Oikodomisis

The Coefficient of Synchronization (Heterosynchronism): The secret of engineers to avoid laying huge cables for no reason

Let's do a thought experiment: Imagine a typical apartment building with 20 apartments. As we calculated in a previous chapter, each apartment has electrical appliances (ovens, air conditioners, water heaters) with a total power of approximately 15,000 Watts (15 kW).

If we do simple Elementary math, the block of flats as a whole has installed power devices: 20 apartments x 15 kW = 300 kW. To carry 300 kW of electricity from the DEDDIE substation to the clock of the apartment building, we would need a copper cable the thickness of... a tree trunk! Such a thing would be technically impossible to pass through the streets and economically unapproachable (it would cost a fortune in pure copper).

And yet, if you look at the cable that powers your apartment building, it's the thickness of a human wrist. How is that possible? Did the contractors "discount" the insurance?

At all. The answer is hidden in the most beautiful application of statistics in the science of mechanics: The Coefficient of Synchronization (or Coefficient of Heterochronism, as it is often referred to in the Greek piatsa).

1. Logic: The Statistics of the Everyday

Electrical engineering is based on an indisputable truth of human behavior: It is statistically impossible for all devices, of all people, to operate at 100% of their power at the exact same time.

  • The tenant of the 1st floor can take a bath (he turns on the water heater).
  • The tenant of the 2nd floor is away at work (only the refrigerator is on fire).
  • The family on the 3rd floor is cooking (turning on the oven).

Even inside the same apartment, the oven does not draw 2,500W continuously. Once it reaches 200°C, the thermostat closes the resistance and "rests" the network for a few minutes.

Illustration for 1. Logic: The Statistics of the Everyday

2. What is the Coincidence Factor?

Illustration for 2. What is the Coincidence Factor?

It is a number (multiplier) from 0 to 1, which expresses the probability that the loads of an installation will work at the same time.

Engineers take the total (theoretical) power of all devices and multiply it by this factor to find the Actual Maximum Demand. Based on this actual demand, they choose the thickness of the cables.

How does the coefficient decrease as the building grows:

The law of probability says that the more users there are, the less likely they will all be doing the same thing at the same time.

For 1 Apartment

The coefficient is usually 0.5 to 0.6 (We estimate that 50-60% of the devices work at the same time).

For a 5-apartment apartment building

The overall coefficient drops to 0.4.

For a 20-apartment apartment building

The coefficient can drop to 0.25 or 0.3. (From the 300 kW we theoretically produced at the beginning, DEDDIE calculates that in the most extreme case only 75 kW to 90 kW will be requested at the same time. Based on this, it sizes the neighborhood cables!).

3. Its Application in Practice (In the Individual Circuits)

Engineers apply this rule even inside your own electrical panel, depending on the type of circuit:

Illustration for 3. Its Application in Practice (In the Individual Circuits)

Lighting Circuit

If you have 10 10W lamps in the living room, the coefficient is almost 1.0 (100%). Usually when you press the switch, they all light up together.

Socket Circuit (Socket)

You have 5 sockets on the bedroom wall. Theoretically, each one can withstand 3,600W. Will the electrician put in a cable for 5 x 3,600 = 18,000W? No! The coefficient at the outlets is extremely low (eg 0.1 to 0.2). We know that usually the laptop will be in one socket, the mobile charger in the other and the remaining three will be empty.

4. The Absolute Exceptions (When the Coefficient is 1.0)

Illustration for 4. The Absolute Exceptions (When the Coefficient is 1.0)

The concept of simultaneity "saves" our pocket, but there are cases where its application is strictly prohibited by law, because the loads are "continuous". In these cases, the wiring must withstand 100% of the load for an infinite time (Factor = 1).

Such cases are:

  1. Electric Vehicle (EV) Chargers: As we mentioned before, a car will "suck" 11 kW non-stop, at most, for 8 hours. There is no "rest". If everyone puts chargers in an apartment building, the synchronization factor collapses and the network of the apartment building risks a "blackout" (this is the huge bet of the future for DEDDIE).
  2. Data Centers (Server Rooms): Infrastructure computers run 24/7 under constant, massive loads.
  3. Industrial Pumps & Motors: Conveyors and shift water pumps.

Summarizing

The next time you look at your electrical panel or the central cable of your apartment building and ask yourself "Is this little thing holding up the whole house?", remember the Coefficient of Synchronization. It is not the "stinginess" of the electrician, but the impressive application of mathematical probabilities, which makes the electrification of the modern world economically and practically viable.

Next Step: We have seen that Electric Car Chargers "ruin" the synchronization statistic, threatening the cables. How does modern technology solve this problem without tearing down the walls? Continue to our guide: Dynamic Load Management: How the car charger "talks" to the house so it doesn't blow the fuse, to meet the smart "traffic policeman" of the current.

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