What is a Restriking current in a circuit breaker?

The term “restrike” is defined as a re-establishment of the current, one-quarter cycle or longer, following interruption of a capacitive current at a normal current zero [1]. Abnormal transients are a result of trapped charges and energy. Reignitions and restrikes can lead to very magnitude transients.

What is Restriking in circuit breaker?

Restriking voltage: The transient voltage appear across the contacts of circuit breaker at current zero period during arcing is known as Restriking voltage.

What is Restriking current?

When the current across the contact of the circuit breaker is zero, a high-frequency transient voltage develops in the whole breaker contact and is produced by the sudden distribution of energy between the electric and magnetic field. This transient voltage is called restriking voltage.

What is Restriking and recovery voltage in circuit breaker?

RestrikingVoltage : it is the transient voltage that exists during the arcing time. ( natural frequency kHz ). Recovery Voltage : it is the rms voltage after final arc extinction. ( normal frequency 50 or 60 Hz).

What is the cause of restriking voltage?

Restriking voltage:

At current zero, a high-frequency transient voltage appears across the contacts and is caused by the rapid distribution of energy between the magnetic and electric fields associated with the plant and transmission lines of the system. This transient voltage is known as restriking voltage (Fig.

Restriking Voltage and Recovery Voltage

What is meant by Restriking voltage?

The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction is called restriking voltage. It is measured in peak value. Restriking voltage is the transient voltage appearing across the breaker contacts immediately after the opening of breaker contacts.

What is the difference between Restriking voltage and recovery voltage?

The waveforms of arc voltage, recovery voltage and restriking voltage are shown above. From the waveform, it can be seen that restriking voltage and recovery voltage are simply the voltage across the circuit breaker contacts. The only difference between them is their period of existence.

What is rate of restriking voltage?

The transient voltage appear across the contacts of circuit breaker at current zero period during arcing is known as Restriking voltage. The rate of rise of re-striking voltage is directly proportional to the natural frequency.

On what factor does the rate of rise of restriking voltage depends?

The rate of rise of re-striking voltage is directly proportional to the natural frequency. So, the rate of rise of re-striking voltage (RRRV) is dependent upon both the inductance and capacitance of the system.

Why the value of RRRV is important for circuit breaker?

This is because the average RRRV is much greater in the former case. In the latter case the voltage across the circuit breaker contacts rises slowly thereby giving longer time for building up of the dielectric strength.

What is circuit breaker What is Restriking voltage and arc voltage?

It is the transient voltage that appears across the contacts at or near current zero during arcing period. If dielectric strength rise is greater than the rise of restriking voltage then the arc will not restrike.

What are fault diverters?

Fault diverters, or crowbars, have proven to be very effective protection against transient-induced power arcs within accelerator oscillator tubes. This device short circuits the oscillator-plate power supply in the event of an over-current, thus removing the power flow from the fault within a few microseconds.

What is the average rate of rise of restriking voltage up to the first peak?

The average rate of rise of re-striking voltage upto first peak is. A 50 Hz, 11 kV, 3-phase alternator with earthed neutral has reactance of 7 ohms per phase and is connected to bus-bar through a circuit breaker.

How do you find the maximum value of restriking voltage?

We are now required to find the voltage across the breaker contacts immediately after the breaker contact opening. where ω₀ = 1 / √LC and hence f₀ = (1/2π√LC) where f₀ is the natural frequency of oscillation. Expression (3) is the restriking or transient recovery voltage.

What is the zero current?

Current zero (CZ) refers to the interruption phenomena in high power circuit-breakers. Today it seems improbable that high voltage circuits could be interrupted economically by other means than the electric arc.

What is prospective voltage?

When a low inductive current is being interrupted and the arc quenching force of the circuit breaker is more than necessary to interrupt a low magnitude of current, the current will be interrupted before its natural zero instant.

What is meant by overcurrent protection?

Overcurrent protection devices include circuit breakers and fuses. Overcurrent protection devices are meant to protect against the potentially dangerous effects of overcurrents, such as an overload current or a short-circuit current, which creates a fault current.

What is current chopping?

What is current chopping ? Definition: it is the phenomenon of current interruption before the natural current zero is reached. Current chopping mainly occurs in air-blast circuit breakers because they retain the same extinguishing power irrespective of the magnitude of the current to be interrupted.

What is active recovery voltage?

Active Recovery Voltage

It may be defined as the instantaneous recovery voltage at the instant of arc extinction.

What is arcing voltage?

Arc Voltage is that amount of voltage that exists on contacts separated by a small gap that will cause an electric discharge across the gap. And, lastly, Arc Current is that amount of current necessary to just sustain an arc caused by the arc- voltage electric discharge.

What is the purpose of back up protection 1 point?

If due to some reason, the Main protection fails, the Back-up protection serves the purpose of protection. Main protection can fail due to failure of one of the components in the protective system such as a relay, auxiliary relay Current Transformer, PT, trip circuit, circuit-breaker, etc.

What is the average RRRV if a short-circuit?

While short-circuit test on circuit breaker a protection engineer obtained following readings on single frequency transient. The average RRRV is: 2.5 kV/µsec.

Where voltage is high and current to be interrupted is low the breaker preferred is?

05․ Where the voltage is high and current to be interrupted is low, Which of following the breaker is preferable? Oil CB.

Are voltage produced in AC circuit breaker is always?

[Solved] The arc voltage produced in A.C. circuit breaker is always. Q.

Why are the isolators used?

Isolator is a manually operated mechanical switch that isolates the faulty section of substation. It is used to separate faulty section for repair from a healthy section in order to avoid the occurrance of severe faults. It is also called disconnector or disconnecting switch.