Electrical surges can damage sensitive equipment, disrupt operations, and reduce the service life of electrical systems. Knowing how to select surge protection devices correctly is therefore important for residential, commercial, industrial, and solar applications. Choosing an SPD is much more than just matching a voltage rating. The class of the system, operating nominal voltage, surge level, surge current to be diverted, level of protection required, installation location, and relevant standards must all be examined. The appropriate SPD may offer very effective transient protection to ensure system stability and availability. This article explores some of the crucial aspects to consider when choosing and applying an SPD.
What Is a Surge Protection Device and Why Is It Important?
A Surge Protection Device (SPD) is a passive electrical protective device that has the sole purpose of protecting connected electrical equipment by diverting transient overvoltages and surge current from the associated wiring. Thus, while an MCB or fuse is mainly intended for overcurrent protection, an SPD deals with short-term transient conditions. Electrical surges are often caused by lightning strikes, utility switching, motor and transformer switching, and other electrical disturbances present on an electrical network.
In solar systems, risks can increase due to the possibility of exposing the PV array and wiring to the elements over long distances.
An SPD limits the voltage a downstream device experiences by creating a controlled pathway into the surge's energy source. AC and DC circuits, communication lines, or both, depending on the system application, may require SPDs.
Understanding what is spd in electrical can help users understand the basic function, applications, and importance of surge protection before moving into product selection.
Why Is Choosing the Right Surge Protection Device Important?
Not every SPD applies to every electrical installation. If a device with the wrong voltage rating, configuration, discharge capacity, or degree of protection is installed, then insufficient protection or a mismatch with the system will occur.
The correct SPD should be chosen based on the properties of the total electrical installation. In the system, we consider the following aspects:
- Type of electrical system
- AC or DC operation
- Nominal system voltage
- Maximum continuous operating voltage
- Required voltage protection level
- Expected surge exposure
- Nominal and maximum discharge current
- Number of poles or protected conductors
- Earthing and system configuration
- Required backup protection
- Applicable standards
- Installation location
This makes a surge protection devices selection guide useful for comparing products based on actual application requirements rather than selecting a device solely by its current or voltage rating.
The clearest example is that an SPD that was designed for an AC distribution board cannot just be wired in a PV DC circuit, as AC and DC systems operate very differently and thus need to be suitably protected.
Types of Surge Protection Devices
SPDs can be classified according to their intended application, installation location, and ability to handle different types of surge conditions. Selecting the appropriate type depends on factors such as the system configuration, surge exposure, and location where the SPD will be installed.
Type 1 SPD
The Type 1 SPDs are suitable for installation where high energy surge current may impact an installation and where protection of partial lightning current is also required. It is typically located at the incoming to an electrical installation if the risk analysis and configuration used require this classification of protection.
They are designated for applications where a considerable thunderstorm-related surge climate is expected.
Type 2 SPD
Type 2 SPDs, usually fitted to a distribution board, are used to protect the electrical or electronics downstream against transient overvoltage. They are frequently implemented in residential, commercial, industrial, and solar electrical systems.
Type 2 protection can provide a critical part of the distribution-level protection scheme, especially when downstream devices are sensitive to transient events.
Type 3 SPD
These are type 3 SPDs and offer point protection. Normally, they would be found at the points of sensitivity. Normally, they would not be the primary means of surge protection and should form part of a coordinated scheme.
They will offer an extra layer of protection to equipment particularly sensitive to transient overvoltages.
AC and DC SPDs
One should be very careful in choosing the type of SPD; AC or DC protection should be given paramount importance. AC SPDs are designed for AC-operated circuits, and DC SPDs for DC applications like PV panels or other DC circuits.
Blitz Energy India can serve the purpose of both single-phase and three-phase AC SPD and DC SPD are available for 600V and 1000V operations.
Key Factors to Consider When Choosing a Surge Protection Device
One part of your selection process is understanding the technical specifications you find in a datasheet for an SPD and recognizing that each specification outlines how the unit is designed to operate in an electrical system.
1. System Voltage
First, ascertain the nominal voltage of the system being protected. The SPD should be compatible with the actual system voltage and system configuration. For example, for protection of an LVAC distribution system, the rating of the SPD should correspond to that of the system.
When protecting a PV array, the SPD must also be DCDC compatible, and a DC SPD must be used with a voltage rating corresponding to the maximum operating voltage for the circuit.
Protection and device reliability cannot be guaranteed when devices are selected without a complete check of system voltage characteristics.
2. Maximum Continuous Operating Voltage (Uc)
Uc is the maximum continuously sustainable voltage across the SPD (when operated under defined conditions) where the SPD does not conduct any surge current.
The UC selected should be suitable for the intended normal system voltage and earthing conditions. If the Uc for a particular SPD is too low for the real system, unwanted operation/premature degradation could occur.
As a result, Uc must always be compared to the electrical system and not by itself.
3. Voltage Protection Level (Up)
Up refers to the voltage level associated with the SPD's protection performance under specified test conditions.
A lower Up generally means that the SPD limits the transient voltage to a lower level at the protected circuit. However, this specification should be considered together with the withstand capability of the equipment being protected and the overall system design.
Sensitive electronic equipment may require closer attention to Up because excessive transient voltage can place additional stress on electronic components.
4. Nominal Discharge Current (In)
Nominal discharge current, or In, is the nominal discharge capacity of an SPD under normal test conditions.
When considering how the surge protection device works, it should be evaluated in relation to the expected surge environment and the device's intended installation location.
The correct size rating represents a trade-off between surge tolerance, on the one hand, and electrical system needs on the other.
5. Maximum Discharge Current (Imax)
Imax gives the maximum surge current rating for the SPD under the test conditions specified.
Installations that have higher risks of surge currents might benefit from higher surge handling capability SPDs; however, the highest-rated SPD will not necessarily be the optimum for this application.
Selecting the right Imax is dependent on the properties of the installation, risk assessment, standards to be complied with, and the recommendations of the SPD manufacturers.
6. Lightning Impulse Current (Iimp)
For applications requiring Type 1 protection, Iimp becomes an important specification. It relates to the impulse current capability of the SPD under the specified test waveform.
This parameter is particularly relevant where an installation has significant lightning exposure or where the SPD is intended to handle part of a lightning current.
7. Number of Poles
The number of poles and wiring configurations are determined by the system to be protected. One needs to distinguish the SPD configuration required when designing the protection for a single-phase and a three-phase installation. Blitz Energy offers AC products labeled as the 1-phase 2-pole and 3-phase 4-pole devices, respectively.
Thus, one must verify the wiring configuration prior to ordering an SPD.
8. Response Time
Response time shows how fast an SPD can respond to a transient event. This specification should not be used as the only comparison of protection performance but should be a useful one if comparing two similar and appropriate products.
Blitz Energy specifies a response time of 25 ns for their AC and DC SPD products listed above. It should be taken into consideration with other parameters like voltage protection level, discharge current, and appropriate standards.
How to Select an SPD Based on Your Electrical Application?
The right SPD will largely depend on its installation location and the equipment or circuit it is intended to protect. Different applications can generate transients in different ways, resulting in different protection requirements. For AC circuits, AC surge protection devices can be selected based on the system voltage and configuration, while DC surge protection device options are suitable for protecting DC circuits and equipment.
Residential Electrical Systems
You might need to protect distribution boards and electronics within your home electrical system. You'll choose your SPD based on the house electricity supply setup, the house voltage and earthing, and how vulnerable the equipment within your house is to the occurrences of transients.
Electronic equipment that has to be protected includes TV sets, home networking, computers, control systems, domestic appliances, etc.
Commercial Buildings
These may include computers, networking, HVAC, lighting, security, and all other electronic systems present in the office, retail, or industrial facility.
The protection required in these facilities might need to be analyzed at incoming electrical distribution and at downstream panels according to the building's electrical configuration, equipment sensitivity, and possible surge exposure in this location.
Industrial Facilities
Internal transients may originate from various inductive loads that make up an industrial plant, including motors, transformers, variable speed drives, switching equipment, etc.
PLCs, instrumentation, automation, motor drives, and the like control equipment can be more susceptible to electrical disturbances, and SPD selection must be integrated into the overall electrical protection plan.
Solar PV Systems
A solar PV system is a special case due to its requirement for SPD for both the DC and AC systems. A DC system consists of PV modules, string cables, combiner boxes, and the DC side of the inverter itself. An AC system is an interface between the inverter output and the site electrical system.
Therefore, a DC SPD selected will be suited to the appropriate DC maximum voltage and layout of the PV system.
An appropriate AC SPD can then be suited to the AC output and site electrical system.
Blitz Energy offers dedicated DC SPD 600 V and DC SPD 1000 V options for applications requiring DC surge protection.
Data Centers and Sensitive Electronic Systems
Since these facilities, along with their servers, network devices, and storage arrays, and their operational uptime could all be subjected to transients, it makes data centers critical facilities that require some attention.
For these, protection should be seen as a completely coordinated system that possibly includes incoming power distribution, downstream panels, grounding, equipment vulnerabilities, and multiple levels of protection.
What Are the Relevant SPD Standards and Certifications?
Standards provide a framework for testing, evaluating, and specifying surge protective devices.
For low-voltage AC power systems, IEC 61643-11 is an important standard covering surge protective devices connected to low-voltage power systems. For photovoltaic DC applications, IEC 61643-31 addresses SPDs intended for use in photovoltaic installations.
Buyers assessing an SPD need to examine the manufacturer's technical documentation in order to determine which standards apply to the product and usage.
The validation documentation, such as test reports, should also be accessed instead of vague claims like 'international quality' and 'high protection.' Product documents might give clearer ideas for intended environments and verified performance of the device.
Blitz Energy mentions its protection products meet IEC standards and has included the details on testing and performance characteristics for their SPD range.
How to Coordinate Multiple Surge Protection Devices?
Using several SPDs will allow you to achieve staged protection over the full length of an electrical installation. However, it is essential that SPDs are selected and correctly installed to form a coordinated protection scheme.
For example, the main incoming SPD might provide the first stage, with devices downstream of the distribution boards acting to limit the transient voltage.
Coordination should take into account:
- Location of each SPD
- Surge current capability
- Voltage protection level
- Wiring length between devices
- Upstream and downstream protection
- Equipment sensitivity
- Manufacturer recommendations
Just because multiple SPDs are installed doesn't mean that the electrical installation will be inherently better protected. These must be coordinated correctly so that each protection stage does what is required.
This method can achieve surge energy sharing amongst various points of the electrical installation and provide extra protection further downstream.
Installation and Maintenance of Surge Protectors
The right SPD choice is only one part of a successful SPD strategy; the installation plays a major part in how the SPD performs.
The connections should be kept as short and direct as possible because a too-long length of conductor can produce a larger voltage at sensitive equipment.
The grounding and bonding scheme of the electrical installation should also be adequate. A surge protection device relies on a healthy path along which to dissipate the surge energy: inadequate wiring practices will diminish SPD performance.
Before installation, installers should verify:
- System voltage and configuration
- AC or DC circuit type
- Earthing arrangement
- SPD rating
- Wiring requirements
- Backup protection requirements
- Installation location
- Manufacturer instructions
For a more detailed explanation, surge protection device installation can help installers understand the key considerations involved in installing an SPD correctly.
Visual inspection, together with the checking of any status indicator in the SPD itself, should be conducted at regular intervals. Where there is an indication in an SPD that its internal protective element is due to be replaced, it shall be done in accordance with the manufacturer's instructions.
How to Choose a Reliable Surge Protection Device Manufacturer?
Choosing the manufacturer is another important part of selecting an SPD. Buyers should look beyond the product's price and basic electrical ratings. The manufacturer's technical expertise, product quality, documentation, and after-sales support can significantly influence the long-term reliability of the protection system.
A reliable manufacturer should ideally provide:
- Clearly documented technical specifications
- Applicable standards and testing information
- Suitable AC and DC product options
- Product status indication where applicable
- Product documentation and traceability
- Technical support
- Installation guidance
- After-sales service
- Appropriate warranty and replacement support
Another piece of information that will be helpful is to identify if there are some components manufactured especially for such applications rather than generic general-purpose components.
Having a specialized company in electrical protection simplifies and guides the user (installer, electrician, contractor, project developer) to choose the right protection element for the appropriate parts of an installation.
Why Choose Blitz Energy for Solar Surge Protection Solutions?
Blitz Energy India offers a range of surge protection device solutions, including electrical protection products, AC and DC surge protection devices, MCBs, PV solar fuse terminals, and PV solar fuse links. Its SPD portfolio includes dedicated solutions for both AC and DC applications.
For solar projects, dedicated DC surge protection is particularly important because PV circuits operate differently from AC distribution systems. Blitz Energy's range includes DC SPD 600 V and DC SPD 1000 V products, alongside AC SPDs for single-phase and three-phase applications.
The company also lists IEC compliance and the response time of 25 ns, and a status indication for these listed SPD products.
These specifications can be used to evaluate these products by Solar Installers, Electrical Contractors and System Designers. But the actual voltage, configuration, surge level, and site conditions, along with applicable standards, must be used to determine final product choice.
Conclusion
When it comes to selecting an SPD, it must be an engineering selection and not a product purchasing choice. Consideration needs to be made regarding the voltage the electrical system is running at, whether it is an AC or DC system, the earth configuration, the expected surge environment, the requirements for discharge and degree of protection, location of installation, and finally the type of SPD used. The different roles of Type 1, 2, and 3 SPDs and protection at the DC and AC side for solar installations needs to be evaluated. Examination of technical datasheets, the applicable standards, instructions, and manufacturer support is crucial for selection. A systematic approach to how to size surge protection device requirements can also help prevent the selection of protection that is either inadequate or unnecessarily oversized. An SPD, with proper selection, coordination, installation, and maintenance, can be a vital component of a trustworthy electrical protection plan.
