hereinafter identical references or identical variable identifications belong to different specific operating situations , but basically concern identical components , physical parameters or adjustments . fig1 shows a basically known wind power installation in which a method according to the invention is implemented . the rotor blades can adjust the rotor blade angle . fig2 shows by way of illustration and in idealizing fashion the underlying wish of reducing the power which is to be generated at a maximum with a wind power installation , by a given value . thus a solid line shows the power p 1 for a first operating mode in which maximum power is generated by the wind power installation , namely the power which can be generated on the basis of the prevailing wind conditions . that can also be below a nominal power . shown in broken line is a power characteristic curve identified by p 2 showing a second operating mode of the wind power installation , in which it is operated at a reduced value which is specified in fig2 by way of example as 10 %. that is effected from the time t 1 . that differential power between p 1 and p 2 is to be determined in order for example to be able to recompense same or to be able to predetermine it if the wind power installation is operated in the second operating mode at the power p 2 . fig3 shows that however under real conditions it is generally not possible to assume that there is a constant wind speed and thus also a constant power . the wind speed v w is plotted there in relation to time t . to illustrate the problems involved the wind speed v w varies in height . shown as p 1 is a power characteristic curve which specifies the power which could be generated at a maximum with the prevailing wind v w , with the wind power installation in question . in principle there is a cubic relationship between wind speed and the power which can be generated therefrom . that non - linear relationship is intended to be discernible in fig3 . nonetheless fig3 only diagrammatically shows the power variation p 1 to illustrate the problems . at the time t 1 there is a reduction in the maximum power p 1 which can be generated , to the reduced power p 2 . the reduction implemented is identified by δp . fig3 clearly shows that determining the differential power with a fluctuating wind and thus fluctuating initial power output is difficult . as a solution , it is proposed that different rotor blade angles , namely α1 , α2 or α3 , be set , even in the part - load range . fig4 shows the differing height of the power which can be generated in dependence on the wind speed and in dependence on the choice of the rotor blade angle , in which respect the rotor blade angles α1 , α2 and α3 are also shown only by way of example here . accordingly a different cp value is plotted for each rotor blade angle . in that respect , the cp value cp1 = 100 % is assumed for the rotor blade angle α1 , that is to say the maximum achievable cp value . in comparison the rotor blade angle α2 is slightly altered and has a cp value which is slightly reduced , namely cp2 = 90 %, accordingly cp2 is 90 % below the value of cp1 which is adopted here as the basic value . for the further configuration shown by way of example for the rotor blade angle α3 , that gives a cp3 = 40 %. accordingly fig4 not only shows that wind speed - dependent differing powers can be achieved depending on the respective rotor blade angle set , but also that a relationship which is at any event is basically known can be adopted as a basic starting point . it will be noted however that possibly such a relationship has to be determined for the specific installation . it will be appreciated that here too there can be slight deviations , if it is taken into consideration that the wind speed is not the same either for different locations or for different times . nonetheless a quite good association of the power is possible in wind speed - dependent relationship with different rotor blade angles . accordingly it is possible to infer from a power at a rotor blade angle , for example α2 , the power which could be produced in the situation upon setting the rotor blade angle α1 . a corresponding implementation is shown in fig5 illustrating two possible wind speed - dependent power characteristic curves . both characteristic curves , namely that associated with the rotor blade angle α1 and that associated with the rotor blade angle α2 , start at the wind speed v activate , at which the wind power installation is switched on and which specifies the beginning of the part - load range . both power characteristic curves then rise to the nominal wind speed v wn which specifies the end of the part - load range which is thus between v activate and v wn . the linear configuration of the two characteristic curves is only by way of illustration . the power characteristic curve for α2 concerns a second operating mode in which the wind power installation is operated in a reduced mode . the characteristic curve in respect of the rotor blade angle α1 identifies a non - reduced mode . for , in the illustrated embodiment , a differential power δp is shown , which is approximately constant for the full - load range , that is to say for wind speeds above v wn , but is proportional to the respective power for the part - load range . fig5 is intended to show in that respect that there can be two characteristic curves depending on the set rotor blade angle . those characteristic curves are plotted in dependence on the wind speed and are basically known . if a power point is set for example on the characteristic curve relating to the rotor blade angle α2 , the corresponding operating point of the other curve can be directly determined because both curves are known . as an example for that purpose the operating points b2 for use of the rotor blade angle α2 and the corresponding operating point b1 of the curve for the rotor blade angle α1 are plotted . when therefore the operating point b2 occurs the operating point b1 and thus the maximum power which can be generated can be directly ascertained or read off from the characteristic curve . although the illustration is in dependence on the wind speed v w there is no need for express knowledge or designation of the underlying wind speed . therefore the operating point b2 can be set without knowledge of the wind speed and the operating point b1 can be ascertained and that can also directly give the differential power δp . it is thus possible to advantageously react to requirements from network operators , namely to reserve a percentage active power of the current fed - in active power , which can be released again for network support in critical network situations , in particular in the case of an underfrequency . in addition the following can also be explained by way of example . reserving active power in dependence on the currently prevailing feed - in power is difficult in the case of wind power installations in the part - load range . the aerodynamic conditions at the installation are altered by downward regulation of the installation , which possibly makes it almost impossible to detect the real wind speed and the possible feed - in power resulting therefrom . an active power reserve power at the installation level and at the wind park level can also be achieved and possibly even guaranteed in the part - load mode of operation , by artificially targetedly controlled worsening of the level of efficiency of the installation , that is to say the wind power installation . in the nominal load mode of operation an upper limit is imposed , that is to say the provision of a reserve , by limiting the maximum power . thus entire wind power plants can be operated with a reserve power controlled centrally by way of the scada system . the release of reserve power can be implemented for example at the network frequency , thus being established on the basis thereof . the network frequency is basically the same everywhere in the network and a threat of underfrequency signals a collapsing electrical network . the worsening of the level of efficiency in the part - load range is achieved by targetedly setting the minimum blade angle , that is to say targetedly setting the rotor blade angle in the part - load range . as a one - off procedure for each type of installation or for each blade profile in the case of a series installation , but possibly also for each individual installation , rotary speed - dependent characteristic curves are measured for the minimum blade angle , those curves reflecting the respective percentage reserve powers . that reserve power can in that respect also be interpreted as or identified as the differential power between the maximum power which can be generated , and the power which is reduced in the case of providing a reserve power . the proposed solution can also be inexpensively used insofar as possibly only a one - off software implementation may be required . it is to be mentioned that almost all network operators are in the meantime demanding that installations automatically react or can react to changes in frequency in the network with a change in power . as the requirements of the network operators can be very different , it may be necessary to introduce a large number of new parameters which are then to be set by way of example or in part only at the installation display . when using a program in accordance with an embodiment of the invention , initialization of the frequency - dependent power regulation which satisfies the requirements of most network operators is firstly automatically implemented as a one - off procedure . it will be noted however that it may be necessary to check , in co - operation with a network operator at each installation , whether the settings correspond to the requirements of the network operator . at the display of the installation there is then the possible option of switching frequency regulation on and off . when it is switched on it is possible to select whether the installation is to react to a frequency deviation dynamically or statically . in dynamic regulation the power of the installation is lowered when the predetermined frequency is exceeded with a given gradient thus — for example a given percentage value per second — and raised again if the frequency falls below the limit value again . in static regulation the power is regulated proportionally to the frequency , depending on which respective frequency limits and which associated power values are set . some network operators require a so - called ‘ return frequency ’. that is generally only a little above the nominal frequency . that return frequency provides that the installation initially only reduces the power upon a rise in frequency . it is only if the frequency falls below the return frequency again that the power is increased again . if the return frequency is set higher than the uppermost downward regulation frequency , it is ineffective . it is also possible to set whether frequency regulation is to operate in dependence on the nominal installation power or the current installation power . if the nominal power is selected as the reference point then all target values of the frequency - dependent power regulation are related to that power . in other words , if an installation for example is still to make 50 % power at 51 hz , that would correspond to a p - max ( f ) of 1000 kw at a nominal power of 2 mw . if however the installation only runs 500 kw because of little wind , that would have no influence on the installation power and the installation would thus not make any contribution to frequency regulation . if the current installation power is selected as the reference point , then the installation power is stored as 100 % value at the moment when frequency regulation begins . upon a further rise in frequency p - max ( f ) is related to that value . in other words , from the above example , the installation would only still make 250 kw at 51 hz and thus would make a contribution to stabilization of the network frequency independently of the prevailing supply of wind . a point in frequency regulation is the so - called reserve power which has already been partly described . in that case the installation is operated in the region of the nominal frequency at reduced power . in the case of nominal wind that is effected by limiting p - max . in the part - load mode of operation the installation is operated with a blade angle which represents the required regulating reserve . the regulating reserve can therefore be read off from the blade angle . if now the network frequency falls below a given value of for example 49 . 5 hz then the installation automatically increases the power and thus supports the network frequency . that reserve power represents an option which is only used in rare cases . for , if an installation has to constantly reserve power , that signifies high yield losses under some circumstances . with active park regulation the reserve power can also be predetermined by the park computer . fig6 shows a method of operating a wind power installation . at 602 , the wind power installation is operated in a first operating mode . at 604 , the wind power installation is operated in a second operating mode . at 606 , at least one of a maximum power that would be generated with the first adjustment parameter set or a power difference between the maximum power and the power generated in the second operating mode is determined using or without using angles of rotor blades of the wind power installation . fig7 shows a method of determining power associated an adjustment parameter set . at 702 , the power associated with the second adjustment parameter set and the maximum power that would be generated with the first adjustment parameter are determined by at least one of comparative measurements , interpolation and extrapolation . fig8 shows a method of generating rotary speed - power characteristic curves . at 802 , rotary speed - power characteristic curves are generated based on the second adjustment parameter set . fig9 an example of parameter sets . a first parameter set 902 includes a first rotary speed power characteristic curve and a first rotor angle blade . a second parameter set 904 includes a second rotary speed power characteristic curve and a second rotor angle blade . fig1 shows an example of a wind power installation . the wind power installation 1000 includes an electric generator 1002 coupled to a rotor 1004 . the wind power installation 1000 includes a microcontroller 1006 . fig1 shows an example of a wind park . the wind park 1100 includes a plurality of wind power installations 1102 . the various embodiments described above can be combined to provide further embodiments . all of the u . s . patents , u . s . patent application publications , u . s . patent applications , foreign patents , foreign patent applications and non - patent publications referred to in this specification and / or listed in the application data sheet are incorporated herein by reference , in their entirety . aspects of the embodiments can be modified , if necessary to employ concepts of the various patents , applications and publications to provide yet further embodiments . these and other changes can be made to the embodiments in light of the above - detailed description . in general , in the following claims , the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims , but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled . accordingly , the claims are not limited by the disclosure .