Selectivity

Combine safety with continuity of service, and easy fault location

Low-voltage selectivity

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Basic concepts

What is selectivity?

Selectivity

Total selectivity

Partial selectivity

Selectivity

There is selectivity between two circuit-breakers in series when, owing to an overcurrent flowing through both of them, the load-side circuit-breaker opens thereby protecting the circuit, whereas the one on the supply-side remains closed, thus guaranteeing power supply to the rest of the installation.

Total selectivity

Selectivity for any overcurrent value there may be in the installation.

Partial selectivity

Selectivity only up to a certain Is current value (ultimate selectivity value). If the current exceeds this value, selectivity between the two circuit-breakers is no longer guaranteed.

Selectivity techniques

The different selectivity techniques, also from the operational point of view.

Service continuity

Power quality

Stress reduction

Easy maintenance

Do the right thing: avoid power outage

"Service continuity is a better customer experience and always plays a vital role in electrical power plants. With ABB low and medium voltage products you can always achieve maximum selectivity, thus service continuity."

When there is no selectivity among electrical devices, one minor fault along the electrical line can cause a general outage. This is certainly annoying in a residential building, but it can also be very dangerous in an industrial or critical environment.

ABB devices rapidly identify and exclude the area involved without indiscriminate trips that reduce the availability of energy in areas not affected by the fault.

Take care of your business

"Prevent damage to electronic devices and motors, faulty operation and outage: selectivity is a key factor in high power quality."

If you assess the cost of power interruptions, you’ll soon find out that every second of power outage could be incredibly costly in terms of lost business. If you add penalties and service costs, you’ll agree that it’s much more convenient to plan a better quality electrical installation. Selectivity is a known key factor for preventing general outages.

Better power quality through selectivity also prevents voltage instability and network disturbances. These phenomena damage the DC power supplies of computers, shorten the life of electronic equipment and can lead to loss of data.

If you’re dealing with industrial processes, a good quality energy flow maintains stability in rotating machines. A properly energized machine lasts longer and performs better, thus saving money.

Keep your electrical plant healthy

"Thanks to advanced selectivity techniques (e.g. zone selectivity), short circuit current is quickly interrupted at any level. This means less stress on the plant components, which will last longer."

Mechanical stress can be destructive, especially inside power enclosures where high current peaks may occur and high fault currents can flow for up to one second.

Thermal stress is harmful for plastic materials, such as cable insulation. Temperature rises, which occur during faults, can shorten the life of cables. Shorter life means more money must be invested in service, maintenance and renovation.

A plant where zone selectivity is implemented ensures fast fault clearing at every level and prevents both mechanical and thermal stress.

Fast troubleshooting

"Just think if only the fault-affected zone could be highlighted. Problem-solving and repairs would be over in no time. That’s always the case if you opt for a selective electrical network."

Easy maintenance means being able to activate service procedures as fast as possible if faults occur because you know exactly what has happened.

Whether you use an ECS (Electrical Control System) or not, if a minor fault trips a main switch, finding out where the problem is can be a long and tedious job.

When it comes to critical industrial processes (paper, rubber, plastics, glass, chemicals, petroleum industries, and many more), energy disruption is one of the worst scenarios.

Selectivity is now a standard feature of the digital industry, telecommunications and data centers included.

Every minute of power outage is incredibly costly. Creating a selective system from the start will save you time - and thus money - if sudden faults occur.

Tools & Support

SOC

SOC is a tool that can be used to choose and coordinates ABB protection devices.

Curvesweb

Curvesweb is a tool which is used for setting the trip characteristics of the protection devices and verifying selectivity in low voltage plants. You can find Curvesweb also in ABB PartnerHub.

DOCweb

DOCweb is a tool for calculating and sizing medium and low-voltage electrical installations, and for selecting and coordinating ABB protection devices. You can find DOCweb also in ABB PartnerHub.