Name: fault current in a series r-l circuit
Uploaded: 2024-11-21T14:54:30.000Z
Duration: 1 min 22 s
Channel: JoVE

Considere un circuito R-L en serie.
Cuando el interruptor se cierra en un momento igual a cero, imita un cortocircuito trifásico en una máquina síncrona descargada.
Dada una impedancia de falla cero o una falla atornillada, y una corriente inicial cero, el ángulo de la fuente determina el voltaje de la fuente inicial.
La ecuación KVL de este circuito produce la corriente de falla asimétrica total y sus dos componentes.
La corriente de falla de CA, también llamada corriente de falla simétrica o de estado estacionario, es una sinusoide.
La corriente de compensación de CC decae exponencialmente con una constante de tiempo como la relación inductancia a resistencia.
Su magnitud varía con el ángulo de la fuente, alcanzando su punto máximo cuando el ángulo de la fuente es igual a theta más pi sobre dos.
La corriente de falla más grande ocurre en un ángulo de fuente específico.
A continuación, se calcula y simplifica la corriente de falla asimétrica rms con el máximo desplazamiento de CC sustituyendo la constante de tiempo y el tiempo en términos de ciclos y frecuencia.
Esta corriente es igual a la corriente de falla de CA rms por un factor de asimetría y la corriente rms disminuye a medida que aumenta tau.
Una mayor reactancia a las relaciones de resistencia produce valores más altos de corriente rms.

transitorios del circuito serie r-l

Series R&#8212;L Circuit Transients

En un circuito de resistencia-inductor en serie (R-L), cerrar el interruptor al comienzo del período de tiempo simula un cortocircuito trifásico, una condición de falla en la que las tres fases de una máquina sincrónica sin carga están en cortocircuito. Cuando no hay impedancia de falla ni corriente inicial, la tensión inicial está determinado por el ángulo de fase de la tensión de la fuente.

El uso de la Ley de tensión de Kirchhoff (LTK) para analizar este circuito ayuda a determinar la corriente de falla asimétrica total, que consta de dos componentes principales. La corriente de falla de CA, también conocida como corriente de falla simétrica o de estado estable, sigue un patrón sinusoidal. Por otro lado, la corriente de compensación de CC disminuye exponencialmente con el tiempo, y su tasa de decaimiento está definida por la relación entre la inductancia y la resistencia. La magnitud de la compensación de CC varía con el ángulo de la fuente y alcanza un pico en un ángulo de fase específico de la fuente.

El cálculo de la corriente de falla asimétrica RMS, incluida la desviación máxima de CC, implica expresar la constante de tiempo y el tiempo en términos de ciclos y frecuencia. Esta corriente asimétrica RMS se obtiene multiplicando la corriente de falla de CA RMS por un factor de asimetría. El factor de asimetría refleja la influencia de la corriente de desviación de CC. A medida que aumenta la constante de tiempo, la corriente RMS disminuye, lo que demuestra el efecto de la relación inductancia-resistencia en la corriente. Relaciones más altas de reactancia-resistencia dan como resultado valores de corriente RMS más altos.

Este análisis es esencial para comprender las condiciones de falla en los circuitos eléctricos y diseñar sistemas para manejar tales eventos. Al considerar los diferentes componentes de la corriente de falla y su dependencia de los parámetros del circuito, los ingenieros pueden predecir y mitigar mejor los efectos de las fallas en los sistemas eléctricos. Este conocimiento es fundamental para garantizar la confiabilidad y la seguridad de los sistemas eléctricos.

Transitorios del circuito serie R-L

Considere un circuito R-L en serie.
Cuando el interruptor se cierra en un momento igual a cero, imita un cortocircuito trifásico en una máquina síncrona descargada.
...

Education

Educación

JoVE Core

Electrical Engineering

Ingeniería Eléctrica

Unit 1

Unidad 1

Symmetrical and Unsymmetrical Faults

Fallas Simétricas y Asimétricas

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

fault current in a series r-l circuit

A series resistor-inductor, or R-L, circuit can model a three-phase short circuit when the switch closes at the start of the time period. In this fault condition, all three phases of an unloaded synchronous machine are short-circuited. With no fault impedance and no initial current, the starting voltage depends on the source voltage phase angle.

Kirchhoff's Voltage Law, or KVL, is used to analyze the circuit and find the total asymmetrical fault current. This current has two parts. The AC fault current, also called the symmetrical or steady-state fault current, follows a sinusoidal pattern. The DC offset current is the other part, and it decays exponentially with time. Its decay rate depends on the inductance-to-resistance ratio.

The size of the DC offset changes with the source angle. It reaches a maximum at a specific phase angle of the source. To calculate the RMS asymmetrical fault current, the time constant and time are written in terms of cycles and frequency. The result is found by multiplying the RMS AC fault current by an asymmetry factor.

That asymmetry factor shows how much the DC offset affects the current. As the time constant increases, the RMS current decreases. Higher reactance-to-resistance ratios produce higher RMS current values. This analysis helps explain fault conditions in electrical circuits and supports the design of systems that can handle them safely and reliably.

Fault Current in a Series R-L Circuit

series r&#8212;l circuit transients

A series resistor-inductor, or R-L, circuit can model a three-phase short circuit when the switch closes at the start of the time period. In this fault condition, all three phases of an unloaded synchronous machine are short-circuited. With no fault impedance and no initial current, the starting voltage depends on the source voltage phase angle. Kirchhoff's Voltage Law, or KVL, is used to analyze the circuit and find the total asymmetrical fault current. This current has two parts. The AC...

three-phase short circuit&#8212;unloaded synchronous machine

three-phase-short-circuitunloaded-synchronous-machine

Synchronous Machine Fault Current Decay

A three-phase short circuit on an unloaded synchronous machine shows how fault current changes over time. The AC fault current, with the DC offset removed, starts at a high value and then falls to a steady-state level in one phase of the machine. This change happens because of the magnetic flux created by the short-circuit armature currents. At first, these currents flow through high-reluctance paths. They later shift to lower-reluctance paths, which increases the armature inductance. This...

power system three-phase short circuits

Subtransient Fault Current in Power Systems

Subtransient fault current analysis in a power system uses simplified models for the main equipment. Transformers are represented by their leakage reactances. Transmission lines are modeled with equivalent series reactances, and synchronous machines are treated as constant voltage sources behind their subtransient reactances. Several elements are left out of the calculation because their effect on the immediate fault current is small or they make the model harder without changing the result...

bus impedance matrix

Three-Phase Fault Current Analysis

Three-phase fault current analysis in an N-bus power system uses the positive-sequence network and the bus impedance matrix. It helps estimate subtransient fault currents when a short circuit occurs at one bus. The method uses superposition, which means the problem is split into two circuits that are studied separately. In the first circuit, all machine voltage sources are short-circuited. Only the prefault voltage source at the faulted bus remains. The positive-sequence bus impedance matrix...

circuit breaker and fuse selection

Protective Devices in Power Systems

Circuit breakers and fuses protect electrical systems from fault current and overcurrent. They help stop damage when current rises above safe limits. Both devices are chosen based on the needs of the electrical system. A circuit breaker interrupts fault current by separating its contacts. This creates an arc, which must be extinguished by elongation, cooling, or splitting, depending on the breaker design. Breakers are grouped by operating voltage and by the arc-extinguishing medium, such as...

sequence networks of rotating machines

Generator Sequence Currents and Impedances

Generator sequence currents and impedances explain how a Y-connected synchronous generator behaves under balanced and unbalanced conditions. When the generator is grounded through a neutral impedance, it is set up to produce balanced internal phase voltages with only positive-sequence components. The source voltage therefore appears only in the positive-sequence network, and the line-to-ground voltages at the generator terminals show the sequence components of this setup. Zero-sequence current...

per-unit sequence models

Transformer Sequence Networks in Per Unit

Transformer sequence networks in per unit show how three-phase transformers respond to positive-, negative-, and zero-sequence currents. For an ideal Y-Y transformer grounded through neutral impedances, the per-unit sequence networks act much like those of a single-phase ideal transformer when the current is balanced. Balanced positive-sequence and negative-sequence currents do not create neutral current, so they do not cause voltage drops across the neutral path. Zero-sequence current behaves...

fault types

Power System Faults in Sequence Networks

Power system faults can be analyzed by moving between the phase domain and the sequence domain. This approach helps relate fault currents and voltages for three-phase bus faults and keeps the fault impedance in the model. Fault impedance is zero for a bolted fault, equal to the arc impedance for an arcing fault, and it represents the total fault impedance for a transmission-line insulator flashover. For a single line-to-ground fault from phase A to ground, the phase-domain conditions are...

key terms and concepts

Explore fault current in a series R-L circuit, including AC fault current, DC offset decay, RMS asymmetrical current, and the role of source angle.

Fault Current in a Series R-L Circuit | 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

Fault Current in a Series R-L Circuit

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