S5 - System Protection PPT Flashcards
Used in every aspect of activity including the home, communication, transportation, commerce, and power utilities
Relays
An electronic device that is designed to respond to input conditions in a prescribed manner and, after specified conditions are met, to cause contact operation or similar abrupt change in associated electric control circuits
Relay
A relay whose function is to detect defective lines or apparatus or other power system conditions of an abnormal or dangerous nature and to initiate appropriate control circuit action
Protective Relay
Used when there is a need to protect human lives and system equipment from intolerable conditions resulting from natural events, physical accidents, equipment failure, or mis-operation due to human error
Protective Relay
A nonprofit, non-revenue producing item that is not necessary for the normal operation of an electrical system until a fault – an abnormal, intolerable situation – occurs
Protective Relaying
Allow us to both de-energize circuits under faulted conditions and restore power automatically once the faulted condition has subsided
Protective Relay
This branch of electrical power engineering that deals with the protection of electrical power systems from faults through the isolation of faulted parts from the rest of the electrical network
Power System Protection
Provide insulation from the high-power system voltages and reduce the magnitudes to practical secondary levels for use with protective relays
Instrument Transformer
The two types of instrument transformers are:
Current and Potential
Has a primary coil of one or more turns of heavy wire. It is always connected in series in the circuit in which current is to be measured. The secondary coil is made up of many turns of fine wire, which must always be connected across a low burden circuit.
Current Transformer
A carefully designed, extremely accurate step-down transformer. It is normally used with a standard 120-volt circuit, which is a usable level for meters, relays, and other devices. Are selected according to the high voltage to which they are connected to still produce approximately 120V AC on the secondary side.
Potential Transformer
The zones of protection have boundaries that are defined electrically by _____ location. A particular _____ will mark the beginning or end of a protection zone
Current Transformer
Consists of the feeder breaker and all facilities being fed by that breaker. In the figure the CT marks the beginning of the zone, which encompasses the circuit breaker and all the primary conductor.
Feeder Zone
What are three types of protection zones that are used within substations on the EPB system
Bank Zone
Bus Zone
Bank-Bus Zone
Has devices on both the high side and low side of the transformer that are used to trip the _____.
Bank Zone
For a bank fault, the zone is cleared with no impact on the low side bus, therefore, if two banks are in parallel, all load remains in service.
Protected by a bank breaker (high side or low side) and all feeder or line breakers fed from that _____.
Bus Zone
A bus fault will be cleared by these devices and all radial feeder load from the bus will be out.
Protection includes a transformer bank as well as the entire low side bus that the bank serves. The zone is bounded by high side line breakers, a high side bus tie breaker (in some cases), and low side feeder breakers.
Bank- Bus Zone
The key component that is not present in a bank-bus zone that is present in other stations is a low side bank breaker. If a bank-bus zone trips, the bank and low side bus with both be de-energized. This configuration is used at CEN and DIV substation.
Name this protection zone.
Bank Zone w/ High Side Breaker
Name this protection zone.
Bank Zone with Circuit Switcher
Name this protection zone.
Bank Zone with High Side Breaker and a half
Name this protection zone.
Bus Zone
Name this protection zone.
Bank- Bus Zone - 1 Bank
Name this protection zone.
Bank-Bus Zone - 2 Banks
This relay operates when the current flowing through them exceeds a set pickup level.
Overcurrent Relay
When the current reaches that level, the relay is said to be “picked up.” Depending upon the element (time vs. instantaneous) the relay may close an output contact immediately or, as a function of time and current magnitude. When the output contact closes, current will flow in another circuit which will typically trip a breaker or perform some other protective function.
These relays are used together to fully protect a feeder zone from any type of fault.
Phase and Ground Overcurrent Relaying
Name the phase Fault Type that the relay targets: Single phase to ground
One faulted phase and ground
Name the phase Fault Type that the relay targets: Phase to Phase to Ground
Two faulted phases and ground
Name the phase Fault Type that the relay targets: Phase to Phase
Two faulted phases
Name the phase Fault Type that the relay targets: Three Phase
Three faulted phases
This type of relay is wired between all three phases and ground to operate off the sum of the three phases.
Ground Overcurrent Relay
This type of relay is wired to a particular phase CT
Phase Relay
A feeder is said to be perfectly balanced when this occurs.
The residual ground current will sum to zero across all phases
(the same amount of current in each phase)
Is this relay Electromechanical or Electric?
This diagram shows one electromechanical relay per phase plus one more connected to the electrical sum of all three phases or residual ground.
Is this relay Electromechanical or Electric?
This diagram shows Electrical Relays. In this scenario all three phases and ground are being handled by an Intelligent Electronic Device.
This device electronically sample the current signal to be used by the microprocessor to make decisions instead of use the current itself to cause an action. Since all three phases are sampled by the same device, it is able to calculate the residual ground current internally.
Intelligent Electronic Device (IED)
In which type of relay (Electromechanical or Electrical) is monitoring the health of the device not necessary because if one relay were to fail, the feeder would still be protected by the other three for any type of fault.
Electromechanical
In which type of relay (Electromechanical or Electrical) the capability to deal with cold load pickup transformer magnetizing inrush current is present.
Electrical Relay/ IED
These two elements are used in overcurrent protection.
Time and Instantaneous
This element is active (or picked up) when current flowing through the relay is at or above a particular level.
Instantaneous Overcurrent
This element has a pick up with additional settings that require a time factor that considers the more current flowing in the relay the less time will have to pass before the time overcurrent element is active.
Time Overcurrent
In an electromechanical relay the induction disc will turn faster with more current being introduced, but will not begin to turn until what occurs?
The current has to be above the pick up of the relay
Is it easier to coordinate the time overcurrent relay within an IED or the turning induction disc of an electromechanical relay.
An IED is easier to coordinate
In this relay
