Why 400KV not directly Stepped Down to 33KV in Transmission Line?

There are many important reasons why 400 KV is not directly Stepped Down to 33 KV. First, the 440 KV stepped down to 132 KV, then 132 KV to 66 KV, and then 66 KV to 33 KV.  The step up and step down of voltage is depending upon the Transformer. When transformers are designed, many factors are kept in mind. So, the answer to this question mostly depends on the transformer. In this article, we will discuss, what are the problems are to be faced if 400 KV directly stepped down to 33KV or 11KV.

Reason 1

We know that when we step down the voltage using a transformer the current will increase. So in this case, if we step down the 440KV to 33KV, the current will increase. But as there is a big difference between primary and secondary voltage, the difference between primary and secondary current will be high.

In this case, the secondary current would be 12 to 13 times higher than the primary current. As the current increases, the very very thick conductor should be used. For this reason, the size of the transformer will be extremely high.

Not only the current issue but there will be so many other problems that will occur due to a very high voltage difference between the primary and secondary winding.

Reason 2

The different transmission voltages are selected according to the distance of transmission. For very very large distance transmission purposes 440 KV is used and for short transmission purposes, 33KV is used.

So if we transmit electrical power at a medium distance, we must select a voltage level between 440 KV and 33KV such as 132 KV, 66K V, etc. Because if we transmit electrical power at a 33 KV voltage level at a medium distance the loss will be high and if we select a 440 KV voltage level for a medium distance the cost will be high compared to the distance which is not economical. Even at every voltage level, the electrical power is distributed to the consumer or the substations.

Reason 3

As there is a big difference between the primary and secondary voltage so the difference between no. of turns in the primary and secondary winding will be high. For this reason, the placement of windings, insulation arrangements, connections, and tappings may be impractical. So the manufacturing of a 440/33 KV transformer may not be possible. Even this type of transformer produces more losses.

Reason 4

If we step down the 440 KV directly to 33 KV and operate them with a very low load current, then a huge no. of transformers are to be installed in the distribution substation or receiver end. If we transmit power at 440 KV voltage level in all places, the size of the towers will be big and the gap between ground and conductors must be kept very high. So this high voltage transmission consumes very large areas.

These are the common reasons Why 400KV is not directly Stepped Down to 33KV in Transmission Line.

Read Also:

• Why we use 220V, 50Hz AC at home instead of DC or other voltage?
• Which is more dangerous AC or DC-Explained in details
• Why Current, Voltage changes But Power, Frequency constant in Transformer?

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