From OpenStreetMap Wiki
Jump to navigation Jump to search


This tag should also be used for a transformer feed trolleybus overhead contact line, shouldn't it? A trolleybus is not the rail transport, so current comment excluded it.

+1 Fanfouer (talk) 23:21, 26 April 2014 (UTC)
In principle no problems with that. But I believe that such contact lines are fed by dc which requires more than just a transformer. You probably need a power=substation + substation=traction for that. --polderrunner (talk) 07:20, 27 April 2014 (UTC)

phases=* when tagging transformer banks, (with 2 to 3 transformers)

While the phases=* tag applies to the number of phases the transformer converts, but I am not certain if that tag can apply to the number of transformers in a transformer bank, which is composed on two or three single-phase transformers, whether they are mounted on a pole, on a platform between poles, or on a substation? Three-phase transformers are usually a single transformer with three primary windings, or either three secondary windings (in the case of large transformers in substations) or four secondary windings (in the case of distribution transformers to provide three-phase electricity in a wye configuration, but in countries primarily using single-phase transformers, like the US, Canada, Japan, South Korea, and the Philippines, three-phase pole-mounted distribution transformers are rather three single-phase transformers forming a "transformer bank", that are used to provide wye configuration three-phase electricity with either a voltage of 120/208 V 60 Hz (US, Canada), 100/173 V 50/60 HZ (Japan, depending on region in that country), or 220/380 V (South Korea, Philippines); however, three-phase transformers in substations in those countries can be a single unit or three single-phase transformers. Also, two-phase transformer banks, composed of two single-phase transformers (one with two secondaries with center tap, and the another, that may be larger, with two secondaries, having one connected to one secondary of the other transformer, but without a center tap) exist, and are used to provide "high leg" delta power with voltages that can be 120/208/240 V, 100/200/173 V, or 220/380/440 volts, usually for larger users, usually larger businesses, for example, a bank, where three-phase is used for ATM's and single-phase is used for lights, air conditioning, and most appliances, or a fast-food restaurant, where three-phase is used for larger kitchen appliances, and single-phase for lights, air conditioning, and single-phase appliances.

Below is a table providing possible tagging for certai:

Description Image Tags
37.5 kVA three-phase pole-mounted transformer bank. Example pictured in Illinois, United States 37.5kVA three phase utility stepdown.jpg

power=pole transformer=distribution rating=* phases=3 voltage=[primary voltage];208

Two-phase pole-mounted transformer bank, used to provide "high leg" delta. Example pictured in Bulacan, Philippines. 0815jfCamias Poblacion Supermarket San Jose San Miguel Bulacan Bulacanfvf 10.jpg power=pole

transformer=distribution rating=rating (in kVA) of each transformer, separated by bars. Not necessary when transformers have the same rating operator=Meralco phases=2

Can phases=* be used to tag the number of transformers in a transformer banmk?--TagaSanPedroAko (talk) 15:24, 23 December 2016 (UTC)

I don't think so, because you won't be able to make the difference from 1 trafo with 3 phases and 3 trafo with 1 phase each.
It is important to keep phases=*, cables=* to one single feature.
The picture showing 3 different transformers at top of a pole should be mapped with 3 independent node with phases=1 on each around the node's node.
It may be the same with many radio antennas on a single support. Fanfouer (talk) 16:34, 23 December 2016 (UTC)
If transformers on a pole-mounted transformer bank should be mapped as three nodes, that wouldn't be a good idea, as it will mean unnecessary repetition of the feature. One possible idea is to map the transformers on one node along with the pole, then tag the phases and ratings of each transformer, separated by bars (|), so when tagging a three-phase pole mounted transformer bank composed of 50 kVA single-phase transformers, the tags would be phases=1 and rating=50 kVA. I tried to tag a three-phase transformer bank, composed of three 333 kVA single-phase transformers placed on a platform between two poles and serving an industrial customer, using three nodes, but seeing it as repetitive, I reduced it to one node.
But, a two-phase or three-phase transformer bank in a pole or platform will rather function as one transformer, instead of two or three transformers, as each single-phase transformer secondary there is connected to each other, so, considering two or three transformers in a pole as one transformer unit, they will be in one node, either along with the node for pole (in case of a pole-mounted transformer bank), or on a node between poles (in the case of a three-phase transformer bsnk in a platform between two poles), then tag each transformer with phases=2 or 3 and the rating of each transformer with rating=*, having the ratings (in kVA or MVA) of each transformer separated by bars (e.g. 37.5 kVA|37.5 kVA|37.5 kVA, for a three-phase transformer bank with three 37.5 kVA single-phase transformer, or 25 kVA|50 kVA for a two-phase transformer bank with one single-phase transformer rated 25 kVA and the other 50 kVA), however, for the case of a transformer bank in a substation, it may be based on the distance between the phase conductors in a bay connected to it, so, it can be mapped as one node, if each cable is too close to each other, like in a line with voltages below the approximate limit of 300 kV, or as three nodes, when the bays connected to the transformer bank are far enough, like in a 400 kV or 500 kV line.
I respect your opinion about mapping transformer banks, but, it is best to map transformer banks on a pole as one node (the same node as the pole); however, mapping a transformer bank in a substation should be considered in a case-by-case basis.--TagaSanPedroAko (talk) 18:30, 23 December 2016 (UTC)
Multivalues keys actually exists on OSM with ; separated lists. But these are not convenient to work with in automated processes.
We currently got the case with power=switch : several chambers can be electrically linked and operate as a single switch. It is recommended to map them with a single node.
No problem to do so with transformer banks as well, but they must share the same properties. If not, several nodes should be preferred as for ensuring data usability.
Which key do you propose to get the number of transformer in a consistent bank? Fanfouer (talk) 19:04, 23 December 2016 (UTC)
One possible solution is proposing this tag: transformer_bank=*, which will have the values two, for two single-phase transformers, and three.
But, I still have problems tagging a single-phase transformer with two bushings, which are prevalent in the provincial areas in the Philippines. These are called "phase-to-phase" transformers, which are used where a neutral is not used, like in long distribution lines, but these not always connect to another phase wire in the primary windings. See this images.
Power Transformer.jpg

240v transformer - - 1062014.jpg
The first image shows a phase-to-phase transformer in the United States. Notice the second bushing is not connected to another phase in the primary lines, but with the grounded/earthed side of the transformer. This will be have phases=1 instead of phases=2.
But for the second image, showing a phase-to-phase transformer in the United Kingdom, tagging is challenging, because the transformer is connected to two primary wires. While it serves as a single-phase transformer, the two primary wires will call for phases=2, but its function as a single-phase transformer will call for phases=1.
While the first example above can be easily tagged, because the second primary wire is connected to the grounded side of the transformer instead of another phase of the primary line, the second example, is however, confusing, because it is a single-phase transformer with two primary phase wires connected instead of one. I encountered phase-to-phase pole-mounted transformers in the Philippines, used to step down 34.5 kV or 13.8 kV into 220/440 volt split-phase power for residential and small commercial customers, and I tagged them with phases=2, like the tagging of two single-phase pole-mounted transformers forming a transformer bank and are used to provide 220/380/440 volt "high leg" delta service for commercial users. What will be the best tagging for a phase-to-phase transformer, which has two primary wires connected and two or three secondary wires, providing either split-phase (hot-neutral-hot) or single-phase (hot-neutral)?--TagaSanPedroAko (talk) 08:33, 24 December 2016 (UTC)


This type of transformer is used to measure current on high voltage substations or meters of large customers, either single-phase or three-phase. And I came up with this tag when those I mapped as SVCs have a connection to a box containing a meter and are actually transformers used for metering large customers with high current usage (200 amperes and above). Should the tag transformer=current be introduced, that such kind of transformer be mapped? TagaSanPedroAko (talk) 00:27, 7 April 2017 (UTC)

Rating in VA

Suggestion to write rating in VA (i.e. without "MVA") was raised only by one person in the proposal voting and was not accepted properly. I believe that it's far more important to make data easier to add by hands, than to make it (a very slightly) easier to process. Requiring rating to be in VA is error-prone and it's an unpleasant papercut for humans, also it makes tag to behave differently from the same tag for substations and we have a lot of existing data which uses MVA units, retaging them will require a lot of churn for very debatable profit. If we want symmetry with the voltage tag, we could instead allow use of kV units. So instead of voltage="110000;35000;10000" we'll be able to input voltage="110 kV; 35 kV; 10 kV". Thus I propose to revert rating description to the old one, which allows usage of MVA units. --Newpavlov (talk) 11:00, 26 July 2018 (UTC)

Rating in VA was kept in the proposal because it brings actual benefits in data consistency. Units in values are a complete mess. While you propose voltage="110 kV; 35 kV; 10 kV", I can also write voltage="110kV; 35KV;10 kiloV" without any restrictions or warning.
If we have to make editors check the units, then we'd better to adapt them to display units to users and allow them to eventually type "135 MVA" or "135MvoltAmpere" or whatever and store 135000000 in the db.
Units make visually equals values look not equal at all, we shouldn't store them Fanfouer (talk) 13:14, 26 July 2018 (UTC)
In which proposal was VA-only rating was introduced? If this change was done only based on the one comment without any proper discussion, then it should be reverted. And about what consistency are you talking about? We still have units based rating for substations and A LOT of existing data. "Mess" (which I haven't seen in regions of my mapping btw) about which you are talking can be easily solved by listing accepted units (with prefixes) and specifying that any other combinations must be considered invalid. And editors can add validation rules based on this specification. Regarding "not equal at all", almost always you have values which do not differ from each other more than on one order (so you'll use the same suffixes), and plain values have two serious problems: 1) you can't distinguish between different units, e.g. MW != MVA 2) they are error prone in regards to humans. For example can you tell at a quick glance without counting zeros what is 10000000? Is it 1 MVA, 10 MVA or 100 MVA? Even with voltage I sometimes use 11000 instead of 110000, and with VA it will be much much worse. Again, you have wrong priorities, you make data a tiny little bit easier process by machines, at the cost of making it harder for humans to input and verify this data. --Newpavlov (talk) 17:46, 26 July 2018 (UTC)
I completely agree with Newpavlov. I would even prefer voltages to allow kV too btw. M!dgard
Given issue is we can't write [rating>'135 MVA'] in Overpass API or any other query language on Earth. This is the mess I'm talking about. Human reading and editing is a special use case whatever we agree or not which need suitable tools and visualisations. That's why I'm not only promoting values without multiple units in OSM but to improve editors and tool chains as to enable humans to get displayed values with any multiple units they want.
The point is we agree on that 10000000000 isn't a convenient value to read, so are the most raw data stored in many databases. Then let's solve it by improving the display and not tag for the humans.
Why can't I replace all MVA values with GVA values arguing I personally find it more beautiful to read (editors won't warn, ban or eat me since both MVA and GVA may be accepted)?
My priorities are really bad so is my current planning, so let's not waste our time all of us Fanfouer (talk) 18:32, 26 July 2018 (UTC)
Ok, so no proper proposal process was held for this change? If yes, then I'll revert the change. We don't have a consensus here, and you can't impose your view on others just by editing wiki page. Otherwise it will be the true path to mess for OSM. --Newpavlov (talk) 18:39, 26 July 2018 (UTC)
If you think that revert is the most constructive solution, then feel free. You talk about proposal process like if it's an easy thing, so I may not have written enough of such proposals to say no.
Anyway your point on distinguishing MW and MVA isn't right here since rating has always been xVA only. Fanfouer (talk) 19:02, 26 July 2018 (UTC)
Revert is done. Regarding MW rating I was specifically referring to the power=substation. (btw we should probably explicitly allow VA rating for substations) I fully understand that proposal process is not an easy one, but it does not make a reason to introduce arbitrary changes to the existing tagging scheme. I was pointed to this change after tagging more than 100 substations, and lets say I was surprised then all my edits suddenly became outdated by a simple wiki edit. --Newpavlov (talk) 19:22, 26 July 2018 (UTC)
I don't see any reference to rating in VA on power=substation. Substations are technical sites while rating=* only refers to devices. Since substations can host several transformers of different ratings and operating at different voltages, there is no point tagging substation with a sum of ratings. 400MVA at 320 kV + 20 MVA at 110 kV doesn't mean you can transmit 420 MVA through the substation. Fanfouer (talk) 19:45, 26 July 2018 (UTC)

Question about references

Imagine a pole with a transformer. Both have its own reference number. How to tag this? And what if there are two switches also on the pole that have reference too? -- Kogutowicz Manó (talk) 14:41, 30 December 2021 (UTC)

This is clearly a limit of OSM tagging model, particularly when it comes to merge several physical objects on the same node. For sake of One_feature,_one_OSM_element, place each component on different nodes around the pole. Fanfouer (talk) 20:36, 30 December 2021 (UTC)
Why not simply do ref:pole and ref:transformer? Pretty common type of key when combining things. Gazer75 (talk) 20:53, 30 December 2021 (UTC)
Because they're hard to gather in processing. Consumers will have to look for ref, ref:pole, ref:whatever to be sure to get into every situation. Fanfouer (talk) 21:01, 30 December 2021 (UTC)
pole:ref=* (pole=* used in transit stops) and transformer:ref=* (transformer=* used here) are more hierarchical. Kovposch (talk) 10:30, 31 December 2021 (UTC)
It gets really complicated when there are multiple switches on the pole (like seen in Japan or Philippines). It's ok to combine features, not making a hierarchy on a single node. Fanfouer (talk) 13:55, 2 January 2022 (UTC)

Separate nodes for each object? surprised Let's have a look on the first three items at Tag:power=transformer#Distribution_transformers. They are combined nodes:


(BTW. this is quite funny on page Tag:power=transformer. smile) Even if it is the "official" I don't like this method because it does not describe the matter. It says: This is a pole. Well, incidentally it has a transformer too but never mind. It is the pole who has voltages, windings and other attributes. IMHO the main feature here is the transformer that is actually located on a pole:


-- Kogutowicz Manó (talk) 05:48, 31 December 2021 (UTC)

There is no main feature here. The pole is as important as the transformer. There is a combination of features with respective attributes that can undoubtedly mapped to each feature.
Despite it is a workaround, it allows concise mapping on a node for common situations. If things get a few more complex, we're quickly forced to separate OSM objects and here it comes for references. Fanfouer (talk) 13:55, 2 January 2022 (UTC)
Do you say that two references is so complex situation that it requires separate objects? Well. Let's think over it. How would you connect the power=pole, the power=transformer and some (potentially non-terminating) power=minor_line objects each to other? And how if we had a switch too? Could you provide some simple graph like this?
                     ------ 0.4 kV line
----P-------------P-------------P----- 22 kV line
                  | \
                  |  \
                  S   |
                  |  /
          primary | /  secondary
          side    T    side

-- Kogutowicz Manó (talk) 16:36, 2 January 2022 (UTC)

Yes it's a complex situation, because it forces to use less predictable namespaced keys like ref:transformer=* or ref:switch=*. Consumers will have to import them all, which lead to an actual mess. Solution is to use more specific and defined keys for them if they exist on the particular network you try to describe or to use different OSM objects as to keep on using ref=* everywhere.
Your graph is accurate, nothing to change on it, each P, S and T are OSM nodes and pipes are power=line/minor_line or cable sections. Fanfouer (talk) 22:47, 2 January 2022 (UTC)