Power quality

Question 1

What is power quality and what does it attempt to achieve

Answer 1

Study of characteristics of voltage and current to determine if it is suitable up supply electrical loads

Question 2

What are the 7 power quality problems

Answer 2

1) transients
2) short duration voltage variations
3) long duration voltage variations
4) voltage imbalance
5) waveform distortion
6) voltage fluctuation
7) frequency variations

Question 3

What are 2 high tolerance loads

Answer 3

Heading and motors

Question 4

What are 2 mid tolerance loads

Answer 4

Vsd (variable speed drives) PLC (programmable logic computers)

Question 5

What are 2 low tolerance loads

Answer 5

Signal and data processing equipment

Question 6

How long do short duration voltage variations last

Answer 6

Less than 1 minute

Question 7

What is a voltage swell

Answer 7

Anything over 110% of rated voltage

Question 8

What is a voltage sag

Answer 8

Any voltage between 10 and 90%

Question 9

What is a voltage interruption

Answer 9

Voltages that are less than 10% of rated

Question 10

How long is an instantaneous variation

Answer 10

0.5 to 30 cycles

Question 11

How long is a momentary variation

Answer 11

30 cycles to 3 seconds

Question 12

How long is a temporary variation

Answer 12

3 seconds to 1 minute

Question 13

What is a common cause for a voltage sag?

Answer 13

Startup of loads with large startup current

Question 14

What is the difference between non-periodic impulse transients and periodic impulse
transients?

Answer 14

Non periodic occur once, periodic regularly occur

Question 15

What is used to protect against transients

Answer 15

Surge suppressors

Question 16

3 common causes of voltage surge

Answer 16

Loads being switched out
Lightning
Switching of pf correction caps

Question 17

What is BIL

Answer 17

basic impulse level- amount of vintage and quick DC impulse level a device can be subjected to without damage

Question 18

When installing surge arresters their conduction voltage should be less or more than the BIL
rating of the equipment they protect?

Answer 18

Less than BIL

Question 19

What is station class arrester

Answer 19

3 to 612kv

Question 20

What is intermediate class arrester

Answer 20

3 to 144kv

Question 21

What is distribution class arrester

Answer 21

1 to 36kv

Question 22

What is secondary surge arrester

Answer 22

Less than 1kv

Question 23

Most common surge arrestor used

Answer 23

MOV metal oxide varistor

Question 24

What are 4 tires of arrestors

Answer 24

Rod gap surge
Expulsion type
Silicon carbide multiple gap
Horn gap

Question 25

How does a rod gap work, what is it’s disadvantage

Answer 25

Gap that allows flashover at high voltage to ground, arc needs a means of interruption once established

Question 26

How does MOV operate

Answer 26

During normal times it acts like a high impedance path to ground. During transient it acts as a low resistance path to ground allowing harmful voltages to bypass equipment

Question 27

What is UPS and what is it used for

Answer 27

Uninterruptible power supply
Used to provide regulated voltage to equipment during voltage fluctuations

Question 28

What are two types of UPS systems, list an advantage

Answer 28

Rotary can operate without any power disruption
Static is expandable

Question 29

Name 2 types of rotary UPS systems

Answer 29

Motor generator battery
Engine coupled rotary