The Seven Types of Power Problems: Summary of APC White Paper
In today’s ever evolving technologically advanced world, our dependence on reliable power has become more and more crucial to the success of businesses world-wide. With the importance of power considerations in the IT world comes the need for standardization of terminology and communication. For both consumers and IT professionals alike straight-forward accepted language needs to be established so that problems can be correctly identified and appropriate solutions suggested.
The following article borrows from Joseph Seymour’s White Paper titled: The Seven Types of Power Problems. This White Paper was published through APCs June 2010 newsletter. To view the White Paper click here. Mr. Seymour used the IEEE (Institute of Electrical and Electronics Engineers) as the basis for the vocabulary and terminology in his white paper. In this article the seven types of power problems will be briefly discussed as well as symptoms and proposed solutions.
There are seven main types of power disturbances:
• Transients
• Interruptions
• Sags
• Swells
• Waveform Distortions
• Voltage Fluctuations
• Frequency Variations
Transients are potentially the most damaging type of power disturbances. These types of power disturbances are sudden high peak events that raise the voltage and/or current levels in either a positive or a negative direction. One type of this power disturbance is caused by electrostatic discharge (ESD). Other causes are lightning and poor grounding. The results of Transient power disturbances can range from loss or corruption of data to physical damage of equipment. Potential solutions for these types of power problems include surge suppression devices (SPDs), uninterrupted power supply (UPSs) air conditioning units (while reducing heat this also reduces the humidity), anti-static mats, anti-static wristbands and temperature/humidity sensors. Cascading SPDs and UPS devices are the most effective method of protection against power disturbances.
Power Interruptions are defined by complete loss of power for certain durations of time. Causes of this type of power disturbance can be some type of electrical supply grid damage, equipment failure or a basic circuit breaker tripping. An interruption can cause disruption, damage and downtime. The most common solution to this type of power disturbance is the use of a UPS. When the power goes out the UPS acts as an alternative source of power for the equipment (for a designated amount of time depending on the UPS used).
Power sag refers to a reduction of AC voltage at a given frequency for a given duration of time. Sags are usually caused by system faults, and are also often the result of switching on loads with heavy startup currents. Sags cause significant voltage drop to the rest of the circuit it resides on. Possible solutions to this type of power disturbance include adding a dedicated circuit for large startup loads, using an alternative power starting source (e.g. adjustable speed drives or reduced-voltage starters).
On the other end of the spectrum is the power swell. This type of power disturbance results in having an increase of AC voltage for a given duration of time. The result of swells can vary from data errors, flickering of lights, degradation of electrical contacts, semiconductor damage in electronics, and insulation degradation. Solutions for swells include power line conditioners and UPS systems.
There are four subsets of Waveform Distortion that will be briefly discussed:
• DC offset
• Harmonics
• Notching
• Noise
DC offset can occur when transformers are overheated or saturated with power. This results in the inability to deliver full power to the load. The solution for DC offset problems is to replace the faulty equipment.
Harmonic distortion is the corruption of wave frequencies due to the distribution of power. Symptoms of this type of power disturbance include overheated transformers, tripping of circuit breakers and loss of synchronization on timing circuits. Harmonic distortion has been a prevalent problem within IT equipment and newer equipment has been designed with power-factor corrected power supplies in order to correct the power loads.
Notching and Noise are similar but have distinct differences. Notching refers to periodic voltage disturbances caused by other electrical devices. The solution to this power problem is to move the disturbing device or use an UPS. Noise refers to unwanted or superimposed voltage and can result in data corruption, data errors, equipment malfunctions, component failure, hard disk failure and distorted video displays. There are a number of suggested solutions and more than one solution may need to be deployed. The first thing to try is to isolate the load via a UPS, secondly a grounded, shielded isolation transformer can be installed. In addition to these solutions the following are also suggested: relocate the load away from the interference source, install noise filters and install cable shielding.
The last two power disturbances that will be discussed are Voltage Variations and Frequency Variations. Voltage Variations are systematic variations of power and the proposed solution is installing a UPS. Frequency Variations are extremely rare and are usually produced by poor power infrastructures or standby generators. The only solutions for this type of power issue is to determine the cause and then repair, correct or replace as needed.
The widespread use of electronics has raised the awareness of power quality and its affect on business continuity. When downtime is money and the majority of business functionality is inextricably linked to electrical equipment, reliable power becomes less of a commodity and more of a requirement.
Please contact CIO Solutions if you have any power related questions. We will be happy to help assess your current power situation and make recommendations.