Formative Question DET50083 Power System Protection

When fault at F,

• CB open,

  CT sense the current

• CB open,

  Trip circuit closed thus trip coil energized,

  Relay coil energized and close,

  CT sense the current

• CT sense the current,

  CB open

• CT sense the current,

  Relay coil energized and close,

  Trip circuit closed thus trip coil energized,

  CB open

Each protection zone consist of primary and protection zone which are.....

• Primary protection is main protection has delay action time.

• Backup protection operate when primary protection fail to function

• Primary protection is second line of defense

• Backup protection ensure quick action than primary protection

Miniature Circuit Breaker (MCB) and Molded Case Circuit Breaker operate in overload and short circuit condition by using......

• Overload protection by solenoid

  Short circuit protection by bi-metallic strip

• Overload protection by using arc chute

  Short circuit protection by bi-metallic strip

• Overload protection by bi-metallic strip

  Short circuit protection by arc chute

• Overload protection by bi-metallic strip

  Short circuit protection by solenoid

SF6 Circuit Breaker offer more advantages compared to oil circuit breaker, air circuit breaker and vacuum circuit breaker which are......

• No risk of explosion

• Expensive due to high cost of SF6 gas

• Complicated safety regulation

• Quite large size

The formula for new per unit

• True

• False

Steps for fault current calculation are.......

• 1. 1. New Vbase

  2. 2. New pu

  3. 3. Reactance diagram

  4. 4. Total pu value

  5. 5. Fault current

• 1. 1. Single line diagram

  2. 2. New Vbase and New pu

  3. 3. Reactance diagram

  4. 4. Total pu value

  5. 5. Fault current

• 1. 1. Single line diagram

  2. 2. New pu and total pu

  3. 3. Reactance diagram

  4. 4. Fault current

• 2. 1. New Vbase and New pu

  3. 2. Reactance diagram

  4. 3. Total pu value

  5. 4. Fault current

  6. 5. Single line diagram

Distance relay operate depending upon the impedance between point of fault and point the relay installed.

• True

• False

Time operating for Inverse Difinite Minimum Time (IDMT) relay is

• 
• 
• 

Busbar protection is namely ..........

• Balanced Earth Fault Protection

• Differential Protection

• Merz-Price Protection

"The converted AC is used on-site or stored in the battery. The charge controller monitor the battery capacity. When the battery reach full capacity, the excess energy is fed to electricity grid".

This PV system is.........

• Off -grid DC system

• Off-grid AC system

• Grid-tied without battery backup

• Grid-tied with battery backup