OVERHEAD DESIGN MANUAL

Transcription

1 OVERHEAD DESIGN MANUAL Section 4 Poletop Constructions Approved by: F ZAINI ENERGEX 2018 MANUAL 00302

2

3 CONSTRUCTION SELECTION General Notes 1. Constructions should be selected according to: spanning and angular limitations (refer layout guides in this manual or mainsdes application). suitability for local environment consider visual impact, vegetation, wildlife, pollution, reliability ease of construction and maintenance phasing 33kV Construction Vertical Delta Vertical Offset Application Preferred construction for new feeders. Suitable replacement for existing wishbone constructions, subject to spanning constraints. Suitable for replacement of other older construction types subject to adequate clearances from subcircuits. Refer note 4 Preferred construction for new feeders in narrow easements. Suitable for double circuit applications, either side of the pole combined with special crossarms. 2. Constructions that do not include timber cross-arms, eg vertical delta or trident, are preferred on new feeders. These generally have superior reliability and life in the field. 3. Flat and trident constructions are suited where pole height is limited or where the line presents a hazard to birds or bats. 4. On pole replacements, if the existing constructions are flat, it is preferred to use another same flat construction or trident on the new pole. This avoids conductor rolling to and from a vertical delta construction. If a continuous run of poles were to be replaced from shackle to shackle, then the vertical delta or trident constructions are preferred. 5. Insulated lines have superior reliability to bare mains and are especially suited to areas where vegetation is in the vicinity of the line, where there is significant wildlife, where lines may be contacted by boat masts etc. 6. Equipment subject to ongoing operational requirements (e.g. drop outs or EDO ), should be no more than 11m above ground level. LV Construction Application LVABC Preferred construction for new feeders. Can be parallelled to increase current rating of circuit. Open Wire Used for replacement of existing constructions. Suitable for industrial areas with high load currents. Suitable for rural applications where long spans are required, subject to absence of vegetation in vicinity of line. Trident Preferred replacement for existing 33kV flat constructions (subject to application constraints) where overhead earth wire does not exist. Double Circuit For limited use only. Use where 2 single circuit feeders cannot be accommodated in easements or other restricted space situations. Use overhead earth wire for entire length of all new 33kV feeders. 11kV Construction Trident 11A, 11P, and 11FP Vertical Delta Vertical Offset Application Shall be the 1 st choice for all new and replacement constructions subject to application constraints. Unsuitable for subcircuits. 11A shall be 1 st choice as subcircuit construction below 33kV subject to application constraints. Suitable for narrow corridors and easements. Rural better suited to longer spans than 11A and other flat constructions. Refer note 4 Preferred construction for new lines in narrow easements. Rural (greater phase separation for long spans) and Urban (compact) styles. Double Circuit For limited use only where short sections of double circuit construction are required. Same as 33kV application. 11ABC For use as an alternative to CCT and open wire where clearances would otherwise be inadequate A APP D CKD DATE APP D DATE REC D F. ZAINI 20/10/2015 POLETOP CONSTRUCTIONS SELECTION GUIDELINES Constructions & CCT ATHR ORIGINAL ISSUE COPYRIGHT 2015 ENERGEX This drawing must not be reproduced in part or whole without written permission from ENERGEX CKD AUTHR P. RELF K. GOSDEN WORD A4 SEC 4 SUB 2 SHT 1 REV A

4 A APP D CKD 11 KV CCT GUIDELINES For planning and design purposes, 120 sq mm CCT maximum continuous current rating is approx. 400 Amps at 80 deg C compared to Moon 7/4.75 AAC rated at 400 amps at 75 deg C. CCT has an emergency operating temperature (2hrs) at 100 deg C. Maximum allowable stringing tension is Table 220. Design Considerations for New Feeders and Reconductoring Old Feeders CCT is generally used in areas with trees or heavy vegetation to minimise reliability problems associated with wind blown branches, debris, or wildlife. When reconductoring, CCT cannot be used with existing pin or disc types of insulators because of voltage stress grading issues. Therefore, if no supercircuit exists (eg 33 kv above), all intermediate constructions shall be replaced with the expanded trident construction. This construction uses post insulators, and the crossarm has provision for mounting surge arresters. When reconductoring and a supercircuit exists, the first choice is to replace the construction with vertical delta. However, since most of these situations will be constrained by available pole space, the second choice will be to replace all intermediate constructions with an 11A. Refer drawing 7100-A4 for layout guides. Mounting brackets are available to mount surge arresters on this construction. Reconductoring with CCT will increase the pole tip loads, and designers must check existing poles to ensure they are capable of withstanding the increased loadings. Where the CCT loads exceed the tip load strength of existing poles, those poles shall be replaced with new poles of sufficient tip load strength. Where the feeder has previously been constructed using the older narrow based trident at intermediate structures, this construction may be retained for use with CCT only at structures where surge arresters will not be required. CCT shall not be installed at railway crossings. Surge Arrester Requirements Surge arresters are required to be installed on CCT feeders to protect against high voltage surges from lightning strikes. When CCT is installed in areas with trees, buildings, or heavy vegetation (closed areas), to provide adequate protection surge arresters are to be installed at or near the beginning and end of the conductor route and also at approximately 200 metre intervals and no more than 250 metre intervals. Where the CCT route passes through open areas (where there are no surrounding trees, buildings, or vegetation), surge arresters will be required at 100 metre intervals due to the increased risk of lightning strikes. The following alternative guidelines are also acceptable and may be more practical in some instances: DATE ATHR ORIGINAL ISSUE APP D DATE REC D COPYRIGHT 2015 ENERGEX CKD This drawing must not be reproduced in part or whole without written AUTHR permission from ENERGEX F. ZAINI 20/10/2015 P. RELF K. GOSDEN WORD 1. In closed areas, one set of surge arresters installed will protect the CCT for a distance up to 125 metres on either side of the arresters. HV surge arresters fitted to other pole mounted plant eg UG Cable Terminations, Load Break Switches, and PT Stations nearby the CCT route or along the CCT route will offer the same level of protection. The nearby feeder needs to be electrically connected to the CCT feeder without any normally open points and HV surge arresters need to be no further than 125 metres away. In open areas the protected distance is halved, so twice as many arresters are required. 2. Surge arresters cannot be fitted to flat shackle constructions due to the complexity of the bridging required. For this reason, although arresters would be preferred, they cannot be fitted in practice. Where there is a continuous run of shackle to shackle spans totaling 200 metres or more, refer the proposed design to Network Standards Department to assess surge arrester requirements and fitment options. CCT TYPES There are 2 types of CCT used in ENERGEX for 11kV mains alloy. This is the current type of CCT being supplied and can be used for 11kV bridging as well as 11kv mains. Drum length is 600 metres. The method used to terminate the cable is by the use of wedge clamps fitted directly to the wire conductors. The Compatible Unit (CU) is 11CCT alloy. This was the original type supplied by OLEX until the end of Due to the hard XLPE covering, this type of CCT was terminated by the use of a helical wrapon dead end applied over the outside of the cable insulation. POLETOP CONSTRUCTIONS SELECTION GUIDELINES A4 SEC 4 SUB 2 SHT 2 REV A

5 HVABC GUIDELINES There are two 11kV Aerial Bundled Conductor types available. 35 mm 2 will give a continuous current rating of 145 Amps and will be suitable for radial spurs. 120 mm 2 will give a continuous current rating of 300 Amps and will be suitable for feeder backbone. 11ABC cannot be strung any tighter than T ABC does not have exposed live parts and does not require safe approach distance except on terminations and joints where the earthed screen is broken out from the conductors. These joints and termination require a 700mm safe approach distance to live conductors 11ABC is light duty screened. As a result its application is limited to areas where the phase to ground fault current does not exceed 2.1 ka. Use 11ABC only if any of the following situations prevent the use of open wire or CCT: Where there is sensitive vegetation in the vicinity of the new feeder, and the clearing profile must be minimized. Where feeder clearances to objects such as buildings and awnings cannot be maintained using bare or CCT constructions. Where blowout of conductor needs to be minimized. Because of its weight 11ABC will have less midspan blowout than other conductors at the same stringing table and span length. Where an existing 11ABC feeder or 11ABC section of a feeder requires replacement or upgrading. (Replace 11ABC with 11ABC.) Where differences in conductor sags need to be minimized under hot/cold conditions. Because 11ABC has a catenary wire to support the conductor, there is little change in sag between hot and cold operating temperatures. New features that allow 11ABC to be used in areas where open wire and CCT is unsuitable: 11ABC can be used on feeders that require tee-offs. 11ABC can be used on feeders that require pole mounted plant to be installed. (Eg, transformers, regulators, remote controlled load break switches, load transfer switches, sectionalisers,& reclosers) Where the pole mounted plant requires an LV supply, (usually for remote controlled load break switches and reclosers), the LV supply should be from LVABC mains attached to the plant pole. If LV mains do not exist, a small PT will need to be installed nearby and LVABC mains run to the plant pole. With 11ABC installations, this method of LV supply to the plant equipment is preferable to using an 11kV voltage transformer, commonly used with the open wire or CCT feeder situation. Joints and Earthing 11ABC requires the catenary wire to be earthed at regular intervals at least every 300 metres. 11ABC has a screen wire that is required to be earthed at one end only for each cable run from joint to joint. 11ABC should have joints at no more than 300 metres apart. Dual Circuit Construction Dual 11ABC circuits on the same pole is to be avoided wherever possible. Engineering Standards to be consulted before proceeding with any dual circuit designs. To avoid safe approach distance issues designs should stagger the 11ABC joint and terminations by only having 1 leg of HVABC terminate or join on any one pole. Each 11ABC circuit when installed in a double circuit construction is to be identified by reflective and coloured tag at each pole. A DATE APP D F. ZAINI APP D DATE 20/10/2015 CKD REC D ATHR COPYRIGHT 2015 ENERGEX CKD P. RELF ORIGINAL ISSUE This drawing must not be reproduced in part or whole without written AUTHR K. GOSDEN permission from ENERGEX WORD POLETOP CONSTRUCTIONS SELECTION GUIDELINES A4 SEC 4 SUB 2 SHT 3 REV A

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28 HV INSULATOR SELECTION UP TO 33 kv Designers need to nominate insulator types for use on poletop constructions. In general, long rod synthetic insulators are preferred to normal disc insulators on strain or suspension constructions since they are light, inexpensive, and non-puncturable. Normal disc insulators may be shorter than synthetic insulators. This may be of importance in determining clearances from a suspension construction to subcircuits below. Normal disc insulators have a smaller surface creepage length than long rod synthetic insulators. Fog disc insulators have a very high surface creepage length and shall be used in areas of heavy salt pollution or industrial pollution. Heavy salt pollution areas are typically within 3km of the marine coast with continual direct exposure to salt spray i.e. no vegetation, landscape, buildings, and prevailing winds to block the salt spray from contaminating the surface of the insulators. Industrial pollution areas are typically sites or localities where there is a continual problem with dirt, dust, and smoke that can contaminate the surface of the insulators. Eg, mining sites and quarries. Pin insulators are unsuitable for use with 11kV covered conductor thick (CCT). Post type insulators must be used for this application. Post insulators are preferred over Pin insulators (subject to application constraints) for HV conductors All insulation in contact with CCA-treated poles, concrete poles or steel cross-arms (all of which must be considered conductive to some degree, especially when wet) must be either: Two part, eg 2 or more disks, OR Non-puncturable, eg porcelain post or long rod synthetic insulators. For additional information, Refer AS/NZS 7000:2010 Appendix P. B APP D CKD ATHR DATE 15/07/16 F. ZAINI P. RELF P. RELF POST INSULATORS NOTE ADDED APP D DATE REC D COPYRIGHT 2015 ENERGEX CKD This drawing must not be reproduced in part or whole without written AUTHR permission from ENERGEX F. ZAINI 20/10/2015 P. RELF K. GOSDEN WORD POLETOP CONSTRUCTIONS H.V. INSULATOR SELECTION GUIDELINES A4 SEC 4 SUB 13 SHT 1 REV B

29

30

31

32

33

34

35

36 APPLICATION GUIDELINES Voltage LV Overhead Horizontal (Flat) Construction N-A-B-C from the property to the road. HV A-B-C from left to right ** with HV bushings closest to observer. Overhead Vertical Construction N-A-B-C from top to bottom. Conductors roll as required (refer Sheet 2). ** This does not indicate source/substation phasing. Notes: Table: Standard Configuration of Conductors It is recommended (not mandatory): 1. Pole transformers are located so the neutral of the transformer is on the same side as the LV mains neutral. This will reduce the requirement to cross the transformer LV bridging. 2. Where cost effective and practical, pole transformers should be located in low speed streets that carry low traffic volumes. 3. Pole transformers and stays not be located on the same side of the pole (except for a termination where the transformer may be located on the same side as the stay). 4. Transformer phase transpositions be done on the HV. Phasing, Phase Rotation and Phasing Out are specialised areas. They are dealt with in detail in the following references: 1. Phasing Out Manual Operating Practices Manual, Section 2.10 Phasing Out. 2. Phasing and Phase Rotation Standard Substation Design Standards, Part 1, Section 5 Energex Phasing Standard. In rural/bush situations (i.e. where a property/road reference is not available), select best possible phase configuration by: 1. attempting to conform with the above 2. agreement between designer and commissioning crew. Designers need only refer to the above Table to complete Works Plans. A APP D CKD DATE APP D DATE REC D F. ZAINI 20/10/2015 POLETOP CONSTRUCTIONS PHASING APPLICATION GUIDELINES ATHR ORIGINAL ISSUE COPYRIGHT 2015 ENERGEX This drawing must not be reproduced in part or whole without written permission from ENERGEX CKD AUTHR P. RELF K. GOSDEN WORD A4 SEC 4 SUB 17 SHT 1 REV A

37

38 APPLICATION GUIDELINES Ideal application is a single circuit pole with no other plant / switches located on the pole. Other pole configurations may be used provided care is exercised. 1. SITE SELECTION Select the cleanest possible pole. Do not use on poles with concentrated sources of magnetic fields such as transformers, underground cables, magnetically operated switches etc. At `tees' mount the indicator a span away from the junction, on the load side. Do not use on Tee-off poles. LINE VOLTAGE SEPARATION LINE VOLTAGE SEPARATION 11kV 25m 66kV 100m 22kV 35m 132kV 200m 33kV 50m kV 500m For other voltages distances are proportional to voltage. 2. POLE LOCATION For combined HV/LV circuits mount as indicated below: on the sunniest side of pole with the solar panel pointing in the same direction as the HV conductors directly above. between 1.2 (preferred provided safe working limits are maintained) and 3.5 metres below the lowest HV conductor. Do Not use indicators in the following instances: 1 phase lines, 3 phase lines or 2 wire lines that are fused or protected by single pole reclosers. (as remaining live conductors will prevent triggering) 4 wire HV systems with MEN (Multiple Earthed Neutral). The indicator should be kept the following distances from nearby lines that may remain energised after a fault: A APP D DATE APP D DATE F. ZAINI 20/10/2015 POLETOP CONSTRUCTIONS LINE FAULT INDICATORS CKD REC D ATHR ORIGINAL ISSUE COPYRIGHT 2015 ENERGEX This drawing must not be reproduced in part or whole without written permission from ENERGEX CKD AUTHR P. RELF K. GOSDEN WORD A4 SEC 4 SUB 18 SHT 1 REV A

39 APPLICATION GUIDELINES These guidelines are for LV supply to all: Pole Mounted Reclosers (PMR) Load Transfer Switches (LTS) and Sectionalisers. LV supply is required at these sites to charge the DC batteries used to provide supply for the control circuitry in these devices. In general supply is to be made available from a 11kV / 28V voltage transformer. However, if necessary LV can be supplied directly from LV mains in CMEN locations, or from LV mains via a 240V / 240V 15kV isolation transformer in new non-cmen locations. DSA schemes involve the remote control of: Regulators Pole Mounted Reclosers (PMR) Load Transfer Switches (LTS) and Sectionalisers. In all cases contact: References: Design Group Secondary Systems Team. Overhead Construction Manual, 4920-A4, Section 2, p20 and Section 7. Distribution System Automation (DSA) Schemes A APP D CKD DATE APP D DATE REC D F. ZAINI 20/10/2015 POLETOP CONSTRUCTIONS PMR, LOAD TRANSFER SWITCH & SECTIONALISER - LV SUPPLY ATHR ORIGINAL ISSUE COPYRIGHT 2015 ENERGEX This drawing must not be reproduced in part or whole without written permission from ENERGEX CKD AUTHR P. RELF K. GOSDEN WORD A4 SEC 4 SUB 19 SHT 1 REV A

40 ENGINEERING BACKGROUND LAYOUT GUIDES The Layout Guides indicate practical maximum (sometimes minimum) values of span length, and line deviation angle allowable for each construction, conductor type and stringing table combination. These limits are based on several underlying factors: The effect of these factors on span/angle capability Uncontrolled of a poletop Document construction When is Printed illustrated in the graph below. Note that it may be possible to exceed the stated maximum span slightly provided that the deviation angle is very small. Likewise it may be possible to exceed the stated maximum deviation angle slightly provided that the span length is less than the stated maximum. 1. Conductor mid-span clashing. The probability of mid-span conductor clashing increases as conductor sag increases, which in turn increases with span length. Increasing separation between phase conductors at supports reduces the probability of clashing. In general, to avoid clashing between conductors, the following condition must be met: (X 2 + Y 2 ) U / (D + l i ) where: X is the horizontal distance between the conductors at mid-span (m) Y is the vertical distance between the conductors at mid-span (m) U is the rms difference in potential between the two conductors (kv) D is the greater of the two conductor sags (m) No Wind, 50C l i is the length of any freely swinging suspension insulator with either conductor (m) 2. Strength of insulator assemblies, conductor ties, kingbolt, crossarms and other fittings. The forces on these elements increase with span length and line deviation angle. 3. Clearances of conductors and insulator discs from pole and cross-arms. This problem is illustrated in the diagram below. With certain deviation angles there may be inadequate spacing between these elements to maintain effective insulation. For angle constructions where disk insulators are fitted to a pole, eg 33TA, a minimum deviation angle may be specified as well as a maximum. clearance problem when deviation angle is too great Refer AS/NZS 7000:2010 Appendix Q for further details. Notice that for constructions such as 11P and 11SU maximum span lengths are greater if the centre phase is staggered, ie attached to alternate sides of the pole on alternate poles. Designers wishing to take advantage of this extended spanning should indicate that staggered construction is to be use on the works plan. For spans with different construction types at either end, the span length should not exceed the lesser of the two spanning limitations. When changing from flat to vertical construction, the maximum span length should be reduced by a further 30%. Where mid-span spacers are installed (normally as a remedial measure on an existing span), these effectively act as a support structure in terms of preventing midspan clashing. A APP D CKD DATE APP D F. ZAINI 20/10/2015 POLETOP CONSTRUCTIONS ENGINEERING BACKGROUND LAYOUT GUIDES ATHR ORIGINAL ISSUE DATE REC D COPYRIGHT 2015 ENERGEX CKD This drawing must not be reproduced in part or whole without written AUTHR permission from ENERGEX P. RELF K. GOSDEN WORD A4 SEC 4 SUB 20 SHT 1 REV A