What is symmetrical and asymmetrical current?

The waveform that equals the sum of the sine wave and the decaying exponential is called the asymmetrical current because the waveform does not have symmetry above and below the time axis. The sine wave alone is called the symmetrical current because it does have symmetry above and below the time axis.

What does RMS symmetrical amperes mean?

Symmetrical (RMS) Current In 8 or more cycles (typically 15), the fault current will decay to a symmetrical waveform which, ofcourse , would have no DC offset. Figure 4: Symmetrical RMS current. In this figure the waveform is symmetrical starting with the 5th cycle.

What is symmetrical and asymmetrical short circuit?

Asymmetrical short-circuit current: A fault current whose waveform is asymmetrical to the zero axis. The peak positive current at any of the waveform loops will be greater than 1.414 times the rms symmetrical current. Symmetrical short-circuit current: A fault-current whose waveform is symmetrical about the zero axis.

What is symmetrical breaking current?

– Symmetrical breaking current is the RMS value of AC component of short circuit current at the instant of separation of the contacts. It does not take into account the DC offset.

What is initial symmetrical short circuit current?

The initial symmetrical short-circuit current, I”k, is an r.m.s. value of short-circuit current and can be interpreted as – PSCC, defined in this EREC. The peak short-circuit current, ip, is an instantaneous value of the short-circuit current and occurs at the first a.c. peak after fault inception.

What is RMS rating in breakers?

It is a means of describing the amount of fault current that a breaker can withstand, and still be able to perform its function of opening (thus terminating the fault). If you have a breaker rated for a 35,000 AIC, then the 35,000 amps is an RMS value.

What is an AIC and SCCR?

Note: The difference between SCCR and AIC is that AIC applies to overcurrent protection devices only, and the SCCR applies to the entire assembled device, which may use as part of its assembly overcurrent protection devices with an AIC rating.

What is the difference between symmetrical and asymmetrical fault?

Answer: Symmetrical faults are those faults which involve with all the three phase. it simply means that symmetrical faults affect all the three phases. On the other side, unsymmetrical faults are those faults in which either one or two phase involve. In unsymmetrical faults the three phase lines become unbalanced.

Why making current is 2.5 times the breaking current?

As the rated short circuit making current of circuit breaker is expressed in maximum peak value, it is always more than rated short circuit breaking current of circuit breaker. The normal value of short circuit making current is 2.5 times more than short circuit breaking current.

What is the difference between making current and breaking current?

Making current of a circuit breaker is the peak value of maximum current loop during sub transient condition including DC component when breaker closes. Breaking current of a circuit breaker depends on the instant on the current wave where the contacts of breaker start separating.

What is asymmetrical fault?

An unsymmetrical or asymmetrical fault is defined as a fault that affects one or two phases of a three-phase system in contrast with the previously studied balanced or symmetrical faults which equally affect each of the three phases.

What is ik fault current?

Ik: steady-state short-circuit current It can be defined as the r.m.s value of the fault current once the transitional period has ended (a few cycles). It is “applicable” in any point of the circuit. That means it is the generic term to indicate the value of the short circuit current.