EOS COMPACT SUBSTATIONS 11KV AND 6.6KV

Transcription

1 Document Number: EOS Network(s): Summary: ENGINEERING OPERATING STANDARD EOS COMPACT SUBSTATIONS 11KV AND 6.6KV EPN, SPN This engineering standard details the use of 11kV and 6.6kV compact substations from 50kVA up to 315kVA. Owner: Kevin Burt Approved By: Steve Mockford Approved Date: 12/12/2014 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. Circulation UK Power Networks All UK Power Networks Asset Management Capital Programme Connections HSS&TT Network Operations UK Power Networks Services Other External G81 Website Contractors ICPs/IDNOs Meter Operators THIS IS AN UNCONTROLLED DOCUMENT, THE READER MUST CONFIRM ITS VALIDITY BEFORE USE

2 Revision Record Version 4.0 Review Date 12/12/2017 Date 09/12/2014 Author Paul Dyer Why has the document been updated Periodic review What has changed no content changes, references to CDL changed to Alfresco. Version 3.1 Review Date 03/09/2014 Date 10/09/2012 Author Lee Strachan Document reviewed for publishing on G81 site Version 3.0 Review Date 03/09/2014 Date 15/07/2011 Author Sinead Hogan Section 5 revised. Reclassified from an EI to an EOS Version 2.0 Review Date 03/09/2014 Date 31/05/2011 Author Sinead Hogan Section 4 revised Version 1.0 Review Date 03/09/2014 Date 18/03/2011 Author Sinead Hogan Original document replacing EI 4/1/2, EI 4/3/2 and EDM V13/S2/3ss3 UK Power Networks 2014 All rights reserved 2 of 17

3 Contents 1 Introduction Scope General Equipment Description Application Site Dimensions and Foundations Land Acquisition and Siting Foundations Installation and Operation of Compact Substations Cable Termination High Voltage Connections Low Voltage Connections Earthing HV and LV Earths Protection Substations up to and including 100kVA HV Fusing LV Fusing kVA and 315kVA Substations HV Fusing LV Fusing HV and LV Fuse Sizes Voltage Levels Substations up to and Including 100kVA kVA and 315kVA Substations Labelling Circuit Labelling Statutory Safety Notices and Equipment Labels External Danger of Death Safety Notice HV Labels LV Labels Earth Labels Identification Labels Appendix A Typical (up to 100kVA) Compact Substation Appendix B Typical (200kVA or 315kVA) Compact Substation UK Power Networks 2014 All rights reserved 3 of 17

4 1 Introduction This engineering standard details the use of 11kV and 6.6kV compact substations rated from 50kVA up to 315kVA. It provides details of the compact substations supplied by CG Power Systems (previously Pauwels Trafo Ltd). 2 Scope This document applies to all compact substations supplied by CG Power Systems. This includes the range of compact substations previously known as micro substations, padmounts and mini substations. 3 General Equipment Description Compact substations in UK Power Networks (UKPN) are ground mounted, self-contained, cable-connected prefabricated substations that do not include HV switchgear. Compact substations are provided for installation on sites where an 11kV or 6.6kV ground mounted transformer is required with a rating up to 315kVA and a ring main unit is not required. They are designed for direct tee-off connection to a high voltage underground circuit. They are supplied complete with an integral enclosure which requires no further enclosure or fence. There are no fastenings accessible from the outside. Access to both LV and HV compartments is via a door at the front of the unit. The LV compartment is on the left hand side and the HV compartment is on the right hand side. The door is secured by a padlock in a recess in the door. To remove the cover plate for the recess, use a feeder pillar key. To unlock units used only in the EPN area rotate the key anti-clockwise (standard unlocking). For SPN units rotate the key clockwise to unlock. The transformer tank is sealed with an air-space at the top to absorb pressure variations. A pressure relief valve is fitted in the transformer top which vents into the space below the enclosure roof. The compact substation range is split into two categories: Compact substations up to and including 100kVA, previously referred to as micro or padmount substations (See Appendix A which shows a typical compact substation). 200kVA and 315kVA compact substations previously referred to as mini or compact substations (See Appendix B which shows a typical compact substation). The main difference between the two categories of compact substations is the protection. Compact substations up to and including 100kVA contain a single set of low voltage fuses whereas the 200kVA and 315kVA compact substations include a three-way LV panel and Bay-O-Net fuses. Refer to Section 6 Protection for more details. The transformer sizes currently available including dimensions and weights can be found in UK Power Networks document EAS Distribution Transformers. They currently range in size from 50kVA single-phase up to 315kVA three-phase. Single-phase units are supplied as split-phase only. Where a 50kVA single phase supply is required, a 100kVA transformer shall be installed and connections made to a single-phase unit. The specification for compact substations can be found in UK Power Networks document EDS Compact Substations 11kV and 6.6kV. However, please note this specification is for the new supply contract and differs in parts to the existing compact substation. UK Power Networks 2014 All rights reserved 4 of 17

5 4 Application Compact substations will be used to provide new supplies and reinforce existing low voltage networks. They may also be used to replace existing free standing pole transformers when the transformer requires replacement. On an overhead network controlled by an Air Break Switch Disconnectors (ABSD) there is a maximum of 1.4MVA of transformer capacity that can be connected between switching points due to the inrush current limitations on these switches. 4.1 Site Dimensions and Foundations Land Acquisition and Siting Compact substations are to be positioned on the site such that there is a minimum of 1.0m clearance to the front of the substation for operational purposes and 0.5m clearance on the back and sides for maintenance and cooling Compact Substations up to and Including 100kVA The maximum foot print dimension of the compact substation up to and including 100kVA is 1.2m by 1.1m. In order to provide sufficient clearance for the operation and maintenance of the substation it is necessary to acquire rights over an area of land 2.2m by 2.6m kVA and 315kVA Compact Substations The maximum foot print dimension of the 200kVA and 315kVA compact substation is 1.8m by 1.3m. In order to provide sufficient clearance for the operation and maintenance of the substation it is necessary to acquire rights over an area of land 2.8m by 2.8m Foundations Details regarding the type and size of plinth to be constructed can be found in UK Power Networks document EDS Secondary Substation Civil Designs. If necessary path edging shall be installed externally around the cable entry area and the void beneath the HV and LV cable terminations shall be filled with a weak mix of sand and cement. UK Power Networks 2014 All rights reserved 5 of 17

6 5 Installation and Operation of Compact Substations Operation of the compact substation shall be in accordance with the UK Power Networks Distribution Safety Rules. Refer to the CG Power Systems Compact Substations IOM Manual located on the Alfresco Asset Management Engineering Library under the following path - Reference Library/Manufacturers/CG Power Systems. 5.1 Cable Termination Refer to UK Power Networks 11kV Jointing Manual and the LV Jointing Manual for details of cable preparation and termination. All cables must be brought in from the front of the site High Voltage Connections The high voltage connection is to be made using an 11kV, 95mm 2 three-core triplex cable terminated in the integral air insulated HV cable end box secured with screws. The high voltage cable shall be terminated using a standard heat shrink termination and reusable universal boot kit. This provides an easy disconnection of the HV cable for fault location or equipment replacement Single-Phase Substations Single-phase compact substations have led to an increase in the number of occasions where a single-phase high voltage underground network extension is required. This results in only two cores being used, leaving the third phase available for possible upgrade to a three-phase system. For 11kV and 6.6kV single-phase transformers provision is made within the cable end box for the connection of all three cable cores. Reference must be made to UK Power Networks document EDS Connection of Single-Phase Micro and Pad Mount Substations to 11/6.6kV Overhead Lines. Figure 1: Typical Arrangement of HV Cable End Box on Single-Phase Compact Substations UK Power Networks 2014 All rights reserved 6 of 17

7 5.1.2 Low Voltage Connections All compact substations will accept low voltage cable up to 300mm 2. The low voltage cable shall be terminated using a standard heat shrink termination with additional heat shrink material applied over the lugs and bolts after the lugs have been bolted to the LV stalk. All exposed parts shall be covered. On units up to 100kVA, the neutral shall be connected to the LV neutral/earth stud with a shear bolt lug mounted back to back with the earth cable lug. On 200kVA and 315kVA units the neutral shall be connected to the neutral bar of the LV panel. 5.2 Earthing Earthing shall be installed in accordance with UK Power Networks document EDS Earthing Standard. All parts of the cabinet are connected together using copper braid to ensure all parts of the cabinet are at the same potential. Figure 2: Earthing of Cabinet UK Power Networks 2014 All rights reserved 7 of 17

8 5.2.1 HV and LV Earths Combined earthing is preferred where the required conditions can be met. This is likely to be the case if there is an associated LV underground network with significant lengths of sheathed cable. Where the network consists of mainly overhead line or plastic sheathed underground cable, separate LV and HV earths shall be provided in accordance with the earthing manual Compact Substations up to and including 100kVA Compact substations up to and including 100kVA are supplied with the HV and LV earth connection separated. An LV neutral/earth connection and a separate HV earth busbar located in the LV compartment are provided. A label inside the LV door states Separate HV and LV earths (refer to Section 8 on labelling). The earths are separated since it is anticipated that it will not be possible to achieve the requirements for a combined earth at most rural sites. If a combined earth is possible the LV and HV earths can be joined with a length of 70mm 2 cable. If the earths are connected the warning label for separate earths must be removed. LV neutral/earth Connection HV Earth Busbar Figure 3: Earthing Arrangement on Compacts up to 100kVA UK Power Networks 2014 All rights reserved 8 of 17

9 kVA and 315kVA Compact Substations As standard the 200kVA and 315kVA compact substations are supplied with the HV and LV earth connections connected. To separate the HV and LV earth, it is necessary to disconnect the flexible earth lead between the LV panel neutral/earth bar and the HV steelwork earth. The LV earthing shall then be connected to the LV neutral/earth bar and the HV earth to the HV earthing connection (steelwork earth). If the earths are separated a warning label denoting that the HV and LV earths are separated shall be fitted inside the left-hand door. Figure 4: Flexible Earth Lead on 200kVA and 315kVA Compact Substations 6 Protection 6.1 Substations up to and including 100kVA HV Fusing The HV protection is provided by high voltage full range fuses fitted under oil in the transformer tank. The replacement of the high voltage fusing can only be carried out by qualified staff in a workshop environment following a full test of the transformer winding. If the fuses have operated, this may be detected by testing for continuity between the HV terminals. No attempt is to be made to investigate or replace a suspected blown fuse on site. A replacement compact substation is to be installed. The failed compact substation shall be returned to stores for investigation if it is less than five years old. UK Power Networks 2014 All rights reserved 9 of 17

10 6.1.2 LV Fusing Compact substations up to and including the 100kVA contain a single set of low voltage standard J type fuses for connection to a low voltage cable up to 300mm 2 Waveform. This takes the form of a 300A single pole heavy-duty cut-out on each phase of the transformer. The maximum fuse ratings are shown on a label in the LV compartment. These are designed to grade with the HV fuses. To avoid blowing the HV fuse due to the through passage of fault current the LV fusing is strictly limited to the maximum size indicated on the label. Similarly the use of Rezap is strictly limited to settings below the maximum LV fuse size indicated. There are no LV transformer links. For isolating the outgoing cables the fuses shall be removed. For isolating the neutral, the flexible connection from the bushing to the neutral busbar will need to be disconnected, either from the neutral connection stem or from the neutral bushing. The LV bushing cover will need to be removed to gain access kVA and 315kVA Substations HV Fusing 200kVA and 315kVA compact substations incorporate a two fuse protection system. The transformer is protected by a current limiting back up fuse and a Bay-O-Net current sensing fuse. This arrangement allows secondary faults and over-currents to be cleared by the Bay- O-Net fuse, and high level faults in the winding to be cleared by the current limiting fuse. The two fuses are connected in series, and are co-ordinated so that the current-limiting fuse operates only upon internal equipment failure, in which case both the current-limiting and the Bay-O-Net fuse will operate. The replacement of the Bay-O-Net fuse can be carried out on site in accordance with the Distribution Safety Rules. The Bay-O-Net fuses are situated behind a labelled metal cover and are accessible once the front doors are opened and the cover removed, as is shown in Figure 5. Note: Before the Bay-O-Net Fuse is unclipped and removed it is important to relieve any pressure built up in the transformer tank. This is achieved by gripping the dome of the pressure relief valve and gently pulling it towards you, air will be heard to escape. Failure to carry out this procedure may result in oil being discharged from the fuse holder. Figure 5: Bay-O-Net Fuses UK Power Networks 2014 All rights reserved 10 of 17

11 If the Bay-O-Net fuses are to be removed for a period greater than one hour then the fuse link shall be removed from the withdrawable fuse holder and stored in the HV cable box. The withdrawable fuse carriers shall then be repositioned in their holders. The replacement of the current limiting fuse can only be carried out by qualified staff in a workshop environment following a full test of the transformer winding. If fuses have operated, this may be detected by testing for continuity between the HV terminals. No attempt is to be made to investigate or replace a suspected blown current limiting fuse on site. If this situation arises then normally a replacement substation is to be installed. The failed compact substation shall be returned to stores for investigation if it is less than five years old LV Fusing 200kVA and 315kVA compact substations have an LV panel with up to three outgoing ways and a set of transformer links. To avoid blowing the HV fuse due to the through passage of fault current the LV fusing is strictly limited to the maximum size indicated in UK Power Networks document EDS Fuse Ratings at Distribution Substations. Similarly the use of Rezap is strictly limited to settings below the maximum LV fuse size indicated HV and LV Fuse Sizes For HV Bay-O-Net fuse ratings for compact substations refer to Appendix F of EDS For LV fuse ratings for compact substations refer to Appendix H of EDS Voltage Levels The compact substation is available with a nominal primary voltage of 11kV and 6.6kV. All transformers are equipped with a five position off load HV tap changer operating in the ranges of +5%, +2.5%, Nominal, -2.5%, and -5%. In order to change the tap when the transformer is in service, the incoming cable must be made dead, the HV cable box opened under a Permit to Work or a Sanction for Test, and the cable proved dead. To change the tap, the tap switch must be pulled outwards sharply, rotated to the correct tap position, and pushed in, checking that the guides on the switch correctly locate on either side of the position indicator tag. Operating instructions can be found on a label adjacent to the tap changer. 7.1 Substations up to and Including 100kVA A grip-handle tap change switch is located within the high voltage cable box. The tap position switch must not be locked. It cannot be interfered with since it is inside the HV cable box, and a lock would interfere with the HV insulation. UK Power Networks 2014 All rights reserved 11 of 17

12 kVA and 315kVA Substations The control for the tap changer is situated between the HV cable box and the LV fuse unit. This tap changer must be locked. 8 Labelling 8.1 Circuit Labelling The incoming and outgoing circuit distributor ways shall be labelled clearly. 8.2 Statutory Safety Notices and Equipment Labels External Danger of Death Safety Notice The compact substation is supplied with the Statutory Danger of Death Safety Notice and a standard identification label fitted to the outside of the right hand door. Drawings of these labels can be found in UK Power Networks document EDS Signs and Labels for Operational Sites HV Labels The safety label on the cover to the HV cable box reads DANGER OF DEATH LIVE HV CONDUCTORS BEHIND THIS PANEL SAFETY DOCUMENT REQUIRED FOR ACCESS. Figure 6: Safety Label on HV Cable Box A tap changer operation label is provided adjacent to the tap changer handle. UK Power Networks 2014 All rights reserved 12 of 17

13 8.2.3 LV Labels Above the LV fuse way on compact substations up to and including 100kVA a label is fitted stating: MAX. FUSE RATING A. ONLY USE REZAP TO RE-ENERGISE FAULTS. Figure 7: LV Fuse Label Earth Labels On compact substations up to and including 100kVA, the separate HV and LV earths are identified with labels. See Figure 3 for details. Also, as per Section 5.2, any warning labels denoting whether the HV and LV earths are combined or separated shall be fitted inside the left-hand door. These are supplied with the smaller compact substations up to 100kVA as the earths are supplied separated Identification Labels Figure 8: Separate Earth Label The rating plate and connections diagram are provided on the inside of the left hand door. There is also an identification plate on the outside above the door. UK Power Networks 2014 All rights reserved 13 of 17

14 Appendix A Typical (up to 100kVA) Compact Substation Figure 9: Outline Drawing for 100kVA Three Phase 11kV Design UK Power Networks 2014 All rights reserved 14 of 17

15 300A single pole heavy-duty cut-out LV Earth HV Earth HV Cable Box (shown open) Tapchanger within the HV cable box (shown open) Figure 10: Single/Split Phase Design ( V) Figure 11: External View UK Power Networks 2014 All rights reserved 15 of 17

16 Appendix B Typical (200kVA or 315kVA) Compact Substation Figure 12: Outline Drawing for 100kVA Three-phase 11kV Design UK Power Networks 2014 All rights reserved 16 of 17

17 Three Way LV Fuse Board Transformer Links Remove cable to separate HV and LV earths Tapchanger Bay-o-net Fuses HV Cable Box Pressure Relief Device Figure 13: 200kVA Compact Substation UK Power Networks 2014 All rights reserved 17 of 17