Should a protection scheme trip during abnormal conditions?

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What are the five components of the protection scheme?

Components of Protection System:

  • Relays.
  • Circuit Breakers.
  • Tripping and Other Auxiliary Supplies.
  • Current Transformer (CT)
  • Voltage Transformers (VT)
  • Linear Coupler.

What are the attributes of protection schemes?

Performance and design criteria for system-protection devices include reliability, selectivity, speed, economy, and simplicity. Reliability: Devices must function consistently when fault conditions occur, regardless of possibly being idle for months or years. Without this reliability, systems may cause costly damages.

What are the functions and necessity of protection?

The objective of power system protection is to isolate a faulty section of electrical power system from rest of the live system so that the rest portion can function satisfactorily without any severe damage due to fault current.

What are the three basic components of a protective relay scheme?

There are three principal components of a protection system: Transducer. Protective relay. Circuit breaker.

What are the 7 requirements of protective system?

Protection System Requirements and some basic terminologies used

  • Reliability:
  • Speed:
  • The Relay Time :
  • The Breaker Time:
  • Selectivity:
  • Sensitivity:
  • Stability:
  • Adequacy:
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What are the types of protection scheme?

Protection Schemes

  • Overcurrent Protection Scheme.
  • Differential Protection Scheme.
  • Distance Protection Scheme.
  • Directional Protection Scheme.

What does a protection system really provide?

Their purpose is to limit, to the extent possible, further damage to equipment, to minimize danger to people, to reduce stress on other equipment and, above all, to remove the faulted equipment from the power system as quickly as possible so that the integrity and stability of the remaining system is maintained.

What are the requirements of protection of lines?

The protection scheme must satisfy the following requirements: a) Under normal conditions the breakers are not tripped. b) Under fault conditions only the breakers closest to the fault on the source side are tripped. c) If the closest breaker fails to operate, the next breaker closer to the source should trip.

What are the good features of protective relaying?

Functional Characteristics of Protective Relaying

  • Selectivity.
  • Speed.
  • Sensitivity.
  • Reliability.
  • Simplicity.
  • Economy.

What are the operating principles of protective relay?

Protective relay work as a sensing device, it senses the fault, then known its position and finally, it gives the tripping command to the circuit breaker. The circuit breaker after taking the command from the protective relay, disconnect the faulted element.

What is primary protection?

Primary Protection:

The main protection or primary protection is the first line protection which provides quick-acting and selective clearing of a fault within the boundary of the circuit section or element it protects. The main protection is provided in each section of an electrical installation.

What is a through fault?

In the power transformer protection, through-fault is the system fault that are external to the transformer protection zone. It is a well known concept that the zone of the protection in transformer differential relay will be defined by the location of the CTs secondaries.

How do you protect transmission lines from active faults?

Overcurrent and Earth-Fault Protection of Transmission Lines: The general practice is to employ a set of two or three overcurrent relays for protection against phase-to-phase faults and a separate overcurrent relay for single line-to-ground faults.

What is an example of an abnormal condition?

For example, cuts or obvious wounds, breathing problems, skin rashes, blood tests with abnormal results, and the like clearly are abnormal conditions.

What are the criteria of abnormality?

Abnormal behavior is any behavior that deviates from what is considered normal. There are four general criteria that psychologists use to identify abnormal behavior: violation of social norms, statistical rarity, personal distress, and maladaptive behavior.

Which is the circuit breaker preferred for the interruption of high voltage and low current?

The SF6 circuit breakers are preferred for the substation with: 33 kV. 11 kV. 110 kV.

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What is interrupting time of circuit breaker?

The breaker interrupting time is a fraction of the clearing time between the breaker actuation and the end of the clearing process. This time is the “breaker operating time.”

How do relays detect a fault?

A phase angle comparison relay compares the relative angle of phase between the AC voltage and the AC current, measuring the power factor angle. This comparison determines the direction of flow of the current with respect to the voltage, with the magnitude of the angle measured giving an indication of faults.

Which of the following is unit type protection scheme *?

a) Unit Protection Scheme: Unit type schemes protect a specific area of the system i.e. a transformer, transmission line, generator or bus bar. The unit protection schemes are based on Kirchhoff’s Current Law – the sum of the currents entering an area of the system must be zero.

What is the difference between unit protection and non-unit protection?

Non-unit protection is time graded. It is arranged so that the protection within the faulted zone operates first and removes the fault, thus allowing protection in other zones to reset before completing their tripping function. This contrasts with unit protection which will not operate for a fault outside its zone.

What is the drawback of protection system?

There are many challenges concerning protection; especially in fault location detection, absence of natural current zero-crossing and associated breaker issues, high rate of rise of fault currents due to low cable impedance, relay coordination problems and lack of standards [1] [23]. …

What does protection Class II mean?

Class II power supplies

Protection is maintained by double or reinforced insulation, rather than relying on both protective earthing and basic insulation. In this way, IEC Class II power supplies are not mandated to have a safety ground conductor brought to the power supply.

Can RCD be used for fault protection?

The RCD has become an indispensable protective device, selected to provide fault protection, additional protection and, in certain circumstances, protection against fire. RCDs are widely used and, therefore, it is necessary for electricians to have a sound understanding of this type of protective device.

What are the five causes of main protection failure?

Reasons of Primary Protection Failure

  • Current or Potential Transformer failure.
  • Loss of Auxiliary Control Voltage.
  • Defective Primary Relays.
  • Open Circuits in Control & Trip Coil.
  • Failure of Breaker.

Why primary protection does not operate in faulty condition?

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 are the types of protection scheme?

Protection Schemes

  • Overcurrent Protection Scheme.
  • Differential Protection Scheme.
  • Distance Protection Scheme.
  • Directional Protection Scheme.
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What are the two types of protection?

It is a usual practice to divide the Types of Protection scheme into two classes viz. primary protection and back-up protection.

What are main problems with distance relaying scheme?

The major problem to the distance relay is to measure correct impedance from relaying point to fault point when series capacitor remains in fault path.

What is stability in protection system?

Definition: The quantity whereby a protection system remains inoperative under all conditions other than those for which it is specifically designed to operate.

What is through fault stability?

In practice, this is difficult to achieve – especially for very large through faults, due to the non-ideal nature of the current transformers used to measure the currents. The term used to specify the system’s ability to cope with these imperfections is called Through-fault Stability.

What is meant by the through fault and the in zone fault condition?

Through fault occurs outside of the protective zone. In other words,occurrence of the external faults outside of the equipment protective zone is called through fault. A transformer has a unit protection or differential relay for protection from the internal fault inside of the transformer.

Which of the following features is not desirable while protecting a transmission line?

‘Multiple pole switching’ is NOT desirable while protecting a transmission line.

What is the need of protection of transmission line?

As you already know, the real purpose of transmission line protection is to detect faults or abnormal operating conditions and to initiate corrective action. Protective relays must be able to evaluate a lot of parameters to choose and establish right corrective action. Obviously, a relay cannot prevent the fault.

What does abnormal mean medically?

Not normal. Describes a state, condition, or behavior that is unusual or different from what is considered normal. In medicine, an abnormal lesion or growth in or on the body may be benign (not cancer), precancerous or premalignant (likely to become cancer), or malignant (cancer). Also called atypical.

What is the medical term for abnormal?

anomaly – an irregularity or deviation from normal; an abnormal structure.

What is abnormal behavior?

behavior that is atypical or statistically uncommon within a particular culture or that is maladaptive or detrimental to an individual or to those around that individual.

What term refers to an abnormal condition of all or part of the body?

A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury.

What are the four main categories of abnormal behavior?

They are:

  • Statistical Criterion.
  • Social Criterion.
  • Personal Discomfort (Distress)
  • Maladaptive Behavior.
  • Deviation from Ideal.