What is “selectivity”? Complete selectivity means that the protective devices will minimize effect of a short circuit or other undesirable event on the power system. The amount of the power system that must be shut down in response to the event is kept to the absolute minimum.
What does selectivity ensure in the event of a fault?
Selectivity implies that the product downstream will open first in the case of a fault, in other words that the product upstream is less “sensitive.” To guarantee selectivity, the upstream protection will not trip.
What is selectivity limit?
Selectivity limit current, Is, is defined in EN/IEC 60947-1 (4.2) as “the current co-ordinate of the intersection between the total time-current characteristic of the protective device on the load side and the tripping time-current characteristic of the other protective device.” The selectivity limit current is a …
How do you define selectivity?
the state or quality of being selective. Electricity. the property of a circuit, instrument, or the like, by virtue of which it can distinguish oscillations of a particular frequency. Radio. the ability of a receiving set to receive any one of a band of frequencies or waves to the exclusion of others.
Is selectivity required?
It’s necessary to have full Selectivity if danger may occur if an upstream device operates before the downstream device under overcurrent conditions. An example of this is where a building has Life Safety Services (LSS) such as fire lifts, smoke extracts, sprinkler pumps and fire pumps.
How can we achieve selectivity?
Selectivity is achieved by overcurrent and earth fault protective devices if a fault condition, occurring at any point in the installation, is cleared by the protective device located immediately upstream of the fault, while all other protective devices remain unaffected (see Figure H48).
What is breaker discrimination?
Circuit breaker discrimination (also known as selectivity) is the ability of the local circuit breaker to operate before any upstream circuit breakers under fault conditions. … The intention is to limit the service interruption to the minimum amount for any fault, whether this fault is overload or short-circuit.
Does selectivity indicate safety?
Selectivity is an important attribute of effective and safe drugs, and prediction of in vivo target and tissue selectivity would likely improve drug development success rates.
Which part of the CB is helpful in breaking the current?
Q. Which part of the circuit breaker is helpful in breaking the current? a. Trip coil.