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High-Voltage Direct-Current Power Transmission Systems

High-Voltage Direct-Current Power Transmission Systems
High-Voltage Direct-Current Power Transmission Systems
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Product Code : HVDC
Product Description

Powertransformers for high-voltage direct-current (HVDC) transmission systems

Tailored-to-fit and delivered fully-assembled, HVDCtransformers by Siemens enable reliable and highly-efficient HVDC powertransmission systems

Siemens expertise and experience produces superiortransformers for the HVDC schemes, HVDC Classic and HVDC Plus, in bulk powertransmission, offshore and onshore grid connections, back-to-back systems andother HVDC use cases. Portfolio: transformers, upgrades, replacement, repair,refurbishment, and the supply of selected components HVDC ratings: up to 12 GWand up to 1,100 kV DC AC grid connections: up to 1,050 kV AC Features: Compactdesigns, high reliability, and proven technology from Siemens’ globalmanufacturing network

Deregulation, privatization, growing demand, andenvironmental considerations have grid operators facing a new challenge:building secure and efficient power grids that delivers clean, reliable, andaffordable power over long distances to increasingly urbanized societies.Innovative HVDC transformers play a key role in shaping environmentallysustainable power grids while offering economic efficiency.

Smart grids are emerging as a necessary response to theenvironmental, social and political demands placed on energy supply.

With their capacity to increase transmission efficiency,innovative HVDC solutions will play a key role in making sustainable low-lossAC/DC hybrid grids a reality. With the transmission power capability of HVDCsystems steadily on the rise, requirements for converter transformer technologyand design have greatly increased. Customers rely on Siemens’ experienceddesign teams to help them master transmission and grid challenges around theglobe.

Bringing stability and security to grid and transmission

HVDC transformers are key components of HVDC stationsfor long-distance DC transmission lines or DC sea cables. As coupling elementsbetween AC grids and high-power rectifiers, they adapt the voltage, insulatethe rectifier itself from the AC grid, and generate a phase shift.

Back-to-back station

Back-to-back links are an easy solution for connecting twoAC networks with deviating frequencies. Grid operators not only strengthen andoptimize the performance of their grids with back-to-back links. They alsoallow both network users to balance varying loads and generation caused bydifferent time zones or usage patterns.

Long-distance overhead and submarine transmission

HVDC transformers are used as coupling elements between ACgrids and high-power rectifiers for very long overhead lines or submarinecables. Converting AC lines to DC can help increase the power transfer volumethrough existing rights of way and typically cuts line losses by 30-50%. HVDCis most efficient for overhead lines above 1,000 Mega Watt (MW) and600 kilometers. 

Replacement of HVDC transformer originals

With about one third of HVDC lines worldwide past the25-year mark, operators need to decide – invest in repairs that will give theman as-good-as-new transformer from the 1980s, or benefit from the latesttechnology? Siemens engineers excel in replacing HVDC transformer originals,producing units that replicate performance, capacities, and dimensions of theoriginal unit but offer the latest in transformer innovation.

HVDC technologies for long distances and low losses

Siemens offers two HVDC technologies: HVDC Classic and HVDCPlus. Siemens transformers meet all requirements for power, voltage, mode ofoperation, low-noise, connection types, types of cooling, transport, and installation.They also comply with specific national design requirements.

 

HVDC converter transformers for remote energytransmission

HVDC transformers are subject to operating conditions thatset them apart from conventional system or power transformers. These conditionsinclude:

·       combined voltagestresses with both AC and DC

·       high harmonics contentof the operating current

·       DC pre-magnetizationof the core

·       ideally, equalperformance parameter, when installing multiple units.

In addition, the valve windings connected to the rectifierand the converter circuit are subject to the combined load stress of DC and ACvoltage.

 

HVDC Classic

HVDC Classic transformers are line-commutatedcurrent-sourced converters. Siemens delivers HVDC Classic Convertertransformers for transmission lines up to 12 GW, up to 1,100 kV DC withconnections to AC grids up to 1,050 kV.

The high harmonics content of the operating current resultsfrom the virtually quadratic current blocks of the power converter. Theodd-numbered harmonics with the ordinal numbers of 5, 7, 11, 13, 17 causeadditional losses in the windings and other structural parts. Furthermore,additional DC currents on the valve and/or neutral terminals need to beconsidered and managed. The high bulk power ratings also require a high ratingof HVDC classic converter transformers which must share specific performanceparameters, e.g. short circuit impedance.

HVDC Plus

HVDC transformers are used for self-commutatedvoltage-sourced converters. Siemens delivers HVDC Plus Converter transformersfor transmission lines up to 1,200 MW, up to 500 kV DC with connections to ACgrids up to 525 kV.

   

In HVDC Plus mono-pole applications, no DC voltage stressesoccurs at the transformer valve terminals. In HVDC Plus, bi-pole applicationsthe valve windings which are connected to the HVDC Plus rectifier/convertercircuit are subject to the combined load stress of DC and AC voltage. Theharmonics content of the operating current is much lower than in HVDC Classicapplications. It usually meets grid code requirements. Additional DC currentson the valve and/or neutral terminals have to be considered. They are muchlower than in HVDC Classic applications.    

 

 

 


RELISERV SOLUTION
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RELISERV SOLUTION
Office No.-9, Plot 53/54, Sector-34, Space Heights, Near Tawa Hotel, Kamothe, Navi Mumbai - 410209, Maharashtra, India
Mr Piyush Lalchand Rathi (Partner)
Mobile :+919819614841, +919769207841
Mr. Dnyanesh Gawande (Partner)
Mobile :+919833686249