Which is better, type 1 or type 2 SPD?

A lightning arrester (alternative spelling lightning arrestor) (also called lightning isolator) is a device, essentially an air gap between an electric wire and ground, used on electric power transmission and telecommunication systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrester, in most cases to earth.

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In telegraphy and telephony, a lightning arrester is placed where wires enter a structure, preventing damage to electronic instruments within and ensuring the safety of individuals near them. Smaller versions of lightning arresters, also called surge arresters, are devices that are connected between each conductor in power and communications systems and the earth. These prevent the flow of the normal power or signal currents to ground, but provide a path over which high-voltage lightning current flows, bypassing the connected equipment. Their purpose is to limit the rise in voltage when a communications or power line is struck by lightning or is near to a lightning strike.

If protection fails or is absent, lightning that strikes the electrical system introduces thousands of kilovolts that may damage the transmission lines, and can also cause severe damage to transformers and other electrical or electronic devices. Lightning-produced extreme voltage spikes in incoming power lines can damage electrical home appliances or even cause death.[1]

Lightning arresters are used to protect electric fences. They consist of a spark gap and sometimes a series inductor. Such type of equipment is also used for protecting transmitters feeding a mast radiator. For such devices the series inductance has usually just one winding.

Lightning arresters can form part of large electrical transformers and can fragment during transformer ruptures. High-voltage transformer fire barriers are required to defeat ballistics from small arms as well as projectiles from transformer bushings and lightning arresters, per NFPA 850.[United States-centric]

Components

A potential target for a lightning strike, such as an outdoor television antenna, is attached to the terminal labeled A in the photograph. Terminal E is attached to a long rod buried in the ground. Ordinarily no current will flow between the antenna and the ground because there is extremely high resistance between B and C, and also between C and D. The voltage of a lightning strike, however, is many times higher than that needed to move electrons through the two air gaps. The result is that electrons go through the lightning arresters rather than traveling on to the television set and destroying it.

A lightning arrester may be a spark gap or may have a block of a semiconducting material such as silicon carbide or zinc oxide. "Thyrite" was the trade name used by General Electric for the silicon carbide composite used in their arrester and varistor products.[2] Some spark gaps are open to the air, but most modern varieties are filled with a precision gas mixture, and have a small amount of radioactive material to encourage the gas to ionize when the voltage across the gap reaches a specified level. Other designs of lightning arresters use a glow-discharge tube (essentially like a neon glow lamp) connected between the protected conductor and ground, or voltage-activated solid-state switches called varistors or MOVs.

Lightning arresters used in power substations are large devices, consisting of a porcelain tube several feet long and several inches in diameter, typically filled with discs of zinc oxide. A safety port on the side of the device vents the occasional internal explosion without shattering the porcelain cylinder.

Lightning arresters are rated by the peak current they can withstand, the amount of energy they can absorb, and the breakover voltage that they require to begin conduction. They are applied as part of a lightning protection system, in combination with air terminals and bonding.

See also

• Lightning rod
• Surge arrester
• Thyristor switched capacitor
• Faraday cage

References

SPD concept: Surge Protective Device (SPD) is an electrical appliance designed to protect circuits and associated facilities from damages caused by transient overvoltages and spikes. They can provide precise protection to minimize equipment downtime and guarantee smooth operation.

Type 1 Surge protective device: Type 1 SPD, also known as Class I SPD, installed at the service entrance of an electrical system, is designed to withstand high-energy surges, protecting severe transient events for equipment and circuits within the electric system.

Type 2 Surge protection device: Type 2 SPD, or Class II SPD, is typically installed downstream from type 1 or at distribution panels. It offers protection against residual surges and lower-energy transients, working in combination with the type 1 surge protective devices.

Type 3 Surge protector device: Type 3 SPD, or Class III SPD, is installed at the point of use, near or within significant or sensitive individual devices, providing accurate and localized surge suppression against low-energy surges that is relatively minor but may enough to damage specific equipment as well.

A waveform refers to the specific shape and characteristics of the transient voltage or current surge that the SPD is designed to withstand. Different types of SPDs are tested and rated against different waveform standards, which represent different types of potential surges. Here are some of the most common:

10/350 µs Waveform (Type 1 SPDs): features a rise time of 10 microseconds and a more protracted duration of 350 microseconds. The waveform is employed in defining the ratings of type 1 SPDs, specialized devices crafted to protect against direct lightning strikes. The extended rise time reflects the slower buildup of voltage typical in such lightning events.

8/20 µs Waveform (Type 2 SPDs): This waveform exhibits a rapid rise time of 8 microseconds and a relatively extended duration of 20 microseconds. It is a standard for defining the ratings of type 2 SPDs. The devices are engineered to protect against fast-rising, high-current surges that may arise from activities like switching operations or nearby lightning strikes. The waveform effectively replicates the swift increase in voltage associated with these events, guiding the design and performance expectations of type 2 SPDs.

For protection of signal or data lines, the 1.2/50 µs Waveform is indispensable. Characterized by an extremely fast rise time of 1.2 microseconds and a brief duration of 50 microseconds, this waveform is utilized in defining the ratings of SPDs designed for safeguarding signal and data lines. Signal and data lines are highly sensitive to rapid voltage changes, and this waveform simulates a very fast-rising, lower-current surge often encountered in these applications.

Three types of SPDs differently in their energy handling capacity as they are designed to function against varied end-of-use scenarios, classified according to their location and protection level:

Type 2 surge protective device (SPD), classified as Class C, addresses medium-sized surges more common than type 1 but still potent enough to damage electronics. With an energy handling capacity ranging from In & Imax (8/20 µs) 20kA to 75kA.

Type 3 surge protective device (SPD), classified as Class C, specializes in handling the smallest surges from switching transients within the building&#;s electrical system. Operating with an energy handling capacity of Uoc (1.2/50 µs) 6kV to 20kV.

A type 1 SPD is generally crafted to manage the high-energy surges linked with direct lightning strikes. However, type 1 arresters alone do not fully protect the electrical system. From the standpoint of energy handling capacity, they do surpass that of type 2 SPDs, whereas type 1 SPDs confront greater surge currents. Although they can endure a significant portion of the energy, there remains residual current that requires the functionality of type 2 surge arresters.

Consider a large concert venue where the main entrance is equipped with sufficient security checks (functions as a type 1 SPD) to prevent any major threats or unauthorized items from entering the venue. At the same time, inside the concert hall, there are additional security personnel and checks (similar to a type 2 SPD) to handle smaller issues to guarantee the concert is going on smoothly.

The choice between type 1 and type 2 SPDs depends on factors such as installation location and the anticipated energy currents they need to handle. It&#;s worth noting that neither type 1 nor type 2 SPDs are inherently superior; their effectiveness is contingent on specific application requirements.

Type 1 Surge Protective Devices are intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures, and are intended to be installed without an external overcurrent protective device.

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It will be installed in the primary distribution board at the origin of the electrical installation. Type 1 surge protection device is particularly useful in a high lightning density area where the risk of heavy surge current or even direct strike is high (eg.: buildings equipped with lightning rods).

On the other hand, type 2 SPDs are positioned at the sub-panel or branch circuit level within the electrical system and on the load side of the service equipment overcurrent device, including SPDs located at the branch panel. They are designed to provide protection against localized surges and moderate to high-energy transients that may still pose a threat to sensitive equipment.

By being closer to the point of use, type 2 SPDs offer a secondary layer of defense, effectively preventing surges from traveling further into the electrical network.

The device would normally be installed in sub-distribution boards and in the primary distribution board if there was no requirement for a type 1 surge protective device.

When it comes to industrial sites, advanced plants, or residential house and buildings exposed to lightning strikes that require serious surge protection, type 1 surge arresters emerge as the indispensable option. They are designed to handle extreme energy that without protection would severely damage the whole system and facilities there connected, which could potentially result in operational downtime or even fire incidents.

If you are protecting electrical systems that have a lower susceptibility to lightning strikes and electrical disturbances, coupled with a relatively moderate circuit load, then type 2 surge protective device can be a great choice.

For single and sensitive electrical eqipment such as PCs, televisions, chargers and meters, etc. Filtered by type 1 and type 2 SPDs installed upstream, the surge energy is greatly minimized, whereas there is still residual energy that can pose a threat to the sensitive devices.

Installed at outlets or near the specific terminal equipment, type 3 SPDs are specialized for the point-of-use protection that offer accurate surge protetion for individual electronic equipment and appliances from lower-level surges that may originate within the immediate vicinity.

In addition to commonly used SPDs mentioned above, specialized devices cater to specific surge protection needs for various applicance. Examples include PoE (Power over Ethernet) surge protector, data and signal line arresters, LED surge protector. Combined with type 1 and type 2 devices, together they establish a comprehensive surge protection system that contributes to normal operation.

The decision to use both type 1 and type 2 SPDs depends upon various factors. Considerations include the risk of lightning strikes in the area, the sensitivity of the electronic equipment being used, budget plans, and adherence to local electrical codes and regulations.

In situations where the risk of lightning is high or where critical and sensitive equipment is in use, the installation of both types of SPDs is often recommended.

Type 1 surge arresters are required to be installed directly under the incoming breaker, especially when there is a lightning rod on the building roof.

For industrial and commercial sites, it is a must to have both surge arresters installed in place as lightning protection to these areas dense in popularity comes more urgent, the lack of protection could not only bring in equipment and facility damage but potentially extend to putting the safety of people at risk.

Consulting with a qualified electrician or electrical engineer is necessary to assessing the specific needs of the electrical system and determining the most effective combination of SPDs for sustained protection.

Cascading or layering type 1 and type 2 Surge Protective Devices (SPDs) in an electrical system is a strategic approach that creates a tiered defense system against surges of varying intensity.

The primary benefit lies in the comprehensive protection it offers. Type 1 SPDs, positioned at the service entrance, are designed to divert high-energy surges. Combined with type 2 SPDs at distribution or branch panels within the facility, the comprehensive system is protective against both high-energy and low-level surges.

Another significant advantage is the redundancy in surge protection it brings. In the event that the type 1 SPD at the service entrance encounters overwhelming surges or experiences a failure, the type 2 SPDs act as a backup, delivering continued protection and resilience for the electrical system.

However, the specific cascading approach lies on requirements of each electrical settings as blindly employing a vast array of devices doesn&#;t necessarily equal to improved protective effects.

From BS : , 18th Wiring Regulations, the wiring and cables of SPDs mounting can be concluded as follows:

When incorporating Surge Protective Devices (SPDs), the necessity for an OCPD backup is contingent upon two primary factors:

If the main OCPD is less than or equal to the recommended maximum backup OCPD of the SPD, there is no need for an additional OCPD for the SPD.

Conversely, if the main OCPD rating exceeds the maximum backup OCPD rating of the SPD, the installation requires a backup OCPD. In such cases, it is imperative to install a backup OCPD, and the recommended maximum backup OCPD should be followed.

LSP&#;s reliable surge protection devices (SPDs) are designed to meet the protection needs of installations against lightning and surges. Contact our Experts!

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