1、AN AMERICAN NATIONAL STANDARDNECA 410-2013 Standard forInstalling and Maintaining Liquid-Filled TransformersPublished byNational Electrical Contractors AssociationTMStandard forInstalling and MaintainingLiquid-Filled TransformersNECA 410-2013An AmericanNational StandardPublished byNational Electrica
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3、Standards transformer weights often exceed the capacity of forklifts, and transformer termination compartments and radiator fins are easily damaged. g) Use the manufacturer recommended points for lifting, jacking, and/or pulling transformers. Do not lift or drag by placing a loop or sling around tra
4、nsformers. Do not use radiator fins for lifting or jacking. Use all lifting lugs when lifting transformers. Lifting lugs or ears are designed for vertical strain only.h) Use jacking plates at the corners of the tank base plate to jack transformers. Transformers should be jacked evenly on all four co
5、rners to prevent warping or tipping over. Do not place jacks under radiator fins, termination compartments, drain valves, pipe connections, or other attachments.5 nStandard for Installing and Maintaining Liquid-Filled Transformers NECA 410i) Exercise care not to damage the tank base structure when h
6、andling transformers using skids or rollers. Use skids to distribute stresses over the tank base when using rollers under large transformers.3.3 Storage a) Store transformers in accordance with manufacturer recommendations.b) Transformers may be stored outdoors. If possible, store transformers at fi
7、nal installation locations on concrete pads. If dry concrete surfaces are not available, use pallets of adequate strength to protect transformers from direct contact with the ground. Ensure transformer is level.c) Ensure that the transformer storage location is clean and protected from severe condit
8、ions. Protect transformers from dirt, water, contamination, and physical damage. Do not store transformers in the presence of corrosive or explosive gases. Protect transformers from weather when stored for more than 3 months.d) Store transformers with compartment doors closed.e) Regularly inspect tr
9、ansformers while in storage and maintain documentation of storage conditions, noting any discrepancies or adverse conditions. Verify that an effective pressure seal is maintained using pressure gauges or the pressure relief valve. Visually check for insulating liquid leaks and rust spots.3.4 Pre-Ins
10、tallation Checks a) Complete the following checks at the end of the storage period. Contact the manufacturer for acceptable results and for recommendations for deficient test results.b) Draw liquid samples and test characteristics, such as dielectric strength, power factor, and water content, in acc
11、ordance with Section 10.2.c) Test insulation resistance and insulation power factor and compare to factory test data in accordance with Section 9.3 and 9.8.d) Consult the manufacturer for recommendations for deficient test results.n 61. Scope4.1 General Installation Requirements a) Observe safety pr
12、ocedures in accordance with 7.1. Verify that there is no voltage on the incoming cables.b) Locate and coordinate transformer installations in accordance with manufacturer instructions and specific transformer markings.c) Consult the manufacturer for high altitude applications. At altitudes above 100
13、,650 m (3300 ft), decreased air density reduces transformer cooling efficiency.d) Coordinate installation of raceways and conductors at locations designated by the transformer manufacturer.e) Follow applicable national codes and any applicable local codes or ordinances when locating transformers in
14、close proximity to public thoroughfares or buildings, considering that transformer insulating liquid may be flammable.f) Do not install transformers near heat-generating equipment or heat-sensitive equipment.g) Avoid opening transformer termination compartments during inclement weather conditions, u
15、nless the opening is completely protected from weather.h) Verify that site drainage is adequate to prevent groundwater from entering transformers.i) Install bollards, fences, barriers, etc., as required to protect transformers and transformer accessories from physical damage and vehicular traffic, i
16、f applicable.4.2 Transformer Pad and Mounting a) Installing transformer pads may require the evaluation of soil characteristics, concrete and reinforcement, and structural characteristics. Clay soils are compressive and may require stabilizing backfill to prevent transformers from settling. Consult
17、qualified personnel regarding soil characteristics, concrete and reinforcement, and structural requirements for transformers.b) Install flat, level concrete pads in accordance with contract drawings and specifications prior to setting transformers in place. Install transformers level and plumb. When
18、 no drawings or specifications are available, consult transformer manufacturer for recommendations. Ensure that pad surfaces are flat. Prevent transformers from tilting more than 1-1/2 degrees in any direction while energized to ensure that energized parts remain submerged in insulating liquid. Inst
19、all shims under frames or bases to level transformers, if necessary.c) When installed, footings for transformer pads should be below the frost line to prevent settling and heaving in areas where the ground is subject to freeze and thaw.d) Coordinate conduit locations with concrete pad construction f
20、or underground entry into conductor termination compartments of transformers.e) Install vibration isolators or neoprene pads between the transformer enclosure and the concrete pad in accordance with manufacturer recommendations, where required.f) Use anchors and bolts suitable for the conditions of
21、installation to anchor transformers to concrete pads. Hold-down cleats or brackets, when supplied, should be used to bolt transformers securely to 4. Installation7 nStandard for Installing and Maintaining Liquid-Filled Transformers NECA 410concrete pads. Transformers have a relatively high center of
22、 gravity. Consult qualified personnel regarding seismic restraint of transformers. g) Ensure that interfaces between concrete pads and transformers, including termination compartments, are sealed to prevent foreign objects, rodents, or vermin from entering termination compartments. To preserve trans
23、former tamper-resistance, there must be no gaps between the transformer and the pad.4.3 Grounding and Bonding a) Transformer grounding is necessary to dissipate static charge and to provide a low-impedance path to ground for fault current in the event that the transformer windings inadvertently cont
24、act the transformer core or enclosure.b) Connect transformer and related accessories and components to ground in accordance with manufacturer recommendations and in accordance with the National Electrical Code.c) Bond exposed non-current-carrying metal parts of transformer installations, including f
25、ences, guards, etc., to the system ground in accordance with the National Electrical Code and National Electrical Safety Code requirements.d) Ensure that there is a solid, low-resistance ground available. Install grounding electrodes for transformers in accordance with the National Electrical Code.e
26、) Ensure that factory-installed transformer grounding and bonding straps and conductors are properly connected.f) Terminate all grounding and bonding conductors on a common equipment grounding terminal on the transformer enclosure. Install supplemental terminal bars, lugs, and bonding jumpers as req
27、uired to accommodate the number of conductors for termination and in accordance with manufacturer recommendations.g) Bond the transformer grounded conductor or neutral connection, if so equipped, to ground. Coordinate the neutral-to-ground bonding location with service entrance equipment, switchboar
28、ds, panelboards, and on-site generation, where applicable. The low voltage neutral is typically an insulated bushing grounded to the tank by a removable ground strap. Wye-wye transformers typically have the high and low voltage neutrals internally tied with a removable strap that is brought out thro
29、ugh the low voltage neutral bushing.h) Tighten grounding connectors and terminals, including screws and bolts, according to the manufacturers published torque tightening values for equipment connectors.4.4 Lightning Arresters 4.4.1 Live-Front Transformers Install lightning arrestors in accordance wi
30、th manufacturer recommendations. 4.4.2 Dead-Front Transformers Dead-front transformers use elbow-type surge arrestors. Coordinate the configuration of the primary bushings on dead-front transformers to ensure adequate space for these surge arresters, where required. 4.4.3 Other Transformers Consult
31、the manufacturer when arresters are required on loop feed transformers or on transformers with 600-ampere, one-piece bushings. 4.5 Electrical Connections a) Complete transformer tank grounding and surge arrester connections prior to making any other electrical connections.b) Make connections and ope
32、rate transformers at voltages indicated by the diagrams and information on the transformer nameplate. Connect transformer neutrals to system neutrals.n 8NECA 410 Standard for Installing and Maintaining Liquid-Filled Transformersc) Install medium-voltage cables and terminations in accordance with NEC
33、A 600, Recommended Practice for Installing Medium-Voltage Cables.d) Observe National Electrical Code wire-bending space requirements within transformer termination compartments.e) Remove insulating and phase barriers as needed to install cables. Reinstall insulating and phase barriers after completi
34、ng cable installation.f) Transformer primary bushings will be either porcelain live-front bushings with exposed metal eyebolt terminals or molded dead front bushings for use with molded separable connectors.g) Install stress relief terminations on shielded cable installed on live-front transformers.
35、h) Separable insulated connector components for dead front installations may be universal bushing wells, integrated bushings, or bushing wells with inserts installed, and may be either load-break or non-load-break rated. All separable connector components must be clean and dry before connections are
36、 made. Follow manufacturers instructions for installing separable, insulated, high-voltage connectors. Leave the red protective plastic cap in place on transformers equipped with one-piece integrated bushings until separable connectors are installed.i) Install low voltage cables and listed lugs suit
37、able for the purpose in accordance with manufacturer recommendations. Secondary bushings are typically blade-type spade terminals with NEMA standard hole spacings arranged for vertical take-off. Provide manufacturer recommended cable lugs suitable for the cables and conductors installed and suitable
38、 for installation on low voltage transformer spade terminals. Lugs may be stacked or mounted on either face of the spade. Install manufacturer recommended hardware. Do not install washers between the cable terminal lug and the terminal spade that may increase connection impedance and heating, and ma
39、y increase the likelihood of connection failure. If required by contract drawings or specifications, make low voltage terminations to one or more appropriately-rated molded case circuit breakers mounted in the low voltage termination compartment of the transformer. j) Maintain air clearances between
40、 energized live parts and between live parts and ground for exposed connections in accordance with manufacturer recommendations and the latest ANSI standards.k) Bundle associated phase, neutral, and equipment grounding conductors together within the transformer enclosure. Install and arrange conduct
41、ors such that there is no mechanical stress or excessive strain on connections, bushing terminals or insulators that could cause loose connections or damage to the bushings or insulators. Allow adequate slack for expansion and contraction of conductors.l) Use a calibrated torque wrench to tighten el
42、ectrical connectors and terminals according to manufacturers published torque-tightening values. After applying proper torque, re-torque bolts after a period of several minutes.m) Seal connections with an electrical joint compound where recommended by the manufacturer.n) Insulate unused leads and co
43、nnections from other leads and connections. Install ground caps or insulating caps on unused terminals and bushing wells or inserts prior to energizing transformers to avoid contamination, partial discharge and damage. Do not energize transformers with shipping caps on the bushings or inserts.9 n1.
44、ScopeUse appropriate Personal Protective Equipment (PPE) in accordance with established safety procedures when working on or near energized electrical equipment. Before performing any cleaning, testing, or maintenance procedure, electrically isolate the transformer in accordance with established pro
45、cedures and in accordance with Section 7.1.5.1 Visual and Mechanical Inspection a) Perform specific inspections and tests as recommended by the transformer manufacturer.b) Compare the transformer nameplate with drawings and specifications. Verify the presence of surge arresters, if specified.c) Veri
46、fy the settings of tap changers, if so equipped, with transformer nameplates. Transformers are typically shipped with the tap changer connected for nominal nameplate voltage.d) Operate transformer switches in accordance with Section 7.8.e) Check tightness of all electrical connections using a calibr
47、ated torque wrench. Check the clearance of all electrical connections.f) Visually inspect transformers for physical damage. Repair physical damage, if practical, and provide suitable protective barriers to prevent future damage.g) Inspect accessible components for cleanliness, mechanical and electri
48、cal integrity, and damage or deterioration. Clean all dirt and foreign material from transformer primary bushings. Do not proceed with tests until deficiencies are corrected. Consult transformer manufacturer for recommendations. h) Visually check the transformer termination compartments, enclosure,
49、conduits, raceways, and conductors for proper grounding and bonding. See Section 4.3. Ensure that the transformer is permanently and effectively grounded before energizing transformers.5.2 Acceptance Testing a) Test transformers in accordance with transformer and test equipment manufacturer recommendations and maintain test results for future comparisons. Where the transformer manufacturer does not specify test procedures, follow the procedures described in Section 9.b) Sample and test transformer insulating liquid characteristics and dissolved gases in accordance with Sect
