Introduction
Voltage drop occurs in electrical circuits and systems where the voltage level at a specific point is reduced as current flows through conductors.
This reduction in voltage happens due to the inherent resistance of the materials used as electrical conductors. Voltage drop can lead to several consequences such as:
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Exploring Voltage Drop
Reduced Performance
If the voltage drop is significant, electrical devices may not operate optimally. Motors might run slower, lights might be dimmer, and sensitive electronics might malfunction.
Inefficiency
Excessive voltage drop leads to wastage of energy, as some of the electrical power is converted into heat due to the resistance.
Safety Concerns
In situations where voltage drop is severe, electrical devices might not function as intended, which could potentially compromise safety systems or create hazards.
Overheating
In cases of significant voltage drop, conductors and components might carry more current than they’re designed for, leading to overheating and potential damage.
Factors contributing to conductor resistance
Several factors contribute to resistance and, consequently, voltage drop the mainly being:
Conductor material choice
Different materials have different resistances. For example, copper has lower resistance than aluminum, making it a preferred choice for many electrical conductors.
Conductor Length
The longer the path that the current has to travel, the higher the resistance and voltage drop. Longer conductors offer more resistance than shorter ones.
Conductor Size
Thicker conductors have lower resistance because they provide more space for the current to flow, reducing the voltage drop.
Ambient Temperature
Resistance increases with temperature. As current flows through a conductor, it generates heat due to the resistance itself. This can cause a slight increase in resistance and voltage drop.
Load Current
Higher current loads result in higher voltage drops. More current means more collisions between electrons and atoms within the conductor, leading to higher resistance.
Voltage Drop Limits
AS/NZS3000 states that the cross-sectional area of every current-carrying conductor shall be such that the voltage drop between the point of supply for the low voltage electrical installation and any point in that electrical installation does not exceed 5% of the nominal voltage at the point of supply.
Also, where the point of supply is the low voltage terminals of a substation located on the premises containing the electrical installation and dedicated to the installation, the permissible voltage drop may be increased to 7%.
In simper terms the nominal allowed maximum voltage drop is 5%, but that can be increased to 7% if the installation has a dedicated transformer.
Note that the standards set the minimum requirements, clients may have more stringent conditions.
I have worked on projects where the maximum allowed voltage drop is 3%, so please do check with your clients.
In cases where you have conductors in parallel, the voltage drop for a circuit in which conductors are connected in parallel shall be taken as the voltage drop in one of the conductors when that conductor is carrying the current determined by dividing the value of the current of the circuit by the number of conductors in parallel.
In general Voltage drop becomes more significant in long circuits, circuits with smaller conductor sizes, or when the current load is high.
Proper sizing of conductors and components, considering factors like material, length, and current load, helps manage and minimize the effects of voltage drop.
Rounding Up
That’s all we have for you today on this topic. If you’ve learnt something new from this post, you might also be interested in other articles we offer on related subjects available on our blog’s homepage.
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