Overcurrent protection is a protective measure used in a power system or electrical equipment to prevent the current from exceeding the allowable range of the equipment or line. Overcurrent protection is usually used to avoid safety problems such as damage to electrical equipment or fire caused by overload or short circuit. Overcurrent protection can generally be divided into the following types, each type has a different solution:

1. Instantaneous overcurrent protection
  Features:
      Instantaneous overcurrent protection means that when the current instantaneously exceeds the preset value, the protection device immediately acts to cut off the power supply.
      This protection is mainly used to prevent overcurrent caused by short circuits, usually triggered when the current reaches several times the normal operating current in a very short time.
      Solution:
      Use an overcurrent relay: Select a relay with a short-time overcurrent protection function to trigger protection when the current reaches the overcurrent value instantaneously.
      Use circuit breakers: Use instantaneous triggered circuit breakers in the circuit to ensure that the instantaneous overcurrent can be quickly cut off.

2. Time delay overcurrent protection
  Features:
      Timing delay overcurrent protection will be delayed for a certain amount of time after the current exceeds the preset limit. This time usually varies according to the degree of overload.
      This kind of protection can avoid the instantaneous current fluctuation to trigger the protection, which is suitable for some load temporary overload.
      Solution:
      Set up time delay relays: This protection is achieved through relays that delay action. The relay can be set to trigger the action of the time, so that temporary overcurrent fluctuations do not misoperate.
      Equipped with circuit breaker with delay function: Choose a circuit breaker with time delay function to avoid the wrong triggering of short-term overload of the load.

3. Overload protection
  Features:
      Overload protection is to prevent damage to equipment or circuits due to current exceeding the rated value for a long time. Typically, overload protection comes into play when the current exceeds the device rating, but not enough to constitute a short circuit.
      Overload protection will be activated after the current exceeds the rated operating value for a period of time.
      Solution:
      Thermal overload relay: The thermal overload relay determines whether there is an overload by sensing the temperature change caused by the current. When the current is too large, the relay will delay the action according to its set time and disconnect the circuit to avoid damage to the equipment due to overload.
      Electromagnetic overload protector: Electromagnetic overload protector can sense the change of current in real time and disconnect the circuit according to the set current threshold.

4. Short circuit protection
  Features:
      Short circuit protection is to prevent serious damage caused by short circuit current. The short circuit current is usually much greater than the normal working current, which may cause damage to electrical equipment or fire in a short time.
      Short-circuit protection is usually responsive and almost instantaneous.
      Solution:
      Fast circuit breaker: In order to prevent short-circuit current from causing damage to the circuit, choose a circuit breaker with short-circuit protection, such as air switches, fuses, etc., which can quickly cut off the circuit.
      Overcurrent protection relay: with the use of short-circuit protection relay, in the occurrence of short-circuit protection quickly trigger protection, cut off the power supply.

5. Common solutions and equipment for overcurrent protection:
  Circuit Breaker: Used to quickly cut off the circuit in case of overcurrent or short circuit. Common circuit breakers include air switches, leakage circuit breakers, etc., with instantaneous overcurrent protection, delay overcurrent protection and other functions.
      Fuse: Fuse is an overcurrent protection device, when the current exceeds the rated current of the fuse, the fuse will be blown, disconnect the circuit, to avoid damage to the device.
      Overcurrent Relay: Used to detect whether the current exceeds the set value, when it exceeds the immediate action, usually used in conjunction with the circuit breaker.
      Intelligent overcurrent protection equipment: In recent years, with the development of intelligent electrical equipment, intelligent overcurrent protectors have more functions, such as digital display, setting flexibility and remote monitoring.

In SUMMARY:
  Overcurrent protection Different protection policies are adopted according to different application requirements and overcurrent types. Common overcurrent protection includes instantaneous overcurrent protection, timed delay overcurrent protection, overload protection and short circuit protection. In practical applications, reasonable selection and configuration of overcurrent protection equipment (such as overcurrent relays, circuit breakers, fuses, etc.) can effectively avoid equipment damage and improve safety.