Monday, August 3, 2020

High voltage

Voltages up to & Including 1000V is known as Low voltage system and Voltages 1001 and above is called as High Voltage system in maritime practice for ships.
Why High Voltage in Ships
  • Higher power requirements onboard vessels is the foremost reason for the evolution of HV in ships.
  • Higher power requirements have been necessitated by development of larger vessels required for container transort particularly for reefer containers.
  • Gas carriers needing extensive cooling electrical propulsion.
  • For ships with a large electrical power demand it is necessary to utilize the benefits of a high voltage HV installation.
  • The design benefits relate to the simple ohms law relationship that current (for a given power)is reduced as the voltage is increased. 
  • Working at high voltage significantly reduces the relative overall size and weight of electrical power equipment.
As per Ohms law, POWER = VOLTAGE x CURRENT
For a given Power, Higher the Voltage, Lesser is the Current
440 KW = 440,000 watts              
               = 440 Volts x 1000 Amps              
                -1100 volts x 400 Amps              
               -11000 volts x40 Amps 
When large loads are connected to the LV system the magnitude of current flow becomes too large resulting in overheating due to high iron and copper losses.
P= V I cosĪ¦
Copper Loss = I2 R
Advantages:
  • For a given power, Higher voltage means Lower current, resulting in Reduction in size of generators, motors, cables etc.
  • Saving of Space and weightEase of Installation
  • Reduction in cost of Installation
  • Lower losses — more efficient utilisation of generated power.
Disadvantages:
  • Higher Insulation requirements for cables and equipment used in the system.
  • Higher risk factor and the necessity for strict adherence to stringent safety procedures.
  • Trained crew.

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