S5 - System Protection PPT

Question 1

Used in every aspect of activity including the home, communication, transportation, commerce, and power utilities

Answer 1

Relays

Question 2

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

Answer 2

Relay

Question 3

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

Answer 3

Protective Relay

Question 4

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

Answer 4

Protective Relay

Question 5

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

Answer 5

Protective Relaying

Question 6

Allow us to both de-energize circuits under faulted conditions and restore power automatically once the faulted condition has subsided

Answer 6

Protective Relay

Question 7

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

Answer 7

Power System Protection

Question 8

Provide insulation from the high-power system voltages and reduce the magnitudes to practical secondary levels for use with protective relays

Answer 8

Instrument Transformer

Question 9

The two types of instrument transformers are:

Answer 9

Current and Potential

Question 10

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.

Answer 10

Current Transformer

Question 11

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.

Answer 11

Potential Transformer

Question 12

The zones of protection have boundaries that are defined electrically by _____ location. A particular _____ will mark the beginning or end of a protection zone

Answer 12

Current Transformer

Question 13

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.

Answer 13

Feeder Zone

Question 14

What are three types of protection zones that are used within substations on the EPB system

Answer 14

Bank Zone
Bus Zone
Bank-Bus Zone

Question 15

Has devices on both the high side and low side of the transformer that are used to trip the _____.

Answer 15

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.

Question 16

Protected by a bank breaker (high side or low side) and all feeder or line breakers fed from that _____.

Answer 16

Bus Zone
A bus fault will be cleared by these devices and all radial feeder load from the bus will be out.

Question 17

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.

Answer 17

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.

Question 18

Name this protection zone.

Answer 18

Bank Zone w/ High Side Breaker

Question 19

Name this protection zone.

Answer 19

Bank Zone with Circuit Switcher

Question 20

Name this protection zone.

Answer 20

Bank Zone with High Side Breaker and a half

Question 21

Name this protection zone.

Answer 21

Bus Zone

Question 22

Name this protection zone.

Answer 22

Bank- Bus Zone - 1 Bank

Question 23

Name this protection zone.

Answer 23

Bank-Bus Zone - 2 Banks

Question 24

This relay operates when the current flowing through them exceeds a set pickup level.

Answer 24

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.

Question 25

These relays are used together to fully protect a feeder zone from any type of fault.

Answer 25

Phase and Ground Overcurrent Relaying

Question 26

Name the phase Fault Type that the relay targets: Single phase to ground

Answer 26

One faulted phase and ground

Question 27

Name the phase Fault Type that the relay targets: Phase to Phase to Ground

Answer 27

Two faulted phases and ground

Question 28

Name the phase Fault Type that the relay targets: Phase to Phase

Answer 28

Two faulted phases

Question 29

Name the phase Fault Type that the relay targets: Three Phase

Answer 29

Three faulted phases

Question 30

This type of relay is wired between all three phases and ground to operate off the sum of the three phases.

Answer 30

Ground Overcurrent Relay

Question 31

This type of relay is wired to a particular phase CT

Answer 31

Phase Relay

Question 32

A feeder is said to be perfectly balanced when this occurs.

Answer 32

The residual ground current will sum to zero across all phases
(the same amount of current in each phase)

Question 33

Is this relay Electromechanical or Electric?

Answer 33

This diagram shows one electromechanical relay per phase plus one more connected to the electrical sum of all three phases or residual ground.

Question 34

Is this relay Electromechanical or Electric?

Answer 34

This diagram shows Electrical Relays. In this scenario all three phases and ground are being handled by an Intelligent Electronic Device.

Question 35

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.

Answer 35

Intelligent Electronic Device (IED)

Question 36

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.

Answer 36

Electromechanical

Question 37

In which type of relay (Electromechanical or Electrical) the capability to deal with cold load pickup transformer magnetizing inrush current is present.

Answer 37

Electrical Relay/ IED

Question 38

These two elements are used in overcurrent protection.

Answer 38

Time and Instantaneous

Question 39

This element is active (or picked up) when current flowing through the relay is at or above a particular level.

Answer 39

Instantaneous Overcurrent

Question 40

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.

Answer 40

Time Overcurrent

Question 41

In an electromechanical relay the induction disc will turn faster with more current being introduced, but will not begin to turn until what occurs?

Answer 41

The current has to be above the pick up of the relay

Question 42

Is it easier to coordinate the time overcurrent relay within an IED or the turning induction disc of an electromechanical relay.

Answer 42

An IED is easier to coordinate

Question 43

In this relay