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Protective device co ordination with etap

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Shibram Mazumder

Protective device coordination is important to isolate faults to minimize damage and outages. If a failure occurs, protective devices like fuses and circuit breakers should isolate only the faulty portion of the system. A coordination study analyzes tripping times to optimize selectivity, where a fault isolates at the nearest protective device without operating other upstream devices. E-tap simulation verifies device operation and selectivity via time-current characteristic curves showing opening times under faults. Fuses, MCBs and MCCBs are common protective devices, with fuses sacrificing for overcurrent and the others automatically interrupting faults or overloads. The objectives of coordination are to minimize the affected area and duration of outages from faults.

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Protective Device Co-ordination SHIBARAM MAZUMDER 12013002002039 EE UEM, Jaipur
INTRODUCTION • Power system is subjected to fault & transients. These will result in over current & over voltages that can causes damages to conductor or insulation. That result in equipment damages & system failure. • Most electrical power distribution systems are not planned with protective device coordination in mind, and can fail miserably in the proper coordination of the protective devices. • In distribution system Fuse & Circuit breaker are the main device for fault current or over current protection. They pay a very important role in the system design for good quality & reliability.
What is Protective device co-ordination • If a failure occurs, it would be desirable that a short circuit would affect only the portion of the electrical system where the failure occurs, instead of the entire system. A circuit breaker coordination study is used to analyse the tripping times for the series of overcurrent devices being compared. • The methodology is to optimize the selectivity of the devices. Selectivity is the isolation of a faulted circuit to the point of fault without disturbing any of the other protective devices in the system. A properly coordinated system has each of its protective devices adjusted as to minimize the negative impact of equipment failures.
E-tap simulation for Protective device Sequence-of-operation Star Sequence-of- Operation (SQOP) verifies, and confirms the operation and selectivity of the protective devices for various types of faults for any location directly from the one-line diagram and via normalized Time Current Characteristic Curve (TCC) views.
Time Current Characteristic Curve (TCC) • If a fuse or CB has been selected, the designer can use the curve for that fuse or CB to check its opening time versus a given overcurrent or fault current.
Devices for co-ordination FUSE • A fuse is a type of low resistance resistor that act as a sacrificial device to provide over current protection of either the load or the source circuit. • Its essential components is a metallic wire or strip that melts when too much current flows through it, interrupting the circuit that it connects. • The fuse elements is generally made of material having low melting point, high conductivity and least deterioration due to oxidation. E.g. Silver, Copper etc.
MCB(miniature circuit breaker) • Nowadays we use more commonly miniature circuit breaker or MCB in low voltage electrical network instead of fuse. • It automatically switches off the electrical circuit during abnormal condition of the network means in over load condition as well as faulty condition. MCB is much more sensitive to over current than fuse. • The ratings usually end up to 100. A miniature circuit breaker which is used to break small currents. Like in domestic LT circuits.
MCCB(Molded case circuit breaker) • A moulded case circuit breaker, abbreviated MCCB, is a type of electrical protection device that can be used for a wide range of voltages, and frequencies of both 50 Hz and 60 Hz. The main distinctions between moulded-case and miniature circuit breaker are that the MCCB can have current ratings of up to 2,500 amperes, and its trip settings are normally adjustable. • MCCB has two main functions: Protection against overload & electrical fault – currents above the rated value can’t last longer than what is normal for the application. During a fault such as a short circuit or line fault, there are extremely high currents that must be interrupted immediately.
Objectives of co-ordination • Minimize the extent of fault in order to reduce the number of customer affected. • Minimize the service interruption due to fault. • Minimize the duration of the service outages to identify the location of the fault.
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Protective device co ordination with etap

  • 2. INTRODUCTION • Power system is subjected to fault & transients. These will result in over current & over voltages that can causes damages to conductor or insulation. That result in equipment damages & system failure. • Most electrical power distribution systems are not planned with protective device coordination in mind, and can fail miserably in the proper coordination of the protective devices. • In distribution system Fuse & Circuit breaker are the main device for fault current or over current protection. They pay a very important role in the system design for good quality & reliability.
  • 3. What is Protective device co-ordination • If a failure occurs, it would be desirable that a short circuit would affect only the portion of the electrical system where the failure occurs, instead of the entire system. A circuit breaker coordination study is used to analyse the tripping times for the series of overcurrent devices being compared. • The methodology is to optimize the selectivity of the devices. Selectivity is the isolation of a faulted circuit to the point of fault without disturbing any of the other protective devices in the system. A properly coordinated system has each of its protective devices adjusted as to minimize the negative impact of equipment failures.
  • 4. E-tap simulation for Protective device Sequence-of-operation Star Sequence-of- Operation (SQOP) verifies, and confirms the operation and selectivity of the protective devices for various types of faults for any location directly from the one-line diagram and via normalized Time Current Characteristic Curve (TCC) views.
  • 5. Time Current Characteristic Curve (TCC) • If a fuse or CB has been selected, the designer can use the curve for that fuse or CB to check its opening time versus a given overcurrent or fault current.
  • 6. Devices for co-ordination FUSE • A fuse is a type of low resistance resistor that act as a sacrificial device to provide over current protection of either the load or the source circuit. • Its essential components is a metallic wire or strip that melts when too much current flows through it, interrupting the circuit that it connects. • The fuse elements is generally made of material having low melting point, high conductivity and least deterioration due to oxidation. E.g. Silver, Copper etc.
  • 7. MCB(miniature circuit breaker) • Nowadays we use more commonly miniature circuit breaker or MCB in low voltage electrical network instead of fuse. • It automatically switches off the electrical circuit during abnormal condition of the network means in over load condition as well as faulty condition. MCB is much more sensitive to over current than fuse. • The ratings usually end up to 100. A miniature circuit breaker which is used to break small currents. Like in domestic LT circuits.
  • 8. MCCB(Molded case circuit breaker) • A moulded case circuit breaker, abbreviated MCCB, is a type of electrical protection device that can be used for a wide range of voltages, and frequencies of both 50 Hz and 60 Hz. The main distinctions between moulded-case and miniature circuit breaker are that the MCCB can have current ratings of up to 2,500 amperes, and its trip settings are normally adjustable. • MCCB has two main functions: Protection against overload & electrical fault – currents above the rated value can’t last longer than what is normal for the application. During a fault such as a short circuit or line fault, there are extremely high currents that must be interrupted immediately.
  • 9. Objectives of co-ordination • Minimize the extent of fault in order to reduce the number of customer affected. • Minimize the service interruption due to fault. • Minimize the duration of the service outages to identify the location of the fault.