Selective coordination is
required for systems related to life safety
(as defined in the NEC), and is achieved when an overcurrent on a circuit is interrupted and only the closest upstream device opens such that only the section of the electrical system with a problem is taken offline.
Is selective coordination A circuit condition?
Selective coordination generally describes the design of an electrical system in which the upstream protective device (fuse or circuit breaker) nearest to
the system fault clears the fault without
affecting the protective devices that are upstream from it.
Is a coordination study required?
The NEC requires a
selective coordination study
to be implemented by a licensed engineer. The design engineer typically runs a preliminary study with one manufacturer's equipment and estimated feeder lengths.
What does selective coordination mean?
Although the definition has changed slightly over the years, NEC 2014—the most recent version of the code—defines selective coordination as: “
Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective
…
When overcurrent devices are selectively coordinated?
Two overcurrent devices are selectively coordinated
when the downstream overcurrent device closest to the fault opens before the upstream overcurrent device can
. Code Change Summary: The selective coordination requirements in Article 700 have been expanded.
What is coordination study?
What is a protective device coordination study? A protective device coordination study is
a survey of a facility's electrical systems
. It analyzes the impacts of short circuits, equipment failure, and other core faults in a facility's operation. It should always be conducted by qualified electrical engineers.
What is a breaker coordination study?
What is Circuit Breaker Coordination? … A circuit breaker coordination study is
used to analyze the tripping times for the series of overcurrent devices being compared
, generally from the source through the largest branch circuit device.
What is non selective coordination?
A fault on a branch circuit opens protective devices “D”, “C” and “B.” The entire power supply to the building is completely shut off. This non-selective operation is normally the
result of a medium to high level short circuit
. This fault may be line-to-line, line-to-ground, or 3 phase bolted in nature.
What is a type of circuit condition?
The following conditions can exist in any given circuit:
open – no current can flow
.
closed
– current is flowing. shorted – current is flowing through a shorter path and load in the circuit is bypassed.
What is selective tripping?
Selective Tripping means that
when a fault occurs anywhere in the distribution system, one and only one breaker will trip
. That breaker will always be located upstream and closest to the fault.
What is the type of coordination?
Answer: The two primary types of coordination are
internal coordination or establishing a relationship between all the employees
, departments, etc. and external coordination or establishing a relationship between the employees and the outsiders.
Why is electrical Discrimination important?
Discrimination (or selectivity) is the selection of protective devices so that the device nearest to a fault will operate rather than any upstream device. The purpose is
to ensure that the fault is isolated and supply is maintained to other parts of the installation without disruption
.
What is a coordination panel?
The Littelfuse Coordination Panel provides
a simple, time-saving solution for circuits that require selective coordination
. This UL Listed product saves time and money, and increases safety by minimizing system downtime.
What is selective time interval?
“selective-time interval,” is
the sum of the breaker, over travel, and factor-of-safety times
. A. vertical line drawn through any assumed fault location will intersect the operating-time.
Which Standard's devices are designed for time delay fuses and circuit breakers?
| Question Answer | 18. Which standard's devices are typically larger and costly? NEMA | 19. Is it possible to have motor control devices which meet both standards? yes page 8 | 20. Which standard's devices are designed for time delay fuses and circuit breakers? NEMA |
|---|
Is Ground Fault A circuit condition?
A ground fault is a
type of fault in which the unintentional pathway of the straying electrical current flows directly to the earth (to the ground)
. Here, too, the circuit is “short,” in that it has bypassed the circuit wiring, so a ground fault can technically be defined as one type of short circuit.
