# HVDC transmission system and its three different transmission modes

**URL:** <https://forumautomation.com/t/hvdc-transmission-system-and-its-three-different-transmission-modes/6109>\
**Category:** Electrical\
**Created:** [March 19, 2019, 5:21pm UTC](https://forumautomation.com/t/hvdc-transmission-system-and-its-three-different-transmission-modes/6109 "2019-03-19T17:21:21Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ashlin](https://forumautomation.com/user_avatar/forumautomation.com/ashlin/32/3775_2.png) [@ashlin](https://forumautomation.com/u/ashlin)\
**Post date:** [March 19, 2019, 5:21pm UTC](https://forumautomation.com/t/hvdc-transmission-system-and-its-three-different-transmission-modes/6109/1 "2019-03-19T17:21:21Z")

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**HIGH VOLTAGE DIRECT CURRENT TRANSMISSION**

Electrical power is generated and transmitted as alternating current but for long distance transmission, it will create much loss or in the case when two AC systems cannot be synchronized. So we could use DC transmission method massive [transmission](https://forumautomation.com/t/what-are-the-elements-of-a-distribution-system/6379) of the direct current over a long distance by using submarine cable or the overhead transmission line is the HVDC while doing long distance transmission in AC the cost, loss and many other things and thus we could use HVDC

 ![image](https://cdn.forumautomation.com/original/2X/5/5047ebbae271e6b85c5e18288a58c93ec0abea79.jpeg)

**ADVANTAGES OF HVDC TRANSMISSION**

- HVDC uses simpler and cheaper tower
- Reduced conductor and insulator cost
- Dc line requires less right of way
- Decrease in power loss in Dc transmission because there are only two conductors
- Skin effect is not seen
- Lower power loss than HVAC
- More power will reach to the destination
- It requires fewer overhead lines when compared to HVAC
- Dielectric strength of the cable is high
- Corona and radio frequency interference losses are less
- Voltage regulation and control ability is high
- Needs less insulation
- Reliability and asynchronous interconnection is possible
- Line cost reduced because of fewer conductors

**HVDC TRANSMISSION SYSTEM**

The power is generated as Ac and it must be converted to Dc for this we use rectifier then we could [transmit](https://forumautomation.com/t/how-to-compensate-the-reactive-power/6282) the power as DC and then at the [destination](https://automationforum.co/advantages-of-three-phase-over-single-phase-transmission/) this will be converted to AC by the inverter in the receiving end

 ![image](https://cdn.forumautomation.com/original/2X/e/e96abc3865e8c6a30fcbb8dd99c93df0e32eb58c.jpeg)

**TOWER AND LAND COST**

 ![image](https://cdn.forumautomation.com/original/2X/8/80d67d9b84ff47c07a1174323f504568e376f979.png)

**TRANSMISSION FOR LONG DISTANCE WATER CROSSING**

In AC [transmission](https://automationforum.co/what-are-power-plants-types-of-power-plants/) the power flow will be affected by the cable capacitance for long distance transmission by using HVDC there is no such problem

![image](https://cdn.forumautomation.com/original/2X/e/e6d0bdd5fa516eb4dcbef0232800d41ebe1cd13e.png)

**THERE ARE THREE DIFFERENT TRANSMISSION MODES**

Monopolar, Bipolar, Homopolar

Monopolar

In this case, one pole is used at DC voltage level and the ground is a permanent return path this is used for submarine/underground cables

BIPOLAR

This type uses two poles one is positive and other is negative at each conversion substation midpoint of the converter is earthed current carried by the ground is less if one of the poles is not in service

HOMOPOLAR

It consists of two conductors of the same polarity on the same tower

The ground is used as a return path it is used for the overhead DC line feeding into the DC cable