User:Dmitry G/gallery/Electricity/Designing paradise

Here you can find typical industrial designing of electrical installations.

Little theory[edit]

While designing you must consider the worst conditions
All circuits, which lenght exceeds 3 meters must be protected by fuse or circuit breaker
All risky circuits (like wet rooms or available altitude) must be protected by RCD or GFCI
All bared metal parts on available altitude must be grounded to main earthing busbar

Fire safety[edit]

Circuit breakers[edit]

Trips, when load exceed 1.45 x I(n) after 2 hours
Trips immediately (0.02 seconds), when load exceed 3 or 5 or 10 or 12(14) or 20(50) x I(n), according to letter before amperage
- A or Z - 3 x I(n)
- B - 5 x I(n)
- C - 10 x I(n)
- K - 12 x I(n) in Europe and 14 x I(n) in Russia
- D - 20 x I(n) in Europe and 50 x I(n) in Russia

K-type circuit breakers trip very slowly to supply transients for cranes or elevators, where they are commonly used. But usually I use K-breakers for selectivity. In West-Europe you can find E circuit breaker as selective, but they are not widespread in East Europe.

Advantages[edit]

You can use them lot of times after short-circuit
Very easy way to install
Very easy to calculate, even secondary-school students understand explanations

Disadvantages[edit]

Sometimes (especially when their age exceeds 20 years) mechanism begin to jam and breaker still feed circuit even if short-circuit happens. This way fire is question of time. That is why I've replaced old circuit breakers in my panel despite neigbours still wait fire.

Fuses[edit]

If everything is clear with circuit breakers, fuses have more difficult time-current plot. To have exact result, you need to calculate some integrals. Short circuit current for fuses is regulated only to overhead powerlines - short circuit should be 3 x I(n) in the end of powerline or fuses should burn in 15 seconds after begining short circuit.

Row from slow to qucick-acting[edit]

Slow:

aTr - the slowest, burning time for 1.3 x I(n) is 10 hours
gTr
aM - widespread in motor circuits, Soviet analogue ПН-2 ("Knife Fuse - 2")

Medium:

gM
gG (gL) - widespread in living houses, Soviet analogue ППН-2 ("Knife Fuse Melting - 2")
aS - Soviet analogue ПРС ("Fuse Distributing for AC Grid")

Quick:

gS
aR
gR - ultra rapid

Advantages[edit]

No broken mechanisms, construction is very reliable
Easy selectivity

Disadvantages[edit]

You can use them only 1 time
Construction allow to use metal wire if fuse is blown
Construction of knife fuses is very danger due to arc
Soviet fuses were arcing often due construction lacks in catridge, lot of homeowners scared to replace them
Not easy to calculate

Cable resistance to 1 kilometer with frequency 50Hz[edit]

Copper[edit]

0.5mm² - 87.2Ω
0.75mm² - 58.13Ω
1.0mm² - 43.6Ω
1.5mm² - 28.98Ω
2.5mm² - 17.37Ω
4mm² - 10.9Ω
6mm² - 7.26Ω
10mm² - 4.36Ω
16mm² - 2.725Ω
25mm² - 1.744Ω
35mm² - 1.25Ω
50mm² - 0.872Ω
70mm² - 0.623Ω
90mm² - 0.485Ω
120mm² - 0.365Ω
180mm² - 0.243Ω
240mm² - 0.182Ω

Aluminium[edit]

NB! Aluminium up to 16mm² is not allowed!

16mm² - 3.75Ω
25mm² - 2.44Ω
35mm² - 1.7143Ω
50mm² - 1.2Ω
70mm² - 0.86Ω
90mm² - 0.67Ω
120mm² - 0.5Ω
180mm² - 0.34Ω
240mm² - 0.25Ω

Well, I think, you guess how to calculate short-circuit. Everything is calculated for you, you need only to apply Ohm's law from school.

Short circuit[edit]

One of important idea of installation designing is supply quick disenergizing during failure. To do it, you should know exact short-circuit current and match it with circuit breaker or fuse charateristics. But lot of times I saw problem, when designers made copy-paste from IEC 60364 without any calculating.

What is the problem: after long disputes, we hadn't come to a common denominator:

1) old designers saying, that voltage drop is more important and they use wire gauges from standart IEC 60364;
2) I put their attention to economical question - lot of Soviet tower blocks have 10mm² aluminium wires (which are not allowed nowadays), but public services can't provide money for overfat wiring; as result they still use forbidden 10mm² aluminium wiring even after rewiring and even the same TN-C earthing.

Houses, which were rewired by me have copper wiring, which gauge was taken considering short-circuit currents (their budget can't allow consider voltage drop). As result, no more fragile aluminium neutrals in TN-C and even money left for doing normal TN-C-S with equipotential bonding.

But lot of companies limit rewiring only by replacing circuit breakers and electricity meters. They left the same fragile PEN wires as they were installed during Soviet times and their explanation is very simple, but absurd - "If we do new copper cabling, public services should pay enough money to take gauges from IEC 60364".

So, decide yourself - old 4-wire aluminium wiring or new copper 5-wire cabling with normal erathing.

Shock safety[edit]

Voltage, which value exceeds 48V is danger for human. Long contact with voltage can cause heart failure and kill human. There is used some safety actions to prevent shock.

Earthing[edit]

Is direct connection of metal parts on available for human altitude with ground. Commonly, in old houses ground is missing. In new houses ground is used and should cause disenergizing if somewhere hot wire has leakage to metal cover. Ground resistance should be <30Ω and resistance of ground wire should be <2Ω.

Table with earth resistivity (p, Ω/meter) you can find here

Equipotential bonding[edit]

Is connecting of all metal parts on available for human altitude with main earthing busbar. Some inspectors require to connect metal parts on ceiling with ground, but in fact it protects against nothing there. But donkeys still be stubborn =)

TN-C (not allowed in new installations)
TN-C-S (the most widespread nowadays)
TN-S (as rule, used in Great Britain)
TT and IT (fuel tanks and hospitals)

RCD/GFCI[edit]

In addition to ground, all circuits on available altitude should be protected by RCD/GFCI. Ceiling lights can't be touched and ground wire is enough there (except wet rooms). In Great Britain wiring rules require at least two RCDs. Imagine, energy will disappear everywhere if somewhere is leakage to ground.

Where are disadvantages?

First - native leakage. Dust gives 3-5mA of leakage. If you use 6 devices on the same line, RCD will trip even if everything is serviceable.
Second - TN-C earthing system. In old Soviet tower blocks homeowners make rewiring in some apartments. And they rewire according to current rules. For example, 5 apartments from 36 are rewired, 31 still have old wiring. Electricians line cable from subpanel in apartment to electricity meter in stairs and can't find ground wire. More exactly - everything is grounded to thick aluminium neutral. After little thinking they connect ground wire with PEN wire. When both of homeowners using washing machines, RCD trips without any reason. And reason is simple - using TN-C can't provide normal equipotential bonding and PEN will give some little current between metal parts in different places (as waching machines are linked by pipes). This current is not danger for human (I've measured voltage between PEN and metal parts in different places in old house and multimeter shown 15 volts, which are not danger for human), but it's enough to trip RCD without any reason.

Wiring diagrams[edit]

Apartments[edit]

As for apartments, I've designed over 1000 different installations for different Europe countries. Some of them are saved and I'm converting them into JPG format when I have free time, so they will appear here time after time. And secret here is very simple - officially you shouldn't order designer's services if you need to wire or rewire installations up to 35-40 Amperes.

Apartment in Khrushchyovka (1-phase)
Single-phase 25A fuse box
3-phase 40A fuse box
old school
3-room apartments
4-room in new house
406m² penthouse

Other installations[edit]

Here I work not many times, but I decided to improve my skills and take on big industrial installations. I mean diversify work, cause it is boring to do one action every time by template to template. This work requires to have special permission, but year ago I asked myself: "Why should I die from hunger cause some fat sons of the b***hes in safety boards invent insane conditions allegedly to supply safety in their ***holes? Let they observe their stupid laws by themself and don't worry normal people."

Here I'll upload works in process of receipt, but I do them very rare.

Apartment houses[edit]

Commonly old Soviet tower blocks built after 1960 (where Y 220/380 or 230/400V is already build). Houses built till 1960 (Δ 3x220 without neutral wire) or new houses (where act of acceptance/passing of object is required) I design only as subcontractor.

As you can see, forbidden 10mm² of aluminium is replaced by copper cables everywhere, the same about going from danger TN-C to TN-C-S ;-) Imagine 125A and fragile 10mm² aluminium PEN... can't imagine? But estonian electrical companies do it very boldly everywhere and their excuse about this fact no less stupidly - public services have not enough money for fat (35mm² or 50mm²) copper wires and they decided to leave the same illegal wiring as it have been done during Soviet times (40 years ago it was normal, but this decrepit wires can't more handle all powerful home appliences). I can't imagine more dumbiest things from old specialists, but I decided to go other way - why can't they save money without throwing to the extreme (as designers do it) and replace old aluminium wires to the same gauges or little bigger, but to copper wires? If estonian electrical companies replace only circuit breakers (cause they have no money due to stupidnes in brians of their enginers), I do there whole upgrade and new circuit breakers are only little part of project.

Rewiring of Kruschev's house.
5-storey house.
10mm² of Al replaced to 16mm² of Cu and even money left for ground.
9-storey house.
10mm² of Al replaced to 25mm² of Cu and even money left for ground.
Rewiring of 16-storey house.
Dormitory
Wooden house
23-storey apartment house (new building)
14-storey house (each floor has independent power cable)
Stalin-era house