Purpose of this article
This article is based on the concern expressed by a person in relation to its proximity to a commuter rail line. We will briefly analyze the situation, theoretical and measured levels.
Radio level measurement during the passage of a train
As always, K2 Ingenieros reserves its opinion on the health effects that emissions may have. These are specialties outside our field of action. This article is informative and is not intended to be a rigorous study.
The calculations presented here are theoretical, although quite conservative. An actual measurement may differ greatly from them.
Our specialty is the measurement and control of radioelectric emissions.
Theoretical analysis of possible radiation sources
According to the data consulted, a commuter or subway train is powered by a voltage of between 1,500 and 3,000 V direct current (or perhaps at 50Hz in some cases) and consumes, at its maximum power, about 2,500 Amperes.
With these premises, we will base our calculations on the following assumptions:
- In direct current or at such low frequency the current intensity generates a magnetic field.
- We will calculate the magnetic field using Ampere's Law.
- We will assume, that a train line emits as an infinite rectilinear conductor. This simple calculator allows us to find the magnetic field at a given distance and for a given amperage.
- We will assume that we have a direct view of the line, without obstacles or interferences.
The formula that allows us to calculate the magnetic field level as a function of distance is this:
It is, in short, a ratio between the current intensity (I) and the distance (r). The constant, for vacuum, is this:
In short, for a distance of 10 meters, an intensity of 2500 amperes we have a magnetic field of 50 micro-teslas or 0.5 Gauss.
Evaluation of results
The framing that can be made of these results is as follows:
| (Microteslas) | |
| Calculated theoretical value: | 50 |
| Earth's natural magnetic field: | 50 |
| Legal maximum: | 100 |
| Magnetic field current magnet:(It decreases very quickly with the cube of the distance) | 5000-10000 |
We see that only at less than 10 meters from a railroad line and in the most unfavorable situation of direct view, the magnetic field can reach (in theory) a value similar to that of the earth's magnetic field.
For any clarification or measurement on radioelectric levels you can contact us. We only offer objective, neutral and rigorous advice.