Surge Protection Device OR Circuit Breaker?

What should you use?

In this article, we’ll dive into the differences between Surge Protection Devices (SPDs) and Circuit Breakers. By the end, you’ll grasp how they differ in use, function, and types. SPDs, which are devices installed in systems like electrical power transmission and distribution, communication, and industrial control, guard these systems against electrical surges and spikes, often caused by lightning. Smaller SPDs also find their way into residential electrical panels to shield home electrical setups, including consumer units, wiring, and accessories, from power surges, known as transient over-voltages. Moreover, SPDs protect devices such as computers, TVs, washing machines, and critical safety systems—like fire alarms and emergency lights—from these surges. Such electronic devices are at risk of damage from sudden voltage spikes.

Surges can instantly damage equipment, so Surge Protection Devices (SPDs) are essential in consumer unit circuits to shield electrical setups. Various SPD types offer protection against different surge kinds. Short-lived surges, known as transient overvoltages, happen due to energy suddenly released from natural or artificial sources. Lightning indirectly hitting nearby power, phone, or internet lines typically causes natural transient overvoltages. These surges travel through the lines, risking significant harm to electrical systems and connected devices. Man-made surges stem from activities like switching motors, transformers, and certain lights. Although once uncommon in home settings, the rise of new technologies like electric vehicle chargers, modern speed-controlled washing machines, and heat pumps for air or ground sources has made such surges more frequent in households. These devices tend to trigger surges, posing a higher risk to home electrical systems.

In AC circuits, transient overvoltages, or voltage spikes, last from 1 to 30 microseconds and can surpass 1,000 V. Lightning hitting an overhead power line may cause surges over 100,000 V. Similarly, turning off a running electrical motor might produce a spike exceeding 1,000 V. Failures in power transformers, such as a lost neutral, or issues in other companies’ distribution lines can lead to long-lasting surges, from seconds to hours, without SPD protection. These prolonged surges can irreversibly harm the protective devices within a building, network, or area. Surges lasting just milliseconds may exceed the endurance of devices like fuses and overvoltage relays, highlighting the risk of lasting damage without adequate surge protection.

How does Surge Protection Devices (SPDs) function?

When an SPD detects a transient overvoltage, also called a voltage spike or power surge, in a circuit, it works by redirecting the current away from the circuit and through the surge protector, acting as an alternate path for the current.

SPDs use a component known as a Metal Oxide Varistor (MOV), which functions similarly to a pressure relief valve in a water main. Without this valve, excessive pressure could harm the water line. In the same way, when the MOV detects high voltage, it lowers its resistance significantly, allowing the current to pass through the SPD and reducing the voltage to a safer level in the circuit. Once the surge is managed, the SPD resets itself to its original state of high resistance. If the voltage falls too low, the MOV’s resistance increases, stopping the current from passing through the SPD. This process helps SPDs lower transient voltages to levels that are safe for electrical and sensitive electronic devices, preventing damage or operational disruptions.

Types of Surge Protection Devices

Broadly there are 4 types of SPDs as listed below:

Type 1 SPD

Also Known as Class B SPDs, they are ideal for the LPZ 1 zone. Install them in the main panels of industrial settings prone to frequent lightning surges. Type 1 SPDs are designed to withstand high energy levels, constructed using spark gap materials, consisting of two metal pieces separated by a gap filled with gas or air. This design effectively manages intense surges.

Type 2 SPD

Also known as Class C SPDs, suitable for the LPZ 2 area, are designed to manage switching surges. They incorporate a Metal Oxide Varistor (MOV), an electrical component with resistance that changes based on voltage levels. Type 2 SPDs offer quicker response times compared to Type 1 but can handle less energy. Thus, it’s advisable to place Type 2 SPDs in distribution panels downstream from where Type 1 SPDs are installed in the main panel.

Type 3 SPD

Type 3 SPDs, or Class D SPDs, are recommended for use in the LPZ3 area. They are designed with a low energy handling capacity and are typically installed at the endpoints of the electrical system, like sockets, to ensure quick response to surges. Diodes and similar materials are utilized in their construction, allowing them to effectively control surges and protect the system safely.

Type 1+2

Also known as Class B+C SPDs, positioned where cables enter a building, serve a similar purpose to Type 1 SPDs and are installed in the same locations. They are crafted from a blend of Metal Oxide Varistors (MOVs) and Spark Gaps, providing an economical alternative to Type 1 SPDs while maintaining effective surge protection capabilities.

Checkout all the types of SPDs here

SPDs according IEC61643-1

The IEC standard categorizes an SPD as a device designed to mitigate transient overvoltages and redirect them, incorporating at least one nonlinear component. There are three main types:

a)   Voltage Switching Type SPD: Characterized by high impedance under standard conditions, its impedance sharply decreases during a voltage surge, allowing for effective surge diversion.

b)  Voltage Limiting Type SPD: This SPD maintains high impedance during normal operation, but its impedance gradually lowers as surge current and voltage increase, effectively limiting the surge impact.

c)   Combination Type SPD: This variant merges the features of both voltage switching and voltage limiting types. Its response to voltage surges can mimic either type or a blend of both, adapting to the specific characteristics of the surge encountered.

Low Voltage Circuit Breakers

A circuit breaker serves as an electrical switch to safeguard circuits from damage due to overcurrent, overload, or short circuits by halting the flow of current, thus preventing potential overheating and fire risks. Unlike fuses, which need replacement after a single use, circuit breakers can be manually or automatically reset to continue their protective function, offering multiple uses. Low-voltage circuit breakers, commonly found in homes, hospitals, hotels, and commercial buildings, are categorized into MCCB (moulded case circuit breaker), MCB (miniature circuit breaker), and RCCB (residual current circuit breaker). An MCCB is designed for medium to low voltage with three poles, while an MCB, smaller in size, operates at low voltage and is single-poled. Both types are aimed at guarding against overcurrent and short circuits. Conversely, an RCCB is specifically designed to prevent current imbalances that occur due to ground faults, enhancing safety by detecting and interrupting fault currents.

How does a Low Voltage Circuit Breaker work?

The fundamental principle of a circuit breaker revolves around halting the flow of electrical current in a circuit to prevent damage. It comprises stationary and movable contacts, operating akin to an automatic switch set to a specific current level. When the current surpasses this threshold, the circuit breaker disconnects the circuit.

The operational sequence of a circuit breaker unfolds as follows:

·    Fault Detection: It identifies faults within the system, such as overloads or short circuits.

·    Activation of Mechanism: Upon detecting a fault, it triggers its spring-loaded mechanism, releasing stored energy.

·    Contact Separation: This energy separates the contacts, both fixed and moving, effectively breaking the circuit.

·    Current Interruption: The disconnection of contacts halts current flow, averting potential damage from the fault.

·   Resetting: Once the fault is resolved, the circuit breaker can be reset, re-establishing the connection between contacts for current to resume its flow.

Understanding the operation of Residual Current Circuit Breakers (RCCBs) is crucial alongside circuit breakers. RCCBs operate based on Kirchhoff’s Law, which dictates that the sum of incoming current in a circuit must match the sum of outgoing current. Normally, the current through live and neutral wires is balanced. However, if a fault occurs, like damaged insulation or someone touching a live wire, some current diverts to the ground, causing an imbalance between live and neutral currents. RCCBs detect this imbalance and instantly activate their tripping mechanism to cut off power, preventing potential electric shock or damage. This tripping occurs in milliseconds, ensuring immediate protection.

Surge Protection Devices vs Circuit Breakers

A Surge Protective Device (SPD) is designed to safeguard electrical appliances from power surges, such as voltage spikes or transients, while a circuit breaker focuses on preventing wire-related fires by addressing overcurrent, overload, or short circuits. Specifically:

·    Circuit breakers act as a defense against fire hazards by interrupting the circuit when excessive current is detected.

·    Residual Current Circuit Breakers (RCCBs) offer protection against electrical shocks that may occur from accidental contact with live parts.

·   SPDs provide a shield for electronic devices and appliances against voltage spikes, offering critical protection against lightning-induced surges and other system voltage fluctuations.

While circuit breakers prevent electrical system damage due to overloads or shorts, and RCCBs protect individuals from electrocution, neither is designed to handle power surges. Installing SPDs at the main electrical panel and at points of use, like outlets or power strips, is an effective strategy to protect valuable electronics and appliances from the adverse effects of power surges.