GB2101340A - Method for the measurement of consumption of energy and power - Google Patents

Abstract

Described herein is a method for the measurement of consumption of energy and power, and particularly for the measurement of consumption of electrical energy and power. According to the invention the power to be measured is in advance divided into steps of power, an energy- measurement register (R1) of its own being assigned to each of these steps, whereby each register (R1 to Rn) is alternately allowed to measure and to register a predetermined value of energy consumption, whereupon the measurement is shifted to a next register. After a predetermined cycle of measurement the measurement is shifted back to the first register (R1) for the start of a new cycle of measurement. Hereby the readings of the different registers, after a desired number of measurement cycles, give an approximation of the cumulative power distribution curve.

Description

SPECIFICATION Method for the measurement of consumption of energy and power The present invention concerns a method in accordance with the preamble in claim 1.

Energy, and especially electricity, is produced in a great number of different ways, each of these ways having a different cost structure of its own. The costs of electricity consist of two main components: invariable annual costs and variable costs. The invariable costs include, among other things, the capital costs of the production plant and the invariable operating expenses. The invariable costs are to a great extent dependent on the amount of production capacity, i.e. power. They can, e.g. be expressed as units of FIM (= Finnmarks)/kw,a. The variable costs include e.g., the fuel costs and the variable operating expenses. The variable costs are proportional to the energy produced. They are expressed as units of FlM/MWh.

The curve P in Fig. 1 illustrates the annual time distribution of the demand of electrical power, and the area remaining inside the curve illustrates the annual demand of energy. The electricity is produced optimally in the production modes A, B, C, etc. so that the annual overall costs are as low as possible.

Let us assume that in the production mode A - the invariable costs are a(FIM/kW,a), -the variable costs are A(FIM/MWh), - the energy produced is WA(MWh), and - the power capacity is Pa (kW), as well as in the production mode B - the invariable costs are b(FIM/kW,a), -the variable costs are B(FIM/MWh), - the energy produced is WB(MWh), and - the power capacity is Bb(KW), etc.

In such a case, the annual overal costs of the production of electricity can be illustrated by means of the formula: Pa.a+WA . A+Pb . b=Wb. B In order that the producer of electricity could sell electricity to the wholesale buyers as precisely as possible according to the costs and in accordance with the principle of causing, the sales tariff ought to follow the formula (1) as added by the distribution, sales, etc. expenses. This is, however, impossible in practice, because there are dozens of different modes of production. The tariff would be all too complicated. In practice, attempts are made to follow the principle of causing by means of a tariff in which the power is divided into two components: basic power and peak power (Fig. 2).Thus, the tariff has the following form: Pe e + We E + Pf F + WF WF (2) Moreover, basic charges independent of power are applied. The power charges are additionally stepwise variable depending on the magnitude of the purchase of power, and the energy charges depending on the time of the day.

The buyer may himself divide his purchase of electricity into basic power (E) and peak power (F) optimaliy.

The structure of the tariff is such that it attempts to guide the consumption in such a direction that the load were divided as uniformly as possible in respect of time i.e. that the peak use time, which is illustrated by the formula:

were as high as possible.

Further, power companies sell electricity to large consumers and small consumers.

They also aim at the prinicple of meeting the costs. In such a case, the ideal tariff would be a minute sale tariff that follows the structure of their own purchase (2) as added by distribution, sales, etc.

expenses. By means of the present-day technology, the measurement of electricity would however, become too expensive in relation to the quantity of electricity sold.

Power companies sell electricity to large consumers at a power tariff (Fig. 3), which is of the following form: Pg - g + Wg G (4) Additionally, invariable charges independent of power are applied. This tariff form gives a satisfactory result if the peak use time WG (5) Pg is the same as was assumed when the tariff was prepared. In practice it may, however, differ from this, whereby some consumers may obtain advantage at the expense of other consumers, and the incomes of power companies may be reduced.

Electricity is sold to small consumers at an energy tariff (Fig. 3), which is of the form: WG G (6) Additionally, invariable annual charges are applied.

At present, the measurement of power is too expensive in relation to the electricity sold to small consumers. The tariff corresponds to the costs as long as the peak time T is what it was assumed to be when the tariff was prepared. In practice the time of use is, however, all the time changing, e.g. as new apparatuses of consumption are introduced more and more commonly. as a result of energy conservation action, etc. This means economic risks for power companies as well as advantage to some consumers at the expense of other consumers. Nor does this tariff form in any way motivate for an evening up of the consumption in respect of time, which would be very important in view of the energy economy of the whole country.

All of the tariff forms mentioned above may involve different energy price in the daytime and in the night-time, which is intended to reduce the daily variation of annual overall consumption.

It is a well-known procedure to measure the wholesale electricity so that the consumption meter (MWh-meter) is read every hour by means of a so-called printometer (Fig. 4). In such a case, out of this material, by means of ADP processing, the consumption and its time distribution, powers by the hour, and possible other necessary (and also unnecessary) additional information are obtained. The power is divided into basic power and peak power by means of ADP processing. The method of measurement is the best possible, but it is also very expensive. Its expenses are about 50,000 FlM/a per point of measurement.

Printometer measurement and output requires, e.g., measurement means, timing means, memory registers in a number equal to the number of measurement periods, (in practice tens of thousands) as well as ADP processing.

Information obtained then is, among other things, a load curve (Fig. 4), stability curve (by ADP processing), as well as the energy of several measurement points (by ADP processing).

Besides the very high cost, a further drawback of the use of a printometer is that it requires constant supervision and maintenance.

The power tariff measurement of large consumers (formula (4)) takes place so that, on one hand, the energy consumed is measured cumulatively and, on the other hand, the maximum energy consumed during a reading interval is measured for a certain period of time (e.g. 15, 30, or 60 minutes). The latter measurement takes place so that a clockwork resets the indicating energy meter to zero at intervals of the period of time indicated above, the indicator needle pushes another needle ahead of itself, which other needle is not reset to zero but remains indicating the maximum energy of the period of time concerned during the interval of readings. The average power of the period of time concerned is obtained by dividing the energy indicated by the indicator needle by the time of measurement.

The maximum meter is read, e.g. once in a month and reset to zero. In order that occasional power peaks of the consumer should not have an unreasonable effect on the price of the electricity, the average of two months with the highest power peaks is adopted as the basis of invoicing. A second, separate clockwork measuring real time or a remote control device may shift the energy measurement from one counter to another if the energy has a different price in the night-time and in the daytime. The expenses of this mode of measurement are about 1 500 FlM/a.

The maximum energy and its output requires, e.g. a measurement means, a timing means, one or several registers depending on whether the energy is connected with time, as well as means indicating the maximum energy of a period of time.

Information obtained then is the peak power during the reading interval as well as the energy, whereby the energies of the various measurement points can be added together arithmetically.

However, by means of this method, neither a load curve nor a cumulative distribution curve is obtained.

Moreover, the peak powers at different measurement points cannot be added together (at different measurement points the peaks may occur at different times, sp that the common peak of the measurement points is not the sum of the peaks of the different points). Moreover, the meters must be read, e.g. monthly, and they require a certain amount of maintenance. The measurement expenses are about 1 500 FIM per annum.

In the case of small consumers, the energy consumed is measured alone by means of a kWhmeter. That measurement may also include a control clock connected to a real time or a remote-control device if the energy has different prices at night and in the daytime. The meter is usually read once a year, and the measurement expenses are about 1 50 Fm/a.

The measurement requires, among other things, a measurement unit as well as one of several registers.

The information obtained is the energy consumed, and the energies of several measurements can be added together.

However, by means of this method, it is not possible to determine the load curve, the cumulative distribution curve, or the peak power.

The object of the present invention is to eliminate the drawbacks present in the prior art technology and to provide a simpler method of an entirely novel type for the measurement of the consumption of energy and power.

The invention is based on the ideal that the power to be measured is in advance divided into steps of power, an energy-measurement register of its own being assigned to each of these steps, whereby each register is alternately allowed to measure and to register a predetermined value of energy consumption, whereupon the measurement is shifted to the next register. After a predetermined cycle of measurement the measurement is shifted back to the first register for the start of a new cycle of measurement. Hereby the readings of the different registers after a desired number of measurement cycles give an approximation of the cumulative power distribution curve.

More specifically, the method in accordance with the invention is mainly characterised in what is stated in the characterising part of claim 1.

By means of the invention, considerable advantages are obtained. Thus, by means of the invention, both the cumulative distribution curve and the energy consumed are found out by simple means. Moreover, the energy consumptions of different measurements can be added together to give a sum.

Below, the invention will be examined in more detail with the aid of the attached Figures 6 to 8, which are illustrations of principle of the method of measurement in accordance with the invention.

The power to be measured is in advance divided in programmed power steps P 1 ... Pn (Fig. 6).

The number of steps may be any number sensible from the point of view of the precision of measurement (at least 2). In the measurement mechanism, as many registers are required as there are power steps. In addition to the measurement unit, a timer is required that starts the measurement process from the beginning after a programmed measurement cycle (the length of the cycle may be continuously adjustable, e.g. 10 minutes to 2 hours).

The measurement takes place as follows: At the beginning of the measurement cycle, the meter measures energy to register 1 (R1 ) until a preprogrammed amount of energy has been accumulated in it (e.g. 1 kWh, 1 OkWh, 100 kWh or 1000 kWh).

Hereupon the counting is automaticaliy shifted to register 2, and further to higher registers until the timer starts the measurement cycle from the beginning. Then the measurement starts again to register 1 and is continued as above.

The following example illustrates the measurement: EXAMPLE 1 Let us assume that the consumer's peak power is 1 OOkW. Let us assume further that a 5-step power measurement gives adequate information. A meter is used that has 5 registers and in which the measurement is shifted from one register to the other after each 10 kWh.

Since the magnitude of the power step is 100 kW/5 = 20 kW and the measurement is shifted from one register to the other after 10 kWh, the length of a measurement cycle is set in the timer as 30 minutes (0.5 h x 20 kW = 1 OkWh).

Let us assume that the power of the consumer concerned varies during the different measurement cycles as follows: Cycle Time Elapsed Power Energy 1 0.5 h 30 kW 15 kWh 2 1 h 50kW 25kWh 3 1.5 h 100 kW 50 kWh 4 2 h 110 kW 55 kWh 5 2.5 h 70 kW 35 IcWh 6 3 h 60 kW 30 kWh The energies (kWh) measured at the various registers by the cycle are as follows: Cycle Reg. 1 Reg. 2 Reg. 3 Reg. 4 Reg. 5 1 10 5 - - - 2 10 10 5 - - 3 10 10 10 10 10 4 10 10 10 10 15 5 10 10 10 5 - 6 10 10 10 - - Sum 60 55 45 25 25 By reading the energies accumulated in the registers, information in accordance with Fig. 7 is obtained for the above period of 3 hours.

It comes out from Fig. 7 that on the basis of the energy measurement readings of the various registers alone, it is possible to construct a cumulative distribution curve. It is only the peak portion of the curve that requires a procedure of estimation, because the factual peak is not known. This drawback can also be eliminated if the meter is provided with peak indication.

In the method in accordance with the invention, only a measurement unit, a timer, 2 . . . n registers, as well as, if necessary, a unit measuring the maximum energy of a period of time are required.

In the following tables 1 and 2, the properties have been compared with those of prior art methods: TABLE 1 Equipment and costs

k\Wh-peak kWh Printometer measurement measurement Invention Measurement unit yes yes yes yes Timer yes yes no yes No. of registers over 10,000 1 to 2 1 to 2 2 to 10 Data processing ADP manual manual manual Peak indication not required yes no if required Measurement costs 50,000 FlM/a 1,500 FlM/a 150 FlM/a 200 FIM/a (with peak measurement 1,500 FIMIa) TABLE 2 Information obtained

kWh-peak kWh Printometer measurement measurement Invention Load curve ADP no no no Sum of load curve ADP no no no Load curve ADP no no no Sum of load curve ADP no no no Cum. distrib. curve ADP no no manually Power peak ADP or manual yes no if required Sum of power peaks ADP no no approximate Energy consumption ADP yes yes yes Sum of energy consumptions manually manually manually manually interval between readings 1 h 1 month 1 year 1 year When the curves in Fig. 8 are compared with each other, it can be noticed that by means of the method in accordance with the invention a tariff is obtained that is simple but follows the costs closely.

It can be noticed that by selecting the power steps of the different registers correctly, it is possible to obtain a tariff corresponding to the costs by means of a mere energy tariff alone.

EXAMPLE 2 If the overall costs of the production of energy, including all capital, raw-energy, refining, loss and overhead expenses, as well as taxes and profits, are as follows: Mode of production A : 0.15 FlM/kWh Mode of production B ; 0.20 FlM/kWh Mode of production C :0.25 FIM/kWh Mode of production D :0.50 FlM/kWh the tariff is simply as follows: Energy of register 1 0.15 FlM/kWh Energy of register 2 : 0.20 FlM/kWh Energy of register 3 :0.25 FlM/kWh Energy of register 4 : 0.50 FlM/kWh Out of the readings of the different registers of his meter, the consumer sees how much he has to pay, exactly in the same way as when using the conventional kWh-meters.

Within the scope of the invention, it is also possible to conceive solutions differing from the solutions described above.

-The meter may be mechanical or electronic or a combination thereof.

- The number of registers may be at least 2 and at the maximum the number required by the precision of measurement. A very precise result is already obtained with 10 registers, in practice an adequate number is 3 to 5 registers.

- The power steps can be accomplished by adjusting either the amount of energy required for change of register or the time of the measurement cycle on the timer, or both.

- The power steps of the registers may be equally high or of different heights.

- The meter may be provided with peak indication, or it may not have peak indication.

- Each register may notify (or may not notify) the consumer of the register at which the meter is at each particular time measuring energy. Thereby the consumer may automatically or manually switchoff unessential consumption when the meter is counting expensive energy. In other words, the tariff guides the consumption in a direction correct in view of energy economy.

-To the meter it is possible to connect a clockwork provided with a daily and/or weekly and/or annual programme or a remote-control device by means of which it is possible to by-pass the internal measurement commands of the meter so that the meter measures energy, part of the time, at one register or at some registers, only. In such a case the tariff may include energy of different prices for different power steps, e.g.

- by day and by night, - on weekdays and during weekends, - in summer and in winter, during daily peaks during annual peaks, as well as during closed down periods.

- In accordance with the same principle, the meter may also measure other energy than electrical energy, e.g. heat energy, water and other material flows.

Claims (7)

1. A method for the measurement of consumption of energy and power, particularly for the measurement of consumption of electrical energy and power, wherein - the power to be measured is in advance divided into at least two power steps so that their sum is preferably an approximation of the expected peak power.

- an energy-measurement register of its own is assigned to each power step.

during a predetermined measurement cycle, each register is alternatingly, in a predetermined sequence, allowed to measure and to register a predetermined consumption of energy, after the reaching of which the measurement is shifted to the next register in the order, and - after the expiration of the predetermined cycle of measurement, the measurement is shifted from the register that was last in the turn of measurement, back to the first register in the order to start a new cycle of measurement, whereby the readings of the different registers, after a desired number of measurement cycles, gives an approximation of the cumulative power distribution curve during the period of observation.

2. A method as claimed in claim 1, wherein power steps of equal magnitude, as compared with each other, are used.

3. A method as claimed in claim 1, wherein power steps of different magnitudes, as compared with each other, are used.

4. A method as claimed in claim 1, wherein the number of registers used is 2 to 20, preferably 3 to 5.

5. A method as claimed in claim 1, wherein the power steps are obtained by adjusting the predetermined registration-energy value of the registers.

6. A method as claimed in claim 1, wherein a timer is used for starting and ending the measurement cycles.

7. A method as claimed in claim 6, wherein the power steps are obtained by adjusting the time of the measurement cycle of the timer.