Document Number: EDS 05-4001 Network(s): Summary: ENGINEERING DESIGN STANDARD EDS 05-4001 FUSE RATINGS AT DISTRIBUTION SUBSTATIONS EPN, LPN, SPN This design standard details the HV and LV fuse ratings to be used within distribution substations. Author: John Moutafidis Approver: Paul Williams Date: 11/08/2017 This document forms part of the Company s Integrated Business System and its requirements are mandatory throughout UK Power Networks. Departure from these requirements may only be taken with the written approval of the Director of Asset Management. If you have any queries about this document please contact the author or owner of the current issue. Applicable To UK Power Networks External Asset Management G81 Website Capital Programme UK Power Networks Services Connections Contractors Health & Safety ICPs/IDNOs Legal Meter Operators Network Operations Procurement Strategy & Regulation Technical Training THIS IS AN UNCONTROLLED DOCUMENT, THE READER MUST CONFIRM ITS VALIDITY BEFORE USE
Revision Record Version 8.1 Review Date 11/08/2022 Date 12/03/2018 Author John Moutafidis Reason for update: Minor version update What has changed: Note added to table on Appendix A Version 8.0 Review Date 11/08/2022 Date 04/08/2017 Author John Moutafidis Reason for update: Periodic review What has changed: Section 3.1 updated for glass barrel type and LPN interconnected network. Appendix B and C removed Version 7.0 Review Date 31/12/2016 Date 18/12/2013 Author Jesse Garcia Reviewed, commodity codes updated Version 6.0 Review Date Date 15/08/2010 Author Morgan Ryan Removal of requirement to change all three LV fuses when one or more fuses operate, and clarification of HV fuse replacement requirements. Clarification of clause K.2 in Appendix K Version 5.0 Review Date Date 30/10/2009 Author Morgan Ryan Add requirement to use WinDebut to check fuse operation along entire circuit when selecting a source fuse size. Version 4.0 Review Date Date 06/02/2008 Author Lionel Mackay Add HV fuse ratings for 1250kVA and 1500kVA HV customers. Corrected manufacturer s part number for 11404A Version 3.0 Review Date Date 11/04/2007 Author Lionel Mackay HV fuses, LV SAP codes added; corrected fuse rating in 3.1.2 Version 2.0 Review Date Date 20/11/2006 Author Craig Jeffrey Split table of LV fuse ratings into Ground Mounted and Pole Mounted applications Updated LV fuse ratings to allow for transformers protected by a switch-fuse Version 1.0 Review Date Date 08/11/2006 Author Craig Jeffrey Original UK Power Networks 2018 All rights reserved 2 of 16
Contents 1 Introduction... 4 2 Scope... 4 3 HV Fuses... 4 3.1 HV Time Fuse-Links (TLFs)... 5 3.1.1 Installation and Replacement of Tag-type TLFs... 5 3.1.2 Fuses for distribution substations with Air Circuit Breakers (ACB) including LPN LV interconnected network... 5 3.1.3 Replacement of Glass Barrel-type TLFs... 5 3.2 HV Fuses in Ground-Mounted Switchgear... 5 3.3 Fuses for Compact Substations... 5 3.4 HV Expulsion Type Fuses... 6 3.5 HV Fuse Replacement... 6 4 LV Fuses... 6 5 References... 6 5.1 UK Power Networks Standards... 6 Appendix A HV Protection: Tag-type TLF s: EPN and SPN Networks; LPN Radial Network... 7 Appendix B HV Protection: Glass Barrel-type TLF s: LPN Interconnected Network for replacement only... 8 Appendix C HV Fuse s for Switch-fuses... 9 Appendix D HV Fuse s for Fused End Boxes... 10 Appendix E HV Bay-O-Net Fuse s for Compact Substations... 11 Appendix F HV Expulsion Type Fuse s for Protection... 12 Appendix G LV Fuse s: Ground Mounted s... 13 Appendix H LV Fuse s: Pole Mounted s... 14 Appendix I LV Fuses: SAP Codes for UK Power Networks Use... 15 Appendix J Fault Clearance Requirements... 16 J.1 All Underground Networks except LPN Interconnected LV Network... 16 J.2 LPN LV Interconnected Network... 16 UK Power Networks 2018 All rights reserved 3 of 16
1 Introduction This document details the HV and LV fuse ratings to be used in UK Power Networks distribution substations. The fuse ratings for HV protection are common to all UK Power Networks distribution networks with the exception of the LPN LV interconnected network. The LV fuse ratings are common to all UK Power Networks distribution networks. Items in this standard relating to the replacement of existing fuses following faults or other operations relating to existing assets are intended for information and application by UK Power Networks staff or approved contractors working on their behalf. Where specific fuse manufactures types and reference numbers are used in this document these may be replaced with equivalent fuses of different manufacture provided that the replacement complies in all respects with the same specifications and standards including testing. Where SAP references are quoted in this standard they are for UK Power Networks internal use and relate to a stock control system. 2 Scope This standard applies to all HV and LV fuses within distribution substations owned or adopted by UK Power Networks on 6.6kV and 11kV distribution networks and shall be applied to all new and existing networks as follows: Where there are new installations or major alterations (such as switchgear or transformer replacement). In the event of fuse replacement after a fuse operation. 3 HV Fuses HV fuse sizes and characteristics have been chosen to make available the full cyclic rating of the transformer, whilst providing protection to the associated LV connections and busbars. See Appendix J for further information on the basis for the protection requirements. Ground mounted distribution transformers are protected by means of one of: HV circuit breakers equipped with time fuse-link (TLF) protection. HV switch-fuse. Fused End Box (FEB). HV expulsion fuse (when fed from overhead network). Pole mounted transformers may be protected by HV expulsion fuses when fed by cable from an underground network. For new installations with more than one transformer, there shall be separate HV protection for each transformer. HV fuses protecting a transformer must be replaced in complete sets. UK Power Networks 2018 All rights reserved 4 of 16
3.1 HV Time Fuse-Links (TLFs) TLFs for use on all new HV switchgear will be of the tag type only. 3.1.1 Installation and Replacement of Tag-type TLFs The fuse sizes for tag-type TLF protection, in association with a circuit breaker, for radial networks on the three areas are given in Appendix A. 3.1.2 Fuses for distribution substations with Air Circuit Breakers (ACB) including LPN LV interconnected network The fuse sizing instructions provided in Appendix A do not apply to distribution substations with Air Circuit Breakers due to additional protection provided in these Ring Main Units. The additional protection (usually Schneider Micrologic) reduces flexibility in discrimination between LV, Micrologic and HV. In order to achieve discrimination, it it is required to raise the rating of HV TLFs. For these kind of substations sizing shall be defined in EDS 05-2011 Air Circuit Breaker Protection Settings. At the moment of writing this document, EDS 05-2011 suggests 10A or 15A fuses depending on the size of transformer used and the LV load. Due to different possible scenarios it is beneficial to consult with a protection engineer, if maloperation is observed following the application of EDS 05-2011 values. The LPN LV interconnected network employs ACBs in all distribution substations due to the requirement for reverse power relays. Hence when sizing HV TLF for the LPN interconnected network, engineers shall consult EDS 05-2011. 3.1.3 Replacement of Glass Barrel-type TLFs Glass Barrel type TLFs have been discontinued from manufacturing, can no longer be used and the strategic spares depleted. Therefore tag-type will be used as replacement. The table in Appendix B provides sizing information for equipment still in the network for legacy reasons. 3.2 HV Fuses in Ground-Mounted Switchgear Details of the fuses to be used are given in: Appendix C HV Fuse s for Switch-fuses Appendix D - HV Fuse s for Fused End Boxes 3.3 Fuses for Compact Substations Compact substations rated at 100kVA and below are fitted with in-tank HV fuses. These cannot be replaced on site. In the event of a suspected fuse operation the substation must be replaced. Compact substations rated at 200kVA and 315kVA are fitted with in-tank HV backup fuses, and overload Bay-O-Net fuses. The Bay-O-Net fuses may be replaced on site, however, in the event of a suspected operation of the backup fuse the substation must be replaced. Details of the Bay-O-Net fuses for this equipment are given in Appendix E. UK Power Networks 2018 All rights reserved 5 of 16
3.4 HV Expulsion Type Fuses HV expulsion type fuses may be used for protecting transformers in the following situations: a) Pole mounted transformers which are cable connected, and fed from an otherwise underground network. b) Ground mounted transformers which are fed from an overhead network via not more than 250m of cable. The HV expulsion fuse ratings for these applications are shown in Appendix E. 3.5 HV Fuse Replacement Whenever one or more HV fuses protecting a circuit operate, all three fuses shall be replaced with new fuses at the same time. The old fuses shall be discarded regardless of whether they have operated or not (i.e. they shall be discarded whether they are electrically continuous or not). The old fuses shall be returned to the Stores at Maidstone or Bury St Edmunds for disposal. This applies whether the fuses incorporate explosive charges or not. 4 LV Fuses The LV fuse ratings specified within this standard apply to all UK Power Networks distribution networks. LV fuse sizes have been specified to align with LV cable ratings, whilst providing discrimination with HV fuses. LV fuses for use in substation fuse-boards, pillars, cabinets and pole mounted cut-outs must be selected in accordance with the nameplate rating of the feeding transformer and the outgoing conductor size of the circuit protected. UK Power Networks personnel involved in the selection of source fuse sizes shall use WinDebut to confirm fuse operation along the entire length of the mains circuit. Networks designed and installed by third parties for adoption by UK Power Networks must conform to this standard with appropriate calculations carried out using industry standard software. LV fuse ratings for ground mounted transformers are given in Appendix G. LV fuse ratings for pole mounted transformers are given in Appendix H. UK Power Networks SAP codes for LV fuses are given in Appendix I. 5 References 5.1 UK Power Networks Standards EDS 05-2011 Air Circuit Breaker Protection Settings UK Power Networks 2018 All rights reserved 6 of 16
Appendix A HV Protection: Tag-type TLF s: EPN and SPN Networks; LPN Radial Network Voltage CT Ratio TLF SAP Code Manufacturer / Type 6.6 kv 11 kv 200 kva 300/315 kva 500 kva 750/800 kva 1000 kva 200 kva 300/315 kva 500 kva 750/800 kva 1000 kva 40/5 12.5 A 11946S 50/5 10 A 11945H 80/5 7.5 A 11944X 50/5 12.5 A 11946S 80/5 12.5 A 11946S 100/5 10 A 11945H 80/5 15 A 11947C 100/5 12.5 A 11946S 80/5 15 A 11947C 100/5 12.5 A 11946S 15 A* 11947C 40/5 5 A 11943N 50/5 3 A 11942D 40/5 10 A 11945H 50/5 7.5 A 11944X 40/5 12.5 A 11946S 50/5 12.5 A 11946S 80/5 10 A 11945H 100/5 7.5 A 11944X 80/5 12.5 A 11946S 100/5 10 A 11945H 1250/1500/ 1600 kva 100/5 12.5A 11946S *Only for large LV supplies, where the transformer LV tail is less than 5m Note: The above table does not apply to distribution substations with Air Circuit Breakers (ACB). See Section 3.1.2 in this document for further info. When sizing HV TLF fuses for distribution substations with ACB, engineers shall consult EDS 05-2011. UK Power Networks 2018 All rights reserved 7 of 16
Appendix B HV Protection: Glass Barrel-type TLF s: LPN Interconnected Network for replacement only Voltage CT Ratio Glass TLF 6.6 kv 11 kv 500 kva 750/800 kva 1000 kva 2x500 kva 500 kva 750/800 kva 1000 kva 2x500 kva 2x750/800 kva 50/5 10 A 70/5 10 A 75/5 7.5 A 80/5 7.5 A 75/5 10 A 80/5 10 A 100/5 7.5 A 75/5 10 A 100/5 10 A 75/5 10 A 100/5 10 A 50/5 7.5 A 70/5 7.5 A 75/5 5 A 80/5 5 A 50/5 10 A 70/5 10 A 75/5 7.5 A 80/5 7.5 A 75/5 10 A 80/5 10 A 100/5 7.5 A 75/5 7.5 A 80/5 10 A 100/5 7.5 A 80/5 10 A 100/5 10 A UK Power Networks 2018 All rights reserved 8 of 16
Appendix C HV Fuse s for Switch-fuses (kva) System Voltage (kv) Cooper Bussmann Type Reference Air Fuses (EPN only) (A) SAP Code Maximum Overload 1 Cooper Bussmann Type Reference Oil Fuses (A) SAP Code Maximum Overload 100 11 - - - - 12OEFMA16 16 11387R - 200 11 12BDGHC20UKB 20 11390G - 12OEFMA25 25 11395F - 300/315 11 12BDGHC31.5UKB 31.5 11391R - 12OEFMA31.5 31.5 11396Q - 500 11 12BDGHC40UKB 40 11400L - 12OEFMA50 50 11397A - 750/800 11 12BFGHD56UKB 56 11401V 33% 12OEFMA63 63 11384M 45% 1000 11 12BFGHD63UKB 63 11402F 16% 12OHFMA71 71 11388B 31% 1250 3 11 12BFGHD80UKB 80 11403Q 17% 12OHGMA100 100 11389L 38% 1500 3 11 12BFGHD100UKB 100 11404A 16% 12OHGMA100 100 11389L 15% 100 6.6 - - - - 12OEFMA25 25 11395F - 200 6.6 12BDGHC31.5UKB 31.5 11391R - 12OEFMA31.5 31.5 11396Q - 300/315 6.6 12BDGHC45UKB 45 11392B - 12OEFMA50 50 11397A - 500 6.6 12BFGHD63UKB 63 11402F 40% 12OHFMA71 71 11388B - 750/800 6.6 12BFGHD80UKB 80 11403Q 10% 12OHGMA100 100 11389L 34% 1000 6.6 12BFGHD100UKB 100 11404A 4% 12OHGMA100 100 11389L 7% Notes: 1. Maximum overload ratings are shown where these are less than 50%. These ratings have been selected in order to achieve satisfactory LV fault clearance times. 2. In the event of a fuse operation, all three fuses must be replaced. 3. These ratings are only to be used for HV customers who are using transformers of these ratings prior to July 2007. UK Power Networks 2018 All rights reserved 9 of 16
Appendix D HV Fuse s for Fused End Boxes BS Fuses (SPN only) DIN fuses (EPN only) (kva) System Voltage (kv) Cooper Bussmann Type Reference (A) SAP Code Maximum Overload Cooper Bussmann Type Reference (A) SAP Code Maximum Overload 1 200 11 12FFGN4916 16 11951C - 12FDLNJ16 16 11436V - 300/315 11 12FFGN4925 25 11956B - 12FDLNJ25 25 11406U - 500 11 12FFGN4940 40 11957L 41% 12FFLNJ35.5 35.5 11437F 35% 750/800 11 12FFLNJ50 50 11438Q 5% 1000 11 12FFLNJ63 63 11408P 3% 200 6.6 12FFGN4925 25 11956B 43% 300/315 6.6 12FFGN4940 40 11957L 35% 500 6.6 12FFGN4950 50 11958V 3% Notes: 1. Maximum overload ratings are shown where these are less than 50%. These ratings have been selected in order to achieve satisfactory LV fault clearance times. 2. In the event of a fuse operation, all three fuses must be replaced. 3. There are no Fused End Boxes on the 6.6kV network in the EPN area. UK Power Networks 2018 All rights reserved 10 of 16
Appendix E HV Bay-O-Net Fuse s for Compact Substations (kva) System Voltage (kv) Type Reference (A) SAP Code Manufacturer / Type 200 11 C10 25 11848E 315 11 C10 25 11848E 200 6.6 C10 25 11848E 315 6.6 C10 25 11848E Notes: 1. In the event of the operation of a Bay-O-Net fuse, all three fuses must be replaced. UK Power Networks 2018 All rights reserved 11 of 16
Appendix F HV Expulsion Type Fuse s for Protection Type (kva) System Voltage (kv) Manufacturer/Type Reference (A) SAP Code 100 200 315 11 Cooper-Bussmann/15TU25 Lawson/FL8T25 25 2 11939N Pole mounted 1 100 6.6 Cooper-Bussmann/15TU25 Lawson/FL8T25 25 2 11939N 200 315 6.6 Cooper-Bussmann/15TU40 Lawson/FL8T40 40 2 11938D 200 315 500 11 Cooper-Bussmann/15TU40 Lawson/FL8T40 40 2 11938D Ground mounted 3 200 315 6.6 Cooper-Bussmann/15TU40 Lawson/FL8T40 40 2 11938D 500 6.6 Cooper-Bussmann/15TU65 Lawson/FL8T65 65 11940J Notes: 1. These ratings are for use with single HV and LV cable connected pole-mounted transformers forming part of an otherwise underground network. 2. Except for 315kVA and 500kVA transformers, it is not possible to achieve clearance times for LV terminal zone faults in accordance with Appendix J. 3. Fed from an overhead network. 4. In the event of a HV fuse operation, all three fuses must be replaced (for split phase 100kVA, both fuses must be replaced). UK Power Networks 2018 All rights reserved 12 of 16
Appendix G LV Fuse s: Ground Mounted s Cable Type and Size Ground Mounted (inc. Micros and Compacts) (kva) Imperial (in²) Metric (mm²) 50 3ph 50 2ph 50 single phase 100 3ph* 100 2ph* 200 300/ 315 500 750/ 800 1000 Stranded copper 0.0225 16 100 100 100 100 100 100 100 100 100 100 0.04 25 100 160 160 160 160 160 160 160 160 160 0.06 35 100 160 250 200 250 200 250 250 250 250 0.1 70 100 160 250 200 250 200 315 315 315 315 0.15 95 100 160 250 200 250 200 315 355 355 355 0.2 120 250 200 250 200 315 400 400 400 0.25 150 200 315 400 500 500 0.3 185 200 315 400 500 500 0.4 240 200 315 400 500 500 0.5 300 200 315 400 500 500 Stranded/ Waveform Aluminium 0.1 70 100 160 250 200 250 200 250 250 250 250 0.15 95 100 160 250 200 250 200 315 315 315 315 0.2 120 100 160 250 200 250 200 315 355 355 355 0.25 150 250 200 250 200 315 355 355 355 0.3 185 200 315 400 400 400 0.4 240 200 315 400 500 500 0.5 300 200 315 400 500 500 The conductor size referred to above is normally that of the first section of circuit from the substation. However, ensure that the fuse selected will operate for faults along the whole length of the circuit. Ground mounted transformers may have lower LV fuse ratings than the Pole Mounted equivalents due to the grading with the local HV protection. *For 100kVA transformers protected by a switch-fuse the maximum LV fuse size is limited to 160A in order to grade with the HV protection. For transformer tails less than 5m in length the maximum LV fuse size used may be 630A. UK Power Networks 2018 All rights reserved 13 of 16
Appendix H LV Fuse s: Pole Mounted s Conductor Type and Size Pole Mounted (kva) Imperial (in²) Stranded copper Metric (mm²) <16 25 2ph or 3ph 25 single phase 50 3ph 50 2ph 50 single phase 100 3ph 100 2ph 200/300/ 315 0.0225 16 100 100 100 100 100 100 100 100 100 0.04 25 100 100 160 100 160 160 160 160 160 0.06 35 100 100 160 100 160 250 200 250 250 0.1 70 100 100 160 100 160 250 200 250 315* 0.15 95 100 100 160 100 160 250 200 250 315* 0.2 120 160 250 200 250 315* 0.25 150 315* 0.3 185 315* 0.4 240 315* 0.5 300 315* Stranded aluminium 0.1 70 100 100 160 100 160 250 200 250 250 0.15 95 100 100 160 100 160 250 200 250 315* 0.2 120 100 100 160 100 160 250 200 250 315* 0.25 150 160 250 200 250 315* 0.3 185 315* 0.4 240 315* 0.5 300 315* ABC Stranded aluminium 35 100 100 160 100 160 160 160 160 160 50 100 100 160 100 160 160 160 160 160 70 100 100 160 100 160 200 200 200 200 95 100 100 160 100 160 250 200 250 250 120 100 100 160 100 160 250 200 250 315* The conductor size referred to above is normally that of the first section of circuit from the substation. However, ensure that the fuse selected will operate for faults along the whole length of the circuit. *This is the maximum rating of an LV fuse that can be fitted in a Pole Mounted fuse carrier without risk of overheating. UK Power Networks 2018 All rights reserved 14 of 16
Appendix I LV Fuses: SAP Codes for UK Power Networks Use Fuse Centre Fuse rating (A) 76mm 82mm 92mm Standard LPN Interconnected Network (silver element) Standard LPN Interconnected Network (silver element) 63 11443A 100 11440V 11926A 11931K 160 11441F 11927K 11932U 200 11442Q 11928U 11933E 250 11459S 11469B 315 11929E 11173D 1 11934P 355 11464C 11471G 400 11930A 1169D 11935Y 500 11473B 11179M 1 630 11180H 800 11182C Notes: 1. If fuses with silver elements are unavailable standard fuses of the same ratings may be used. UK Power Networks 2018 All rights reserved 15 of 16
Appendix J Fault Clearance Requirements The design of Pole Mounted LV fuse carriers reduces the likelihood that an LV phase-to-phase or phase-to-earth flashover will occur, and therefore overhead networks are exempt from the following: J.1 All Underground Networks except LPN Interconnected LV Network The HV fuse ratings chosen allow for a 1 second clearance of an LV busbar fault, for transformer tails up to 30m, whilst discriminating with the magnetic inrush of the transformer. Energy Networks Association TS 12-08 Application of Fuse-links (1986) Fuses must operate within 1 second for a three-phase fault in the LV terminal zone of the transformer. This is defined as being up to the busbar terminals on the LV fuse board. Fault current is determined by the HV fault level, transformer impedance, number of phases involved in the LV fault, impedance of any LV cables, and the arc voltage at the point of the fault. Fault current is calculated using an overall impedance of 5% based on transformer rating. A factor of 0.6 is then applied to allow for the effect of arc voltage, average source impedance, and where applicable, impedance of low voltage cables and connections. Phase-earth faults are excluded from this document based on the reasoning detailed within Energy Networks Assoication ACE report No 86 (1983). J.2 LPN LV Interconnected Network Due to the use of ACBs on the LPN LV interconnected network it is necessary that, for downstream discrimination, HV fuses allow up to 5 seconds for an LV busbar fault to be cleared. UK Power Networks 2018 All rights reserved 16 of 16