Map Preparation Date: 23 Nov 2020
What can I learn from the map?
- The map indicates transformer capacity available at each distribution High Voltage (HV) substation. The HV data is intended to guide industrial/large commercial scale users to HV substations where a connection is more likely to be achieved without
significant reinforcement. This is relevant as substation and transformer installations are the longest lead time component of connections if they must be built or reinforced.
- In the map HV substations are classified into two categories corresponding to the supply voltage i.e., 38kV or Medium Voltage (MV).
- The map also gives the location and available demand capacity for all 3 phase Medium Voltage to Low Voltage (MV/LV) substations.The LV data capacity is in the range of customers looking to connect demand less than 500kVA. This scale would be of most
interest to small businesses, farming, and small community projects. If the indicated capacity meets your needs, then you can be reasonably assured no new substation development is required. However, site specific detail such as proximity and
physical access could still be an overarching limiting factor.
- Available capacity for LV generation is not specified because of additional considerations that are mainly site specific, see point No 5 below.
- The pins on the map are colour coded by ranges of available capacity which can be separately filtered. Filtering can also be independently applied by voltage level.
How do I know which substation to review for my site?
- For LV substations, use the map to locate your own site and then find the nearest LV substation to it. Typically, a substation must be within 300m or less to be suitable for connecting at LV otherwise a new substation must be provided nearer to you.The
pop-up box also shows the parent HV substation that supplies the LV substation. Also check this for available capacity.
- For HV substations, the best indication of which one supplies your site is to find the nearest LV substation and identify its parent HV substation. Review the HV substation for available capacity and the parent of that station if one is listed in
the pop-up panel.
Does the Capacity Available value mean I can connect the amount shown?
Not necessarily. There are many site-specific issues and detailed technical checks that must be completed to give that assurance and they can only be completed as part of an application. Below are some of the factors that influence the answer:
- Am I the first to apply? All connection offers are provided on a first come first served basis so other customers may have applied ahead and used a proportion of the available capacity.
- Proximity to the substation: typically for LV, you must be a maximum of 300m from the substation and much closer for the higher level of LV capacity. For 38kV and MV circuits, capacity is not assured, and new lines may need to be constructed or existing
- HV substations are sometimes a parent supply to other downstream substations. In cases where the parent substation has limited capacity then all child substations will be curtailed by that limit. Furthermore, if just one child substation absorbs all
the available capacity then that will result in no spare capacity for the other child stations. This form of interaction requires continual re-assessment to ensure no system overload occur.
- A similar interaction can occur on circuits where apparently available capacity cannot be contracted because of customer increases on other circuits which share a common source with a capacity limit.
- Generation, at all voltages, is particularly onerous due to the limited latitude to accommodate the associated voltage rise. This has an acute effect on the necessary proximity to a substation.
- Capacity available is also influenced by disturbing load such as flicker and harmonic emissions.
- The stated available capacity may exceed the maximum rating for an individual network component such as transformer capacity or standard circuit connection capacity. In such cases, a single customer/connection will be constrained by the network component
and therefore will not be able to avail of the full value indicated.
Why are there no specific available capacity values for LV generation provided?
Each substation has been given an overall classification (Red/Amber/Black) based on the calculated available capacity. The colour meanings differ for HV and LV and for Demand and Generation as shown below:
DEMAND: 38kV and MV
GREEN Greater than 5MVA
AMBER Between 0 and 5MVA
BLACK No capacity available
Generation: 38kV and MV
GREEN Greater than 15MVA
AMBER Between 0 and 15MVA
BLACK No capacity available
Demand and Generation: LV
GREEN Greater than 200kVA
AMBER Between 20 and 200kVA
BLACK 20kVA or less available
Connections to the substations/transformers with an overall BLACK classification are still possible, however there might be a requirement for significant network reinforcement to overcome the impact on the network constraints.
How has the data been produced?
The data has been produced by a basic analysis of the available transformer capacity, existing loads and contractual commitments to new customers. Detailed assessment aspects, necessary for connection offers, such as upstream circuit capacity and
service contingency requirement are not included.
What are the available capacity figures based on?
- HV station capacity in winter 2019/20.
- MV station capacity at the start of May 2020.
- Base load information comes from Special Load Readings 2019/20, which include 2019 Summer Valley load used in the Generation capacity preparation.
- Demand calculation incorporate demand contracts and offers up to 28th September 2020.
- Generation calculations incorporate generation contracts and offers up to 28th September 2020.
How often is the Network Capacity Map updated?
The Generation Map is updated once a quarter. The Demand Map is updated once a year.
Are the substation locations accurate?
HV substation locations are only indicative. The exact locations of MV/LV substation are provided.
How long does a connection take?
In general, where HV substation capacity is adequate, MV connections up to a maximum of 10MVA will entail construction of overhead line or new underground cable network, associated civil works and minor station works only and typically do not require
planning permission. These would not be expected to take longer than 6-9 months. However, any instances requiring significant station work such as the installation of a new transformer or MV switchgear will require increased time, and possibly planning
permission and would typically be expected to take approximately 2-3 years.
LV connections alone are usually completed within 6 months of application.
What other important points should be kept in mind about the data in the map?
- The map does not replace a full formal application in determining network capacity.
- The map does not provide capacity figures for the final connection from HV substation to customer premises. Such connections will need to tap into the existing MV (10kV or 20kV) network and capacity availability are subject to many variables and bespoke
assessment is necessary.
- In some cases, the available capacity shown in the Demand Map may already be contracted to individual customers but is not currently being fully utilised.
- The information provided in the Generation and Demand Maps does not guarantee the same capacity is available in the upstream DSO networks.
- Any increased load on the Distribution System will impact on the upstream Transmission System and reinforcements may be required on the Transmission System in order to cater for these loads. This will be separately assessed by the TSO.
- An individual connection cannot be greater than the capacity of an individual transformer. In the case of 38kV and MV, the available capacity shown is the total of all transformers in the substation at the respective voltage. Therefore,
full capacity utilisation may, sometimes, only be possible with more than one connection. (Note, a single premises cannot have more than one connection).