Testowanie przewodów-W przypadku testów przewodów można sprawdzić wytrzymałość na rozciąganie i korozję miedzi Ponadto można przetestować grubość izolacji i pęknięcia izolacji Jednak odpowiednia odporność na przewody jest najważniejsza dla efektywnej pracy urządzeń elektrycznych Dlatego testowanie przewodów jest niezbędne do testowania kabli
Rysunek: Testowanie kabli światłowodowych
Dlaczego trzeba przeprowadzać testy kabli
Ściskanie, pękanie i zginanie są typowymi uszkodzeniami kabli, które można codziennie zobaczyć Te awarie kabli wpływają na wydajność elektryczną sprzętu Jeśli jednak znajdziesz je wcześniej, możesz uniknąć poważnych problemów w przyszłości
Testy pomagają sprawdzić wydajność elektryczną obwodu Można go użyć do sprawdzenia jakości kabli i spójności kabli Ponadto można przetestować funkcjonalność kabla
Testowanie kabli to skomplikowane zadanie Specjaliści korzystają z różnych technik testowania kabli, aby zapewnić bezproblemowe i ciągłe połączenia kabli Niektóre z nich to pomiar oporu izolacji, pomiar wytrzymałości dielektrycznej, pomiar ciągłości, test oporu przewodnika itd
Tutaj omówimy szczegółowo test oporności przewodnika
Testowanie przewodów-Co to jest test oporności przewodnika
It checks if the quality of the cable conductor is good. You can do this on the complete. Or you can take a cable length of 1m based on. With this, you can test the direct current resistance of copper or aluminum conductors. High resistance means that the current flow is low. This indicates possible cable faults.
Is expressed as ohms per km. There are two tests for cable conductor testing. These are the Kelvin Double Bridge test which gives an accuracy of 0.2%, and the Wheatstone bridge test with 0.5% accuracy.
Factors Affecting Conductor Resistance
Why is there a need for conductor resistance testing for cables and wires? Well, it is because some factors change the conductor resistance. These are:
Testowanie przewodów-Length:
The resistance of a conductor is directly related to its length. Let’s understand this with an example. Suppose you take two wires of different lengths. Now, you give the same voltage to their ends. The longer wire will have less voltage per cm. As a result, the electric slope or the potential gradient that moves electrons is less steep. This decreases the velocity of moving electrons. So, with the longer length, the current decreases, and the resistance increases.
Cross-sectional area:
The more the diameter, the more electrons pass through a definite point. More electrons moving means more current flowing. And more current means less resistance. Thus, resistance is inversely related to the cross-sectional area.
Testowanie przewodów-Nature of material:
It’s the electrons that carry current. So, the flow of current largely depends on the availability of free electrons. Some atoms have more free electrons in their outer shell. As a result, the material will have ample free electrons. Thus, it will be a good conductor with loss resistance. On the other hand, if the outer shell is full, the atom will not allow its electrons to move. Thus, the material will have more resistance. For example, copper has four electron shells with one electron in the outer shell. On the other hand, Silicone has four shells with four electrons in its outer shell. Thus, copper is one of the best conductors, and silicone is the best insulator.
Image: copper wire
Temperature: When the temperature increases, it leads to more vibration in the atomic lattice. The vibration in the lattice causes more hindrance in the movement of electrons. As a result, the resistance increases, and the current flow decreases. Thus, conductor temperature measurements are an important part of cable testing.
Image: electric aluminum cable
Testowanie przewodów-Conductor resistance testing
Traditional cable test techniques use the difference in voltage across known resistors to know the unknown resistance. Alternatively, modern equipment calculates cable conductor resistance based on. In this, you calculate current and voltage across a sample. With this, you can calculate resistance.
Things to know before conductor resistance testing:
This method can calculate the direct current resistance of class 1, 2, 5, and 6 type conductors. For the test, conductors can be Aluminium, its alloy, plain copper, or metal-coated copper. The specimen used in this cable testing must have a cross-sectional area between 0.5mm2 to 2500mm2. You will get results in ohms/km.
As temperature affects resistance, keep the test sample in the test area for a sufficient measurement time. This stabilizes the conductor temperature. This allows accurate measurement. According to BS EN 60228, for accuracy of performance, the conductor temperature should be 20oC.
Conductor resistance testing procedure:
First, you need to collect the test sample. You can take any solid conductor having a drum length of 1m. Or take any solid conductor up to a size of 25mm2. The drum length should be 5m. You can also take sector solid conductors with a size greater than 25mm2. The drum length should be 10m. Length here refers to the length between the voltage terminals.
Testowanie przewodów-Then perform the test:
First, connect the test specimen to the bridge that measures resistance.
Secondly, check all the considerations related to contact resistance before the test
Thirdly, calculate the resistance
Finally, note down conductor measurements
Now, convert the measured resistance into equivalent resistance at standard temperature (20 degrees Celsius) and length.
Conductor Resistance Testing Calculation:
You can calculate the measured resistance with the following formula
R=((Rt*k)/L) *1000ohms/km
Here,
Rt=Observed Resistance
K=Temperature correction factor
L = Length of specimen in m.
Your conductor resistance must meet standard resistance readings. For this, compare observed resistance with conductor resistance at 20oC. Use this formula for comparison.
R20 > (Rt*kt*1000)/L ohms/km
If your observed resistance is more than R20, you may have some conductor issues. However, before that, check for the following whether
The conductor temperature is less than 20
The cable length is correct, as the longer cable will give higher resistance.
Your conductor is pure
Your conductor has a sufficient quantity
Testowanie przewodów-Result
Based on the results, you can say whether the sample meets or does not meet your requirements.
Conclusion
A high resistance results in the heating effect. It can result in a fire or a short circuit that can be life-threatening. But don’t worry. Good quality cables can minimize resistance issues. If you need any help in this regard, contact me. We deal in high-quality wires and assemblies. We can cater to all your cable testing needs.