What is the voltage level of LT and HT line

full form of LT and HT

 LT - Low tension ( Low voltage )

• voltage range - Below 1000 Voltage
• Used in secondary distribution system

HT - High Tension ( High Voltage )

Voltage range - 1000 V to 33 kv

Used in primary distribution system

EHT - Extra High Tension ( Extra High Voltage )

Voltage range - Above 33 kV

Used in transmission system 

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Why we use HT motors

 HT Motors - High Tension Motors

 HT motors take high voltage the increase in voltage leads to decrease in current which thereby leads to decreases in size of conductor. Thus the size of the cables and distribution line reduces. The protection equipment size and cost also reduced and also the size of the machine reduces as compared to that LT motor size.

Power losses = I^2 R

Here 

I - current flow through the winding 

R- Resistance of the winding 

Resistance R = R = ρ L / A

1. Low power losses

2. High efficiency

3. Smaller construction 

4. Cable cost is low

What is the difference between HT and LT lines

LT - Low Tension ( Low Voltage )

        

Low tension lines have low voltage less than 1000 volts and high current distribution system Example of 440V 3 phase supply and 230v Single phase supply.commonly we used LT  in Secondary distribution system like our household applications are working in LT. It is used to transmit power at very small distances and use thicker conductor.

 ( P= VX I ) 

Here Low voltage and higher current , conductor size depending up on current.

HT - High Tension ( High voltage )

  

High Tension lines are using higher voltages ( 11kV, 33kV, )  it is used to Distribute power to large distances by in creasing voltage and decreasing current so as to reduce I^2 R losses. HT line uses thinner conductors than LT  line conductor.

Why do LT motors have high winding resistance and HT motors have low winding resistance

Power P = V X I 

V = Voltage 

I = Current 

LT motors used lower voltage so its take higher current and larger size of copper conductor for stator winding. 

Power loss = I^2 R losses

 Here 

I - Current flow through the conductor

R- Resistance of the conductor

 Resistance   R = ρ L / A     

Here

ρ = resistivity of the conducting materials

L - Length of the conductor

A - Cross sectional Area of the conductor 

The resistance of a wire is directly proportional to its length and inversely proportional to its cross sectional area. So LT motors have high winding resistance and HT  motor have low winding resistance. 

HT motor takes high voltage and low current in same power so we used smaller size of conductor for stator winding.

 

What is the different between HT and LT Motors

 HT Motor - High tension (Voltage ) motors 

    HT motor called high tension motor usually supply above 1.1 kv and its rating mostly above 150 KW

The increase in voltage leads to decrease in current which there3by leads to decrease in size of conductor. Thus the size of cables and transmission line deduces. The protection equipment required for the same also reduces. Also the size of machine reduces as compare to that of LT Motor size.

LT Motor - Low Tension (Voltage) Motors

     LT motor called low tension motor usually supply from 230V single phase and 440v 3 phase system. It’s rating less than 150 kW.