Quae sunt praestantiae commutationis directae alti voltus (HVDC) super commutationem alternatam alti voltus (HVAC) in transmissione electricitatis

Quae sunt praestantiae HVDC super HVAC?

Electricitas per longas distancias transit antequam ad consumidores perveniat. Stationes electricitatis, saepe remotae, electricitatem per centenas milliarum et plures substationes suppeditant. Transmissio altae tensionis lineas perditorum reducit, utrumque AC et DC utens. Licet AC sit familiares per stipes utilitatis et foramina domesticos, HVDC praebet unica praestantia in transmissione electricitatis.

Scopus transmissione electricitatis est minuere perdita et costus. Utrumque facit cum factoribus influentibus, HVDC tamen plus praestantias habet. Hoc articulus explorat praestantias HVDC super HVAC:

Minores Costus Transmissionis
Costus transmissionis dependet ab aequipamento conversionis tensionis terminalis, quantitate/magnitudine conductorum, dimensionibus turrium, et perditis. HVAC utitur transformatoribus pro conversione—simplius et vilior quam convertere thyristor-based HVDC, cuius sola est praestantia costi.

HVAC requirit saltem 3 conductores pro transmissione 3-phasic. HVDC, utendo terra ut via regressiva, utitur 1 conductore (monopolar) aut 2 (bipolar), costus resecans. Etiam 3-phasic conductores possunt portare duplam potentiam per HVDC double bipolar links.

HVAC postulat maiorem spatium inter phase-to-ground et phase-to-phase, necessitantes turres altiores et latiores. Turres HVDC costus installationis minuant. HVDC etiam habet significanter minus perditorum transmissionis, id efficacius faciens.

Totus costus transmissionis dividitur in duas categorias principales: costus stationis terminalis et costus lineae transmissionis. Primus est expensa fixa, independens a distantia transmissionis, secundus variat cum longitudine lineae. Costus terminales AC sunt relativiter parvi, ubi costus terminales HVDC multo maiores sunt. Tamen, costus per 100 km pro lineis transmissionis HVAC multo maior est quam pro lineis HVDC. Itaque, curvae totales costus HVAC et HVDC se intersecano in puncto quod vocatur punctum aequilibrii.

Punctum aequilibrii est longitudo transmissionis ultra quam totus costus investimenti HVAC excedit illud HVDC. Haec distantia varietur secundum typum transmissionis: circa 400–500 millia (600–800 km) pro lineis overhead, 20–50 km pro lineis subaquaticis, et 50–100 km pro lineis subterraneis. Ultra hanc limen, HVDC fit optio magis efficiens et economicus pro transmissione electricitatis.

Transmissio HVDC incurrit significanter minus perditorum comparata HVAC, cum clavis meliorationibus in sequentibus areis:

Absentia Perditorum Potentiae Reactivae

Transmissio HVAC patitur a perditorum potentiae reactivae, quae directe proportionalis sunt longitudini lineae, frequentiae, et oneribus inductivis in extremitate recipientis. Haec perdita diminuunt transferentiam potentiae effectivam et dissipant energiam, limitantes maximam longitudinem lineae HVAC efficientis. Ad hoc mitigandum, systemata HVAC confidunt in compensationem series et shunt ut reducerent VARs (volt-ampere reactivi) et maintinerent stabilitatem.

Contrariwise, HVDC operatur sine frequentia vel currente charging, eliminans totaliter perdita potentiae reactivae. Hoc removet necessitatem talium measurarum compensationis.

Perditorum Coronae Reducta

Cum tensio transmissionis excedit limen criticum (tensio inceptionis coronae), moleculae aeris circum conductorum ionizantur, creantes scintillas (discharge corona) quae dissipant energiam. Perditorum corona dependent a tensio et frequentia. Quia DC nullam frequentiam habet, perditorum corona HVDC sunt fere unum tertium illorum in systematibus HVAC.

Absentia Effectus Cutis

Current AC exhibet effectum cutis, ubi current concentratur iuxta superficiem conductoris, relinquentes nucleum underutilized. Haec distributio inaequalis currentis reducit effective sectionem transversalem conductoris, augens resistentiam (quae inversa proportionalis est areae) et resultans in maiori I²R perditorum in lineis HVAC. HVDC, cum suo constante currente directo, evitat hunc effectum, assecurans distributionem uniformem currentis trans conductoris et minimizando perditorum resistentiales.

Nulla Perditorum Radiationis vel Inductionis

Lineae transmissionis HVAC patiuntur a perditorum radiationis et inductionis propter suas magneticas campos constantemente variantes. Perditorum radiationis occurrunt quia longae lineae AC agunt sicut antennae, radiantes energiam quae irrecoverabilis est. Perditorum inductionis oriuntur ex currentibus inducendis in conductoribus proximis per alternativum campum.In systematibus HVDC, magneticus campus est constans, eliminans totaliter ambo perditorum radiationis et inductionis.

Perditorum Currentis Charging Reducta

Cables subterranei et subaquatici habent inherentem capacitatem parasiticam, quae charging requirit antequam possint transmittere potentiam. Capacitas crescit cum longitudine cable, et ita currentis charging crescunt proportionally.

In systematibus AC, cables charging et discharging multiple times per second, drawing additional current from the source to maintain this cycle. This extra current increases I²R losses in the cable.Cables HVDC, however, only require charging once during initial energization or switching. This eliminates losses associated with continuous charging currents.

Nulla Perditorum Heating Dielectricorum

Alternating electric field in AC systems affects insulation materials in transmission lines, causing them to absorb energy and convert it into heat—a phenomenon known as dielectric loss. This not only wastes energy but also shortens insulation lifespan.HVDC systems generate a constant electric field, avoiding dielectric losses and the associated insulation heating issues.

3) Conductor Thinner

The skin effect in AC causes current to concentrate near the conductor surface, requiring thicker conductors to increase surface area and accommodate higher currents.HVDC, free from the skin effect, allows current to distribute uniformly across the conductor cross-section. This enables the use of thinner conductors while maintaining the same current-carrying capacity, reducing material costs and weight.

4) Limitations Line Length

HVAC lines suffer from reactive power losses that increase directly with line length. This imposes a critical limit on HVAC transmission distance: beyond approximately 500 km for overhead lines, reactive power losses become excessively high, destabilizing the system.HVDC transmission, by contrast, has no such length restrictions, making it suitable for ultra-long-distance power delivery.

5) Reduced Cable Rating Requirements

Cables are rated for maximum tolerable voltage and current. In AC systems, peak voltage and current are roughly 1.4 times higher than their average values (which correspond to actual power delivered). However, conductors must be rated for these peak values.In DC systems, peak and average values are identical. This means HVDC can transmit the same power using cables with lower voltage and current ratings compared to HVAC. In fact, HVAC systems effectively waste about 30% of a conductor’s capacity due to their higher peak requirements.

6) Narrower Right-of-Way

"Right-of-way" refers to the land corridor required for transmission infrastructure. HVDC systems require a narrower right-of-way because they use smaller towers and fewer conductors.HVAC, by contrast, needs taller towers to support more conductors and larger insulators (rated for AC peak voltages), which demand stronger structural support. This broader footprint increases material, construction, and land costs—making HVDC superior in terms of right-of-way efficiency.

7) Superior Cable-Based Transmission

Underground and submarine cables consist of multiple conductors separated by insulation, creating parasitic capacitance between them. These cables cannot transmit power until fully charged, and capacitance (and thus charging current) increases with length.AC systems repeatedly charge and discharge cables (50–60 times per second), amplifying I²R losses and limiting cable length. HVDC cables, however, only charge once (during initial energization or switching), eliminating such losses and length restrictions.This makes HVDC the preferred choice for offshore, underwater, and underground cable transmission.

8) Bipolar Transmission

HVDC supports versatile transmission modes, with bipolar transmission being a widely used and cost-effective option. It features two parallel conductors with opposite polarities, their voltages balanced relative to the earth.If one line fails or breaks, the system seamlessly switches to monopolar mode: the remaining line continues supplying current, using the earth as the return path.

9) Controllable Power Flow

HVDC converters, based on solid-state electronics, enable precise control over power flow in AC networks. Their rapid switching capability (operating multiple times per cycle) enhances harmonic performance, dampens power swings, and optimizes the network’s power supply capacity.

10) Fast Fault Clearance

Fault currents—abnormal currents from electrical faults—pose significant risks. In HVAC systems, high fault currents can damage transmission lines, stations, generators, and loads.HVDC minimizes such risks: fault currents are lower, limiting damage to specific sections, and its fast-switching operation ensures rapid fault response, enhancing system resilience.

11) Asynchronous Grid Interconnection

HVDC enables interconnection of asynchronous AC grids with differing parameters (e.g., frequency, phase).Regions often use distinct frequencies (e.g., 50 Hz in Europe vs. 60 Hz in the U.S.), and grids may have phase differences, making direct AC interconnection impossible. HVDC, operating without frequency or phase constraints, easily links these independent systems.

12) Enabling Smart Grids

Smart grids integrate small-scale generators (solar, wind, nuclear) into a unified network with intelligent power flow control.This is feasible with HVDC, which supports asynchronous interconnection of generation units and provides full control over power distribution, aligning with smart grid requirements.

13) Reduced Noise Interference

HVDC causes far less noise interference to nearby communication lines compared to HVAC.HVAC generates audible buzzing, radio, and TV interference, with intensity tied to its frequency. HVDC, with zero frequency, produces minimal noise. Additionally, HVAC noise increases in bad weather, while HVDC noise diminishes, ensuring more stable operation.