PowerFactory DIgSILENT tutorial #20 Time Overcurrent protective relays using SEL 751 relay model

You will learn how to import the relay library in Power factory. How to setting our relay model How to plot the Time over-current protective relays and Finally you will learn the tripping of relays in case of fault condition. SEL 751 A1 was used. ************************* Overcurrent protective relays: Overcurrent protections , which is used as a primary protection operate only when the value of the current is greater than the relay setting time. They protects the power system equipment’s such as transmission lines, transformers, generators, and motor from the fault current. Overcurrent Relays Types: They are defined by the time vs. current curve, which is Depend on time of operation. there are various types of Over Current relays, such as 1. Instantaneous over current relay. 2. Time dependent- (Definite time over-current or inverse time relay over current). 3. Mixed (Definite time over-current relay + instantaneous time over-current relay, inverse over current relay + definite time over-current relay. etc. ) 1. Instantaneous Overcurrent Relays This type of relay has no intentional time delay for operation, so it is called instantaneous units (operation time = 0.1 second). The interval of time is very less between the instant pick-up value and the closing contacts of the relay, so the operating time is less than 3 cycles. Definite Time overcurrent Relays. A definite time overcurrent relay operates after a certain time when the current exceeds the pickup value. This relay has both time and current setting adjustment Inverse time overcurrent relay: The operating time is inversely depending on the value of the current. That is, the operation time of the relay gets smaller when the current gets larger. The operation of the relay depends on the magnitude of the current. The pickup current and curve level is the two main setting of these relays. Link PowerFactory-DIgSILENT tutorial:    • PowerFactory-DIgSILENT tutorial #1. introd...