Listed on the right are just some of the symptoms of power quality problems found in wiring systems that were designed for the needs of yesterday.
Yes, these symptoms met, and probably still meet, electrical codes. But the codes are not intended to provide for a system free of transients, power surges, voltage sags and spikes, and other interruptions that can cause expensive downtime or erratic data operations. A recent study indicates that the average office building experiences 106 such power quality problems in a typical month.
Most of these disturbances originate right within the building.
Computers generate the very harmonics they're sensitive to. Personal computers, laser printers and other switched-mode power supply equipment within your building are usually the culprits for most of the power supply irregularities affecting other computers. It's a problem that has only recently begun to be recognized in the building industry, as more and more computers and similar equipment are installed, turning the modern office or factory into a high-tech computer environment.
In new construction or renovation, many power disturbances can be prevented or significantly lessened by designing for power quality assurance, at surprisingly small cost. In fact, the Electric Power Research Institute says: "inadequate grounding and wiring underlie most problems with sensitive microprocessor-based equipment." (EPRI Publication CU.2026.3.90) The average additional cost to install an enhanced electrical distribution system, designed to the currently recommended practice, versus a "standard" system has been estimated at 1% to 2% of the cost of construction. In retrofits, the costs of the solutions will run much higher, so the time to "do it right" is in the initial design.
Landlord or Developer?
Savvy tenants know what to look for when shopping for space. They want a facility that meets their power needs now, and in the future. If your competition is prepared for the modern office, and you're not, guess who gets the tenant?
Engineer or Contractor?
Your implementation of the power quality design considerations itemized here will impact electrical safety and reliability and allow design of a more functional facility resistant to the effects of harmonics and transients.
Factory or Industrial Facility?
The modern factory floor is a high-tech, interconnected manufacturing system. The cost of power quality problems in lost productivity, maintenance and repair at industrial facilities alone has been estimated at over $12 billion annually. What is downtime or lost data worth in your facility, per hour?
Copper Development Association Inc. (CDA) suggests the following steps that may prevent most power quality problems from occurring:
- Use double-size neutral conductors or separate neutrals for each phase.
- Specify a separate, insulated full-size grounding conductor, rather than relying on the conduit alone.
- Use an isolated grounding conductor for sensitive equipment.
- Segregate sensitive loads on separate branch circuits, fed from a separate panelboard, fed from separate feeders (and even separate transformers if possible).
- Run a separate branch circuit for every 4 to 6 duplex outlets.
- Use an outside copper ground ring and multiple ground rods as part of the grounding electrode to achieve lowest practical resistance to ground. Measure ground resistance.
- Use harmonic-rated circuit breakers, panelboards, and transformers.
- Use surge and lightning protection.
- Oversize phase conductors to minimize voltage drop. (This will save energy too, and may even pay for itself through lower I 2R losses.)
- Choose materials based on superior connectability. Poor quality connections are a major consideration. This is where all-copper wiring excels over other materials.
Design these features into new construction or renovation work. Reduced downtime or data loss will more than pay for these measures.
CDA has a bibliography of engineering and technical publications on harmonics, grounding and other power quality issues, available free of charge.
Copper Development Association
260 Madison Avenue, 16th Floor
New York, NY 10016
Telephone: (212) 251-7200, Fax: (212) 251-7234