# Energy Measurement Flashcards

1
Q

What are the three most common single phase meter sockets designed for

A
1. 120/240V three wire service
2. 120V single phase service
3. 120/208V three wire network service
2
Q

Describe a 120/240V three wire service

A
1. The most common meter socket for single phase circuits
2. Can be designed for overhead or underground services
3. 4 jaws
3
Q

Describe a 120V single phase service

A
1. Only one 120V circuit is required
2. 4 jaws
4
Q

Describe a single phase, three wire 120/208V service

A
1. Single phased panel boards are used on this system
2. Has 2 phase conductors and a common conductor
3. Five jaws
4. Contains a tickler
5
Q

What is a tickler?

A
1. It maintains the correct voltage drop and the correct phase relationship with the currents
2. If you remove the tickler the voltage across the potential coil will be cut in half
6
Q

Describe a three phase, four wire, wye connected service

A
1. Can provide power for both three phase and single phase
2. 7 jaws
3. Used in three phase services of 200A or less
7
Q

Describe a three phase, four wire, delta service

A
1. Can provide three phase and single phase power
2. Contains a high leg (A phase) which must be separated by a barrier
3. 7 jaws
4. High leg is always on the right side of the meter
8
Q

What are the 2 types of instrument transformers

A

Potential transformers and current transformers

9
Q

Describe a potential transformer

A
1. Isolate a voltmeter from the high voltage of the circuit being tested
2. They reduce the voltage to the voltmeter
3. Standard rated secondary voltage is 120V
10
Q

Describe a current transformer

A
1. Reduces the current to a safe and manageable value
2. Transfers energy from one circuit to another while maintaining isolation between circuits
3. Connected in series with the load
4. Standard rating current for revenue metering is 5A
5. Acts as a step up transformer
11
Q

What are 3 types of CT’s

A
1. Wound-Primary (both the primary and secondary windings wrapped around a common core)
2. Bar-type (a single primary conductor permanently passing through a core and a secondary winding wrapped around the same core)
3. Toroidal (shaped like a donut)
12
Q

When must CT’s have their secondary windings grounded

A
1. When the primaries of the CT are connected to circuits of 300V or greater
2. They are mounted on switchboards
13
Q

Is the secondary of an energized CT open or close circuited

A

Close circuited

14
Q

Describe a voltmeter transfer switch

A
1. Has eight positions
2. Is able to read 3 line and 3 phase voltages of a wye system with a single voltmeter
3. It’s a break before make
15
Q

Describe an a meter transfer switch

A
1. Is a make before break action to ensure the CT secondary is always close circuited