Interruptible services
At astora there are a total of two service categories, which differ in rank and commercial treatment and the special case of exceedances:
Category 1: firm
Category 2: interruptible
Special case: exceedances
These categories and the special case become relevant as soon as the customer nominations at a storage location exceed the available capacity and thus the interruptible case occurs. In this case, nominations are reduced according to their value - starting with the special case: the exceedance.
The power categories are defined as follows:
Category 1: firm
This is the highest value service category. The booked fixed capacity will be limited by a level-dependent injection/withdrawal curves as stipulated in the contract, if applicable. Besides that, customers who booked firm capacities are entitled to the service, unless a planned or unplanned maintenance measure, disruption or any other case of force majeure prevents full provision. In any of such a cases, the contractual entitlement to firm services is reduced in accordance with the physical restriction, but the customer may nominate its full services. In the event of a restriction, the entitlement to firm capacity is only reduced, whenever all category 2 nominations have been fully reduced. The special case of exceedance never leads to a reduction of firm capacities.
Category 2: interruptible
In addition to firm capacities, astora offers interruptible capacities, which may lead to an overbooking of the storage. These services will be provided subordinately to firm capacities but are never restricted in the special case of exceedances. In the event of a restriction of interruptible services, the nominated contractual capacities within this category will be prioritised according to their time of booking- The capacities that have been booked last will be interrupted first.
Caution: The limitation by a level-dependant injection/withdrawal curve is not applicable to interruptible services - the services can be used regardless of the filling level, provided the utilisation at the storage facility permits this.
Exceptional case: exceedances
astora in entitled to confirm nominations exceeding the booked capacity of a storage customer. These nominations, which are not based on a booking, are always reduced pro rata before interruptible services are reduced.
In principle, exceedances are charged with the fee for exceeding the storage capacity as specified in the storage specification applicable to the customer. As the case may be a free use of the areas restricted by a contractual injection/withdrawal curve may have been agreed between the parties (grey-filled area in Figure 1). More details can be found in the storage specification.
Attention: The usage of capacity in the injection/withdrawal-curve-limited area is also treated as an exceedance.
Combination of Services
Different contracts of the same customer at a storage location are aggregated with regard to their associated service rights in the corresponding time periods and allocated in total to the customer's storage account and managed together. A storage account can therefore contain categories 1 and 2. However, the nomination does not imply any reference to the categories. Therefore, the highest-ranking services will always be saved first with regard to any nomination. A graphical example for the composition of an injection/withdrawal curve is shown in Figure 1.
In this example, the total capacity right is composed of a fixed capacity that depends on the contractual filling-level (dark blue dashed line minus light blue dashed line) and a level-independent interruptible capacity (light blue dashed line). A nomination could also be submitted in the grey streamlined area to which the respective tariff for exceeding the storage capacity applies or in the grey filled area (tariff for exceeding the storage capacity unless expressly stipulated otherwise in storage specification).
Reduction of the interruption risk
To estimate the current risk of interruption, astora provides storage customers with a public tool, the capacity utilisation view in the time series viewer (see figure 2).
The time series viewer displays the available injection and withdrawal capacity (indicative) at the storages, under consideration of maintenance restrictions and relevant injection/withdrawal curves. Correspondingly, the already allocated injection and/or withdrawal quantities as well as currently confirmed and unconfirmed nominations can be viewed.
This way, the difference between available and utilised capacity can easily be viewed graphically and numerically. This can help to assess whether free capacity can be used / is available and to decide whether or not to book additional interruptible services.
