SPD LTDS Appendix 4 Fault Levels (Table 4)

The "SPD LTDS Appendix 4 Fault Levels (Table 4)" dataset provides Plant Fault Levels for the distribution system as at the data freeze date. For ease of reference, the tables are displayed by voltage level. Voltage levels include 33kV, 22kV, 11kV and 6.6kV. Short circuit current are expressed in kA and have been calculated for three phase faults under maximum plant conditions. The fault levels contained within the following table have been calculated in accordance with engineering Recommendation G74, "Procedure to Meet the Requirements of IEC 909 for the Calculation of Short-Circuit Currents - Three-Phase A.C. Power Systems, 1992". Fault infeed from general loads is considered as described in section 9.5 of Engineering Recommendation G74. Similarly, in accordance with G74, the fault infeed from a load connected at 11kV or below is adjusted to give an infeed of 1MVA per MVA of winter demand at the 33kV grid supply point busbar from which it is fed. In the SPD network, this equates to an average load infeed of 1.07MVA per load MVA for local fault. The X/R ration of the equivalent load infeed is not adjusted and a value of 2.76MVA is assumed. The system impedance parameters (R + jX) are determined from the positive sequence network used for calculation of the sub-transient fault current. The peak make current is calculated as described in section 5.2.3 of Engineering Recommendation G74. Note that the equivalent X/R ratio is calculated according to method c) as described in IEC60909-0, section 4.3.1.3. The equivalent X/R ratio used in the peak make current calculation is therefore generally greater than the ration of reactance to resistance of the system impedance given in the fault level tables. It is assumed that the A.C. fault current decays from sub-transient to transient level with a time constant of 40ms. For system voltages of 33kV and below, the RMS breaking current is calculated at 90ms after fault inception. The table indicates those locations where the predicted fault level is equal to or greater than 95%. Where, under credible scenarios, plant capability may be in excess of the design limit detailed in Section 2.4.3 (Substation Fault Levels), system fault levels will always be constrained within the relevant design limit. Where fault levels above the plant capability are possible, operational procedures (based on a detailed risk assessment) are established to maintain the situation, pending the implementation of a substantive solution, such as the installation of new plant, or a fault current limiting reactor. Click [here] to access our full Long Term Development Statements for both SP Distribution (SPD) & SP Manweb (SPM). For additional information on column definitions, please click on the Dataset schema link below. Note: A fully formatted copy of this appendix can be downloaded from the Export tab under Alternative exports. ### Disclaimer Whilst all reasonable care has been taken in the preparation of this data, SP Energy Networks does not accept any responsibility or liability for the accuracy or completeness of this data, and is not liable for any loss that may be attributed to the use of this data. For the avoidance of doubt, this data should not be used for safety critical purposes without the use of appropriate safety checks and services e.g. LineSearchBeforeUDig etc. Please raise any potential issues with the data which you have received via the feedback form available at the Feedback tab above (must be logged in to see this). If you wish to provide feedback at a dataset or row level, please click on the “Feedback” tab above. ### Data Triage As part of our commitment to enhancing the transparency, and accessibility of the data we share, we publish the results of our Data Triage process. Our Data Triage documentation includes our Risk Assessments; detailing any controls we have implemented to prevent exposure of sensitive information. Click [here]to access the Data Triage documentation for the Long Term Development Statement dataset. To access our full suite of Data Triage documentation, visit [the SP Energy Networks Data & Information page]. [Download dataset metadata (JSON)]