A piece of hardware designed to protect electrical or electronic equipment from voltage or current transients is referred to as a surge protective device (SPD).
The main and leading causes of transient voltages or currents are known to be:
- Lighting
- Power generating and distribution equipment switching
- Switching of inductive loads within a facility
Surges mostly last for milliseconds or less. However, it is possible to have surges that last for a couple of seconds, even minutes. Although, these prolonged over voltages or over currents may qualify to be referred to by another name – temporary over voltages.
Temporary over voltages have the potential to degrade the insulation in your home conductors as well as cause arcing.
All these surges are harmful if there is no protection. Some surges are so subtle but detrimental to your home appliances over the long haul.
In exceptional situations, not only can surges cause damage to your appliances but can also cause a fire.
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Lightning Surges
Lightning is further classified as either negative lightning or positive lighting. The negative lighting is the most common and originates from the lower part of the cloud containing negative charges that flow to the ground.
On the other hand, the positive lighting is rare and originates from the top of the cloud that is positively charged.
80% of the negative lightning tends to be less than 30kA compared to 95% of positive lightning.
A few of the lightning ( approximately 2%) will actually go over 60kA.
Utility Switching Surges
Utility Switching does not result in surges with a magnitude as high as lightning.
However, cumulatively, it can negatively affect your electronics and appliances. Utility switching also includes capacitors switching.
Hence, if you live in an area where your utility provider switches their electrical power generation and distribution equipment often, you should be worried by surges getting to your home.
If the over voltage or over current goes beyond a few milliseconds, then you know you are experiencing temporary over voltage (TOC).
TOC will normally lead to the failure of your SPD and hence requires a different kind of protection.
Lets quickly review some statistics of power surges across the United States.
Residential Homes – Insurance Claims on Power Surges
Power surge statistics have been difficult to find in the industry. But despite that, one good source of data related to surges has been insurance claims.
Yes – you can have your home covered for lightning damages including other transient surges. However, the conditions that apply to your policy may comprise having surge protective devices installed in your home.
Industry leaders are for installing lightning arrestors that are grounded properly. This is the easiest way to start having protection against lightning surges.
When the ground is bonded appropriately, it helps to pass the excessive lightning energy through to the ground safely without passing through your home structure or electrical systems.
It is a safe passage of least resistance for the furious lightning charges.
To reiterate, pay attention to have the lightning arrestors in your home properly scoped and installed by a qualified technician.
Lightning surges may hit your home directly by striking your home directly. Alternatively, it may hit an area around your home including power lines and the transient voltages may find their way into your electrical system.
Statistics indicate that fatalities and number of insurance claims have been going down over the years but on the other hand the average cost per claim has generally been going up.
Last year for example, there were 60,851 claims versus 71,551 the previous year. On the flip side, the average cost per claim was $21,578 versus $11,971 two years ago.
On the contrary, the general cost of an adequate SPD may range from $125 to $500 for a residential surge protection.
Standards Governing SPD Installation
For residential electrical service installations, the 2020 NEC has add-on requirements. There is a new section 230.67 that requires the installation of a surge protective device (SPD) in all homes.
The SPD must meet the following requirements:
1. Incorporated with the service equipment, or mounted directly adjacent to the service equipment,
2. A Type 1 (usually placed at the incoming meter) or Type 2 SPD (at the service entrance).
It is worth noting that this SPD requirement applies to both new services as well as services that are modified or upgraded.
To make it more painless and meet the code requirements, the majority of manufacturers have now come up with electrical panels with built-in SPD.
It is a general behavioral observation that a majority of facilities and residential homes owners that had experienced damage attributed to power surges, purchased SPDs immediately after repairs were done.
What is the Technology Used by Surge Protective Devices?
Owing to their characteristics, metal oxide varistors (MOVs) are commonly employed in modern SPDs.
They suppress surges by allowing very high voltages and currents to pass through them. While on low(normal) operating voltages, they have huge resistance (>10MOhms).
Types of whole House Surge Protectors
Type 1 SPDs are installed as close to the incoming utility as possible while type 3 is closest to the point of use, for example a surge receptacle or surge suppressor extension cord.
There are even type 4 SPDs that will be inbuilt in your equipment eg, TV, computer, fridge etc.
Type 2 will be somewhere between the main incomer and final point of power use.
The Payoff
An SPD is as great as the grounding it has!
It has also to be installed according to your local regulations – 2020 NEC, NFPA 70, IEEE
Depending on where you live, consider such factors such as lightning, utility stability in your area.
You can then choose an appropriate type 1 or type 2 surge protection device. An addition type 3 SPD can be included for enhanced surge suppression.
Furthermore, while purchasing new appliances, give thought to the surge protection feature available. That will be a type 4 SPD installed by the manufacturer.
We have an article on the best whole house surge protector and another one on the pros and cons of a whole house surge protector.
I am positive you will find them insightful.