System Protection CH 1 Flashcards
the coordination and application of key equipment so that it functions in a manner that ensures the reliability and safety of a system
System protection
a certain application and coordination of
equipment for a specific portion of the system
protection scheme
the proper operation of several pieces of equipment together and is the key to effective system protection.
Coordination
the quantity of electrical component
that has to be measured for pieces of equipment that interrupt the flow of current.
time current
characteristics
the graphic representation of time current
characteristics of different protective devices and how they relate to each
other.
Protection curves
The engineering done to design the protection for a system or a circuit
coordination study
high voltage, low voltage, excessive current,
incorrect frequency, and/or single-phasing could cause damage to customer
equipment.
Abnormal conditions
a condition where a short circuit has occurred somewhere on the system, either on a line or piece of equipment.
Faulted Conditions
These faults are sustained and cannot be cleared without some type of repair.
Permanent Faults
These faults can be cleared by momentarily de-energizing the line.
Temporary Faults
What are the types of ground faults?
Phase-to-Ground, Phase-to-Phase, Three-Phase, & Two-phase-to-Ground and Three-Phase-to-Ground faults
occur when a phase conductor makes contact with ground.
Phase-to-ground faults
occur when two phases of a circuit make contact.
Phase-to-Phase fault
occur when the neutral breaks and whips around the conductors or when the structure falls to the ground
Two-phase-to-Ground and Three-Phase-to-Ground fault
occurs when all three phases are faulted together, but they aren’t making contact with ground.
Three-Phase Fault
What are the basic objectives for system protection?
Protect the general public by reducing exposure to live conductors. Protect utility personnel who may be working on the lines and equipment. Minimize damage to lines and equipment. Minimize the number of customers out of service and the time they are out of service. Minimize damage to any customer’s equipment by maintaining the proper voltage and frequency. Maintain the reliability of the system by minimizing the potential for a fault condition to affect additional lines and equipment. (This objective relates more to the transmission system.)
Is the most common type of fault permanent or temporary?
temporary
What are the basic rules of coordination?
- For permanent faults, remove only the smallest portion of system that contains the fault. 2. For temporary faults, give all faults a chance to be temporary by providing a reclosing operation for a fault anywhere on the system.