Hv Genration - Transpformation - Converson & Distribution

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SHIPBOARD POWER GENERATION CONVERSION AND DISTRIBUTION SYSTEM

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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General Power Systems • Majority of merchant ships have a 3-phase 3 wire, 440 V insulated neutral earth power systems • This power system falls in the category of LV and meets the power demands of medium capacity motors up to 200 kW

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contd • 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 = VI Cos • Copper loss = I2 R [kW]

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Losses in Electrical Systems • Copper Losses in electrical cables and machine windings • Hysteresis Loss in magnetic cores • Eddy current loss in conductors and cores • All these losses are current dependent and rise to very high levels in LV machines for large power ratings

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Benefits of H V Power Systems • Ships with large electrical loads now operate at high voltage of 3.3-6.6 kV • Such high voltage reduces the magnitude of current and thus lowers iron/copper/eddy current losses and also results in a cooler motor operation • Low current flow reduces conductors size and hence lowers cost of electrical equipment • Power transmission more efficient with low loss

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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contd • A 6 MW motor load at 440 V and 0.8 pf will require SB fault level to be of 90 kA and cable full load current of 3300 A • Same power system at 6.6 kV, needs SB fault level of only 9 kA and cable full load current of 220 A

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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contd • Flexibility of power system layout – Prime Mover-Generator units can be located at convenient location away from the propellers – Propulsion motor can be located at the astern below the water surface – This results in shorter shaft and reduced vibration

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contd • Load Diversity – A set of prime movers can meet the demand of propulsion as well as ships electrical load – Prime movers can be operated at economical speed at all times – Propulsion load can be regulated to meet emergency electrical load without adversely affecting the ships passage time

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contd • Ease of Control – With advancement in power electronics fine speed regulation of ac motors has become common practice

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Typical Marine HV Systems • • • •

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3.3 kV 6.6 kV 11 kV By generating electrical power at 6.6 kV instead of 440 V, distribution and switching power about 6 MW becomes easy

D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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• • • • •

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Principal Components of HV System Main Generators HV Switch Board HV Cables HV Transformers HV Motors (2-12 MW)

D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Typical HV Equipment Rating • Main SB = 6.6 –11 kV, Bus Cap =1250A • Cargo SB = 6.6 kV, Bus Cap =1250 A • Ballast Pp Motor = 6.6 kV, 330 – 2000 kW • • • • OLADOKUN

HD Copm = 6.6 kV, 770 kW, 3560 rpm Bow Thrusters = 6.6 kV, 3 MW, Transformer = 3400 kVA, 6600/450 V Reefer Transformer = 6600/450 V, D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Typical HV Power System

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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HV/LV Power Supply system

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Propulsion Plant Layout

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Propulsion Plant Layout

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Propulsion Plant Layout

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Propulsion Plant Layout

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HV Propulsion Power System

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Concept of Electrical Propulsion

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Typical Azipod Prime Mover

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Azipod Drive Unit

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Typical EL Propulsion

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Twin Shaft EL Propulsion

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Earth Connections • Distribution systems of these high voltage usually have their neutral points earthed to the ship’s hull through a resistor • The resistor in neutral line limits earth faults currents and protects equipment

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Types of Neutral Connections • Insulated Neutral System • Earthed Neutral System • Resistance earth Neutral System

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Insulated Neutral to Earth • This system is totally insulated from the ship’s hull • This system maintains continuity of power supply to the equipment even in the event of single phasing fault. • This ensure power supply to critical equipment • The power supply to the equipment can disrupt only if two single phase faults occur simultaneously in two lines which is then equivalent to short circuiting faults • But such fault occur very rare OLADOKUN

D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Insulated Earth Neutral

Gen

Load

Earth

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Insulated Earth 3-Phase

Gen

Earth OLADOKUN

Load

Single Earth Fault no effect D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Insulated Earth 3-Phase

Gen

Earth OLADOKUN

Load

Double Earth short Circuit D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Neutral Earthed System • Earthed Neutral is done in 3-phase system for supply voltage of 3.3-6.6 kV and above • If a solidly earthed system is used for such high voltage then magnitude of earthed current will be extremely high which can damage the equipment • The earth current is limited by connecting a resistor in series between earth and neutral point • The earth current due to single phasing is limited not to exceed rated current at maximum load

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Neutral Earth 1-Phase

Gen

Load

Earth

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Fault D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Neutral Earth 3-Phase

Gen

Earth OLADOKUN

Load

Fault in Line D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Switch Boards • Switchboard is the main electrical power control center of the ship • All generators deliver their electrical power to the main switch board. • Main switch board supplies power to section boards, motor starters, lighting boards and other distribution lines • Main switch board is connected to emergency switch board/ generator/battery back up

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D1MC Semester 1 / Energy Conservation Management ( ECM06) / May 2007 /

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Types of Switch Boards • Open front Type – All essential switch gears are exposed in front of the panel. Used for dc power system

• Dead Front Type – All switch gears and live parts are concealed behind the front sheet panel – Only the operating handle and instruments appear on the front. Mandatory for ac power system

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Contd • Dead front SB is made accessible by providing hinged doors in the front panel • Some times too many equipment crowd the SB which make maintenance difficult • Indication Lamp is provided in the switchboard to show that the shore supply is available for connection to bus bar

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FPSO Electrical system Layout

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Shuttle Tanker Electrical System Layout

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Shuttle Tanker Electrical Line Diagram

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Drill Ship Electrical System Layout

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