The transient voltage that appears across the circuit breaker contacts immediately after the arc extinction or at current zero during the arcing period is called Restriking Voltage. This voltage is so named because the arc can restrike only during the existence period of this transient voltage.
Simply so, What is Restriking voltage and recovery voltage of breaker? 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.
How do you calculate Restriking voltage? For a re-striking voltage having a single frequency transient component the RRRV is obtained by dividing the maximum amplitude of the oscillation by the duration of the first half wave.
Subsequently, What is distracting voltage?
What is restriking voltage? a. The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction.
What is active Restriking voltage?
The voltage formed across two electrodes in an a.c. circuit at zero current and during the subsequent extinction of an arc between them, causing (if sufficiently high) the restriking of the arc; specifically that across the contacts of a circuit breaker, switch, etc., after they are separated.
How does Restriking voltage affect arc interruption process in circuit breakers? The voltage appears across the breaker contacts at the moment of final current has a serious influence on the arc extinction process. Under the influence of this voltage, the arc tries to restrike and hence it is named as the restriking voltage.
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.
What is resistance switching? Resistive switching refers to the physical phenomena where a dielectric suddenly changes its (two terminal) resistance under the action of a strong electric field or current. The change of resistance is non-volatile and reversible.
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.
What is meant by recovery voltage and restriking voltage what is RRRV how do you obtain RRRV give the expressions for average and maximum RRRV? The expression for the re-striking voltage is ω V C ( t ) = V m ( 1 − cos The maximum value of the re-striking voltage occurs at ω The maximum value of re-striking voltage = 2 Vm = 2 × peak value of the system voltage. The rate of rise of re-striking voltage (RRRV) ω = d d t [ V m ( 1 − cos ∴ RRRV = Vm ωn sin ωnt.
What measures are taken to reduce Restriking voltage and RRRV?
To reduce the restriking voltage, RRRV and severity of the transient oscillations, a resistance is connected across the contacts of the circuit breaker. This is known as resistance switching.
What is the average rate of rise of restriking voltage upto the first pic?
| Q. | What is the average rate of rise of restriking voltage upto the first peak? |
|---|---|
| B. | 453 * 103kV / sec |
| C. | 582 * 103 kV / sec |
| D. | 467 * 103 kV / sec |
| Answer» b. 453 * 103kV / sec |
What is the major drawback of using SF6 circuit breakers?
Sealing problems of the gas. Ingress of moisture in the gas system – dangerous. Deterioration of SF6 gas with time.
What is critical resistance in circuit breaker?
The critical field resistance is defined as the maximum field circuit resistance (for a given speed) with which the shunt generator would just excite.
How resistance switching can be used to reduce peak Restriking voltage? Resistance switching dampens(critically damping) TOV(Transient Over Voltages) developed due to current chopping , interruption of capacitive currents ; Also reduces the oscillatory growth of re-striking voltage and makes it to grow exponentially upto recovery voltage.
What is memristor technology?
A memristor is an electrical component that limits or regulates the flow of electrical current in a circuit and remembers the amount of charge that has previously flowed through it. Memristors are important because they are non-volatile, meaning that they retain memory without power.
How an arc is generated in a switchgear?
During opening of current carrying contacts in a circuit breaker the medium in between opening contacts become highly ionized through which the interrupting current gets low resistive path and continues to flow through this path even the contacts are physically separated.
What is importance of RRRV in fault clearing process? If R.R.R.V is greater than the rate of rise of dielectric strength between the contacts, the arc will re-strike. The arc will fail to re-strike if R.R.R.V is less than the rate of increase of dielectric strength between the contacts of the breaker.
What is the average rate of rise of restriking voltage up to the first peak is?
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.
What is the full name of RRRV for circuit breaker? Voltage that appears between the contacts of the circuit breaker after arc extinction during opening process while clearing a fault. The Rate of Rise of Recovery Voltage (RRRV) is defined as peak transient recovery voltage divided by the total time from zero voltage to peak voltage.
What is current chopping?
Current chopping is the condition where during an ac current interruption the current becomes unstable as it approaches a zero crossing and stops before the zero is reached. Current chopping occurs to some degree in all types of interrupters.
Why are isolators used? Isolators are used to open a circuit under no load (No current condition). Its main purpose is to isolate one portion of the circuit from the other and is not intended to be opened while the current is flowing in the line.
What are the advantages of SF6?
Advantages of SF6 circuit breaker: The SF6 gas is inflammable and chemically stable. Their decomposition products are non-explosive and hence there is no risk of fire or explosion. Electric clearance is very much reduced because of the high dielectric strength of SF6.
What is SF6 used for? SF6 is used in several different industries including: electrical transmission and distribution equipment. manufacture of electronics / semiconductors. production of magnesium.
Why is SF6 used in circuit breakers?
So due to high dielectric strength and high cooling effect, SF6 gas is approximately 100 times more effective arc quenching media than air. Due to these unique properties of this gas, SF6 circuit breaker is used in a complete range of medium voltage and high voltage electrical power system.
What is the rating of circuit breaker? Rated voltage of circuit breaker depends upon its insulation system. For below 400 KV systems, the circuit breaker is designed to withstand 10% above the normal system voltage. For above or equal 400 KV system the insulation of circuit breaker should be capable of withstanding 5% above the normal system voltage.
What is the need for resistance switching? Resistance Switching helps to reduce the voltage transient surge during current chopping and capacitive current breaking.
Which circuit breaker has higher rating?
Detailed Solution
| Circuit breaker | Rating |
|---|---|
| Oil circuit breaker | 3.3 kV – 220 kV |
| Miniature circuit breaker | 240 V |
| Air blast circuit breaker | 66 kV – 1100 kV |
| Vacuum circuit breaker | 3.3 kV – 33 kV |
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