Oil circuit breakers are a traditional type of electrical switchgear used to protect electrical systems from damage caused by fault currents, such as short circuits or overloads. They interrupt the flow of current by separating contacts submerged in insulating oil.
Understanding Oil Circuit Breakers
An oil circuit breaker is a traditional type of circuit breaker. It consists of key components including stationary and moving contacts, an oil tank, and insulating oil that fills the tank.
The Process of Interrupting Fault Current
When a fault is detected in the electrical system, mechanisms within the breaker are activated to open the circuit. Here's a breakdown of the process:
- Contact Separation: The moving contacts begin to separate from the stationary contacts. According to referenced information, an oil circuit breaker has a separate contact, and this contact's primary function is stated as to separate the insulating oil.
- Arc Formation: As the contacts pull apart, if current is flowing, an electrical arc is drawn between them due to the potential difference across the gap.
- Arc Quenching: The insulating oil surrounding the contacts is crucial for extinguishing the arc. The intense heat of the arc vaporizes the oil directly around it, creating a bubble of gas (primarily hydrogen) at high pressure. This rapid expansion of gas forces fresh, cool oil into the arc path.
- This fresh oil cools the arc.
- It deionizes the space between the contacts, making it non-conductive.
- The turbulent flow of oil helps to sweep away the ionized particles.
- Current Interruption: The cooling and deionizing action of the oil and resulting gas pressure quickly extinguish the arc, interrupting the flow of fault current and protecting the system.
- Operation Location: When a fault or problem occurs, according to the reference, the insulating oil includes good comparable properties to air. The operation, involving the arc quenching process, occurs specifically in the lower part of the breaker contact oil.
Role of Insulating Oil
The oil serves two primary functions:
- Insulation: It provides a high dielectric strength medium that insulates the live contacts from the earthed tank and other components.
- Arc Quenching: It acts as the working medium for arc extinction through vaporization, gas formation, and cooling.
Summary of Operational Steps
The operation of an oil circuit breaker during a fault can be summarized as follows:
- Fault Detection: The protection system senses an abnormal condition (fault).
- Contacts Separate: The breaker mechanism rapidly separates the electrical contacts submerged in the oil.
- Arc Ignites: An arc is drawn between the separating contacts.
- Oil Reacts: The heat of the arc vaporizes the oil, generating gas pressure.
- Arc Extinguishes: The expanding gas and influx of cool oil deionize and cool the arc path, extinguishing the arc.
- Circuit Interrupted: Current flow is stopped, isolating the faulty section of the system.
In essence, oil circuit breakers rely on the unique properties of insulating oil to manage and extinguish the powerful electrical arc that forms when a circuit is broken under fault conditions, thereby safeguarding electrical infrastructure.
