Basics of SPD – What is a separator?

SPD (Surge Protection Device) is a device for protecting electrical systems from overvoltage.

This article details the basic concept of SPD and the protective device - the separator.

▷If you want to know the basics of SPD, please refer to the previous article “Basics of SPD that you can’t ask about now”

1. Importance of SPD

Electrical systems can be subject to overvoltages due to external factors such as lightning or power fluctuations.
Such overvoltage can cause electrical equipment failure or system downtime.

SPD is an important tool for mitigating these risks.

2. Role of separator

What is the role of a separator?

SPD deteriorates when lightning surges exceed specifications or when lightning surges are repeatedly handled.
This ultimately leads to failure.

If a short circuit current flows through a deteriorated SPD, there is a risk of heat generation and fire.
Therefore, a separator is required to quickly disconnect the deteriorated SPD from the power supply.

3. Types of separators

There are several types of separators, each with different functions and characteristics.
SPD separators use both a thermal disconnection mechanism to protect against heat generation during deterioration and an overcurrent protection function during short circuit failures.

Thermal disconnection mechanism is a mechanism that physically cuts off the circuit when the SPD generates abnormal heat.
It is provided inside most SPDs.

This mechanism was designed with the intention of increasing leakage current due to expected repeated surges passing through the SPD.

On the other hand, the overcurrent protection function is a separator that responds to failure modes in which the SPD momentarily shorts due to excessive surges or temporary AC overloads.

4. Performance required for separators

The performance required of the SPD installed in the power distribution board and its separator differs depending on whether the SPD to be protected is functioning normally or malfunctioning.

When the SPD is in normal condition, it is required to be able to pass through lightning surges that exceed the SPD's specifications in order to maximize its capabilities.

On the other hand, when an SPD is out of order, it is required to safely and instantly cut off the short-circuit current at the time of the fault.
In other words, it suppresses the heat generation and ignition of the SPD's lightning protection element, and also prevents power outages for the entire system by operating faster than the upper circuit breaker.

5. Comparison of SPD with built-in separator and external separator

Here we will explain separators that support overcurrent protection functions, which until now have often been connected externally.

SPD with built-in separator:

• merit:
  Easy to install, no external parts required. Its compact design makes it suitable for locations with space constraints.
  
• Demerit:
  Separator replacement and maintenance may become difficult.

External separator:

• merit:
  Easy maintenance and replacement of separator. It is customizable and can be tailored to specific requirements.
  
• Disadvantages: Can be complicated to install and may require additional space and wiring.

6. SPD selection

Several factors should be considered when choosing an SPD.
This includes the capacity of the electrical system, the type of electrical equipment used, and the level of risk of failure. It is important to consider these factors to select the optimal SPD and separator.

7. SPD maintenance

SPD requires regular maintenance.
Regular inspection and replacement will maintain the performance of your SPD and ensure the safety of your electrical system.

8. Summary

SPD is an important device for protecting electrical systems from overvoltage.
The separator plays an important role in quickly disconnecting a deteriorated SPD from the power supply in order to reduce the risk of heat generation and fire caused by short-circuit current.

Choosing the right SPD and separator, as well as regular maintenance, can ensure the safety and reliability of your electrical system.

▷ Click here if you would like to know more about lightning damage (Japan Lightning Protection System Industry Association)

Hakusan Inc., Ltd. can make various proposals such as external separators and SPDs with built-in separators.

If you have any questions about SPD/separators, please contact us.