The cargo sling is a programmable automat which maintains the point quarter-schedule below the threshold fixed in advance.
If the power called exceeds the fixed threshold, there is unballasting of the equipment which is connected to the lasting ballast-heaver of the short periods.
This shut-down or with the idle is carried out only when the taken total power, integrated over the period of measurement, is likely to exceed the limiting threshold of power fixed.
The equipment is lightened according to a set of priorities which was established beforehand and memorised by the automat. For example, of the priority levels will be given so that the apparatus whose cut is likely more to be felt either stopped lastly.
When the request weakens and that reconstitutes a reserve of power available, there is "relestage".
To guaranty the impact of the ballast-heaver on the electric invoice, it is obvious that are operation must be able to be synchronised with the metre network.
The ballast-heaver can have much other functions :
One can impose times to him minima of operation of equipment, times maxima of waiting, times minima of stop.
It can take account of ranges where certain apparatuses cannot be lightened.
The automat can have a function "clock" which cuts equipment to fixed hour. This function is usually used with the storage water heater heating water lasting 8 hours with the night charge. It can also be used for hardware of cooking and the heating.
An exemption from the programming can be ordered by the manager according to specific needs. This one must be automatically cancelled at the beginning of the following cycle in order to preserve its exceptional character to him.
Certain apparatuses "dialogue" with the equipment which is connected there so as to know their state and to act consequently.
The unballasting of a hardware can be total or partial (provided that this partial unballasting is envisaged by the manufacturer).
The programmable automat will be called cargo sling or optimiser according to its degree of sophistication (according to the number of functions that it integrates, according to the richness of the parameters whose account the apparatus can hold to choose the apparatuses to be lightened,).
The ballast-heavers are distinguished between-them by:
the full number of impulse inputs
the full number of outputs of unballasting
the algorithm of management of the power
the possibility of creating fictitious points of measurement
the storage capacity of information
programming of the period of integration
the number of tariff periods which can be created
capacities of the management software (on the apparatus even and the PC of management)
means of communication with the PC of management
In traditional electrical installations, the installation of a cargo sling requires to draw a cable between the module from the ballast-heaver and each connected apparatus. For certain apparatuses, the ballast-heaver can act on several parts. In this case, it will be necessary to draw cables as many.
On the level of the equipment, connexions are sometimes envisaged by the manufacturers. If they are not it is always possible to carry it out a posteriori.
Connexion is obviously definitely simpler if one designs an installation managed by bus of ground. In this case, it is fast and easy to modify the equipment délestables (by réadressage) according to the results achieved during the exploitation.
Principle of connexion of the ballast-heaver in a traditional electrical installation.
Management of the unballasting
Algorithm of unballasting
With I = period of sampling (multiple of 1 minute)
td = expressed dead time (in multiple of 1 minute)
Ei = power consumption after period 1 [kWh]
Pmax = maximum power, function of the tariff period [kw]
Emax ⁄ (15’) [kWh]
Emax x 4 [kW]
Emax = maximum energy demand in 15 ’.
Ein = energy limits interlocking (0 99% of Emax)
Eout = energy limits release (0 99% of Emax)
A maximum value of point (Pmax) is fixed and indicated to the ballast-heaver. The apparatuses connected to the ballast-heaver require power. To the beginning of each impulse of change of quarter-at Electrabel time, the ballast-heaver does not react. It "observes" how the request for power evolves/moves. After a certain fixed time (td), the ballast-heaver will act: if the required power is such as after 1 ⁄ 4 of hour, it is likely to exceed the maximum value of point (Pmax), it cuts loads.
To have release of a circuit, it is necessary that the 3 conditions below are met after each time interval "I":
circuits are engaged
Ei(Emax - Eout)x(i ⁄ 15’) + Eout (that is to say the total energy required after interval I cannot exceed the line, Eout .. Emax)
i td... (that is to say the ballast-heaver does not react initially).
To have interlocking of a circuit, it is necessary that the 3 conditions below are met after each time interval " I ":
circuits are started
EiEmaxx (i/15’)-(Emax- Ein) (that is to say the total energy requested from interval I cannot go down under the E0(= 0) .. Ein)
i td.. (that is to say the ballast-heaver does not react initially).
Value Eout is fixed 0 so as to allow the fast increase in energy at the beginning of 1 ⁄ 4 of hour. Indeed a large power at the beginning of 1 ⁄ 4 of hour can be called without fatal consequence on the point quarter-schedule if this one is compensated by a power called much lower in the continuation of quarter-at hour. The variation enters the two Eout lines. Emax and E0. Ein makes it possible not to have a too fast succession of interlocking ⁄ release. This variation is weaker at the end of the 1 ⁄ 4 of hour (that is to say one accepts best the oscillations) to be able to benefit from the maximum point quarter-schedule.
The algorithm thus will manage the power consumption in 15 minutes so that, if it is important, it increases while oscillating between two lines fixed "driving" at the maximum energy authorised in end of quarter-at hour. Energy can slightly exceed these limits because of the period of sampling "I " which is multiple minute.
The fifteen minutes following energy are entered while setting out again of 0 kWh (= E0).
Sequence of release ⁄ interlocking
Here an example of sequence of release of 5 equipment whose 2 last can be crossed only in borderline case. The priority of release of the first 3 equipment occurs in a cyclic way there:
1st period: tripping order 1-2-3-4-5
2nd period: tripping order 2-3-1-4-5
3rd period: tripping order 3-1-2-4-5
4th period: tripping order 1-2-3-4-5
To respect the order of the priorities, the last started equipment is the first with bEing re-engaged. Equipment 4 and 5 is hateful apparatuses into last recourse.
Let us note that certain automats envisage the needs to come according to the history and anticipates the reactions of the hardware in order to obtain an optimal answer for the whole of the controlled uses, while limiting the called total power or the cost of the power consumption. This function is known as "intelligent", because it is related to a memory continuously updating which induces an answer adapted to the stress present, but also on that which succeeds to him. The choice of distribution of energy is thus carried out in the moment and not in a pre-established way.
Autoadaptation of the instruction
The algorithm of evaluation of the point quarter-schedule will be self-adapting according to the parameters of measurement, so as to lighten the maximum of power without harming comfort and by respecting the impositions of the distributor.
In addition, so in spite of the action of the ballast-heaver the critical point fixed at the beginning of month is exceeded, this point reached is automatically selected like new threshold for the remainder of the month.
Follow-up of the operation of the ballast-heaver
When a management system of the power is set up, the follow-up of the results is imperative:
actions of the ballast-heaver and history of the started equipment
follow-up of the power taken with the network
This follow-up will make it possible to make sure of the good performance of the installation on the one hand and, on the other hand, to optimise the parameters of them, thus making its use more profitable still or less awkward for certain equipment.
The follow-up can even be done within the ballast-heaver which has a built-in memory and the possibility of drawing up histories or through a PC by means of a software of follow-up (communication by possible modem).
Example of possibilities of a software of follow-up, via the recorders of the ballast-heaver (these data can be accessible in various forms according to the software):
demand curves (over one day, one month, etc)
simulation of the invoice for various tariffs
relationship between consumption of the full and hollow hours
consumption, reactive consumption
savings made thanks to the cargo sling.
Example of result provided by the software of follow-up of a ballast-heaver.
Particular case of the kitchens
Certain systems of automats are more specific optimisers for collective kitchen.
This type of ballast-heaver is composed of an central processing unit (which concentrate all the functions of calculation and data storage) and of various modules of commands (necessary for the dialogue and the control of the various consumers).
Central processing unit and modules of the commands (for 2 furnaces and 2 fryers).
Each module can be connected 2 times, that is to say with 2 different apparatuses (ex: a static furnace and a pot), are only one apparatus with two resistances to order (ex: a connexion towards resistance of heating of water of washing of a dishwasher and the other towards resistance of the air of drying).
A permanent "dialogue" is maintained between the central processing unit and the apparatuses which are connected there. The central processing unit questions, at the rate ⁄ rhythm of the second, each apparatus connected, on its operating condition:
stop ⁄ functioning
ask thermostat (interlocking ⁄ release)
phase of pre-heating or cooking
enter each second of use.
Obviously, the apparatus must obligatorily be connected on the socket which contains the cable intended to manage its energy consumption. The concept of mobile kitchen thus constrained to mark each socket to recognise, without bEing mistaken, the plug which corresponds to him.
Management supplements of a kitchen with screen of supervision.
The unballasting is always done at the time when the thermostat orders a re-starting of resistance. The ballast-heaver requires of resistance to place after its action of a few seconds. This unballasting is never done in period of rise in temperature.
Change of the temperature in a boiling apparatus with or without unballasting: the ballast-heaver can never cut the apparatus before it reaches the temperature of cut of resistance, or else, the average temperature would fall too extremely.
To know the boarding time in temperature, the ballast-heaver measures time between the startup of an apparatus and the first stop ordered by the thermostat.
The automat, starting from the information of the various thermostats, carries out thus an analysis and a burden-sharing des according to the needs for each hardware and of the priorities recorded in its memory.
There exist particular modules which are used to connect the refrigerating machines, for example. With these modules, there is not a "dialogue" between the apparatus and the ballast-heaver. This last decides unballasting without taking account of the state of the refrigerating machine.
The ballast-heaver has also a "function clock". For each equipment, one can fix certain time ranges where operation is prohibited. In the "authorised" ranges, the hardware functions only if the regulation (thermostat, pressure controller) requires it. By moving the periods of operation of certain equipment, the automat decreases the instantaneous power called without disturbing their operation.