Name: pilot relays and digital protection
Uploaded: 2024-11-21T14:54:35.000Z
Duration: 1 min 21 s
Channel: JoVE

Il relè pilota, una forma di protezione differenziale, utilizza canali di comunicazione per confrontare le quantità dei terminali su linee di trasmissione ampiamente diffuse. Viene tipicamente applicato a linee più corte, con una tensione compresa tra 69 e 115 kV.
Vengono utilizzati quattro canali di comunicazione, con due metodi primari di rilevamento dei guasti: il confronto direzionale, per valutare i flussi di potenza, e il confronto di fase, per valutare gli angoli di fase relativi della corrente.
Come i relè differenziali, i relè pilota forniscono la protezione della zona primaria senza richiedere complesse impostazioni del relè o calcoli dei guasti del sistema.
Rilevano e isolano prontamente i guasti nelle linee di trasmissione ad alta tensione per garantire un'alimentazione ininterrotta.
I relè numerici utilizzano microprocessori e software per il rilevamento dei guasti. I loro vantaggi includono dimensioni compatte, meno cablaggi, programmabilità, minore carico del trasformatore, capacità multifunzione e maggiore sensibilità, affidabilità e velocità. Possono anche resettare automaticamente.
Tuttavia, gli ingegneri devono essere consapevoli delle modalità di guasto più comuni, poiché i relè numerici sono vulnerabili ai transitori esterni del sistema di alimentazione.

relè pilota e relè numerico

Pilot and Numeric Relaying

Il relè pilota è un tipo di protezione differenziale utilizzato nei sistemi di alimentazione. Esso confronta le grandezze elettriche ai terminali delle apparecchiature tramite un canale di comunicazione anziché tramite l'interconnessione diretta dei relè. Questo metodo è essenziale per le linee di trasmissione in cui i terminali sono molto distanti, in genere fino a 80 km per linee con valori nominali da 69 a 115 kV. Per il relè pilota vengono utilizzati quattro tipi di canali di comunicazione:

Cavi pilota: si tratta di circuiti elettrici separati che funzionano a corrente continua, da 50 a 60 Hz, o a frequenze audio.

Portante su Linea di Potenza: questa tipologia utilizza la linea di trasmissione stessa come mezzo di comunicazione, con frequenze comprese tra 30 e 300 kHz.

Microonde: utilizza segnali da 2 a 12 GHz trasmessi tramite percorsi a vista con antenne paraboliche.

Cavo in fibra ottica: impiega la modulazione della luce attraverso cavi non conduttivi, eliminando i problemi di isolamento elettrico e di interferenza.

Esistono due metodi di rilevamento di guasto: il confronto direzionale e quello di fase. Il metodo di confronto direzionale confronta i flussi di potenza ai terminali di linea, mentre il metodo di confronto di fase confronta gli angoli di fase relativi delle correnti ai terminali.

Il relè numerico o digitale utilizza sistemi basati su microprocessore con software per il rilevamento dei guasti. I relè numerici riducono il cablaggio del pannello, semplificano le modifiche delle impostazioni tramite aggiornamenti remoti e riducono al minimo gli oneri sui trasformatori. Offrono maggiore sensibilità, tempi di intervento più rapidi e affidabilità migliorata grazie a un minor numero di componenti. Questi relè possono analizzare i dati post-guasto, controllare il ripristino del sistema e adattare le impostazioni alle condizioni mutevoli.

I relè numerici sono sensibili ai rischi per la sicurezza informatica, pertanto è fondamentale rispettare gli standard di sicurezza stabiliti dal Comitato Elettrotecnico Italiano (CEI) e dalle normative europee.

Nella protezione decentralizzata, ogni relè riceve informazioni dai trasformatori di corrente e tensione locali, facendo scattare solo gli interruttori locali. Questo approccio garantisce affidabilità senza fare affidamento sul relè pilota. I relè numerici possono integrarsi con sistemi centralizzati per migliorare il coordinamento generale della protezione e l'affidabilità del sistema.

Relè Pilota e Relè Numerico

Il relè pilota, una forma di protezione differenziale, utilizza canali di comunicazione per confrontare le quantità dei terminali su linee di trasmissione ampiamente diffuse. Esso...

Education

Didattica

JoVE Core

Electrical Engineering

Ingegneria elettrica

Unit 1

Unità 1

System Protection

Protezione del sistema

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

pilot relays and digital protection

Pilot relays and numeric relays help protect power systems. Pilot relaying is a form of differential protection, which compares electrical quantities at equipment terminals through a communication channel instead of a direct relay link. It is especially useful for transmission lines with terminals far apart, often up to 80 km on 69 to 115 kV lines.

Pilot relaying can use several communication channels. Pilot wires are separate electrical circuits that operate at DC, 50 to 60 Hz, or audio frequencies. Power-line carrier uses the transmission line itself as the communication path, with frequencies from 30 to 300 kHz. Microwave systems send 2 to 12 GHz signals through line-of-sight paths with dish antennas. Fiber optic cable carries light through non-conducting cables, which avoids electrical insulation and interference problems.

Fault detection in pilot relaying uses directional comparison or phase comparison. Directional comparison checks the direction of power flow at the line terminals. Phase comparison checks the relative phase angles of currents at the terminals. Both methods help decide whether a fault is inside the protected section of the line.

Numeric relaying, also called digital relaying, uses microprocessor-based systems and software to detect faults. These relays reduce panel wiring, make setting changes easier through remote updates, and place less burden on transformers. They also offer higher sensitivity, faster tripping times, and better reliability because they use fewer components.

Numeric relays can also study data after a fault, check how the system recovers, and adjust settings when conditions change. They do face cybersecurity risks, so North American Electric Reliability Corporation, or NERC, security standards are important. In decentralized protection, each relay uses local current and voltage transformer data and trips only its local breakers. Numeric relays can also work with centralized systems to improve protection coordination and overall system reliability.

Pilot Relays and Digital Protection

instrument transformers

Voltage and Current Sensing in Power Grids

Instrument transformers help power substations measure voltage and current safely. They create isolated replicas of electrical signals for measurement and protection. These devices support protective relays and other monitoring equipment that keep power systems stable and reliable. The two main types are voltage transformers, or VTs, and current transformers, or CTs. A voltage transformer reduces the primary voltage to a lower level that relays and measuring devices can use. A current...

overcurrent relays

Relay Settings for Circuit Fault Protection

Overcurrent relays protect circuits by sensing excess current through the secondary side of a current transformer. They are an important part of circuit protection and help keep power systems stable when a fault occurs. Two main relay types are used here: instantaneous and time-delay overcurrent relays. An instantaneous relay trips right away when current rises above the pickup current, which is the preset level that starts the relay. It then energizes the circuit breaker trip coil at once,...

radial system protection

Breaker Coordination in Radial Systems

Breaker coordination in radial systems uses time-delay overcurrent relays to limit load interruption. When a fault happens, the nearest breaker should open first. Upstream breakers stay closed because they are set with longer delays. This lets the fault be isolated while the rest of the system keeps running. If a fault is downstream of the third breaker, only the third breaker should trip. That removes power from the load beyond the fault. The second breaker keeps a longer delay setting, so...

reclosers and fuses

Fault Coordination with Reclosers and Fuses

Fault coordination with reclosers and fuses helps protect radial distribution circuits. A recloser is an automatic switch that interrupts AC power and then closes again on a preset schedule. This brief outage can clear temporary faults on overhead lines, such as those caused by tree limbs or wildlife, and it can improve overall reliability. Reclosers and their ground-level hazards also matter. Contact with a recloser or with a broken energized conductor on the ground can be dangerous. That is...

directional relays

Directional Relays in Power System Protection

Directional relays help protect power systems by telling forward faults from reverse faults. They are used when fault current flows mainly in one direction on a line. This makes the relay useful for safe and efficient fault clearing. On a protected line, a fault downstream, or to the right of the current transformer, usually makes the fault current lag the bus voltage by about 90 degrees. This is called the forward direction. A fault upstream, or to the left, may make the fault current lead...

zones of protection

Power System Protection Zones

Power system protection zones divide the network into sections so faults can be isolated quickly. These zones can include generators, transformers, buses, transmission lines, distribution lines, and motors. Each zone is shown with closed dashed lines and contains one or more components. Circuit breakers are placed at the borders where protection zones meet. If a fault happens in one zone, the related breakers open and disconnect only that section. A fault in one area, such as a kitchen in the...

line protection with impedance relays

Impedance Relays for Fault Detection

Impedance relays help protect power lines by watching the voltage-to-current ratio on a line. They measure the apparent impedance, which is the electrical opposition the relay sees at that point in the system. This makes them useful when time-delay overcurrent relays are hard to coordinate in complex radial systems and when directional overcurrent relays are difficult to use in multi-source transmission loops. These relays respond strongly during a fault. As current rises and voltage falls,...

differential relays

Differential Relay Protection in Power Systems

Differential relays protect generators, buses, and transformers by comparing currents at different points in a power system. When the currents do not match, the relay detects the difference and opens the circuit breaker. Under normal conditions, the current entering a generator, i1, equals the current leaving it, i2. If a fault occurs, these currents become unequal, and the difference current flows through the relay operating coil to trip the relay. An electromechanical differential relay is...

pilot and numeric relaying

Pilot relays and numeric relays help protect power systems. Pilot relaying is a form of differential protection, which compares electrical quantities at equipment terminals through a communication channel instead of a direct relay link. It is especially useful for transmission lines with terminals far apart, often up to 80 km on 69 to 115 kV lines. Pilot relaying can use several communication channels. Pilot wires are separate electrical circuits that operate at DC, 50 to 60 Hz, or audio...

key terms and concepts

Learn how pilot relays compare terminal data, how directional and phase methods detect faults, and how numeric relays improve power system protection.

Pilot Relays and Digital Protection | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Pilot Relays and Digital Protection

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