{"id":11153,"date":"2026-08-30T18:09:52","date_gmt":"2026-08-30T10:09:52","guid":{"rendered":"https:\/\/q8bbzjnpm5.wpdns.site\/?p=11153"},"modified":"2026-08-30T18:12:16","modified_gmt":"2026-08-30T10:12:16","slug":"pole-which-carry-transformers-are-usually","status":"publish","type":"post","link":"https:\/\/subian-electric.com\/es\/blog\/pole-which-carry-transformers-are-usually\/","title":{"rendered":"Poste Que Transporta Transformadores Son Usualmente"},"content":{"rendered":"<p>When you drive down virtually any street in the U.S., chances are you will see pole-mounted transformers, either wooden or concrete. The pole supporting the transformer is not just an average pole. For one, there are requirements that determine the strength, height, and loading capabilities of the pole. This is due to the fact that in addition to supporting the distribution wires, a transformer which can weigh in the hundreds of pounds (along with cutouts, lightning arresters, and secondary wires) also rests on the pole. Utilities manufacture these poles in accordance with the National Electrical Safety Code (NESC) and ANSI standards, and when installing electric service, upgrading service, or installing pole-mounted transformers, utilities must be assured that not only does the pole meet the pole class, it has the necessary height and is not damaged.<\/p>\n<p>This publication covers which types of poles carry transformers, the various requirements and standards, the types of transformers used on poles, and what is required during installation and maintenance of the poles.<\/p>\n<blockquote><p>In summary, the transformers are installed on distribution poles, which are mostly made of wood. The steel, concrete, and fiberglass poles are utilized when very strong poles or very attractive poles are needed. The pole must be of a proper size for the load which consists of all conductors, transformers, and hardware according to NESC, there is a need for clearance: meaning the transformer and energized parts must have a distance from the ground; the standard utility pole is around 12 to 15 feet; the poles that are rated for different classes define the amount of load according to its class rating.<\/p><\/blockquote>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-11154\" src=\"https:\/\/subian-electric.com\/wp-content\/uploads\/2026\/08\/Pole-Which-Carry-Transformers-Are-Usually.webp\" alt=\"Poste Que Transporta Transformadores Son Usualmente\" width=\"1448\" height=\"1086\" \/><\/p>\n<h2>What Kind of Poles Carry Transformers?<\/h2>\n<p>A transformer is mounted on a distribution utility pole that also houses medium voltage distribution lines, generally in the range of 4-35 kilovolts (kV). Transmission poles have tall steel girders that house high-voltage electrical lines. The voltage will be reduced to utilization voltage on the distribution system in the poles that will hold the transformer and be done between the primary and secondary circuits.<\/p>\n<p>Three components are bolted to the pole surrounding the transformer. They form a single unit or assembly: the fuse cutout protects the transformer from faults that occur in the same circuit, the lightning arrester diverts excess energy caused by a lightning bolt to the ground, and the secondary wires carry stepped 120\/240V to your service after stepping down the voltage. The pole therefore serves as a complete distribution station in miniature, and everything was designed to work as one system.<\/p>\n<h2>Requirements: Strength, Class, and Height Standards<\/h2>\n<p>There are two standards that affect the pole side, and both have to do with how a transformer mounted to a pole will be specified:<\/p>\n<ul>\n<li>ANSI (American National Standards Institute) O5.1 \u2014 The wood pole standard specifies the dimensions, species, and treatment of a pole, assigning a class (Class 1-Class 7, with lower classes indicating smaller dimensional sizes) such that Class 1 poles are capable of carrying the most load at the top of the pole. This means that the categories of poles will receive the greater burden of weight.<\/li>\n<li>NESC (National Electric Safety Code) \u2014 The safety code specifying clearances and loading criteria. The distribution pole with the transformer receives its governing stipulations mainly through the clearance from the ground of the energized wires and components as they have to be above the minimum distance allotted above the ground (depending on the voltage \u2013 from approximately 15 to 22 ft in urban areas and 12 to 15 ft in rural areas).<\/li>\n<\/ul>\n<p>What does this mean for you?\u200c The pole that is used in mounting the transformer must be properly sized to handle the weight of the new transformer being added. If you have an existing pole and are going up from a 25 kva transformer to a 100 kva transformer, you must first check the class of the pole and determine whether or not it is still in good condition since the weight of the 100 kva transformer is up to 3 times that of the current transformer being used.<\/p>\n<p style=\"text-align: left;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-11155\" src=\"https:\/\/subian-electric.com\/wp-content\/uploads\/2026\/08\/Pole-Types-Compared-Wood-Concrete-Steel-Composite.webp\" alt=\"Pole Types Compared: Wood, Concrete, Steel, Composite\" width=\"1448\" height=\"1086\" \/><\/p>\n<h2>Pole Types Compared: Wood, Concrete, Steel, Composite<\/h2>\n<table>\n<thead>\n<tr>\n<th>Pole Type<\/th>\n<th>Uso T\u00edpico<\/th>\n<th>Transformer Carrying<\/th>\n<th>Notas<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Wood (treated pine\/fir, ANSI O5.1)<\/td>\n<td>Standard distribution, most utilities<\/td>\n<td>Common; class selected to load<\/td>\n<td>Lowest cost; needs inspection for decay; 30-50 year service life<\/td>\n<\/tr>\n<tr>\n<td>Concrete<\/td>\n<td>Coastal, high-wind, high-corrosion areas<\/td>\n<td>Excellent strength<\/td>\n<td>Heavier, pricier; long life; no decay<\/td>\n<\/tr>\n<tr>\n<td>Steel (tapered, galvanized)<\/td>\n<td>High-load urban, transmission-to-distribution<\/td>\n<td>High capacity<\/td>\n<td>Strong, long span; cost and grounding considerations<\/td>\n<\/tr>\n<tr>\n<td>Fiberglass composite (FRP)<\/td>\n<td>Aesthetic, coastal, utility demonstration projects<\/td>\n<td>Sufficient for small\/medium units<\/td>\n<td>Light, non-conductive, corrosion-proof; premium price<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Wooden poles are undoubtedly the preferred material as they are inexpensive, tried, and tested, and serve fully when appropriately classified and maintained. Concrete poles and steel ones are generally used when the requirement is specific to wind resistance, corrosiveness, or load; composite poles are suitable only when there is a specific need for aesthetics or insulation.<\/p>\n<h2>What Transformers Go on Poles?<\/h2>\n<p>A transformer on the power pole is generally a one-phase transformer that is installed on the pole, which is a type of distribution transformer that is immersed in oil.<\/p>\n<ul>\n<li>Typical sizes: 5, 10, 15, 25, 37.5, 50, 75, and 100 kilovolt Amperes, which is used to supply power to individuals in houses, small commercial establishments, on farms, and in residential areas.<\/li>\n<li>Voltage level: People commonly use a voltage level of 7.2 kilovolts, 12.47 kilovolts, 13.2 kilovolts, and 24.9 kilovolts, which is decreased to a 120\/240 volt, one-phase voltage level.<\/li>\n<li>Three-phase service can be used for commercial or industrial purposes. Three transformers can be installed on one pole with single-phase capabilities.<\/li>\n<li>Construction of the transformer: The transformer is constructed in such a way that it is filled with oil and has either a corrugated or a simple steel casing, low voltage and high voltage bushing, and coolers that fix the transformer to the cross arm or the pole.<\/li>\n<\/ul>\n<p>Buying a pole transformer means matching kVA to the load study, primary voltage to the line, and secondary voltage to the service \u2014 the full selection logic is in our <a href=\"\/es\/blog\/distribution-transformer-basics\/\">distribution transformer basics<\/a> article, which also explains how the pole class and transformer rating interact.<\/p>\n<h2>How Heavy Are Pole Transformers?<\/h2>\n<p>Weight is an important factor in determining the pole class and hardware needed to install a transformer. Some typical weights for single-phase pole-mounted oil-filled transformers are:<\/p>\n<table>\n<thead>\n<tr>\n<th>Rating (single-phase)<\/th>\n<th>Peso Total T\u00edpico<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>10 kVA<\/td>\n<td>~200-300 lbs (90-135 kg)<\/td>\n<\/tr>\n<tr>\n<td>25 kVA<\/td>\n<td>~300-500 lbs (135-225 kg)<\/td>\n<\/tr>\n<tr>\n<td>50 kVA<\/td>\n<td>~600-900 lbs (270-410 kg)<\/td>\n<\/tr>\n<tr>\n<td>75 kVA<\/td>\n<td>~800-1,100 lbs (360-500 kg)<\/td>\n<\/tr>\n<tr>\n<td>100 kVA<\/td>\n<td>~1,000-1,400 lbs (450-635 kg)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Exact figures vary with manufacturer, tank style, and winding material (copper adds weight) \u2014 our <a href=\"\/es\/blog\/pole-transformer-weight-guide\/\">pole transformer weight guide<\/a> lists representative weights by rating. If more than one transformer is needed, a three-phase bank of three transformers simply multiplies the above weights by three. These weights are the pole weights since the transformer is capable of supporting its own weight with the mounting hangers. Therefore, the pole and cross arm material must be rated accordingly. If you are considering an existing pole, be aware that the nameplate of the transformer does not always list the total weight of the pole; however, you can obtain this information from the manufacturer\u2019s data sheet or from the utility company since they routinely keep pole load calculations on file for future reference.<\/p>\n<p style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-11156\" src=\"https:\/\/subian-electric.com\/wp-content\/uploads\/2026\/08\/Installation-How-a-Transformer-Goes-Up-a-Pole.webp\" alt=\"Installation: How a Transformer Goes Up a Pole\" width=\"1448\" height=\"1086\" \/><\/p>\n<h2>Installation: How a Transformer Goes Up a Pole<\/h2>\n<p>Installing a pole transformer is considered to be a utility job. Since this work involves working at a high altitude while live wires are in close proximity, only trained line crews are allowed to perform it using cranes or bucket trucks and in either a hot or planned outage situation. Below is the abbreviated list of steps involved in this process:<\/p>\n<ul>\n<li>Checking the pole class and condition: The pole has to be in perfect condition. The pole has to be appropriate for the transformer loads; in case it is not, it is either replaced or reinforced first.<\/li>\n<li>Setting the hardware: Crossarm or transformer bracket, cutout and arrester mounting have to be attached at the proper height ensuring NESC clearances are maintained.<\/li>\n<li>Hoisting the transformer: The transformer is lifted by the crane or the bucket truck winch using its lifting lugs and is placed on the bracket. It is then secured using lock washers and mounting bolts.<\/li>\n<li>Making the connections: Primary leads connected to the cut-out (fused), arrester on the primary and ground, and secondary leads to service drop. All the grounds are bonded as per NESC.<\/li>\n<li>Testing and energizing: Insulation tests, ratio check, and phasing tests are done before the transformer fuse is closed for energizing.<\/li>\n<\/ul>\n<p>If you order a transformer to be installed by a utility or contractor, you must ensure that the same coordination is done: specify the unit, confirm the pole, and allow crew to do the energized work.Our <a href=\"\/es\/producto\/distribution-transformer\/\">distribution transformer product range<\/a> covers the units, with the pole-mount options and accessories listed per model.<\/p>\n<h2>Maintenance and Inspection Considerations<\/h2>\n<p>Once up, the pole-transformer assembly is a low-maintenance asset \u2014 but &#8220;low&#8221; is not &#8220;none.&#8221; The routine checks \u2014 which mirror the broader <a href=\"\/es\/blog\/transformer-maintenance-checklist\/\">lista de verificaci\u00f3n de mantenimiento de transformadores<\/a> scaled to pole duty:<\/p>\n<ul>\n<li>Oil levels and leaks should be checked visually by observing the tank, bushings, and ground, knowing that low oil due to leaks is one of the most frequent failures that can be avoided.<\/li>\n<li>Bushings and cutouts are inspected for porcelain cracking\/tracking, and checking ratings and conditions of the fuse link.<\/li>\n<li>Look at the lightning arresters for damage (blown arresters will have blown off the ground lead or color change).<\/li>\n<li>The condition of poles should also be checked for decayed, rotten wood; insect damage; or leaning.<\/li>\n<li>Tree growth and vegetation clearance will keep the trees away from primary leads and transformers to minimize flashover issues.<\/li>\n<li>Electrical testing will include high insulation and oil testing for critical pieces of equipment, which should be scheduled according to other oil-filled tests.<\/li>\n<\/ul>\n<p>Thermal imaging of the tank and connections in load ensures that loose connections and overloads are caught early, and investigate a transformer that has recurring cutout operations rather than just re-fusing it. The pole and transformer must be inspected at the same time because they fail together; the condition of the pole ultimately determines how long the transformer can operate safely.<\/p>\n<h2>Preguntas Frecuentes<\/h2>\n<h3>What is a transformer on a pole called?<\/h3>\n<p>A transformer mounted on a utility pole is known as a pole-mounted transformer or pole-top transformer (also termed as &#8220;pole pig&#8221; by professionals in the business). This transformer is a single-phase or three-phase transformer through oil maintained; it transforms the voltage of an electrical distribution line to the voltage used in homes of 120\/240V.<\/p>\n<h3>What are the poles that carry electricity called?<\/h3>\n<p>Utility poles or electric poles are also called distribution poles or telephone poles; the original name came from the idea that these poles were meant to transmit both telephone signals and electrical power. High-voltage transmission lines use transmission towers or transmission poles while utility poles distribute power at a low voltage.<\/p>\n<h3>How heavy is a transformer on a pole?<\/h3>\n<p>For a single-phase pole-top transformer, it weighs about 200 to about 1,400 lbs (90 to 635 kg) while depending on its capacity: for a transformer of 10 kVA, its weight is around 200-300 lbs, for 25 kVA it weighs 300-500 lbs, for 50 kVA it weighs 600-900 lbs, and for 100 kVA it weighs 1,000-1,400 lbs. A 3-phase transformer will weigh three times that amount. Hence, the pole should be classified in order to bear the weight of the transformer along with the load on the conductors.<\/p>\n<h3>Why are there transformers on power poles?<\/h3>\n<p>This is because the distribution lines carry about 7.2 to 24.9 kV of medium voltage power for effective transmission while the domestic and commercial usage of electricity is 120\/240V. The pole transformer brings down the voltage of medium voltage to the voltage as required at each site, which is much more economical than bringing down the supply to low voltage lines for a long distance.<\/p>\n<h2>Referencias<\/h2>\n<ul>\n<li><a href=\"https:\/\/www.ansi.org\/\" rel=\"nofollow noopener\" target=\"_blank\">ANSI O5.1 \u2014 Wood poles specifications and classes<\/a><\/li>\n<li><a href=\"https:\/\/www.ieee.org\/\" rel=\"nofollow noopener\" target=\"_blank\">IEEE \u2014 Distribution transformer standards (C57.12 series)<\/a><\/li>\n<li><a href=\"https:\/\/www.nfpa.org\/codes-and-standards\/nfpa-70\" rel=\"nofollow noopener\" target=\"_blank\">NFPA 70 \u2014 National Electrical Code (service and distribution)<\/a><\/li>\n<li><a href=\"https:\/\/www.osha.gov\/\" rel=\"nofollow noopener\" target=\"_blank\">OSHA 1910.269 \u2014 Seguridad en la generaci\u00f3n, transmisi\u00f3n y distribuci\u00f3n de energ\u00eda el\u00e9ctrica<\/a><\/li>\n<li><a href=\"https:\/\/www.energy.gov\/\" rel=\"nofollow noopener\" target=\"_blank\">US DOE \u2014 Distribution transformer efficiency standards<\/a><\/li>\n<\/ul>\n<h2>Conclusi\u00f3n<\/h2>\n<p>This is a pole specifically built to hold a transformer, and it has been designed properly and intentionally rather than as a remedial measure. The ANSI O5.1 wooden pole, concrete pole, steel pole, and composite pole have been manufactured to the proper height and dimensions in accordance to NESC loading regulations and clearance requirements. This pole carries a transformer mounted on the pole itself as well as the necessary cutout, arrester, and secondary wiring. The standard transformer is a dependable source of power; an immersed oil transformer that can either be one phase and have a capacity ranging between 5kVA and 100kVA or a three-phase distribution transformer mainly used for commercial purposes with a total weight anywhere between hundreds of pounds to a ton. Thus the class and condition of the pole will be determined before the pole is installed. When it comes to purchasing; upgrading, and maintaining the pole transformer, an appropriate checklist is followed, which: \u2014 presents the kVA level according to the loading study as well as the reduction in the voltage of the line.<\/p>","protected":false},"excerpt":{"rendered":"<p>When you drive down virtually any street in the U.S., chances are you will see pole-mounted transformers, either wooden or concrete. The pole supporting the transformer is not just an average pole. For one, there are requirements that determine the strength, height, and loading capabilities of the pole. This is due to the fact that [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":11154,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-11153","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"blocksy_meta":[],"acf":[],"_links":{"self":[{"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/posts\/11153","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/comments?post=11153"}],"version-history":[{"count":3,"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/posts\/11153\/revisions"}],"predecessor-version":[{"id":11195,"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/posts\/11153\/revisions\/11195"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/media\/11154"}],"wp:attachment":[{"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/media?parent=11153"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/categories?post=11153"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/subian-electric.com\/es\/wp-json\/wp\/v2\/tags?post=11153"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}