Presentación de resultados

meters by delaying the digitized voltage samples by a time equivalent to 60 elec-trical degrees.

Quadergy—The integral of reactive power with respect to time. (ANSI C12.1 definition.)

Reactance—The measure of opposition to current flow in an electric circuit caused by the circuit properties of the inductance and capacitance. Reactance is normally expressed in ohms.

Reactiformer—A phase-shifting auto transformer used to shift the voltages of a watthour meter 90 degrees when reactive voltampere measurement is wanted.

Reactive Energy—The reactive energy in a single-phase circuit is the time integral of the reactive power.

Reactive Voltamperes—The out-of-phase component of the total voltamperes in a circuit which includes inductive or capacitive reactance. For sinusoidal quantities in a two-wire alternating current circuit, reactive voltamperes are the product of the total voltamperes and the sine of the angle between the current and voltage.

The unit of reactive voltamperes is the VAR.

Reactor—A device used for introducing reactance into a circuit for purposes such as motor starting, paralleling transformers, and controlling currents.

Rectifier—A device which permits current to flow in one direction only, thus converting alternating current into unidirectional current.

Reference Meter—A meter used to measure the unit of electric energy. It is usual-ly designed and operated to obtain the highest accuracy and stability in a con-trolled laboratory environment.

Reference Performance—A test used as a basis for comparison with performances under other conditions of the test. (ANSI C12.1 definition.)

Register—An electromechanical or electronic device which stores and displays information. A single display may be used with multiple electronic memories to form multiple registers.

Register Constant—The number by which the register reading is multiplied to obtain kilowatthours. The register constant on a particular meter is directly proportional to the register ratio, so any change in ratio will change the register constant.

Register Freeze—The function of a meter or register to make a copy of its data, and perhaps reset its demand, at a pre-programmed time after a certain event (such as demand reset) or upon receipt of an external signal. Also called: Self-Read, Auto-Read, and Data Copy.

Register Ratio—The number of revolutions of the gear meshing with the worm or pinion on the rotating element for one revolution of the first dial pointer.

Registration—The registration of the meter is equal to the product of the register reading and the register constant. The registration during a given period of time is equal to the product of the register constant and the difference between the regis-ter readings at the beginning and the end of the period.

Resistance—The opposition offered by a substance or body to the passage of an electric current. Resistance is the reciprocal of conductance.

Retarding Magnet—A permanent magnet placed near the outer edge of a meter disk to regulate the disk’s rotation.

Rheostat—An adjustable resistor so constructed that its resistance may be changed without opening the circuit in which it is connected.

SE Cable—A service entrance cable usually consists of two conductors, with con-ventional insulation, laid parallel with a third stranded bare neutral conductor (which may or may not be insulated). The final covering is a flame retarding and waterproof braid. ASE cable is a variant of the SE cable in which a flat steel strip is inserted between the neutral conductor and the outside braid.

Self-Contained Meter—A watthour meter that is connected directly to the supply voltage and is in series with the customer loads.

Service—The conductors and equipment for delivering electric energy from a street distribution system to, and including, the service equipment of the premis-es served.

Service Conductors—The conductors which extend from a street distribution sys-tem, transformers on private property, or a private generating plant outside the building served, to the point of connection with the service equipment.

Service Drop—That portion of the overhead service conductors between the last pole or other aerial support and the first point of attachment to the building or structure.

Service Entrance Conductors—For an overhead service, that portion of the service conductors which connect the service drop to the service equipment.

The service entrance conductors for an underground service are that portion of the service conductors between the terminal box located on either the inside or outside building wall, or the point of entrance in the building if no terminal box is installed, and the service equipment.

Service Equipment—The necessary equipment, usually consisting of one or more circuit breakers or switches and fuses, and their accessories, intended to constitute the main control and means of disconnecting the load from the supply source.

Shaft Reduction (Spindle Reduction, First Reduction)—The gear reduction between the shaft or spindle of the rotating element and the first gear of the register.

Shop, Meter—A place where meters are inspected, repaired, tested, and adjusted.

Short Circuit—A fault in an electric circuit, instrument, or utilization equipment such that the current follows a lower resistance by-pass instead of its intended course.

Socket (Trough)—The mounting device consisting of jaws, connectors, and enclo-sure for socket-type meters. A mounting device may be a single socket or a trough.

The socket may have a cast or drawn enclosure, the trough an assembled enclo-sure which may be extensible to accommodate more than one mounting unit.

Solid-State Meter—A meter in which current and voltage act on electronic (solid-state) elements to produce an output proportional to the energy to be measured.

Also called static meter.

Standard, Basic Reference—Those standards with which the value of electrical units are maintained in the laboratory, and which serve as the starting point of the chain of sequential measurements carried out in the laboratory.

Stator—The unit which provides the driving torque in a watthour meter. It con-tains a voltage coil, one or more current coils, and the necessary steel to provide the required magnetic paths. Other names used for stator are element or driv-ing element.

Sub-Metering—The metering of individual loads within a building for billing or load control purposes. For billing applications, usually the building is metered by a master meter and the property owner desires to meter and charge individual tenants for their portion of the electricity consumed.

Switchboard-Mount Meter—A meter mounted in a drawn-out case where the meter may be removed as a functional module, with provisions to properly shunt current paths before meter disconnection, leaving behind the outer case to which service connections are permanently made.

Synchronism—This expresses the phase relationship between two or more peri-odic quantities of the same period when the phase difference between them is zero. A generator must be in synchronism with the system before it is connected to the system.

Temperature Compensation—For a watthour meter, this refers to the factors included in the design and construction of the meter which make it perform with accuracy over a wide range of temperatures. In modern meters this range may extend from 20°F to 140°F.

Test Output—An output signal, optical, mechanical, or electrical, which provides a means to check calibration level and verify operation of the meter.

Test-Switch—A device that can be opened to isolate a watthour meter from the voltage and current supplying it so that tests or maintenance can be performed.

Testing, Statistical Sample—A testing method which conforms to accepted prin-ciples of statistical sampling based on either the variables or attributes method.

The following expressions are associated with statistical sample testing:

(a) Method of Attributes—A statistical sample testing method in which only the percent of meters tested found outside certain accuracy limits is used for determining the quality or accuracy of the entire group of meters;

(b) Method of Variables—A statistical sample testing method in which the accuracy of each meter tested is used in the total results for determining the quality or accuracy of the entire group of meters;

(c) Bar X—A mathematical term used to indicate the average accuracy of a group of meters tested;

(d) Sigma—A mathematical term used to indicate the dispersion of the test results about the average accuracy (Bar X) of a group of meters tested.

Thermocouple—A pair of dissimilar conductors so joined that two junctions are formed. An electromotive force is developed by the thermoelectric effect when the two junctions are at different temperatures.

Thermoelectric Effect (Seebeck Effect)—One in which an electromotive force results from a difference of temperature between two junctions of dissimilar metals in the same circuit.

Thermoelectric Laws—(1) The thermoelectromotive force is, for the same pair of metals, proportional through a considerable range of temperature to the excess of temperature of the junction over the rest of the circuit. (2) The total thermoelec-tromotive force in a circuit is the algebraic sum of all the separate thermoelectro-motive forces at the various junctions.

Three-Wire System (Direct Current, Single-Phase, or Network Alternating Current)—A system of electric supply comprising three conductors, one of which, known as the neutral wire, is generally grounded and has the same approximate voltage between it and either of the other two wires (referred to as the outer or

“hot” conductors). Part of the load may be connected directly between the outer conductors; the remainder is divided as evenly as possible into two parts, each of which is connected between the neutral and one outer conductor.

Time Division Multiplication—An electronic measuring technique which produces an output signal proportional to two inputs, for example, voltage and current. The width or duration of the output signal is proportional to one of the input quantities; the height is proportional to the other. The area of the signal is then proportional to the product of the two inputs, for example, voltage and current.

Time-of-Use Metering—A metering method which records demand during select-ed periods of time so consumption during different time periods can be billselect-ed at different rates.

Torque of an Instrument—The turning moment produced by the electric quanti-ty to be measured acting through the mechanism.

Total Harmonic Distortion (THD)—The ratio of the root-mean-square of the harmonic content (excluding the fundamental) to the root-mean-square value of the fundamental quantity, expressed as a percentage. (ANSI C12.1 definition.) Transducer—A device to receive energy from one system and supply energy, of either the same or a different kind, to another system, in such a manner that the desired characteristics of the energy input appear at the output.

Transformer—An electric device without moving parts which transfers energy from one circuit to one or more other circuits by means of electromagnetic fields.

The name implies, unless otherwise described, that there is complete electri-cal isolation among all windings of a transformer, as contrasted to an auto-transformer.

Transformer Ratio—A ratio that expresses the fixed relationship between the primary and secondary windings of a transformer.

Transformer-Rated Meter—A watthour meter that requires external instrument transformer(s) to isolate or step-down the current and possibly the voltage.

VAR—The term commonly used for voltampere reactive.

VARhour Meter—An electricity meter that measures and registers the integral, with respect to time, of the reactive power of the circuit in which it is connected.

The unit in which this integral is measured is usually the kiloVARhour.

Volt—The practical unit of electromotive force or potential difference. One volt will cause one ampere to flow when impressed across a one ohm resistor.

Voltampere—Voltamperes are the product of volts and the total current which flows because of the voltage. See Power, Apparent.

Voltage Circuit—The internal connections of the meter, part of the measuring ele-ment and, in the case of electronic meters, part of the power supply, supplied with the voltage of the circuit to which the meter is connected.

Voltage Transformer—An instrument transformer intended for measurement or control purposes which is designed to have its primary winding connected in parallel with a circuit, the voltage of which is to be measured or controlled.

Watt—The practical unit of active power which is defined as the rate at which energy is delivered to a circuit. It is the power expended when a current of one ampere flows through a resistance of one ohm.

Watthour—The practical unit of electric energy which is expended in one hour when the average power during the hour is one watt.

Watthour Meter—An electricity meter that measures and registers the integral, with respect to time, of the active power of the circuit in which it is connected.

This power integral is the energy delivered to the circuit during the interval over which the integration extends, and the unit in which it is measured is usually the kilowatthour.

Watthour Meter Portable Standard—A special watthour meter used as the refer-ence for tests of other meters. The standard has multiple current and voltage coils or electronic equivalents, so a single unit may be used in the field or in the shop for tests of any normally rated meter. The portable standard watthour meter is designed and constructed to provide better accuracy and stability than would normally be required in customer meters. The rotating standard has an electro-mechanical dial rotating at a specified watthour per revolution; the solid-state standard has a digital display of 1 watthour per revolution, or, essentially, a meas-ured watthour.

MATHEMATICS FOR METERING