Electrical Term Explanations:
(a) Preferential Tripping:
In an electrical system with multiple protective devices (circuit breakers, fuses), preferential tripping refers to the strategy where circuits considered critical are designed to trip (interrupt current flow) less readily compared to less critical circuits. This ensures that essential equipment or functions remain operational during a fault condition, while overloaded or faulty non-critical circuits are isolated.
Here’s an example: Imagine a circuit feeding critical navigation equipment and another feeding cabin lights. In preferential tripping, the circuit breaker for the cabin lights would be set to trip at a lower current value compared to the breaker for the navigation equipment. This way, if there’s a fault, the cabin lights would trip first, isolating the problem and allowing essential navigation equipment to continue functioning.
(b) Sequential Starting:
Sequential starting refers to the controlled starting of multiple electric motors in a specific order. This strategy is used to manage the inrush current (initial high surge of current) drawn by motors when they start. By starting motors one after another with a controlled time delay between them, the overall demand on the power supply is limited, preventing voltage dips or blackouts.
Sequential starting can be achieved using timers, relays, or programmable controllers depending on the complexity of the system. It’s commonly used in applications like multiple pumps or large ventilation systems to avoid overloading the electrical supply during motor startup.
(c) Fuse Back Up Protection:
Fuse backup protection refers to a scenario where a circuit breaker is additionally protected by a fuse upstream in the electrical system. This provides a layered approach to fault protection. The fuse offers a fast-acting response to severe overcurrents, while the circuit breaker provides overload protection and allows for resetting after a fault is cleared.
Here’s an example: Imagine a circuit breaker feeding a motor circuit. A fuse might be installed upstream of the breaker, closer to the main power supply. If a severe fault occurs, the fuse would blow first, interrupting the high current and protecting the circuit breaker from damage. The circuit breaker could then be reset after the fault is addressed.
(d) Discrimination:
Discrimination, in the context of electrical protection devices, refers to the ability of a device to selectively isolate a faulty circuit while allowing healthy upstream and downstream circuits to remain operational. This is achieved through proper selection and coordination of circuit breaker trip settings and fuse ratings.
Effective discrimination ensures that only the circuit experiencing a fault is interrupted, minimizing disruption to the rest of the electrical system. It’s crucial for maintaining power supply to critical equipment during fault conditions.
(e) Non-Essential Consumer:
A non-essential consumer, in an electrical system, refers to a load or device that is not critical for the core operation of the system. These are circuits that can be interrupted without causing a major safety hazard or significant disruption to essential functions. Examples of non-essential consumers include:
- Air conditioning systems
- Cabin lighting
- Entertainment systems
- Kitchen appliances
Non-essential consumers are typically the first to be switched off or disconnected during emergencies or overload situations to conserve power and maintain operation of critical equipment.