Selectivity is a topic in electrical engineering that is often underestimated. However, selectivity is of crucial importance for the functionality of electrical systems.
In this article you will learn what selectivity is and why it is so important in electrical engineering.
If you're interested in electrical engineering, then you definitely need to know about selectivity! After all, certain devices can only function properly with selective components. We'll explain everything you need to know about selectivity.
Contents
What is selectivity?
Selectivity is an important principle in electrical engineering. It describes the ability of a switch to close only the desired circuit and leave all other circuits open. This prevents unwanted current flows that could lead to shutdowns.
Some electrical systems are very complex and have many different components. In these systems, it is very important that the selectivity works. If not, there may be problems with the system.
Why selectivity is so important
Selectivity is very important in electrical engineering because it prevents interference from being transmitted from one area of the electrical system to other areas. Selectivity ensures that only the desired components or areas of the system are affected and not the entire system. This prevents damage to the system and enables faster troubleshooting.
Types of selectivity
Partial selectivity
Selectivity is an important principle of electrical engineering. There are different types of selectivity, but partially selective selectivity is one of the most common. Partially selective selectivity refers to the ability of a switch to conduct current only when it is in the correct position. This is important because it prevents current from flowing unintentionally and damaging equipment or even causing a fire.
Full selectivity
Full selectivity means that a device or system is able to distinguish between different electrical currents and only conduct the current that is required for the respective function. This is important in power grids, for example, as several different currents can be present at the same time. Selectivity ensures that only the current intended for the application in question flows.
Types of selectivity
Time-current selectivity
Time-current selectivity is an essential component of the selectivity sequence in electrical engineering. But what exactly is time-current selectivity?
Time-current selectivity describes the behavior of circuit breakers in the event of faults in electrical systems. The selectivity of circuit breakers is a key criterion for the reliability of electrical systems. The time-current selectivity describes how quickly a circuit breaker reacts to a fault and interrupts the current flow. A circuit breaker with a high time-current selectivity reacts faster to a fault and interrupts the current flow more quickly. This increases the reliability of the electrical system and minimizes sources of faults.
Current selectivity
Current selectivity is the ability to generate or conduct certain types of current Current selectivity is an essential feature of electrical engineering and one of the main reasons why it is so useful.
The selectivity of electricity allows us to design and build different types of devices that work in different ways. For example, we can design a circuit that only allows certain frequencies of electrical current to pass through. This frequency selectivity can be used to develop devices that can only process certain types of signals.
The selectivity of the current is also useful for operating certain types of devices. For example, we can only operate a computer with the correct current. If we tried to operate it with a different type of current, it might not work properly.
Current selectivity is also important for safety. When we use electrical appliances, we want to make sure that they are not powered by a type of current that could harm them. For example, we should not operate electrical appliances in an environment where there is a lot of moisture, as this increases the risk of electric shock.
Time selectivity
The time selectivity feature is a further development of current selectivity. A tripping time is defined in addition to the tripping threshold: A certain current value triggers the protection after a defined time delay. This setting strategy makes it possible to gradually increase the current thresholds and tripping times the closer they are to the power supply sources (setting level in direct correlation to the hierarchy level).
The time selectivity product is an effective means of preventing power failures. The delayed tripping thresholds ensure that the tolerances of the two protective devices and the effective currents flowing through them are taken into account. The difference between the delays of the protection functions connected in series must take into account the times of fault detection and release of the device on the load side and the inertia time of the device on the supply side. As in the case of current selectivity, the setting values are established by comparing the time-current tripping curves of the protection devices.
Energy selectivity
Energy selectivity is the ability to use the right amount of energy at the right time. The coordination of energy selectivity utilizes the current-limiting properties of the molded case circuit breakers. By using current-limiting circuit-breakers, we can ensure that the current is not overloaded and therefore energy is used more efficiently.
Energy selectivity is an important but dynamic phenomenon that is highly dependent on the interaction between the two devices connected in series. Therefore, the end user cannot determine the energy selectivity values. Manufacturers offer tables and programs to determine the limiting current selectivity values under short circuit conditions for different combinations of circuit breakers. These values are obtained by theoretically integrating the results of tests carried out.
Zone selectivity
The zone selectivity system is a further development of time selectivity. Zone selectivity is implemented by a dialog between the current measuring devices, which enables the correct identification of the faulty area immediately after the threshold value detection is exceeded and interrupts the power supply to the faulty area. This system is particularly useful for large industrial plants where a power failure can quickly become very expensive.
Zone selectivity can be realized in two ways:
The measuring devices send the information about the exceeded threshold value to a monitoring system, which determines which protective functions must intervene; the monitoring system can also be directly connected to the protective functions so that they are automatically activated.
If there are current values that exceed its setting, each protection device sends a blocking signal via a direct connection or a bus to the hierarchically higher protection device (on the supply side in relation to the power flow direction) and checks that no similar blocking signal has been received from the protection device on the load side before intervening. This means that only the protection on the supply side is triggered immediately.
Selectivity in electrical engineering succeeds with these 10 tips
1. identify the areas to be processed
2. organize the areas according to importance
3. look for possible improvements
4. make improvements
5. check your results
6. make sure that all areas are covered
7. create a plan B in case something does not go as expected
8. be careful with new technologies
9. keep an eye on the costs
10. work continuously on selectivity
Conclusion
Selectivity in electrical engineering is an essential feature for the quality of electrical systems. It enables major failures to be avoided. It is therefore essential that we pay attention to selectivity when choosing our electrical systems. This is the only way we can ensure that our systems always function reliably.
