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.
25
Electromechanical and Solid State MeterInstallation
| - Proper meter installation consists of:
- Verifying proper meter and meter base selection.
- Disconnecting load
- Test the meter socket for faults or back feed
- Firmly insert the meter into the socket (bottom first)
- Installation of the meter ring
- Installation of the meter seal
- Connect load (if possible) and verify that meter is working properly
- Record (paper or digitally) the meter information
- Record (paper or digitally) the meter seal information to associate the meter seal with this meter
26
Electromechanical and Solid State Meter Removal - Always wear approved personal protective equipment when removing meters. Proper meter removal consists of:
- Read the meter
- Disconnect the load
- Remove the seal and meter ring
- Remove the meter (pull down on the top first)
- Install a socket cover
- Install the meter ring and meter seal
- Complete any necessary paperwork
27
When removing a meter, it is always preferred to:
- first disconnect the customer load.
28
To count the revolutions with an electromechanical meter count the:
- disk rotations.
29
To count the revolutions with a solid state meter:
- there is either a blinking symbol (i.e., square or circle) or a dash that moves across the bottom of the display screen. This represents the disk that is seen on an electromechanical meter.
30
Energy Diversion:
- Energy diversion is theft of power that occurs when a consumer manipulates or bypasses the meter installation. Energy theft is a serious crime, and most utility companies prosecute violators to the full extent of the law.
31
When the seal is opened, attempts to reseal it includes:
- hiding or camouflaging where the seal was cut, using a counterfeit seal, or repairing a damaged seal.
32
Unless the person is trained specifically on the procedure for investigating an energy diversion, the scene should:
- be left untouched and immediately reported.
33
Transformer-rated metering is used when:
- the voltage and/or current are too high for self. contained metering.
34
Self-contained meters typically have a limit of:
- 600 volts and/or 400 amps. Therefore, any service to a customer that exceeds either of these values may require transformer-rated metering.
35
Transformer-rated meters are used on:
- secondary services, primary services, and transmission services.
36
The general concept of transformer-rated metering:
- When the voltage and/or current exceed the limits of self-contained metering, step the voltage and/or current down to a manageable level for a meter.
37
Voltage Transformers(VTs, also known as potential transformers, or PTs):
- are devices that step voltage down for metering purposes
38
Current Transformers (CTs):
- are devices that step current down for metering purposes.
39
PTs and CTs are also referred to as:
- instrument transformers. A transformer-rated meter then reads these reduced values (see graphic below).
40
The voltage and current are stepped down at a fixed ratio:
- The ratios of the VT and CT are multiplied together forming a multiplier of the meter reading and provide an accurate representation of the primary voltage and primary current being measured.
41
Transformer-rated metering is composed of four main components:
- Voltage transformers
- Current transformers
- Test switches
- Transformer-rated meters
42
Voltage Transformers:
- A voltage transformer (VT) is used when the energy to be measured is supplied at a high voltage, such as transmission, primary, or a high secondary voltage. A voltage transformer output will supply a voltage at a manageable level to a meter typically rated at 240 or 120 volts. A voltage transformer is like most transformers except that it does not need to carry any load.
43
Current Transformers are typically designed to operate at a maximum of:
five amperes on the secondary side.
44
When there is current flowing through the current transformer while the meter is not installed, the secondary must be:
- kept short-circuited.
45
Test Switch:
- Transformer-rated meters typically utilize a test switch below the meter to allow for the removal and testing of the meter without opening the secondary circuit from the current transformers. Opening the blades of the switch will isolate the voltage and current supply. The meter will not register but will be safe to remove for replacement or testing.
46
Transformer-rated meters typically utilize a test switch below the meter to allow for:
- the removal and testing of the meter without opening the secondary circuit from the current transformers.
47
Because customers are billed for power consumed, the power multiplier is used to:
- compensate for the reduced reading at the meter.
48
Automated metering systems consist of two different methods of reading the meter:
- 1) Automated meter reading (AMR)
| - 2) Advanced metering infrastructure (AMI)
49
Automated meter reading (AMR):
- Is a one-way communication technology that allows utilities to remotely collect meter data. Each meter has an individual identification and is manufactured or modified to receive and send signals. In this manner, data can flow both from the meter to the utility and from the utility to the meter. This is referred to as an inbound/outbound AMR system. Although the utility can send and receive data, the customer can not view energy usage in real time. The customer must rely on historical data from a monthly bill to manage their energy usage (no different than a electromechanical meter system).
50
Advanced metering infrastructure (AMI):
- Is a two-way communication technology that allows utilities to remotely collect meter data and customers to review and manage usage in real time. It is the next generation of meter reading technologies. The key difference between AMI and AMR is the two-way communication between the utility and the customer. AMI provides utilities with up-to-date information and the customer can play a more active role in their energy usage. With AMI a meter can be read at more frequent intervals than what was previously done with AMR
51
The AMI system has the following benefits:
- Will allow customers to view energy usage in real time, instead of having to wait for a monthly bill
- Utilities can see up-to-date loads on the system and match supply with customer demand
- Utilities can monitor net metering throughout the day and see how much electricity has been consumed or put back on the grid by customers
52
All automated metering systems have four key components which are:
- Head-end software
- The network
- Network infrastructure
- End points
53
Head-end Software:
The head-end software is the communication software that communicates with the meters to send or receive information. This communication software is utilized by the AMR and AMI systems. Both systems are located at a central headquarters where the software is installed to record the data.
54
Network:
- The network is the communication system that carries the data between the meter and the head-end software. The three most popular communication networks are: Radio Frequency Mesh (RF Mesh), Power Line Carrier (PLC), and Wide Area Network (WAN).
55
Radio Frequency Mesh:
- Is a network where data travels by radio frequency from one meter to another meter until the information reaches its destination. RF Mesh uses the meters as receivers and transmitters to send the information to a main router or to the correct meter. An RF Mesh network is more cost effective than Power Line Carrier, but the meters can not be farther than 1,000 feet apart. Therefore, RF Mesh networks are used primarily in urban areas. If this distance is exceeded, the utility will have to use a booster to strengthen the signal to reach the meter. With an RF Mesh network, utilities can receive data in as quickly as 30-second intervals.
56
Radio Frequency Mesh networks are used primarily in:
- urban areas.
57
Power Line Carrier:
- Power line carrier is a network where data travels over existing power lines to send information to the head-end software or the meter. By using the power line as the carrier there is not a need for communication from meter to meter. The average cost per meter to set up a power line carrier system is more expensive than the other network systems because of the requirement of more network infrastructure. The benefit of power line carrier is it can be used in rural areas where the meters are spaced further apart. This gives utilities in rural areas an opportunity to use the new meter technology, and utilities can receive data in as quickly as 2-hour intervals.
58
Wide Area Network:
Wide Area Network is a network similar to RF Mesh because it uses a radio frequency, but the meters communicate directly to a collector instead of reading from meter to meter. For those meters that are too far from the collectors, they will use RF Mesh to communicate to the nearest router, and then the router will communicate directly to the nearest collector. Depending on the terrain and population density, WAN systems can use one collector to receive data from 30 to 300 square miles. In addition, WANs can send and receive data from the end points to the collector up to 40 miles away. The collectors are placed on towers ranging in height from 50 feet to 600 feet depending on the type of terrain and how many meters need to be on the collector. One collector has the capability of collecting data from up to 70.000 meters.
59
The Network Infrastructure:
- The network infrastructure is the hardware needed for the network to communicate to the head-end software and the meter. The hardware consists of routers, collectors, inbound and outbound units, and transformer units. Depending on what network a utility uses will determine what kind of network infrastructure they will need.
60
End Points:
- End points are the devices installed at the customer's location that are used to communicate information to the customer and the utility. The AMR system has only one endpoint, which is the meter. For an AMI system, the most common end points include meters, home-area-display units, smart thermostats, and smart appliances. All of these devices will help the customer conserve energy, which in turn will help with the load placed on a utility’s system.
Metering
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