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

Die Pilotrelais, eine Form des Differentialschutzes, nutzt Kommunikationskanäle, um Endgerätemengen auf weit verstreuten Übertragungsleitungen zu vergleichen. Er wird in der Regel für kürzere Leitungen mit einer Nennleistung zwischen 69 und 115 kV eingesetzt.
Es werden vier Kommunikationskanäle mit zwei primären Fehlererkennungsmethoden verwendet: Richtungsvergleich zur Bewertung von Leistungsflüssen und Phasenvergleich zur Bewertung relativer Stromphasenwinkel.
Wie Differentialrelais bieten Pilotrelais Schutz der Primärzone, ohne dass komplexe Relaiseinstellungen oder Systemfehlerberechnungen erforderlich sind.
Sie erkennen und isolieren Fehler in Hochspannungsleitungen rechtzeitig, um eine unterbrechungsfreie Stromversorgung zu gewährleisten.
Numerische Relais verwenden Mikroprozessoren und Software zur Fehlererkennung. Zu ihren Vorteilen gehören eine kompakte Größe, weniger Verkabelung, Programmierbarkeit, geringere Belastung des Transformators, Multifunktionsfunktionen sowie verbesserte Empfindlichkeit, Zuverlässigkeit und Geschwindigkeit. Sie können auch automatisch zurückgesetzt werden.
Ingenieure müssen sich jedoch der gängigen Fehlermodi bewusst sein, da numerische Relais anfällig für externe Transienten des Stromversorgungssystems sind.

piloten- und numerische weiterleitung

Pilot and Numeric Relaying

Pilotrelais sind eine Art Differentialschutz, der in Stromversorgungssystemen verwendet wird. Dabei werden elektrische Größen an den Anschlüssen von Geräten über einen Kommunikationskanal verglichen, anstatt über eine direkte Relaisverbindung. Diese Methode ist für Übertragungsleitungen unerlässlich, bei denen die Anschlüsse weit voneinander entfernt sind, typischerweise bis zu 80 km bei Leitungen mit 69 bis 115 kV Nennspannung. Für Pilotrelais werden vier Arten von Kommunikationskanälen verwendet:

<ul style="list-style-type: disc; margin-left: 35px;">
	<li>Pilotdrähte: Dies sind separate Stromkreise, die mit Gleichstrom, 50 bis 60 Hz oder Audiofrequenzen betrieben werden.</li>
	<li>Powerline-Träger: Dieser Typ nutzt die Übertragungsleitung selbst als Kommunikationsmedium mit Frequenzen zwischen 30 und 300 kHz.</li>
	<li>Mikrowelle: Verwendet Signale von 2 bis 12 GHz, die über Sichtlinienpfade mit Parabolantennen übertragen werden.</li>
	<li>Glasfaserkabel: Nutzt die Lichtmodulation durch nicht leitende Kabel, wodurch Probleme mit elektrischer Isolierung und Interferenzen vermieden werden.</li>
</ul>

Es gibt zwei Methoden zur Fehlererkennung: Richtungs- und Phasenvergleich. Bei der Richtungsvergleichsmethode werden die Leistungsflüsse an Leitungsanschlüssen verglichen, während bei der Phasenvergleichsmethode die relativen Phasenwinkel der Ströme an Anschlüssen verglichen werden.

Numerische oder digitale Relais verwenden mikroprozessorbasierte Systeme mit Software zur Fehlererkennung. Numerische Relais reduzieren die Verdrahtung der Schalttafel, vereinfachen Einstellungsänderungen über Remote-Updates und minimieren die Belastung der Transformatoren. Sie bieten eine höhere Empfindlichkeit, schnellere Auslösezeiten und verbesserte Zuverlässigkeit durch weniger Komponenten. Diese Relais können Daten nach einem Fehler analysieren, die Systemwiederherstellung überprüfen und Einstellungen an die veränderten Bedingungen anpassen.

Numerische Relais sind anfällig für Cybersicherheitsrisiken. Daher ist die Einhaltung der Sicherheitsstandards der North American Electric Reliability Corporation (NERC) von entscheidender Bedeutung.

Beim dezentralen Schutz erhält jedes Relais Informationen von den lokalen Strom- und Spannungstransformatoren und löst nur lokale Leistungsschalter aus. Dieser Ansatz gewährleistet Zuverlässigkeit, ohne auf Pilotrelais angewiesen zu sein. Numerische Relais können in zentralisierte Systeme integriert werden, um die Gesamtschutzkoordination und Systemzuverlässigkeit zu verbessern.

Piloten- und numerische Weiterleitung

Die Pilotrelais, eine Form des Differentialschutzes, nutzt Kommunikationskanäle, um Endgerätemengen auf weit verstreuten Übertragungsleitungen zu vergleichen. Es...

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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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