Is selective coordination required?

Is selective coordination required?

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.

What is selective coordination in circuit breakers?

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.

What is discrimination of circuit breaker?

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.

What is the purpose of breaker protection coordination?

Breaker coordination refers to the use of breakers specifically—including the latest electronic trip breakers—to isolate electrical problems, stop nuisance tripping and avoid system-wide blackouts.

How do you achieve selective coordination?

To achieve selective coordination with fuses, the fuse ratio tables must be employed. For circuit breakers, if there is an overlap of the TCCs below the available short circuit current at the downstream bus, then the circuit breaker selective coordination tables must be employed.

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. Simulate Circuit Breaker Tripping.

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.

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 the purpose of a coordination study?

A coordination study determines how long equipment can sustain operation without damage or failure by comparing the operating levels and times of protective devices to the withstand levels and times.

How do you do a relay coordination study?

Let us try to understand relay coordination with a real-life case study….The Case Study

1. Analysing Circuit Breaker 5 (CB-5)
2. Analysing Circuit Breaker 4 (CB-4)
3. Analysing Circuit Breaker 3 (CB-3)
4. Analysing Circuit Breaker 2 (CB-2)
5. Analysing Circuit Breaker 1 (CB-1)

What is the importance of short circuit calculations?

The purpose of a short circuit fault analysis ultimately is to provide means to keep the grid safe and operating. A short circuit fault analysis calculates the amount of short circuit current from a system, then compares that figure with the interrupting rate of the devices that protect sections of the grid.