distribution across each disc in Suspension Insulator. Grading Ring nullifies the effect of shunt capacitance of string insulator (suspension type insulator is also called string insulator).
What is guarding in transmission line?
Guarding: A guarding is provided for the safety of life, installation, and communication circuits. The guarding for 11 kV lines is provided at road crossings, canal crossings, railway crossing, crossing over lt lines, or communication lines.
What is corona in transmission line?
Corona Effect in Overhead Transmission Line
The phenomenon of violet glow, hissing sound and production of ozone gas in an overhead transmission line is known as corona. When a very high voltage is applied across two conductors of the overhead transmission line whose spacing is large as compared to their diameters.
What is the purpose of cross arm in OH lines?
One of the most important design elements responsible for the mechanical stability of the overhead line is a cross arm for power lines. They are used to fix securely the wires of the overhead line to the pole.
What is the purpose of guarding electrical equipment with exposed parts?
To avoid the risk of accidental shock, live electrical components operating at 50 volts or more must be guarded with covers or other permanent barriers to prevent accidental contact by workers and their tools. Equipment can also be locked behind an enclosure, in a room, or at an elevated height.
What is 11kV line?
The 11kV lines are used in residential areas and is what feeds the local transformers, which then distributes power to the buildings in the area. 33kV lines on the other hand involve much higher voltages and are used to distribute power from one small sub-station to another.
Which conductor is used in 11kv line?
3 to 7 are all ACSR Conductors and are commonly used on 11kv lines, except Dog conductors.
How many insulators are in a kV?
We usually use as a rule of thumb for determining the number of porcelain/glass suspension disc insulators: 10kV for each disc (standard 5-1/4′ x 10″). For typical system voltages in North America, this would be: 69kV: 4-6 discs; 115kV: 7-9 discs; 138kV: 8-10 discs; 230kV: 12 discs; 345kV: 18 discs; 500kV: 24 discs.
What is sag in overhead line?
In a transmission line, sag is defined as the vertical difference in level between points of support (most commonly transmission towers) and the lowest point of the conductor. The calculation of sag and tension in a transmission line depends on the span of the overhead conductor.
What is Ferranti effect in power system?
In electrical engineering, the Ferranti effect is the increase in voltage occurring at the receiving end of a very long (> 200 km) AC electric power transmission line, relative to the voltage at the sending end, when the load is very small, or no load is connected.
What is ground wire in substation?
A substation grounding system has two main parts: the grounding network and the connection to the earth. The grounding network bonds all equipment frames and metallic structures in the substation, while the connection to the earth is the interface between the electrical system and the earth.
What is angle of deviation in transmission tower?
????? ?????? also called tension tower are used where the line deviates at significant angles (more than 5 degrees). They are classified according to the angles of deviation; Light Angle (up to 15 degrees), Medium (15-30 degrees) and Heavy (up to or past 60 degrees).
Why ground wire has current?
Ground wire acts as defense against unstable electrical currents. Under normal circuit conditions, ground wire isn’t carrying any current. But when an electrical accident such as a short circuit occurs, the ground wire takes the unstable current away from your electrical system and sends it toward the ground.
How do you calculate ABCD parameters?
To characterize transmission lines using ABCD parameters, the line is modeled as a general two-port network.
ABCD Parameters of a Transmission Line.
| Type of Circuit | ABCD Parameter Values or Relationship |
|---|---|
| Symmetrical | A=D |
| Reciprocal | AD-BC=1 |
| Open-circuited | A=C=0 |
| Short-circuited | B=D=0 |