Welcome to HZNRKJ!

Technical Encyclopedia


The difference between over current protection and over load protection

         Action current flow protection is to avoid the maximum load current setting, in some cases can not meet the requirements. So in order to improve the sensitivity of overcurrent protection when short circuit fault occurs in the sensitivity and improve from the maximum load current condition, which is why the installation of low voltage and current protection in atresia.
     Overload generally refers to the power, the current general description of fault. The load is a kind of common appellation, is a quantitative value, namely the power of books written. Overload refers to the load power consumption exceeds the rated value, according to the power is equal to the voltage multiplied by the current can be known, power over the rated value, if the supply voltage is constant, the current will exceed the rated value, or the overcurrent protection of high voltage, load, equivalent to the long delay in the protection of low voltage system (i.e. low pressure system overload protection), general transformer overload protection setting time is 9~15 seconds of action current is greater than the rated electric transformer Flow. 
     In addition high voltage capacitors and motors may also be used for overload protection and the lines generally do not use over-current protection is generally for short circuit protection.
The generator protection as an example, the current generator over a certain time, action on the trip, the generator overload protection also has a certain time, action in the signal, alarm. Its value is less than the current value. From the reasons, the flow is usually due to external fault, such as external short-circuit caused. Belongs to the backup protection, usually with a certain delay; overload caused by overload or asymmetry. From the exit, the overcurrent protection usually symmetric overload trip; usually letters, negative sequence load usually trip delay.
      Overcurrent protection and overload protection are two main differences: one is the setting value is two different action, different action time. Overload protection value is much lower than the overcurrent protection value, but is greater than that of the normal load, to prevent the equipment overload operation, and in order to avoid the starting current equipment also added a certain delay. For some reason when the overcurrent protection maloperation, overload protection can be used as backup protection over current protection. However, overload protection is generally divided into 2 regions of a time limit in an inverse time when more than a little when rated, the overload capacity of a device can withstand less in a period of time, this time is not required To stop tripping when more than one rated when many equipment not often time under high overload must, to stop or tripping of an equipment damage action time can greatly inverse time overcurrent according to the cooling capacity of primary equipment (mainly the overload current increases heating increases lead to burning equipment). Setting calculation. And the flow is the need to protect the external fault tripping immediately. 
      Overload protection value is low, generally 1.2 times rated the long delay, the main protection is due to the load side clamping torque increase, fault type, characteristics of this kind of fault is not caused by current increases rapidly, can long delay does not cause damage to coil overheating, action on the trip. The current protection setting value is higher, generally 3-4 times, mainly used for blocking, do the backup protection of three-phase short-circuit overcurrent protection, short-circuit fault description of the system, a lot of voltage will decrease, and the overload signal when the voltage does not decrease, so the overcurrent protection adopts low voltage closes, and not use current overload protection Protection is to collect three-phase or two-phase current value, and overload protection only need to collect any phase current value can be over-current protection protection will export action, overload protection only signal!
Online Service