With more sophisticated electronic devices in the home and in commercial and industrial environments, the need to protect equipment from lightning surges, and from electrical surges caused by man-made devices, has become much more acute. Ian Parmenter, ABB's Product Manager for Surge Protection Devices, explains how Surge Protection Devices (SPDs) can provide protection from surges, and reduce the cost of replacing damaged equipment:
This is even more so in the workplace, where we rely on electronic equipment such as computers, while the factory floor is dominated by automated machines carrying out a complex set of actions often transmitted by a centralised control system.
In all these environments, we're at a loss should any of these devices break down as a result of a power surge. At work, equipment that is damaged as a result of a surge can cost thousands in lost productivity, not to mention the cost of repair. Many devices, either in the workplace or in the home, can be expensive to fix or replace so ensuring that appropriate SPDs are installed is essential.
Surges can be caused in three main ways:
- Lightning strikes - A direct lightning strike can cause blackout and even the risk of fire to a building. Buildings that have a lightning protection device, such as a lightning rod, to dissipate the power of a strike, can still be indirectly affected. The power absorbed by the protection device can be transferred to the main power supply near or in a building and send a surge to electrical equipment. Underground cables situated near a lightning strike can also transmit the effect of the strike to electrical equipment inside a building.
- Overvoltages - overvoltages can be caused by equipment inside a building, and occur due to current surges - i.e. where a current would exceed its maximum permitted operating level. Short-term overvoltages are also known as transients. Their effect on equipment varies; from crashing PCs, to wearing out a computer's internal components. They can be caused by anything that effects a sudden change in power usage. Common examples include office photocopiers or microwaves, which are both capable of creating surges that are then sent through a building's electrical system.
- Man-made items outside a building - overvoltages can also be caused by surges being transmitted from a distribution or sub-distribution board into a building via telephone lines or data cables.
What can SPDs do?
SPDs divert a current surge harmlessly to the ground. They also limit overvoltages to values compatible with the withstand voltage of the equipment or devices connected - i.e. the upper-limit of the amount of voltage a device uses during operation.
Whilst most houses can typically have standard SPDs installed, office buildings and factories would benefit from an audit before installing suitable surge protection. Ideally, such an audit should consider the following:
- Environmental parameters - should take into account the frequency of lightning strikes in the area, as well as the radius a lightning strike will cover.
- Installation and equipment parameters - should consider what type(s) of equipment are already in place - e.g. lightning rods, and also the location of the distribution board and the equipment to be protected.
- Security parameters - need to assess the potential implications of loss of equipment and/or life, as well as environmental risks.
Such factors can all affect the level of SPD protection required for a building. Those that require the highest level, such as high-rise commercial towers or large automated factories, would benefit from the full protection offered.
Zoned approach:
It is rare that one SPD can provide protection against all types of current surges to a building, so different layers of protection are required. A zoned approach is generally considered to be the best way to maximise protection, by ensuring that all areas of a building are protected against both external and internal surges. At least two zones of protection are required for many commercial buildings.
The following illustrates the different zone levels to consider, to ensure effective protection:
- Zone 1 - the first zone would protect against direct lightning strikes, and would typically be placed outside of a building.
- Zone 2 - would be found inside a building on the main distribution board. This would typically protect against the external surge caused by a lightning strike, and provides a second layer to deal with residual external surges. It is also the first layer of protection from external overvoltages caused by power lines or cables.
- Zone 3 - would be used to protect against internal surges, and provide protection to equipment such as PCs, microwaves and photocopiers. This third layer should be placed near to the location of any critical equipment. In a work environment it will often be on a sub-distribution board.
- Zone 4 - additional protection can be added to the location of the end-user equipment. In the home, this would typically be provided by extension leads with SPDs included. Sockets with SPDs are also now available.
How can ABB help?
ABB's low voltage products feature inbuilt protection against different types of current surges. Type 1 SPDs can manage a current capacity of up to 15kA, and are able to handle a direct lightning strike. They can be supported by Type 2 SPDs, which can handle network voltages from 57V up to 600V. Using Type 2 protectors will serve two purposes, providing both the back-up required to support the Type 1 SPD, and protection against internal surges on distribution boards throughout the facility.
There is also a need in modern offices to protect equipment used for data and telecoms storage and transmission. Such is the reliance of many companies on electronic data, it is vital that companies use SPDs to protect against potential data loss or unavailability. Dedicated SPDs, like ABB's OVR TC SPD, will protect equipment connected either to telephone lines, computer links or looped systems for voltages of 6V, 12V, 24V, 48V or 200V.
The cost of replacing equipment being damaged by either internal or external surges far outweighs the cost of providing adequate protection for a building. In particular, breakdowns caused by surges can result in thousands being lost in business. Providing effective protection against current surges is essential to ensure a smooth-running business and a safe and secure home.