An isolator and a circuit breaker are both electrical devices used in power distribution systems, but they serve different functions and have different characteristics:

Isolator: An isolator, also known as a disconnect switch or isolating switch, is a mechanical switch used to physically disconnect a circuit or piece of equipment from its power source. Isolators are primarily used for maintenance, repair, or isolation purposes and do not provide overcurrent protection. Here are some key features of isolators:

1. Function: Isolators are used to isolate a circuit or piece of equipment from the power supply, either for maintenance, repair, or safety reasons. They provide a visible break in the circuit, physically separating the equipment from the power source.

2. Operation: Isolators typically have a manual operation, meaning they are operated manually by a person using a handle or lever. When the isolator is in the open position, it disconnects the circuit, and when it is in the closed position, it allows current to flow through the circuit.

3. Protection: Isolators do not provide overcurrent protection or fault protection. Their primary function is to provide a visible and physical break in the circuit to allow for safe working conditions during maintenance or repair activities.

4. Construction: Isolators are typically robust and durable devices designed to handle high currents. They may have visible blades or contacts that make it easy to see whether the circuit is isolated or connected.

Circuit Breaker: A circuit breaker is an electrical switch designed to automatically interrupt the flow of current in a circuit in response to overcurrent conditions, such as short circuits, overloads, or ground faults. Circuit breakers provide both overcurrent protection and the ability to manually open and close the circuit. Here are some key features of circuit breakers:

1. Function: Circuit breakers are used to protect electrical circuits and equipment from overcurrent conditions that could cause damage or fire hazards. They automatically open the circuit when they detect an abnormal current condition, such as a short circuit or overload.

2. Operation: Circuit breakers can have manual or automatic operation. In addition to being manually operated like isolators, they also have automatic tripping mechanisms that respond to overcurrent conditions. When the circuit breaker trips, it interrupts the flow of current to the circuit, protecting the equipment from damage.

3. Protection: Circuit breakers provide overcurrent protection and are designed to trip when the current in the circuit exceeds a certain threshold. They can be calibrated to respond to different types and levels of overcurrent conditions, providing flexible protection for various types of loads and applications.

4. Construction: Circuit breakers are complex devices that incorporate mechanical, thermal, and electromagnetic components to detect and interrupt overcurrent conditions. They come in different types, such as thermal-magnetic, electronic, and residual-current circuit breakers, each with specific features and applications.

In summary, while both isolators and circuit breakers are used to control the flow of electrical current, isolators are primarily used for isolation purposes and do not provide overcurrent protection, whereas circuit breakers provide overcurrent protection and the ability to manually open and close the circuit in response to abnormal current conditions.