33KV or 33 kV? 10 MVAr or 10 Mvar? 33/110 kV or 110/33 kV? .... there is a RIGHT way!

© Copyright 2012 Rod Hughes Consulting Pty Ltd

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It has got to the point where “enough is enough” ….
Or should I say perhaps “not enough is not enough” …  it appears that some of our engineers are just not professional enough at least in terms of the somewhat minor details!

It may be that they have just not been told at the earliest part of their career ...

For quite some time I have been reviewing all sorts of (national and international) documents about various electrical matters (letters, specifications, drawings, reports, papers, presentations, visual advertisements (printed/tv), press releases,  …. )
I would say “90%” of those documents are not written correctly in regards to showing quantities and units, or references to Standards!!  (sad) (error)
Not very "professional".
Credibility of what you are trying to write can be severely undermined and or totally misunderstood.  
If you are seen NOT to use industry Standard terminology and units, it might be considered that you may have such cavalier disregard for other Standards that apply to your technical work.
Of course using correct terminology or units is not a guarantee that you are using other Standards correctly, but you don't want to get off on the "wrong foot".

I have often had to correct things like the examples below.

Note is it no longer correct to refer to consumer voltage levels as 240 V single phase and 415 V 3-phase supplies in certain countries.  Some years ago now, these changed phase‑to‑neutral to 230 V, and correspondingly phase‑to‑phase changed to 400 V.

As referenced in https://en.wikip edia.org/wiki/International_System_of_Units, the "thousands" multiplier is a capital letter with the exception of 1000 which is a lower case "k" so as not to to be confused with the temperature measurement in degrees Kelvin designated as "K" (e.g. "22 KV" makes no sense!)

To note there are decimal and binary prefix symbols, the binary ones having a lower case i added to the similar decimal prefix letter e.g. https://en.wikipedia.org/wiki/Megabyte
100 Mb =100 x 10^6 bits = 100,000,000 bits
100 Mib = 100 x 1024^2 bits = 104,857,600 bits   
.... with one anomaly - "numeric" values use lower case k for 1000 whilst "digital" values uses Ki (with capital K) for 1024. 

Quite often technical drawings from electrical single line diagrams to construction manufacturing drawings for labels will write all the text in capitals. 
A drawing or label on a piece of switchgear is no excuse not to follow international Standards.

When typing a unit as squared, cubed, degrees requiring sub/superscript and other symbols like ≥, use the appropriate symbol from the formatting tool bars rather than the number formatted as superscript - there is a difference when copy/pasting text for 300 m2 (superscript font) and 300 m² (symbol squared), or 75oC (superscript font) and 75°C (degrees symbol)  - try copy and paste this sentence as "plain text without formatting" and you will probably get that text as " 300 m2" vs "300 m²" and "75oC" and "75°C").

It is recommended to use the non-breaking space when typing these references so that the number and the quantity stay together on the same line: press Ctrl+Shift+Space. 
Non-breaking hyphens Ctrl+Shift+Hyphen are also useful for example IEC 61850‑7‑4 


11kV”, or worse “11KV” (Kelvin Volts??)



11 kV” .... lower case "k" AND with the space between the number and the units

400 V” or “0.4 kV”  

1500 A” or “1.5 kA

Under the ISO OSI rules (if you don't have a copy of those the easiest reference is https://en.wikipedia.org/wiki/International_System_of_Units), quantities should be referenced with a space between the numeric value and the quantity designation

Apparent power “25000000VA

25000000 V·A” or “25 MV·A” or "25000 kV·A"

Note the use of the "middle dot" symbol between the V and the A.
The "middle dot" is available as a symbol as Character Code 00B7 or shortcut key "Alt+0183" 

You could also use a plain space as the separator:

25000000 V A” or “25 MV A” or "25000 kV A"

Real power “10MW

"10 MW”  Note: Real power watts as upper-case W is a unit in its own right not just related to electricity (metric equivalent of horsepower) even though we have a mathematical derivation in electrical domain based on two Units and the cos of the angle.

Reactive power as either “VAR” or “VAr”   (one of my favourites)

var”   all lowercase  - refer IEC 8000-6 ... the principle is it is a mathematically derived unit with the derivation not directly related to only particular person(s), i.e. two Units and sin of the angle.

100 kB/s” (e.g. as speed of a communications port)

100 kb/s”  ... one hundred kiloBytes is 8 times bigger than 100 kilobits.

a bit is lower case b
a byte (8 bits) is upper case B

time as “20 mS” 

or “10 H” 

20 ms” (milliseconds)

10 h” (hours)

Capital "S" is for Siemens whereas as lower case "s" is for seconds e.g. speed m/s
Capital "H" is Henry, whereas lower case "h" is hour   e.g. MWh

references to Standards like “IEC61850


IEC 61850”,

AS 3000

Standards: these should always be referenced with a space between the organisation and the standard number

the infamous reference breaking space or hyphen across lines:

.blah bah .........  11


or blah blah ....... IEC 61850


But using non‑breaking space or hyphen

blah bah 11 kV,

blah blah IEC 61850‑7‑4

Transformer "400 kV / 132 kV / 11 kV"

Transformer "11 / 33 kV"

Transformer "33 kV / 400 V"

Current Transformer 1.5kA/1A"

Transformer "400/132/11 kV"

Transformer "33 / 11 kV"

Transformer "33 / 0.4 kV"

Current Transformer "1500/1 A

Ratio numbers such as for transformer voltage rating in highest to lowest rating order, all in same units

Power transformers always have the higher voltage first, even if it is a step-up transformer, i.e. "11/66 kV yn1D" should be "66/11 kV Dyn1".

IEC 60076-1:  Letter symbols for the different windings of a transformer are noted in descending order of rated voltage independently of the intended power flow.


https://en.wikipedia.org/wiki/Vector_group : In the IEC vector group code, each letter stands for one set of windings. The high-voltage (HV) winding is designated with an uppercase letter, followed by medium or low-voltage (LV) windings designated with a lowercase letter.

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