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Equipment > Surge Arresters & Insulators > Flashcards

Surge Arresters & Insulators Flashcards

0
Q

Maximum Continuous Operation Voltage (MCOV) - The maximum voltage that the arrestor can operate without ______. The arrestor should be operated at voltages ________or ______ than this value.

A

damage
equal
less

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1
Q

Basic Impulse Level (BIL) - A specific _______ level expressed in terms of the _______ value of a standard lightning impulse.

A

insulation

crest

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2
Q

Withstand Voltage - The voltage that electrical equipment is capable of withstanding without ______ or _______discharge when tested under _______ conditions.

A

failure
disruptive
specified

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3
Q

Lightning - These flashes are currents of electricity flowing one ______ to another, or between cloud(s) and the ______. They always flow by way of the path of_______ resistance.

A

cloud
earth
least

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4
Q

In a dry desert areas where ground rods are not effective, it is necessary to connect long ______ ______ to the tower footings. These conductors are called _______ and are usually connected from tower to tower.

A

buried wires

counterpoise

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5
Q

The continuous type of counterpoise is buried from one to ______feet deep and connected to each tower via a small air gap (approx. _____), that will offer a minimal resistance to a lightning surge of no greater than _____ ohms.

A

three
1/16”
ten

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6
Q

The small air gap between the tower and the counter-poise prevents _______ action by _______ between the copper and the _____ coating on the tower steel.

A

galvanic
electrolysis
zinc

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7
Q

The counter-poise air gaps are about _____ wide and break down at about _______volts, offering no _______ to high voltage produced by lightning.

A

1/16”
1500
resistance

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8
Q

Lightning arresters perform a function on the electric system similar to that of a _____ _____ on a steam boiler

A

safety valve

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9
Q

When a high voltage (greater than the _____ line voltage) exists on the line, the arrester immediately furnishes a ___-_______ path to ground, draining off the excess voltage.

A

normal

low-impedance

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10
Q

When the excess voltage is relieved, the action of the arrester must prevent any further flow of _____ _____, also known as ______ current.

A

power current

follow

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11
Q

The function of a lightning arrester is to provide a point in the _____ at which the lightning impulse can pass to _____ without injury to line insulators, transformers, or other ______equipment, and to prevent any following _____ ______ from flowing to ground.

A

circuit
ground
connected
power current

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12
Q

After the breakdown of the gaps in a protector tube, the current ______ a small layer of the fiber wall and the _____ given off displaces the air in the tube, helping ______ the space between the ______, and quenching the arc.

A

volatilizes
gas
deionize
electrodes

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13
Q

While a protector tube is discharging it is a good ______, but after the arc is extinguished, it becomes a good ______ once again.

A

conductor

insulator

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14
Q

Induced lightning surges are usually much ______ than those occurring after a direct strike. Specifically they rarely exceed _______.

A

lower

500kV

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15
Q

The induced lightning over-voltages are of a concern for distribution lines ______ and below. Higher voltage lines have sufficient ______ to withstand induced voltage surges.

A

35kV

insulation

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16
Q

The most predominant occurrences for over-voltages on distribution, transmission, & generation systems are:
• L______
• N_____ D______ (during line-to-ground faults).
• R_________effects associated with I_______ & C______ in ______.
• A______ contacts with higher-voltage systems
• Forced c_____-z_____ interruptions

A 
Lightning
Neutral Displacement
Resonance, inductance, capacitance, series
Accidental
current-zero
17
Q

When a line-to-ground fault occurs, even on a “_____ _____” system, the line-to-ground voltage of the _______ phases will increase. This is called ______ ______, which occurs throughout the ______ of the surge discharge.

A

solidly grounded
unfaulted
Neutral Displacement
duration

18
Q

The two types of surge arresters in the LADWP power systems are the S_____ C______ G_____ arrester and the M_____ O_____ G______ arrester.

A

Silicon Carbide Gapped

Metal Oxide Gapless

19
Q

The silicon carbide arrester consists of a ______, enclosed spark-gap assembly in series with ______ ______ non-linear resistance, or valve elements, assembled into _______ housing.

A

controlled
silicon carbide
porcelain

20
Q

Surge arresters should be located as _____ _____ ______ to the equipment they are to protect, and the length of the conductor from the arrester to the protected equipment should be kept ____ ___ ______.

A

close as possible

to a minimum

21
Q

Less severe damage may result from strikes on a _______ part of the system, or from strikes to ground ______ the system.

A

distant

near

22
Q

Since lightning voltage may exceed the _______ strength of the transformer, surge _______ is necessary.

A

insulation

protection

23
Q

Each piece of equipment on the power system has a rated voltage that is the ______ voltage that it uses or carries. In addition to the rated voltage, there is a _______ ______ voltage that a piece of equipment can withstand for short period of time, or ______.

A

normal
considerable higher
impulse

24
Q

The impulse insulation strength is called _____ _____ _____ or ___. The _____ _____ _____ is the ____ value of the impulse voltage that a component or component’s insulation is required to ______ without failure.

A 
Basic Impulse Level
BIL
Basic Impulse Level
crest
withstand
25
Q

Insulation coordination is the process of bringing the I______ S______ of electrical equipment into the proper relationship with E______ O______-V______ and with the characteristics of S_____ P______ devices.

A

insulation strengths
expected over-voltages
surge protective

26
Q

The insulation protection that an arrester will provide is dependent on the following three things:

  1. The P______ C______ of the arrester.
  2. The L______ and S______ surges expected on the system.
  3. The I______ C_______ of the protected equipment.
A

Protective Characteristics
Lightning and Switching
Insulation Characteristics

27
Q 
To decide which rating is most appropriate for a particular application, consideration must be given to the following system stress to which the arrester will be exposed:
• C\_\_\_\_\_\_ S\_\_\_\_\_\_ Voltage
• T\_\_\_\_\_\_ P\_\_\_\_\_\_ F\_\_\_\_\_\_ over-voltages
• S\_\_\_\_\_\_ Surges
• L\_\_\_\_\_\_ Surges
• S\_\_\_\_- C\_\_\_\_\_\_ current
A 
Continuous System
Temporary Power Factor
Switching 
Lightning
Short-Circuit
28
Q

When selecting an arrester we are looking for the

_______ rated arrester with a _______ service life on the power system.

A

minimum

satisfactory

29
Q

In a lightning surge generally, only a ______ of any lightning strike current ever ______ an arrester because the lightning charge will travel in ____ ______ if a transmission line is struck.

A

fraction
reaches
two directions

30
Q

Lightning arresters are, generally, located on the _____ side of the apparatus to be protected and ___ _____ to the equipment as possible.

A

line

as close

31
Q

A _____ resistance ground must be _____ and maintained during installation.

A

low

provided

32
Q

If a ground connection is suspect, the connection can be checked with a ______ ohm-meter to determine _______.

A

Digital

acceptability

33
Q

The substations ground system or ground _____ plays an important role in maintaining this resistance at a _____ value.

A

grid

low

34
Q

DO NOT USE the ____ ______for lifting. ____ ______ are not designed for lifting.

A

line terminal

Line terminals

35
Q

Arresters with exhaust _____ should be installed so they will exhaust ______ from ______ arresters and protected equipment.

A

ports
away
adjacent

36
Q

Usually, the leakage properties of insulators are characterized by the ______ of their leakage paths. It is sometimes convenient to distinguish between ______ and leakage paths.

A

length

protected, unprotected

37
Q

It should be recognized that DC lines tend to _______ more _______ than AC lines in the same locations.

A

accumulate

pollutant

38
Q

To reduce the insulator pollution, and to improve deposit distribution along the string, ______ _____ can be mounted at the _____ and ______of the insulator string.

A

collector rings
top
bottom

39
Q

With collector rings, the e_____ f_____ around the insulators will then change because the g_______ c_______ now occurs on the surface of the ring itself. Consequently, the p______ will move to the collector ring instead of the s______.

A

electrostatic field
gradient concentration
particles
string

Equipment (1 decks)

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