Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

EE135 - Power System Protection > LE2 > Flashcards

LE2 Flashcards

1
Q

What type of lightning stroke is shown?

A

Direct stroke

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

This lightning arrester consists of two 1.5cm rods which are bent at right angle with a gap between

A

Rod gap arrester

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Class F insulation is made of …

A

Mica, glass fibres, or asbestos built up mica, glass fibres laminates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What kind of feeder is shown?

A

Parallel Feeder

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

It is the most common failure in the grounding of conductor

A

Insulation failure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

It starts from the cloud towards the earth and carries charge as soon as the air near the cloud breaks down

A

Leader streamer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

This lightning protection consist of a network of copper conductors mounted all over the electrical equipment in the substation and properly connected with low impedance

A

Earthing screen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the two common bus bar protection scheme?

A
  • Differential protection
  • Fault bus protection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

This lightning protection is also called as protector tube and on the occurrence of an overvoltage, the series gap is panned and an arc struck between the electrodes in the tube then gas builds up and carries away ionized air around the arc

A

Expulsion type arrester

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What type of bus bar protection scheme is shown?

A

Fault bus protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The action depends on the distance between the point where the relay is installed and the point of fault

A

Distance protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In this type of lightning stroke, the lightning discharge directly from the cloud to the subject equipment

A

Direct stroke

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

This lightning arrester consists of two horn shaped metal rods separated by a small air gap

A

Horn gap arrester

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

SPDs used at the line side. It is connected between the secondary of the service transformer and the LINE side of the service disconnect over current devices, as well as the LOAD side, including watt-hour meter socket enclosures

A

Type 1 SPD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the two types of lightning strokes?

A
  • Direct stroke
  • Indirect stroke
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

This type of line protection is typically used in radial feeder and it uses a definite time relays and inverse time relays

A

Time-graded Overcurrent Protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

State the maximum allowable temperature for each insulation classes

  • Y
  • A
  • E
  • B
  • F
  • H
  • C
A

↵

  • Y - 90ºC
  • A - 105ºC
  • E - 120ºC
  • B - 130ºC
  • F - 155ºC
  • H - 180ºC
  • C - 180+ ºC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What type of relay is shown?

A

Definite time relay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Class E insulation is made of …

A

Synthetic resin enamels, cotton and paper laminates with formaldehyde bonding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Example of _______ insulation classification is the air or SF6.

A

Gas insulation classification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Class A insulation is made of …

A

Cotton, silk, or paper impregnated with varnish or insulation oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Class B insulation is typically made of …

A

Mica, glass fibers, and asbestos built up mica, glass fibres, asbestos

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

This type of SPD is installed on the load side of the service disconnect over-current devices.

A

Type 2 SPD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What composes the external disturbances in surges?

A

↵

  • Utility load switching
    • Smart grid
  • Lightning strikes
    • cloud to cloud
    • cloud to ground
    • cloud to man-made objects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Point of utilization SPDs, installed a minimum of 10 meters (30 feet) from the electrical service panel.

A

Type 3 SPD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The rolling spheres in lightning protection system must overlap to provide maximum protection from lightning.

TRUE or FALSE

A

FALSE

Overlapping of rolling spheres cancels out each other, thus, creating a dead spot between the lightning protection system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

In order for an electrostatic discharge to occur, two things are necessary:

A
  1. a sufficiently high electric potential between two regions of space must exist; and
  2. a high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Various power stations or substations are interconnected by alternate routes.

A

Ring main system

20
Q

What is the average distance in miles between the lightning strikes?

A

2 - 3 miles

22
Q

Surges originate from …

A

80% internal disturbances

20% external disturbances

24
Q

Why ground electrical power system?

A

↵

  • For safety related to electrical shock hazard
  • Bonding of non-current carrying conductive materials to the mass of Earth fixes their potential to “Zero potential”
25
Q

What type of lightning stroke is shown?

A

Indirect stroke

26
Q

It resist current and keep the current in its path along the conductor

A

Insulation

27
Q

Class Y insulation is typically made of …

A

Cotton, silk, paper,or wood

28
Q

This bus bar protection scheme compares or totalize the currents entering and leaving the bus bar.

When fault current enters the system, it will disturb the balance in the system and produces differential current to operate the relay

A

Differential protection

28
Q

This lightning stroke results from the electrostatically induced charges on the conductors due to the presence of charged clouds

A

Indirect stroke

29
Q

How much current and voltage is associated with lightning?

A

120 kA and 100MV

30
Q

This lightning protection is used on transmission lines

A

Overhead ground wires

30
Q

It consists of an air cored inductor connected in series with the line

A

Ferranti surge absorber

31
Q

These are designed to reduce and divert potentially damaging short-duration voltage spikes safely out of the system to Ground.

A

Surge protective devices (SPD) or Transient voltage surge suppressors (TVSS)

32
Q

What are the causes of overvoltage?

A
  • Internal Causes
    • Switching surges
    • Insulation Failure
    • Arcing ground
    • Resonance
  • External Cause
    • Lightning
33
Q

This lightning arrester consists of a series of metallic cylinders insulated from one another and separated by small intervals of air gaps

A

Multigap arrester

35
Q

It forms an important link between the incoming and outgoing circuits

A

Bus bars

35
Q

In the event of short circuit, which CB would open first?

A

The CB that is closest to the fault

37
Q

This bus bar protection scheme uses earthed metal barrier surrounding each conductor throughout its entire length in the bus structure

A

Fault bus protection

38
Q

This type of lightning arrester incorporates non-linear resistors and extensively used on systems operating at high voltages.

Consists of two assemblies

  1. Series spark gaps
  2. Non-linear resistor disk
A

Valve type arrester

39
Q

Electrical discharge due to lightning results in electrical current from the ground to clouds

A

Return stroke

40
Q

What are the 3 protection against lightning?

A
  • Earthing screen
  • Overhead ground wire
  • Lightning arrester of surge diverters
42
Q

What is the temperature of lightning?

A

30,000 ºC or 54,000ºF

44
Q

Component SPDs, including discrete components as well as component assemblies

A

Type 4 SPD

45
Q

What are the two types of lightning?

A

Negative downward lightning and Positive upward lightning

46
Q

What are the different line protections?

A
  • Time graded over current protection
  • Differential protection
  • Distance protection
47
Q

It includes isolating switches, circuit breakers, and associated connection

A

Bus bar zone

48
Q

State some of the types of cable insulations.

A
  • PVC (Polyvinyl Chloride)
  • PE (Polyethylene)
  • XLPE (Cross-link Polyethylene)
  • EPR (Ethylene Propylene Rubber)
  • Paper Based
50
Q

This insulation classification is divided into two major categories: organic and inorganic.

A

Solid insulation classification

51
Q

In the event of short circuit, the closest CB opens and all other CB will also open.

TRUE or FALSE

A

FALSE

52
Q

Lightning protection system follows what method?

A

Rolling sphere method

54
Q

What is the speed of lightning?

A

60 km/s

56
Q

Damages to insulations are commonly caused by…

(8 answers)

A
  • Mechanical Damage
  • Vibration
  • Excessive heat and cold
  • Dirt
  • Oil
  • Corrosive vapours
  • Moisture from processes
  • Humidity
58
Q

SPDs and TVSSs are made of what component?

A

Metal oxide varistor (MOV)

59
Q

What composes the internal disturbances in surges?

A
  • Load switching
  • Variable frequency drives
  • Lightning and air handlers
61
Q

Insulation oil is an insulation classification of what type?

A

Liquid insulation classification

62
Q

It is the overvoltage produced on the power system due to switching operations

A

Switching surges

63
Q

What type of relay is shown?

A

Inverse time relay

64
Q

What are the five types of lightning arrester?

A
  • Rod gap arrester
  • Horn gap arrester
  • Multigap arrester
  • Expulsion type arrester
  • Valve type arrester
65
Q

A sudden rise in voltage for a very short duration in the power system

A

Voltage surge

66
Q

Take a rest

What are the four main features of lightning protection?

A
  1. Air terminal
  2. Conductors
  3. Ground termination
  4. Surge protection
68
Q

A _______ connected between the line and earth can act as a surge absorber.

Since its reactance is inversely proportional to frequency, it will be low at high frequency and high at low frequency.

It acts as short circuit at high frequency and passes them directly to earth

A

Capacitor or condenser

69
Q

What type of bus bar protection scheme is shown?

A

Differential Protection

EE135 - Power System Protection (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions