Safety and performance. While there are many varying criteria to be considered during the decision-making process for selecting an appropriate surge protective device (SPD), if the design engineer neglects the importance of either of these two areas for the products being specified, there can be serious implications for the client.
Power quality solutions are predicated on the individual requirements of each facility. What works best for large high-rise buildings with massive HVAC, telecommunications and computer networks may not be the wisest approach for a busy textile mill or food processing plant.
The most logical approach to a power quality environment is prevention. It is recommended to use a cascaded approach to system-wide facility protection. It is important to place SPDs at the source of the disturbance as well as in the proximity of the sensitive loads.
If a facility has many devices that generate transients, such as variable speed drives, motors, switch-mode power supplies, or arc welders, an SPD installed within the proximity of these electrical devices will provide additional needed surge protection than an SPD installed at a service entrance alone.
When electrical transient protection is properly specified into the facility’s blueprints along with lighting, HVAC, and other mandatory systems, tenants are saved the unnecessary headache and expense of transient episodes, which can cost production-critical operations — such as major airlines, refineries, television networks and telecommunications operations — as much as one million dollars per minute in damage and downtime.
Compared to this staggering figure, the price of a facility-wide network of integrated power protection is truly a justifiable expense. Human life is also at risk without power protection in place. Imagine the peril of a night airplane landing without the guidance of control tower systems, or the tragedy of a medical misdiagnosis due to a transient-related data error on an MRI.
The commercial configuration for system-wide facility protection typically combines uninterruptible power supplies (UPS) with SPD products. Voltage regulators may be included to maintain minimal 60 Hz voltage fluctuations.
In addition to the products listed above, industrial facilities, such as textile mills or automated production plants, may require specialized protection for motor control centers or electrical busway, both of which provide electrical power for many different pieces of equipment. Suppression systems designed specifically for these applications are available for configuration into a facility-wide protection plan.
It should be remembered that uninterruptible power supplies require power protection to ensure completely reliable operation. Also worth mentioning is the minimal value of isolation transformers and surge arresters in a comprehensive power quality environment.
Frequently installed at the electrical service entrance, surge arresters are designed to limit the surge voltage magnitude to a level that is not damaging to transformers, switchgear or other service equipment; in other words, they must reduce magnitude events to 2,000 – 3,000 volts. While this voltage range is within the withstand capability of some service entrance equipment, there are many devices being included at the service entrance that is very sensitive. Examples would include power quality metering and other Smart Grid devices. Additionally, it will likely still be damaging to electronic loads within the facility unless additional electrical transient protection is installed at strategic electrical distribution points inside.
Isolation transformers, while attenuating common mode noise, fail to provide cross-interference protection for loads connected on the secondary side. Because a majority of system-upsetting noise is load generated, safeguarding one load from affecting another becomes even more critical as increasingly sensitive electronic loads are implemented into a noisier distribution system. Surge protective devices with capacitive filtering offer additional protection.