Surge Arresters & Insulators

Question 0

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.

Answer 0

damage
equal
less

Question 1

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

Answer 1

insulation

crest

Question 2

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

Answer 2

failure
disruptive
specified

Question 3

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.

Answer 3

cloud
earth
least

Question 4

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.

Answer 4

buried wires

counterpoise

Question 5

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.

Answer 5

three
1/16”
ten

Question 6

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

Answer 6

galvanic
electrolysis
zinc

Question 7

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

Answer 7

1/16”
1500
resistance

Question 8

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

Answer 8

safety valve

Question 9

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.

Answer 9

normal

low-impedance

Question 10

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

Answer 10

power current

follow

Question 11

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.

Answer 11

circuit
ground
connected
power current

Question 12

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.

Answer 12

volatilizes
gas
deionize
electrodes

Question 13

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

Answer 13

conductor

insulator

Question 14

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

Answer 14

lower

500kV

Question 15

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

Answer 15

35kV

insulation

Question 16

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

Answer 16

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

Question 17

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.

Answer 17

solidly grounded
unfaulted
Neutral Displacement
duration

Question 18

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

Answer 18

Silicon Carbide Gapped

Metal Oxide Gapless

Question 19

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

Answer 19

controlled
silicon carbide
porcelain

Question 20

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 ____ ___ ______.

Answer 20

close as possible

to a minimum

Question 21

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

Answer 21

distant

near

Question 22

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

Answer 22

insulation

protection

Question 23

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 ______.

Answer 23

normal
considerable higher
impulse

Question 24

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.

Answer 24

``` Basic Impulse Level BIL Basic Impulse Level crest withstand ```

Question 25

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.

Answer 25

insulation strengths expected over-voltages surge protective

Question 26

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.

Answer 26

Protective Characteristics Lightning and Switching Insulation Characteristics

Question 27

``` 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 ```

Answer 27

``` Continuous System Temporary Power Factor Switching Lightning Short-Circuit ```

Question 28

When selecting an arrester we are looking for the | _______ rated arrester with a _______ service life on the power system.

Answer 28

minimum | satisfactory

Question 29

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.

Answer 29

fraction reaches two directions

Question 30

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

Answer 30

line | as close

Question 31

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

Answer 31

low | provided

Question 32

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

Answer 32

Digital | acceptability

Question 33

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

Answer 33

grid | low

Question 34

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

Answer 34

line terminal | Line terminals

Question 35

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

Answer 35

ports away adjacent

Question 36

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

Answer 36

length | protected, unprotected

Question 37

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

Answer 37

accumulate | pollutant

Question 38

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

Answer 38

collector rings top bottom

Question 39

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______.

Answer 39

electrostatic field gradient concentration particles string