BPA - Definitions

BPA Definitions - M

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See mega.

The invisible lines of magnetic force produced by electric current flowing in a conductor, such as a transmission line, service wires in a house, or household appliances. Measured in terms of lines of force per unit area with the measurement unit being tesla (T) or gauss (G) (one tesla equals 10,000 gauss). Also see electric and magnetic fields.

magnetic pole

A location on a device producing a magnetic field from which the field appears to emanate; one type of location is north-seeking and the other is south-seeking.

main and auxiliary bus scheme

See bus scheme.

mainstem

The main channel of a river, as opposed to the streams and smaller rivers that feed into it.

major resource

According to the Pacific Northwest Electric Power Planning and Conservation Act, a resource with a planned capability greater than 50 average megawatts, and if acquired by BPA, acquired for more than five years.

major stationary source

The term used to determine the applicability of prevention of significant deterioration and new source regulations. The cutoff level may be emissions of 100 or 250 tons per year, depending on the type of source.

manual

Operated by hand, and by extension, any non-automatic operation.

manufactured home

A structure, such as a mobile home, that is transportable in one or more sections and is designed to be used as a dwelling.

manufactured housing technical specifications

The energy-efficient design specifications that apply to manufactured housing.

marginal contributions

Revenues less related direct expenses. Amounts represent averages for the period measured and are based on actual costs incurred. Increase and decrease in proportion to changes in energy usage.

marginal cost

The cost of producing the marginal, or next, unit.

marginal cost pricing

As applied in the utility industry, a method of pricing whereby the price for each unit of energy is set equal to the cost of producing the next or most recent unit.

marginal energy costs

1) The cost of producing or saving the last unit of energy. 2) For a generating resource, the cost to produce one more kilowatthour of electricity.

marketing area

For BPA, the area includes the Pacific Northwest and, under P.L. 88-552, any contiguous area within 75 air miles of the Pacific Northwest region served by a cooperative that distributes power both within and without the region and has no generating facilities of its own.

material safety data sheet (MSDS)

Information required under the Occupational Safety and Health Administration on the identity of hazardous chemicals, health and physical hazards, exposure limits, and precautions. The Superfund Amendments and Reauthorization Act requires facilities to submit MSDSs under certain circumstances.

matrix

A two-dimensional (row and column) array of quantities in which the particular location of a quan-tity in the array has a particular meaning, and by extension, an array of any number of dimensions.

maximum contaminant level (MCL)

Under Federal law, the maximum level of a contaminant permitted in water delivery to any user of a public water system.

maximum demand

See demand.

maximum working tension (MWT)

The tension to which a conductor will be stressed under a given set of loading conditions.

MCL

See maximum contaminant level.

MCS

See Model Conservation Standards.

mean water planning

A hydroelectric planning regime that prepares to meet firm loads under average, or mean, water conditions.

mechanical loads

Mechanical forces acting on transmission structures applied by the weight and tension of conductors and by ice and wind. Also called structural loads.

median streamflow

The rate of flow of a stream (usually expressed in cubic feet per second or cubic meters per second) for which there are equal numbers of greater and lesser flow occurrences during a specified period.

mega

A prefix indicating a million (1,000,000).

megahertz (MHz)

One million hertz.

megawatts (MW)

The electrical unit of power which is equal to 1,000 kilowatts, or 1,000,000 watts.

megawatthours (MWh)

Electrical energy equal to one megawatt of power supplied to or taken from an electric circuit for one hour (1 MWh = 1,000 kWh = 1,000,000 watthours).

melded rate

A rate that reflects the combined costs of different sources of power. Typically, costs of existing hydro projects and costs of newer thermal plants are said to be melded when combined or averaged together in one rate.

meltdown

A buildup of heat in the core of a nuclear reactor caused by insufficient cooling, which causes the fuel to melt.

metal oxide surge arrester

See surge arrester.

metal oxide varistor (MOV)

See surge arrester.

meter

1) To measure electricity use. 2) The device used for measuring electricity use. 3) The unit of length in the metric system (m).

billing meter: A device that measures the power or energy flow to a customer with an accuracy sufficient for preparing a bill.
demand meter: A device or system of devices that indicates and/or records the number of kilowatts used over a period of time. Most BPA demand meters use a time interval of 60 minutes.
energy meter: A device that measures the total kilowatthours of energy that a customer uses.
var-hour meter: Same as watt-hour meter, but measures kilovar hours or reactive power, rather than energy.
watt-hour meter: A device that measures and registers the kilowatthours delivered to a circuit and is the typical residential electric meter.

metered requirements customers

See non- and small generating public utilities.

mho

The unit of conductance (and of admittance) of a conductor such that a constant voltage of one volt between its ends produces a current of one ampere in the conductor, or in mathematical terms, mho = 1÷ by impedance.

MHz

See megahertz.

micron

One millionth of a meter.

microprocessor

A small electronic “chip” (or part) that is the basic driver for small computers.

microsievert

A measure of radiation equal to one millionth of a sievert. A sievert is a measurement of absorbed ionizing radiation.

microwaves

In general usage, radio frequencies whose wavelengths are sufficiently short to exhibit some of the properties of light. Usually used in point-to-point communications because they are easily concentrated into a beam. Frequencies of 1,000 megahertz and up are usually considered to be microwave frequencies.

microwave station

A radio station that relays microwave signals.

Mid-Columbia

The section of the Columbia River from its junction with the Snake River up to Grand Coulee Dam.

Mid-Columbia Projects

The collective name for five privately owned dams on the mid-Columbia: Wells, Rocky Reach, Rock Island, Wanapum, and Priest Rapids.

mil

One mil equals .001 inch.

mill

One-thousandth of a dollar; one-tenth of a cent. The cost of electricity is often given in mills per kilowatthour (mills/kWh).

million acre-feet (Maf)

The volume of water needed to cover 1.233 square kilometers of land one kilometer deep or 1.233 km3 (one million acres of land one foot deep).

mills/kWh

The common expression of the cost of electricity; one mill per kilowatthour equals one dollar per megawatthour.

minimum generation constraints

For thermal power plants, the minimum level of operation that must be maintained to keep the plant ready to generate power when needed. For hydro, the minimum flow that must be maintained due to fish, navigation or voltage constraints.

minimum ground clearance

The least distance that a conductor is allowed to approach the ground level under the selected design loading conditions.

minimum safe working distance

The distance from an energized conductor or equipment at which it is safe for the worker to perform his or her tasks. No part of the worker’s body or conductive objects should be moved closer to an energized high-voltage part than an established minimum working distance, unless a barrier is used. The following are BPA’s minimum safe working distances (subject to revision to comply with Department of Labor Standards) :

Nominal Voltage
Between Phases	inches	meters
600 V - 15 kV	26	0.66
33 kV	30	0.77
69 kV	39	0.99
115 kV	40	1.02
138 kV	43	1.10
161 kV	48	1.22
230 kV	52	1.32
287 kV	59	1.50
345 kV	66	1.68
400 kV (DC)	93-105	2.37-2.67
500 kV	126	3.20
500 kV (DC)	120-138	3.05-3.51

mitigate

In environmental usage, to either reduce or avoid an adverse environmental effect through various measures that seek to make the effect less severe, less obvious, or more acceptable.

Model Conservation Standards (MCS)

Construction standards for energy efficiency in new electrically heated residential and commercial structures.

module

A sub-unit of an electronic system that can be plugged in or otherwise easily replaced.

Montana Intertie

See Eastern Intertie.

Monte Carlo Simulation

1) In general, a statistical technique that uses random events, or probability analysis, to simulate the outcome of a process. 2) At BPA, the statistical technique used to determine regional load growth under different economic scenarios that are based on the effects of probable economic events, such as the timing and duration of a recession or the growth and investment of a major regional industry.

monthly sale shaping

Allowance in some contracts that permits shaping of sales to conform to monthly demand.

MOV

See surge arrestor.

MSDS

See material safety data sheet.

multiple use

Use of land or water and associated facilities for more than one purpose, such as hydropower, fish and wildlife, flood control, irrigation, and recreation.

multiplex