Electricity doesn’t generate excess heat or cause electrical hazards under normal conditions. However, an overcurrent condition may occur if the equipment’s current draw exceeds its acceptable current rating, leading to excessive heat generation, equipment damage, and potential worker injuries. This is where an overcurrent protector or overcurrent protection devices (OCPDs) can help. These devices safeguard electrical equipment from conditions like overloads, short circuits, ground faults, and so on. How do these devices work? This post answers this question by discussing overcurrent protection in detail and walks you through different OCPDs and their role in protecting equipment, people, and homes.
What is Overcurrent?
Overcurrent, also referred to as a ground fault or short circuit, describes a sharp rise and fall in current over a limited period. During a short circuit condition, the current value may increase anywhere by six to hundreds of times than the normal rated value of current.
What Are the Causes of Overcurrent?
Some common causes of overcurrent include:
- Excessive Load: When an equipment or motor draws more current than it can safely and efficiently carry, it causes an overload. This can happen due to various factors, such as too many circuits connected to a single circuit, increased load demand, operating equipment beyond its rating, etc.
- Voltage Drops and Spikes: Excessive voltage drop leads to overcurrent, where the electrical system tries to compensate for the voltage drop. Voltage drop happens for various reasons, including high resistance connectors in the system, long cable runs, and undersized conductors. Similarly, voltage spikes can cause a temporary increase in current flow. These spikes occur due to switching of inductive loads, lightning strikes, and power distribution system faults.
- Arc Fault: This occurs due to unintended electrical discharge between conductors or between a conductive material or a conductor. Loose wire connections, overheated wires, nails or screws driven through walls, wires pinched by furniture, and liquid spillage are some common causes of arc faults.
- Faulty Equipment: Defective equipment can draw excessive current than required, leading to an overcurrent situation. This can happen due to various factors, such as internal short circuits, component failures, manufacturing defects, and so on.
- Inrush Current: This refers to the current surge that occurs on the energization of the electrical equipment. Many devices, such as transformers, motors, and capacitors, draw higher currents on magnetization or charging of capacitive elements.
What Are Different Types of Overcurrent Protection Devices
There are three main overcurrent types that need to be addressed, including:
- Short Circuit Overcurrent: There is a sudden surge in current flow when a low resistance path is created between conductors. Short circuits can occur due to damaged conductors, insulation breakdown, or electrical equipment faults. These events draw high current levels, causing damage to insulation, wiring, and equipment.
- Overload Overcurrent: This refers to the gradual increase in current over time when the electrical system is subjected to high current for an extended period. Unlike short circuits, overload produces low current levels, which persist for a long time.
- Ground Fault Overcurrent: A ground fault occurs when a default connection is established between the ground and a live wire. Failure of insulation, improper wiring, and equipment damage are a few common causes of ground fault. A ground fault creates a low-resistance path for current flow, resulting in dangerous conditions.
What Are Overcurrent Protectors and How Do They Work?
Overcurrent protectors or overcurrent protection devices (OCPDs) are designed to protect an equipment or circuit from overcurrent. These devices offer protection by stopping the flow of current entirely.
- Fuses: These are one of the most widely used overcurrent protection devices designed for one-time use. Fuses feature a thin wire or metal strip of low melting point encased in an insulator with two conductors on its ends. The metal strip or wire may melt when too much current flows through it, disconnecting the circuit. These fuses are designed for one-time use and must be replaced when they blow up. Fuses may feature different connectors and are designed for specific current and voltage rating, breaking capacities, response times, physical sizes, etc.
- Circuit Breakers: These overcurrent protectors are reusable unlike fuses. They automatically interrupt the current flow during overcurrent. Circuit breakers use electromagnetic or thermal mechanisms to detect overcurrent. Electromagnetic circuit breakers create a magnetic field using a solenoid and trip the breaker on sensing excess current. Thermal breakers feature bimetallic strips that bend under the heat generated by excess current. These bent strips open the contacts to stop the current flow. Circuit breakers are distinguished into low-voltage, medium-voltage, high-voltage, magnetic, magnetic-hydraulic, thermal-magnetic, solid-state, shunt-trip, and smart, depending on their designs.
- Overload Relays: These devices ensure excellent overcurrent protection for motors. Overload relays monitor the current flow through the motor and trip when it exceeds the rated current flow over a specific period. For instance, if the current remains high for too long in a motor, an overload relay will trip to prevent motor damage.
- Safety Switches: As the name suggests, these overcurrent protectors are designed to isolate electrical circuits or equipment from the power supply during emergency shutdowns or maintenance. These current limiting devices also protect by interrupting the circuit during fault conditions.
Protect Your Equipment with Quality Overcurrent Protectors
Investing in a quality overcurrent protection device is essential to safeguard your electrical systems from damage. These devices help ensure the operational performance and safety of your equipment and people. If you are looking for relays, safety switches, or circuit breakers, North America Phase Converters offers high-quality, reliable solutions for your specific needs. Do not wait for an overcurrent situation to occur, take proactive steps to cut down the downtime and protect your assets. Contact us today to learn more about our overcurrent protection devices and how they can help keep your systems running safely and efficiently.
