DE19858218A1 - Maintaining upper total power limit for group of electrical loads when drawing power from supplier involves switching off load(s) at least temporarily depending on total power trend - Google Patents

Abstract

The method involves detecting (20) the actual total power for the group of loads (10,12,14,16) and the trend of the total power over a measurement period and switching off at least one load at least temporarily when it can be predicted from the trend computation that the mean actual total power will exceed a definable upper limit at the end of the measurement period, whereby the limit value is derived from a given function An Independent claim is also included for an arrangement for maintaining an upper total power limit for a group of electrical loads when drawing electrical power from a power supply company.

Description

The present invention relates to a method for maintaining an upper overall level Performance limit for a group of electrical consumers when purchasing electrical sher energy from a power company and a device for through leadership of the same.

So-called maximum or load optimization devices limit the total output of a company to an adjustable upper total output limit by switching off consumers classified as switchable. The background is the tariff structure of the energy supply companies. The costs that the energy supply companies incur from supplying the affiliated companies consist mainly of two components:

• - quantity-dependent costs for electricity consumption, measured in kWh (electrical work),
• - Costs for the amount of the claimed service, whereby the calculation of the in The measured power used was partly the active power in kW and partly the certificate performance in kVar is taken as a basis (quantity-independent costs).

Although the total power required by a company over a consumption period (typically a calendar year) fluctuates, a single maximum performance value is calculated based on the quantity-independent costs. This is z. B. determined by that the maximum performance of consumption period subunits (typically months) are determined and an average is formed from the three highest values. Recently the quantity-independent costs for each consumption period subunit calculated by the maximum power over a measurement period of typically 15 Mi based on the average services determined in the consumption period subunit becomes. There are also tariff structures in which e.g. B. different for certain seasons Maximum services are specified (e.g. summer / winter tariff) or for those for ver different maximum times are specified at different times of the day (high-load, Low-load tariff), which are valued differently during billing.

Usual maximum or load optimization devices have one for at least several ver Periodic subunits of fixed, programmed upper total output limit and try the average of the total using various control methods performance over a measuring period of typically 15 minutes on the upper total line limit limit. An optimization computer is usually used for this det, which determines the trend of total performance during the measurement period and consumers switches off if it is foreseeable from the trend that at the end of the measuring period the on set upper total power limit is exceeded. It is with the consumers are consumers with known properties that can be switched off for a certain time, without interfering with the operational process (e.g. air conditioners, heaters). Furthermore are the consumer properties in modern maximum or load optimization devices  ten stored so that a consumer does not have a permissible maxi depending on the property Male switch-off time switched off or not before a required minimum switch-off switching time is switched on again. The fixed upper total power limit is in principle only with changed operating conditions, if z. B. the operation ver is enlarged or reduced, changed by a competent employee of the company.

In addition, the fixed upper total power limit is for cost reasons set relatively low, so that the consumers who are legally allowed by the maximum or load optimization device may be switched off in the consumption period with peak loads have to be switched off and on quite often. While consequently the fixed upper total power limit for some consumption periods ode subunits can be too large, which leads to unnecessarily high energy costs too low for other consumption period subunits in terms of wear, because in the long run too many wear-sensitive switching operations have to be carried out, and the set total power limit can often still not be met.

The invention is therefore based on the object of a generic method and a To provide device with which a reduction in energy costs with minimal Impairment of operations is achieved.

According to the invention, this object is achieved in that the method comprises the following steps:

• a) Detection of the actual total power P _{actual of} the group of electrical consumers and determination of the trend of the actual total power P _actual over a measuring period T _measurement and
• b) at least temporarily switching off at least one switchable consumer of the group, if it is foreseeable from the trend calculation that the mean value P _actual the actual total power P _actual in the _measuring period T _{measurement will} exceed a definable upper total power limit value P _limit at the end of the measuring period T _measuring ,
  the upper total power _limit value P _limit before each consumption period subunit ΔT _{Ab, i, j of} the current consumption period T _{Ab, i,} which is decisive for the determination of the quantity-independent energy costs by the energy supply company _, by calculation according to a function
  With
  i Consumption period index
  L usage period index variable
  j Consumption period subunit index
  q consumption period subunit index variable,
  where i ∈ N \ {1}
  j, L, q ∈ N , where L <i and q <j,
  x ∈ R ⁺ is
  and P _{actual, max, m, n} the maximum mean value of the actual total outputs P _actual, when the at least one consumer is actually or fictitiously switched off in a comparison consumption subunit ΔT _{Ab, m, n} with m <i, n ≦ j, is correctable becomes.

Basically, the upper total power _limit P _limit for the following consumption period subunit (e.g. month of March) of the current consumption period (e.g. calendar year 1998) can be a function of the maximum mean of the total output of the comparison consumption period subunits of the previous consumption periods, i.e. March 1997, March 1996,. . ., and of the comparison consumption period subunits of the consumption period subunits preceding the preceding consumption periods, ie the months February 1997, January 1997, February 1996, January 1996,. . ., be calculated. The percentage deduction (-x / 100) serves as an attempt to further reduce costs while at the same time reducing the number of switching operations.

This object is also achieved by a device for complying with an upper total power limit for a group of electrical consumers when purchasing electrical energy from an energy supply company

• - A calculation device for calculating a respective upper total power _limit value P _limit for a respective consumption period subunit ΔT _{Ab, i, j of} the current consumption period T _{Ab, i} prior to the start of the respective consumption period subunit ΔT _Ab for the determination of the quantity-independent energy costs by the energy supply company _{, i, j} according to a function
  With
  i Consumption period index
  L usage period index variable
  j Consumption period subunit index
  q consumption period subunit index variable,
  where i ∈ N \ {1}
  j, L, q ∈ N , where L <i and q <j,
  x ∈ R ⁺ is
• - and P _{actual, max, m, n} the maximum mean value of the actual total outputs P _actual when the at least one consumer is actually or not actually switched off in a comparison consumption subunit ΔT _{Ab, m, n} with m <i, n ≦ j,
• a detection device for detecting the actual total power P _{actual of} the group of electrical consumers,
• - An evaluation device for evaluating the actual total power P _actual with respect to the trend of the actual total power P _actual over a measurement period T _mess and subsequent selection of a combination of consumers to be switched off suitable for compliance with the upper total power _limit value P _{limit, i, j} calculated by the computing device and
• - A control device for controlling the consumer according to the Evaluation device made selection.

According to a first particular embodiment of the method it can be provided that q = 0 and

is. q = 0 means that only the comparison consumption period subunits of the previous budding consumption periods. The function f describes the means value formation over the maximum mean values of the comparison consumption period units.

In particular, it can be provided that L = 0. Then the maximum average ver in the comparison consumption period subunit of the previous consumption period turns.

According to a further special embodiment of the method according to the invention it can be provided that

is. The upper total power _limit value P _{Limits, i, j} then results from the maximum mean value of the total power in the comparison consumption period subunit of the previous consumption period and the mean value of the deviations between the maximum mean value of the total power in a consumption period subunit of the current consumption period prior to the following consumption period subunit and the maximum mean value of the total power in the corresponding consumption period subunit of a previous consumption period over a plurality of consumption periods and consumption period subunits.

It can be provided that q = 1. This means that the mean of the deviation between the maximum averages of the total output only in the immediate previous consumption period subunit of the current consumption period and in the corresponding consumption period subunit of the previous consumption periods several consumption periods is taken into account.

Alternatively or in combination, it can be provided that L = 0. If q = 1 and L = 0 are only the difference between the maximum mean of the total power in the immediately preceding consumption period subunit of the current consumption period ode and the maximum mean value of the total output in the corresponding consumption period subunit of the previous consumption period is taken into account. If only L = 0 the deviations of the maximum mean values of the total output will precede the consumption period subunits of the current consumption period and the maximum Average values of total output in corresponding consumption period subunits single of the immediately preceding consumption period.

On the other hand, it can also be provided that

is.

With such a function, the mean value of the deviations between that for a respective consumption period subunit specified upper total power limit and the maximum average value of the total output actually achieved in the consumption period or subunit of the current consumption period and the previous consumption period or taken into account.

On the other hand, it can also be provided that

is. In this way, the average of the percentage exceedances for each because of the upper total power limit values set for consumption period subunits the current consumption period and previous consumption periods are taken into account.

Alternatively, it can also be provided that

is with
B _{i, n} duration of use in a comparison consumption subunit ΔT _{Ab, i, n} , which results from the quotient of the total energy consumed in the comparison consumption subunit ΔT _{Ab, i, n} and the maximum mean value P Act _{, max, i, n} .

It can be provided that q = 1. Then the mean of the deviations, per central exceedances or usage periods of only the previous ver consumption period subunit of the current consumption period and the corresponding ver sub-units of the previous consumption periods are taken into account.

Alternatively or additionally, it can be provided that L = 0. If q = 1 and L = 0, the deviations, percentage exceedances or service lives for le diglich the previous consumption period subunit of the current consumption period considered. If only L = 0, the deviations, percentage over Inconsistencies or periods of use only of the current consumption sub-units taken into account in the consumption period.

Conveniently, x ranges from 0 to 10. The x value depends on the type of group of Consumers, d. H. usually depends on the type of business. At cold stores the x value is closer to 10, whereas it is closer to 3 for manufacturing companies.

It can also be provided that x = 0.

According to a further special embodiment of the method according to the invention, it can be provided that the upper total power _limit value P _{limit, i, j} determined by calculation is corrected in the consumption period subunit ΔT _{Ab, i, j} to a larger upper total power limit value when the upper total power limit value P _{limit , i, j has} been exceeded despite the shutdown of at least one consumer. If, in order to achieve a low energy cost calculation, a percentage reduction of the upper total power limit value by an x value in the range from 0 to 10 has been carried out in advance, but the calculated upper total power limit value is too low, the more appropriate upper total power limit value will be compared to that State of the art smaller number of switching operations can be set.

The upper total power _limit value P _{limit, i, j} determined by calculation is _{advantageously} corrected before the start of the consumption period subunit ΔT _{Ab, i, j} if the number and / or consumption and / or shutdown properties of the consumers have changed.

The upper total power _limit value P _{limit, i, j} is advantageously corrected if the deviation between at least one of the parameters service life, maximum power that would have been achieved without switching off consumers, and sum of the power of all consumers that can be switched off, over one or more consumption period subunit (s) the current consumption period T _{Ab, i} and the respective parameter in one or more comparison consumption period subunit (s) of one or more preceding the preceding consumption period / consumption periods exceeds a definable limit value.

All values required for the calculations are favorably the previous ones Consumption period subunits saved. This will make it lighter, especially auto Ensures that the procedure can be carried out in a manageable manner, since otherwise the procedure for determining the upper total power limits required sizes such. B. from the accounts of Power supply company must be removed.

In addition, it can be provided that at least part of the results of the calculations gene is saved.  

In particular, it can be provided that the time profile of the maximum mean values P _{Ist, Max, i, j is} stored.

The upper total power _limit values P _{limit, i, j} are advantageously stored. This is also advantageous for an easier and automatic implementation of the method.

Furthermore, it can be provided that the time profile of the upper total power _limit values P _{limits, i, j is} stored.

The number of switching operations to maintain the respective upper total power _limit value P Limits _{, i, j is} advantageously stored in a measurement period T _{measurement of} a respective consumption period subunit ΔT _{Ab, i, j} . The greater the number of switching operations, the sooner the upper total power limit has to be raised. This can be taken into account when calculating or correcting the upper total power limit.

According to a further particular embodiment of the invention, the maximum average values P are _{Is, max, m, n} in actual disconnection of the at least one load from the detected actual total power P _is calculated. This means that maximum average values are used which have been achieved with a corresponding regulation by switching off consumers that can be switched off.

Alternatively, it can be provided that the maximum mean values P _{actual, max, m, n} in the case of a fictitious shutdown by means of measured maximum total powers P _{actual, max, mess, m, n} and the sum of the powers P _{shutdown of} the consumers that can be switched off are calculated as follows: P _{actual, max, m, n} = P _{actual, max, mess, m, n} - P _shutdown . This makes sense in the start-up phase of the method according to the invention, if no regulation has previously been carried out by switching off consumers that can be switched off.

In the device it can be provided that the calculation device is part of a central computer.

On the other hand, it can also be provided that the calculation device has a central Computer is connected. The central computer can perform a variety of functions, such as. B. Calc data management and storage.

The device advantageously has a storage device.

In particular, it can be provided that the storage device is part of the central Calculator. This is particularly advantageous if the remaining components of the Device fail, since it ensures the storage of the data.

It can be provided that the storage device for storing measured values serves.

It can also be provided that the storage device for storing calculations results.

According to a further particular embodiment of the invention, it can be provided that the device has an input device for manual input of the upper total power _limit values P _{limits, i, j} calculated by the calculation device.

In particular, it can be provided that the input device is a keyboard.

The device advantageously comprises a reading device for reading the upper total power _limit values P _{limits, i, j} calculated by the calculation device.

A further particular embodiment of the device is characterized by an additional input device for correcting the upper total power _limit values P _{limits, i, j} calculated by the calculation device.

Finally, the device can have an input device for inputting for the calculations the computation device necessary values include.

The invention is based on the surprising finding that by adapting the upper total output limits to the Lei different over the consumption period needs of the group of electrical consumers to reduce energy costs a small number of switching operations is made possible at the same time. The adjustment is optimal if the upper total determined for the respective consumption period subunit performance limit in each consumption period subunit either just met or is only slightly exceeded.

Further features and advantages of the invention result from the claims and from the following description, in the exemplary embodiments with reference to the schematic drawing are explained in detail. It shows:

Figure 1 shows schematically a particular embodiment of a device for maintaining an upper total power limit for a group of electrical consumers when purchasing electrical energy from a power supply company according to the present invention.

FIG. 2 shows the time course of the mean value P _is the actual total powers for one day without any maximum demand;

FIG. 3 shows the time course of the mean value P _is the actual total performance over a day with a maximum optimization using a total power limit value P _limit of 250 kW;

Fig. 4 is an illustration of events exceeding the total power limit value P _limit and the amounts .DELTA.P _Is to the _limit is exceeded the total power limit value P, in the absence of maximum demand;

Fig. 5 _is the timing of the maximum mean values _{P, max,} the actual total power P _is on the consumption period for a consumption period subunit (month) (year) without Maxi mum optimization (respective left-hand bar); and

6 _Is. The timing of the maximum average values _{P max,} the _day of the actual total power P _Is for the days of a consumption period subunit (months) without (left bar) and with (right bar) maximum optimization.

Fig. 1 is a special embodiment of a device for maintaining an upper total power limit value for a group of electrical loads in the supply of electric power from a power company, a group of four electrical loads 10, 12, 14, 16 with two turn-off electric loads 14, 16 , the group forming an establishment. Furthermore, the device has a calculation device 18 for calculating a respective upper total power limit value P _limit for a respective consumption period subunit (month) T _{Ab, i, j of} the current consumption period T _{Ab, i} before the start, which is decisive for the determination of the quantity-independent energy costs by the energy supply company the respective consumption period subunit DT _{Ab, i, j} according to a function

With
i Consumption period index
L usage period index variable
j Consumption period subunit index
q consumption period subunit index variable,
where i ∈ N \ {1}
j, L, q ∈ N , where L <i and q <j,
x ∈ R ⁺ is
and P _{actual, max, m, n} the maximum mean value of the actual total outputs P _{actual is} correctable when the at least one consumer is actually or fictitiously switched off in a comparison consumption subunit ΔT _{Ab, m, n} with m <i, n ≦ j becomes.

A detection device 20 for detecting the actual total power P _is the group of electrical consumers 10 , 12 , 14 , 16 , an evaluation device 22 for evaluating the actual total power P _actual with respect to the trend of the actual total power P _actual over a measuring period T _Measurement and the subsequent selection of a combination of consumers to be switched off which is suitable for complying with the upper total power _limit value P _{limits, e, j} calculated by the calculation device 18 , and a control device 24 for controlling the consumers in accordance with the selection made by the evaluation device 22 , the evaluation device 22 and the control device 24 are integrated in a so-called maximum optimization computer. In addition, the device comprises a storage device 26 for storing all the measurement values, signals and calculation values of the evaluation device 22 necessary for the calculation. Both the calculation device 18 and the storage device 26 are components of a central computer (not shown). An additional input device 28 serves to correct the upper total power _limit values P _{limits, i, j} calculated by the calculation device 18 . The detection device 20 is connected to the supply network of an energy supply company, from which a start signal 30 is also provided for a consumption period subunit. In the memory device 26 , the measurement and calculation results from the evaluation device 22 are stored together with the date and time.

Figs. 2 and 3 show the time course of the mean value P _is the actual total effective performance over a maximum day without optimization, and with a maximum optimization using a total active power limit value P _limit of 250 kW. The curve profile shown in FIG. 4 results from the difference between the curves shown in FIGS. 1 and 2. The level of the selected total power _limit value P _limit of 250 kW is based on the knowledge that in a defined maximum optimization device a power that can theoretically be switched off is available, which corresponds to the sum of the powers P _{off of} the electrical consumers that can be switched off. However, the power that can actually be switched off only corresponds to part of the power that can theoretically be switched off, since the loads that can be switched off are not always on when they are to be switched off. The power that can actually be switched off in the amount of approx. 20 kW, which leads to the total power _{limit value} P _limit = 250 kW with a power peak of approx. 270 kW, can be seen in principle from the course shown in FIG. 2, since the power peaks (approx. 70 kW), which protrude beyond the basic requirement (approx. 50 kW), differ by 20 kW from the basic requirement. In the present example, the main working time with a high base load is between 9:30 and 13:30; therefore the possible reduction is only in the order of 20 kW. The area below the curve shown in Fig. 3 corresponds essentially to the area below the curve shown in Fig. 2, so that by a maximum optimization no savings in quantity-dependent costs for power consumption, measured in kWh (electrical work) achieved becomes. The maximum optimization, however, reduces the quantity-independent costs, since a lower maximum performance value is achieved.

In order to avoid the exceeding of the total power _limit value P _limit shown in FIG. 3, switching operations are necessary, the number of which essentially depends on the amount of the excess. The lower the total power _limit P _limit below the maximum power value without maximum optimization, the greater the number of switching operations and thus the wear of the device.

The time course of the mean P _Actual total output over a day without maximum optimization does not change too much in most companies over the course of a year (consumption period). The changes occur mainly in the area of basic needs, such as. B. heaters and cooling units. The power that can actually be switched off in February (consumption period subunit) will therefore be similar to the power that can actually be switched off in October (further consumption period subunit).

To explain the essential advantages of the method according to the invention, FIG. 5 shows the time course of the maximum mean values P _{actual, max of} the actual total outputs P _actual in a consumption period subunit ΔT _{Ab, m, n} (month) over a consumption period (year) without maximum Optimization for a sample operation shown. The maximum mean values are between 255 kW and 295 kW. To the right of the respective bars are the minimum overall performance values that can theoretically be achieved for the respective month due to the power that can actually be switched off by means of maximum optimization, whereby according to the above statements it is assumed that the power that can actually be switched off is constant over the whole year. In the prior art, a variant of the maximum optimization would be to use a single total power limit value of 260 kW of 270 kW for all consumption period subunits (months) of the consumption period (year) and to accept that the total power limit value was exceeded in February. In another variant of the maximum optimization in the prior art, in which, after the total output limit value has been exceeded, the same is brought to the actually achieved - higher - total output, and in which an energy saving has priority over the reduction in wear, a very low one Total power limit of e.g. B. 245 kW, but this would have the consequence that a large number of unnecessary switching operations takes place in all months in which this total power limit cannot be met. This can be seen from FIG. 6, which shows the course over time of the maximum mean values P _{actual, max, day of} the actual total output P _actual for the days of a consumption period subunit (month) without (left bar) and with (right bar) maximum - Optimization shows. On all days on which the maximum average values P _{actual, max of} the actual total output P _actual, despite maximum optimization, exceed the total output limit set to 245 kW at the beginning of the month and adjusted in the course of the month (solid line), the maximum Optimization according to the second variant of the prior art with unnecessary switching operations attempts to set an overall power limit that is set too low. Every time the total power limit is exceeded, the operational sequence is impaired, since the maximum optimization device always tries to comply with the total power limit and accordingly, if there is a risk of exceeding, also switches off consumers which have a higher priority. Most maximum optimization devices have a so-called "emergency release", which can also switch off relatively important consumers for a short time if they are exceeded. As can be seen from FIG. 6, the maximum optimization according to the second variant in the prior art, which allows the maximum regulation to find the total power limit value by setting an overall power limit value that is too low, is detrimental to the consumer and to the consumer Operational flow. This is avoided by the present method and device according to the invention, in that based on data from the past years or the past months, the realizable total power limit values to be expected for the individual months are calculated and set with a high probability.

The in the above description and in the claims and the accompanying drawing tion disclosed features of the invention can be used both individually and in any Combination for realizing the invention in its various embodiments be essential.  

Reference symbol list

10th

,

12th

electrical consumer

14

,

16

switchable electrical consumer

18th

Calculation device

20th

Detection device

22

Evaluation device

24th

Control device

26

Storage device

28

additional input device

30th

Start signal

32

Date and Time

Claims (35)

1. A method of meeting an upper total power limit for a group of electrical consumers when purchasing electrical energy from an energy supply company, comprising the following steps:

• a) Acquisition of the actual total power P _{actual of} the group of electrical consumers and determination of the trend of the actual total power P _actual over a measuring period T _measurement and
• b) at least temporarily switching off at least one switchable consumer of the group, if it can be foreseen from the trend calculation that the mean value P _actual , the actual total power P _actual in the _measuring period T _{measurement will} exceed a definable upper total power _limit value P _limit at the end of the measuring period T _measuring ,
  the upper total power _limit value P _limit before each consumption period subunit ΔT _{Ab, i, j of} the current consumption period T _{Ab, i} relevant for the determination of the quantity-independent energy costs by the energy supply company by calculation according to a function
  With
  i Consumption period index
  L usage period index variable
  j Consumption period subunit index
  q consumption period subunit index variable,
  where i ∈ N \ {1}
  j, L, q ∈ N , where L <i and q <j,
  x ∈ R ⁺ ,
  and P _{Ist, max, m, n is} the maximum mean value of the actual total powers P _Ist when the at least one consumer is actually or fictitiously switched off in a comparison consumption subunit ΔT _{Ab, m, n} with m <i, n ≦ j,
  is set correctable.

2. The method according to claim 1, characterized in that q = 0 and
is. 3. The method according to claim 2, characterized in that L = 0. 4. The method according to claim 1, characterized in that
is. 5. The method according to claim 4, characterized in that q = 1. 6. The method according to claim 4 or 5, characterized in that L = 0. 7. The method according to claim 1, characterized in that
is. 8. The method according to claim 1, characterized in that
is. 9. The method according to claim 1, characterized in that
with B _{i, n} duration of use in a comparison consumption period subunit ΔT _{A, b, i, n} which results from the quotient of the total electrical energy consumed in the comparison consumption period subunit ΔT _{A, b, i, n} and the maximum mean value P _{Actual, max, i, n} results. 10. The method according to any one of claims 7 to 9, characterized in that q = 1. 11. The method according to any one of claims 7 to 10, characterized in that  L = 0. 12. The method according to any one of the preceding claims, characterized in that x in loading ranges from 0 to 10. 13. The method according to claim 12, characterized in that x = 0. 14. The method according to any one of the preceding claims, characterized in that the upper total power _limit value P _{limit, i, j} determined by calculation in the consumption period sub-unit ΔT _{A, b, i, j} is corrected to a larger upper total power _limit value if the upper total power _limit value P _{limits, i, j} in the consumption period subunit ΔT _{A, b, i, j has} been exceeded despite the shutdown of at least one consumer. 15. The method according to any one of claims 1 to 13, characterized in that the upper total power _limit P _{limits, i, j} determined by calculation is corrected before the start of the consumption period subunit ΔT _{A, b, i, j} , if the number and / or the consumption and / or switch-off properties of the consumer has changed. 16. The method according to claim 15, characterized in that the upper total power _limit value P _{limit, i, j is} corrected if the deviation between at least one of the parameters service life, maximum power that would have been achieved without switching off consumers, and sum of the power of all switchable consumer, over one or more consumption period subunit (s) of the current consumption period T _{Ab, i} and the respective parameter in one or more comparison consumption period subunit (s) of one or more preceding / preceding consumption period / consumption periods exceeds a definable limit value. 17. The method according to any one of the preceding claims, characterized in that at least part of the results of the calculations is saved. 18. The method according to claim 17, characterized in that the time course of the maxima len average values P _{actual, max, i, j is} stored. 19. The method according to any one of the preceding claims, characterized in that the upper total power _limit values P _{limits, i, j} are stored. 20. The method according to claim 19, characterized in that the time course of the upper total power _{limit values} P _{Limits, i, j is} stored. 21. The method according to any one of the preceding claims, characterized in that the number of switching operations to comply with the respective upper total power _limit P _{limits, i, j is} stored in a measuring period T _{measurement of} a respective consumption period subunit ΔT _{Ab, i, j} . 22. The method according to any one of the preceding claims, characterized in that the _maximum average values P _{actual, max, m, n} actual shutdown of the at least one consumer are calculated from the detected actual total powers P _actual . 23. The method according to any one of claims 1 to 21, characterized in that the maximum mean values P _{actual, max, m, n} with P fictitious shutdown by means of measured maximum total services P _{actual, max, mess, m, n} and the sum of the powers P _{shutdown of} the shutdown consumers can be calculated as follows:
P _{Ist, max, m, n} = P _{Ist, max, mess, m, n} -P _shutdown 24. Device for maintaining an upper total power limit for a group of electrical consumers when purchasing electrical energy from an energy supply company, with

• a calculation device for calculating a respective upper total power _limit value P _limit for a respective consumption period subunit ΔT _{Ab, i, j of} the current consumption period T _{Ab, i} before the start of the respective consumption period subunit ΔT _Ab, which is decisive for the determination of the quantity-independent energy costs by the energy supply company _{, i, j} according to a function
  With
  i Consumption period index
  L usage period index variable
  j Consumption period subunit index
  q consumption period subunit index variable,
  where i ∈ N \ {1}
  j, L, q ∈ N , where L <i and q <j,
  x ∈ R ⁺ ,
• - and P _{actual, max, m, n} the maximum mean value of the actual total outputs P _actual when the at least one consumer is actually or not actually switched off in a comparison consumption subunit ΔT _{Ab, m, n} with m <i, n ≦ j,
• a detection device for detecting the actual total power P _{Ist of} the group of electrical consumers,
• - An evaluation device for evaluating the actual total power P _actual with respect to the trend of the actual total power P _actual over a measurement period T _mess and subsequent selection of a combination of those to be switched off _{that is} suitable for compliance with the upper total power limit value P _{limit, i, j} calculated by the calculation device Consumers and
• - A control device for controlling the consumer according to the selection made by the evaluation device.

25. The device according to claim 24, characterized in that the calculation device Be is part of a central computer. 26. The apparatus according to claim 24, characterized in that the calculation device with is connected to a central computer. 27. The apparatus according to claim 25 or 26, characterized by a storage device. 28. The apparatus according to claim 27, characterized in that the storage device Be is part of the central computer. 29. The device according to claim 27 or 28, characterized in that the storage device serves to store measured values.   30. Device according to one of claims 27 to 29, characterized in that the Spei cher device for storing calculation results. 31. Device according to one of claims 24 to 30, characterized by an input device for manual input of the upper total power limit value P _{limits, i, j} calculated by the calculation device. 32. Apparatus according to claim 31, characterized in that the input device is a Ta stature is. 33. Device according to one of claims 24 to 30, characterized by a reading device for reading the upper total power _limit values calculated by the calculation device P _{limits, i, j} . 34. Device according to claim 33, characterized by an additional input device for correcting the upper total power _limit values calculated by the calculation device P _{limits, i, j} . 35. Device according to one of claims 24 to 34, characterized by an input device for entering the data required for the calculations of the calculation device ten.