Surge Protection Education2019-04-04T15:50:50+08:00
1201, 2018

Does a Type 1 SPD perform better than a Type 2 SPD?

Not necessarily. A Type 1 SPD offers versatility by being able to be connected to either side of service entrance, however UL does not compare the surge clamping performance of a Type 1 SPD versus that of a Type 2 SPD. UL investigates clamping performance of all SPDs equally, without regard for SPD type. UL also evaluates all SPDs for safe operation within their intended installation location. Beginning with UL 1449 3rd Edition, Type 1 approved SPDs will include devices that were formerly known as Secondary Surge Arresters and will also include many devices that were formerly known as TVSS. It is important to understand that many Secondary Arresters type devices were designed with a higher MCOV (Maximum Continuous Operating Voltage) than were TVSS type devices. And since the MCOV rating of an SPD can have a direct impact on surge clamping performance, the best practice for SPD selection should include careful consideration for ratings such as maximum surge current, IEEE clamping voltage, UL VPR, and surge life ratings.

501, 2018

Where Can I Place SPDs to Protect My Facility?

It is impossible to prevent voltage surges from either entering your facility or from occurring inside of your facility. When protecting a facility against transients, the best approach is a networked or cascaded approach. As shown in the graphic below, The Institute of Electrical and Electronics Engineers (IEEE) has developed three categories that every facility can be divided into, location Category A, B and C. See IEEE Standard C62.41.1 and C62.41.2 for further reference.


Category A: outlets/receptacles and long branch circuits (indoor) (least severe)
• All outlets at more that 10m (30 ft) from Category B
• All outlets at more than 20m (60 ft) from Category C

Category B: feeders, short branch circuits and service panels (indoor)
• Distribution panel devices
• Bus and feeder distribution
• Heavy appliance outlets with “short” connections to service entrance
• Lighting systems in large buildings

Category C: outside overhead lines and service entrance (outdoor)
• Service drops from pole to building
• Runs between meter and panel
• Overhead lines to detached building
• Underground lines to well pump

Location Category C devices can be used in […]

501, 2018

How do I select a proper Prosurge SPD for my application?

Though we try our best to offer an extensive, thorough product presentation on our website, catalogs and other documents, we believe the best way for model selecting is to consult with us with your requirement and then our professional will recommend a suitable model.

501, 2018

What are ANSI/UL 1449 Third Edition Versus IEC 61643-1 – Key Differences In Testing

The following examines a few of the key differences between Underwriters Laboratory(UL)’s required test for surge protective devices (SPDs); ANSI/UL 1449 Third Edition and the International Electrotechnical Commission (IEC) required test for SPDs, IEC 61643-1.

Short Circuit Current Rating (SCCR): The capacity of current with which the tested SPD can withstand at the terminals where connected, without breaching the enclosure in any way.

UL: Tests the full product at twice the nominal voltage to see if entire product is completely offline. The entire product (as shipped) is tested; including metal oxide varistors (MOVs).

IEC: Test only looks at the terminals and the physical connections to determine if they are robust enough to handle the fault. MOVs are replaced with a copper block and a manufacturer’s recommended fuse is placed in-line (external to the device).

Imax: Per IEC 61643-1 – The crest value of a current through the SPD having an 8/20 waveshape and magnitude according to the test sequence of the class II operating duty test.

UL: Does not recognize the need for an Imax test.

IEC: An operating duty cycle test is used to ramp up to an Imax point (determined by the manufacturer). This is meant to find “blind points” […]

501, 2018

How to choose the correct surge protection device that must be installed?

Choosing the right surge arrester(s) is a key factor to guarantee correct protection of the installation. A poorly designed Lightning & Surge protection system may lead to early ageing of the SPD and potential failure of the protective devices in the installation allowing damage to the primary systems up stream, thus defeating the rationale behind the protection being installed.

Prosurge does not provide a set of rules and guides to support acorrect design of the protection system according to the application. However we follow the IEC and UL lightning and surge protection standards. With this in mind we provide a cascaded system as laid down in the rules of the standard, not the rules of Prosurge.

In the field of industrial applications, a standard practice is to install a cascaded protection system based on several coordinated protective devices installed at different stages (LPZ’s). The benefit of this strategy is the fact that it allows a high discharge capacity close to the installation entrance along with a low residual voltage (level of protection) at the main incomer of installation of sensitive equipment.

The design of such a protective system is, amongst other factors, based on the assessment of information such as existence […]

501, 2018

Can lightning destroy the photovoltaic system?

Photovoltaic systems are technologically highly sensitive and a direct lightning strike would definitely destroy it. There is also yet another hazard,as a lightning strike could create surge voltage near the solar power system and these surge voltages can also destroy the system. The inverter is the primary point in need of protection. Usually, inverters will integrate surge-voltage protectors into their inverters. However, since these components only discharge small voltage peaks, you should consider using surge protective devices (SPD) in individual cases.

501, 2018

Are joule ratings a specification used for SPD?

In the past, some manufacturers have used joule ratings in their specifications. They are not considered a good indicator for SPD performance and not recognized by any standard organizations. Prosurge doesn’t support this specification also.

501, 2018

Is “Response Time”a valid specification?

Response time specifications are not supported by any standards organizations overseeing Surge Protective Devices.IEEE C62.62 Standard Test Specification for SPDs specifically mentions it should not be used as a specification.

501, 2018

What’re the different power systems in the US and their protection needs?

The US power distribution system is a TN-C-S system. This implies that the Neutral and Ground conductors are bonded at the service entrance of each, and every, facility or separately derived sub-system. This means that the neutral-to-ground (N-G) protection mode within a multi-mode SPD installed at the service entrance panel is basically redundant. Further from this N-G bondpoint, such as in branch distribution panels, the need for this additional mode of protection is more warranted. In addition to the N-G protection mode, some SPDs can include line-to-neutral (L-N) and line-to-line (L-L) protection. On a three phase WYE system, the need for L-L protection is questionable as balanced L-N protection also provides a measure of protection on the L-L conductors.

Changes to the 2002 edition of the National Electrical Code® (NEC®) ( have precluded the use of SPDs on ungrounded delta power distribution systems. Behind this rather broad statement is the intention that SPDs should not be connected L-G as by so doing these modes of protection are creating pseudo grounds to the floating system. Modes of protection connected L-L are however acceptable.The high-leg delta system is a grounded system and as such allows for protection modes to be connected […]

501, 2018

How does installation affect the performance of SPDs?

The installation of SPDs is often poorly understood. A good SPD, incorrectly installed, can prove of little benefit in real-life surge conditions. The very high rate-of-change of current, typical of a surge transient, will develop significant volt drops on the leads connecting the SPD to the panel or equipment being protected. This can mean higher than desired voltages reaching the equipment during such a surge condition. Prosurge suggests that measures to counteract this effect include locating the SPD so as to keep interconnecting lead lengths as short as possible, twisting these leads together. Using a heavier gauge AWG cable helps to some extent but this is only a second order effect. It is also important to keep protected and unprotected circuits and leads separate to avoid cross coupling of transient energy.