I understand that you're working on operating the three-phase circuit breaker based on sensing currents. However, it seems there's some confusion because the circuit breaker is designed to accept voltage as an input.
To resolve your query, let us take a brief look at the construction and operation of circuit breaker.
There are three components involved in the operation of Circuit breaker:
- Current Transformer
- Relay
- Circuit breaker main winding.
The circuit breaker is equipped with a "main winding" and an electromagnet, which are responsible for opening and closing the contacts. When the main winding is energized by a voltage, the contacts close. Conversely, when the main winding is de-energized, the contacts open. It's important to note that the circuit breaker does not have a feature to "sense" currents. This is why Simulink provides a "voltage port" as the input signal instead of a current source. The main winding of Circuit breaker is connected with the excitation voltage source through “NC” (Normally closed) contacts of the relay
Refer to the below links to explore more:
The current sensing part is done by current transformers (CTs). (conventionally called as current sensor). The CT has primary winding and secondary winding. The line current is allowed to flow through the primary winding and a relay coil is connected at the secondary winding of CT. When the line current flowing through the primary winding exceeds its rated value, the relay activates and opens the "main winding" of the circuit breaker. This de-energizes the main winding, which in turn opens the circuit breaker contacts.
Now, coming to the implementation, the “current driven circuit breaker” can be implemented in following approaches:
Approach-1: simplified approach:
The current sensor and relay are modelled in a very simple way as shown below:
Approach-2: (Detailed approach) By using “current sensor”, “relay” and “circuit breaker” block from Simulink library browser:
This model simulates a three phase circuit breaker. Whenever the current in a particular phase exceeds the threshold value, the relay is operated and opens the contacts of Circuit breaker for all the phases. It then waits for some time (determined by “Auto_reclosing_logic” ) and again closes the contacts of circuit breaker (this is called auto-reclosing). You can code your own auto-reclosing logic inside it.
The screenshot of Simulink model is attached below for you reference
Note: Here, the “modelling option” property of “Circuit breaker (three phase)” was configured as “Expanded Three-phase Port | Electrical control Port”
I hope you find this information useful!
