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HVDC AND CHALLENGES HVDC AND CHALLENGES
WITH MULTIWITH MULTI--TERMINAL TERMINAL
HVDCHVDC
BY: NARASIMHARAO
ROLL NO:M080164EE
Presentation outlinePresentation outline
� Introduction
� HVDC advantages & disadvantages.
� HVDC configurations
� Multi-terminal HVDC
� Challenges with multi-terminal HVDC
IntroductionIntroduction
� First only 2.5Kw transmitted in 1882 by using direct.
� In 1889 630Kw at 14kv DC.
� Gives why we need to go for HVDC transmission.
� Gives information about configurations in HVDC
� In multi-terminal HVDC converters can be connected in series
or parallel.
� Parallel converters gives more flexibility and lower losses.
� About the challenges with multi-terminal HVDC
� Require isolation switch for isolate converter from the fault or
disturbance.
Why we need HVDC Why we need HVDC
� No charging currents in HVDC.
� DC link between the two systems.
� Less losses in line.
Advantages HVDC over AC SystemAdvantages HVDC over AC System
� Transfer Large power with low cost.
� power transmission and stability between the two
asynchronous ac systems.
� No skin effect & less corona losses.
� Power per conductor is more
disadvantagesdisadvantages
� HVDC require static inverters which are expensive & limited
over load capacity.
� Need good communication between the all the terminals.
� Difficult to design the HVDC breakers
configurationsconfigurations
MultiMulti--terminal HVDC terminal HVDC
� It is more complex.
� Telecommunications require between the stations also large.
This is large scale HVDC systems operation in the world.
IT 2000MW in England transmission.
Challenges with multiChallenges with multi--terminal terminal
HVDC HVDC
� Parallel converters in the same station.
� Multi terminal schemes.
� Disconnection of fault dc line section.
� Isolation of switches without dc current
breaking.
� Isolation by using HVDC breaker.
� Detection and clearing of converter faults.
� Importance of telecommunication.
� Electric and magnetic fields.
Parallel converters in the same stationParallel converters in the same station
� Operation is easy
� No importance to telecommunication is needed.
� The only challenges to secure the continued operation without
risk for the overload if one of the parallel rectifier or inverter
when the telecommunication is out of service.
multimulti--terminal schemes, all terminal schemes, all
converters with similar rating converters with similar rating
� When the converters in different stations there is an increase need for telecommunication.
� Telecommunication is need for
Proper timing of rectifier at dc line fault.
Identification of faulty dc line section.
Actions for clearing faults in converters or line
sections.
� Restoration of power transmission as far as the possible after an outage of converters or dc line section.
� Challenge is that there must be backup function for
power restoration and for preventing the overload of
equipment in the case that the telecommunication is out of
service.
Disconnection of fault dc line sectionDisconnection of fault dc line section
� It possible to isolate fault section and still operate the remaining converters.
� Necessary fault detection and switching or isolating devices
would be need to identify the specific dc line section.
Isolation by switches without dc Isolation by switches without dc
current brakingcurrent braking
� We can use isolators but it take more seconds to perform the
task.
� We need a high speed switch (HSS)
It can perform the task very short times (<150ms)
Isolation by using HVDC breakerIsolation by using HVDC breaker
� It will perform isolation without waiting for zero current.
� An HVDC breaker will have combination of HSS and non
linear resistors.
� In HVDC insulation levels are high.
Importance of telecommunicationImportance of telecommunication
� increases with a number of converters operating in parallel.
� With out proper telecommunication system may lead to
prolonged disturbances.
� It not possible to change the load without telecommunications.
Detection and clearing of converter Detection and clearing of converter
faultsfaults
� We need master controller and sequence in logic VDCOL setting.
� Even when telecommunication is totally out of service , a
well designed multi-terminal system will use special VDCOL
characteristics to detect faults .
Electric and magnetic fieldsElectric and magnetic fields
� HVDC limit increases with decrease in frequency.
� Use larger diameter conductor
corona loss will also decreases as field around the conductor
decreases
ConclusionsConclusions
� we have to run the system even when telecommunication out
of service
� Design high speed HVDC breakers
� Use isolators with high speed switch.
� Design hardware for isolating parts of HVDC transmission systems.
THANK YOU
THANK YOU
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