2 March 2024

voltage drop or voltage It is the part of the energy that is lost due to the resistance offered by materials to the passage of electric current. In other words, it is the decrease in voltage that occurs along the conductor due to its electrical resistance. In this article we will explain in more detail what is electrical voltage dropwhat effects it has on electrical systems, how it can be calculated and how it can be avoided or mitigated.

## Causes and factors of voltage drop

voltage drop depends on various factorssuch as the length of the conductor, the resistance of the material, the charge or current flowing through the circuit, and the type of voltage (alternating or continuous).

### Effects of cable length

cable length is one of the factors that influences the voltage drop. The greater the distance between the source and the point of consumption, the greater the electrical resistance of the conductor and the energy loss. Therefore, using short cables with the correct gauge for each application will avoid a voltage drop.

### The resistance

resistance is the ownership of materials that opposes the flow of electric current. This value is measured in ohms (Ω) and depends on the type and section of the conductor, as well as the ambient temperature. The use of conductors with low resistivity, such as copper or aluminum, are adequate to support the current that circulates through the conductor section.

The current load on the voltage drop is the flow of electrons through a conductor. This is measured in amperes (A) and represents the amount of electricity consumed at one point in the circuit. The voltage drop will be proportional to the current load, so it is vital to correctly size the conductors and electrical equipment. This in order to avoid overloads or short circuits that can generate excessive voltage drops.

## What is electrical voltage drop?

electrical voltage drop is the difference between nominal voltage and actual voltage in an electrical circuit.

### Difference between nominal voltage and actual voltage in an electrical circuit

• The Nominal voltage It is the theoretical or ideal value that the voltage should have at a point in the circuit.
• The actual tension It is the measured or effective value of the voltage at that same point. The difference between the two values ​​is the voltage drop.

## Consequences of voltage drop

When a voltage drop occurs there can be several negative consequences for electrical systems and equipment connected to them. Some are:

### Impact of voltage drop on the performance of electrical equipment

voltage drop can affect the performance of electrical equipmentsince the voltages drop and the heating in the conductors increases due to the increase in current intensity.

Consequently, problems related to the quality of the voltage wave, electrical harmonics or disturbances in the real frequency can be generated. As well as a reduction in the performance of electrical equipment in general.

### Risks associated with voltage drop

This event can also generate risks to the safety of people and electrical equipment. Some of these risks are:

• Overheating of conductors: causes an increase in the current flowing through the conductors, which generates heat due to the Joule effect. This heat can damage the insulation of the wires and cause fire or electrocution.
• Damage to sensitive equipment: Can cause damage to electrical equipment that requires constant and precise voltage to function properly. Here we can name computers, printers, televisions or household appliances. These equipments can suffer failures, loss of data or irreparable breakdowns.
• Unexpected stops or starts: of electrical equipment that has motors, such as pumps, fans, compressors or industrial machines. These sudden changes can generate water hammer, vibration, wear or breakage.

## Voltage drop mitigation methods

To avoid or reduce the voltage drop in electrical systems, some mitigation methods can be applied, such as:

• Use proper conductors: the type, material and gauge of the conductors must be chosen according to the current they are going to support and the distance they are going to cover. It is also necessary to avoid conductors that are too long or thin that generate a lot of resistance and voltage drop.
• Evenly distribute loads: to evenly distribute electrical charges between the phases and circuits of the electrical system. It is also necessary to avoid concentrating many loads in the same point or circuit that generate a lot of current and voltage drop.
• Use compensators or voltage regulators: it is necessary to use devices that compensate or regulate the voltage at the critical points of the electrical system. These devices can be transformers, capacitors, stabilizers or variable frequency drives that adjust the voltage according to demand.

## Regulations and standards related to voltage drop

The voltage drop is regulated by national and international regulations and standards that establish the maximum limits allowed to guarantee the quality and security of the electrical supply. Some of these are:

Electrotechnical Regulation for Low Voltage (REBT) RD 842/2002:

This regulation establishes the technical conditions and guarantees that the electrical installations in Spain. In its complementary technical instruction ITC-BT-25, it establishes that the maximum voltage drop in a branch circuit must not exceed 3% for lighting or 5% for other uses.

• IEC 60038: IEC standard voltages.
• IEC 60364-1: Low voltage electrical installations – Fundamental principles, evaluation of general characteristics, definitions.
• IEC 60364-4-41: Low voltage electrical installations – Safety protection – Protection against electric shock.
• IEC 60364-4-42: Low voltage electrical installations – Safety protection – Protection against thermal effects.

## Can the voltage drop be calculated?

It is possible to calculate the voltage drop by formulas and mathematical methods that relate the variables involved in the phenomenon, such as resistance, current, length and type of voltage. Some of these are:

### Formulas and methods to determine the voltage drop in an electrical circuit

General Formula to calculate the voltage drop in a conductor is: V = I x R

Where: V = voltage drop in volts (V), I = current in amperes (A), R = resistance in ohms (Ω).

The resistance can be calculated from the resistivity, length and section of the conductor using the formula: R = ρ x L / S

Where: R = resistance in ohms (Ω), ρ = resistivity in ohms per meter (Ω/m), L = length in meters (m), S = section in square meters (m^2).

K-factor method: is a simplification of the general formula that uses a multiplicative factor that depends on the type of voltage, the material and the gauge of the conductor. The formula is: V = I x L x K

Where: V = voltage drop in volts (V), I = current in amperes (A), L = length in feet (ft), K = K factor in ohms per thousand circular feet (Ω/kcmil ft).

### Tools and software available for voltage drop calculation

In addition to mathematical formulas and methods, there are tools and software that make it easy to calculate voltage drop in electrical systems. Some are:

• online calculators: allow you to enter the circuit data and obtain the resulting voltage drop. This is one of the most used: Electric applied.
• Software: some programs allow obtaining the voltage drop and other parameters of interest. Among these computer programs are: AutoCAD Electrical, ETAP and Ecodial.