Metering Flashcards
1
Q
Self-contained meters:
A
- are limited to secondary metering, which is 600 volts or less and 400 amperes or less.
2
Q
One current coil and one potential coil working together to turn:
A
- one disk are the parts that make up one element (or stator) in an electromechanical meter.
3
Q
Meter Stator:
A
- One current coil and one potential coil working together to turn one disk are the parts that make up one element (or stator) in an electromechanical meter. A one-element meter is all that is required to measure the energy in a two-wire 120 V service. A polyphase meter requiring a two- or three- element meter is actually a meter with two or three single elements that influence a disk (or disks) on a common shaft attached to one register. The consumption measured by each element is, therefore, combined to register the total amount of energy consumed.
4
Q
The voltage coil of a meter element is needed to combine with the current coil to induce:
A
- a magnetic field onto the meter disk causing it to rotate.
5
Q
The current coil of a meter element is made up with a wire size big enough to carry:
A
- the rated load of the meter and consists of a small number of turns.
6
Q
In a self-contained meter, the current coil carries:
A
- the entire load current, while in a transformer-rated meter, the current carries a representative current that has been stepped down by a current transformer.
7
Q
The voltage coil of a meter element is needed to combine with the current coil to induce:
A
- a magnetic field onto the meter disk causing it to rotate.
8
Q
The voltage coil is made up of many turns of:
A
- fine wire
9
Q
Typical voltage ratings:
A
- 120 V
- 240 V
- 480 V
- 600 V
10
Q
A meter can measure power with one element less than there are:
A
- wires in the circuit.
11
Q
A two-element meter is used to measure the standard:
A
- three-wire, 120/240 V single-phase service, and a different type of two-element meter can measure a three-wire, three-phase delta service.
12
Q
A three-element meter measures:
A
- four-wire Wye connected service. However, a 2-1/2-element meter is sometimes used. A 2-1/2 element meter has a current coil for each of the three hot legs of the circuit but uses only two potential coils, because the voltage levels in each of the three phases are considered relatively balanced.
13
Q
A solid state meter is a meter with:
A
- no moving parts. It can be an electronic meter or a smart meter.
14
Q
The only difference between an electronic meter and a smart meter:
A
- the smart meter has a circuit board for communication.
15
Q
A disk on an electromechanical meter does not:
A
- rotate once for every watt-hour because it would spin too fast at most services and would cause excessive wear on the meter. A meter is designed to spin slower, and the number of watt-hours per one rotation of the disk is referred to as the kilowatt-hour constant, or Kh constant.
16
Q
Kr Constant:
A
- The Kr constant, also known as a meter multiplier or register constant, is a number that represents the ratio between the register gear train and the value registered on the meter dial. The register constant may be 1, 10, 100, or some integral of 10. A Kr or multiplier of 10 would mean that the amount of energy consumed by the customer is ten times the amount shown on the register.
17
Q
Solid State Meters:
A
- A solid state meter also has a Kh constant; but in the absence of the rotating disk, Kh involves the use of a pulse recorder that is used to determine the number of watt-hours per pulse. This is modified by a scaling factor and is intended to simulate the rotation of a disk by providing a programmed amount of watt-hours per pulse, or series of pulses. There are cases where this is referred to as Ke constant, but it is normally listed on the nameplates as “Kh,” followed or preceded by the numerical value set by the manufacturer.
18
Q
Common Single-Phase Meter Sockets:
A
- A single-phase service will be either a two-wire or a three-wire. A two-wire service is a 120 V service requiring a two-wire meter.
19
Q
What is the most common service in the United States:
A
- Three-wire, 120/240 V single-phase service, which takes a three-wire meter.
20
Q
When testing a meter, testing should be done at:
A
- the meter base to ensure that there is no short circuit, heavy load, or back feed in the customer’s wiring before installing any meter.
21
Q
Voltmeter Method 1:
A
- Using a standard voltmeter, the meter base can be checked for back feed, short circuits, open circuit, or closed customer breaker. With the source side energized and the customer’s disconnect open, proper voltage to the meter socket can be confirmed with the following:
- A voltage reading of 120 volts between S1 and neutral:
- A voltage reading of 120 volts between S2 and neutral; and
- A voltage reading of 240 volts should be read between S1 and S2
22
Q
Voltmeter Method 2:
A
- With the customer’s disconnect open, a voltage reading of zero between L1 and L2 and the neutral will confirm that the service is not back fed from another source
23
Q
Voltmeter Method 3:
A
- With the source side energized and the customer’s disconnect open, there should be no voltage between the source terminals, S1 or S2 and the load terminals, L1 and L2. A voltage reading other than zero means that there is a connected load or a load wire shorted to the neutral or ground.
24
Q
Voltmeter Method 4:
A
- To check for a short between the two load wires a continuity test should be performed. The voltmeter must be turned to the ohms setting. Most testers have an audible setting which should be tested by touching the test leads together. If the voltmeter makes an audible noise then the tester is operating correctly. Check from the neutral to L1 and L2 and then from L1 to L2. There shouldn’t be an audible sound on any test. If there is an audible sound, this means there is a short from L1 or L2 to the neutral or from L1 to L2.
