Power Quality

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Power Conditioning Equipment

Various types of power conditioning equipment are available to protect your sensitive electronic equipment against power quality problems. Power conditioning equipment is highly recommended since unplanned disturbances on the electric utility's system will occur. The hardest decision to make is purchasing the right power conditioning equipment to mitigate your power quality problem.

The following table illustrates the effectiveness of various power-conditioning equipment. Proper selection and application of the equipment requires an understanding of the type of disturbances likely to affect your specific equipment. Without proper conditioning, sags, momentary interruptions or transients could adversely affect the performance of your sensitive equipment.

Green = It is reasonable to expect that the Power Conditioning Technology will correct the Power Quality Condition.
Red = The Power Conditioning Technology may not fully correct the Power Quality Condition.

Power Quality Technology condition

IEEE Std 1100-1992, "Recommended Practice for Powering and Grounding of Sensitive Electronic Equipment."

The two categories of power conditioning equipment are "power enhancers" and "power synthesizers." Some manufacturers and suppliers loosely employ the terms "power conditioner" and "line conditioner." A power conditioner could be either a power enhancer or a power synthesizer, and could also provide more than one mode of power protection. It is important to refer to the product specifications to understand a power conditioner's function. The rationale for choosing power synthesizer over power enhancer may not be obvious.
We will discuss some of the basic qualities of each of the different types of power conditioning equipment below.


Power Enhancers

Power enhancers provide a way to improve your facility's electrical supply. However, power enhancers provide no help for loss of power during a power outage. Some examples of power enhancers are:

  • Surge Suppressors 
  • Voltage Regulators 
  • Isolation Transformers

Surge Suppressors

Surge and transient or spike suppressors are the simplest, least expensive way to condition power. They reduce the size of spikes to levels that are safe for your electronics. High energy surge suppressors are installed at the service entrance. Transient voltage surge suppressors (TVSS) also are installed at the terminals of the sensitive electronic load. They provide protection against lower energy, high voltage spikes. The service entrance suppressor is considered a minimum protection level, even if other power conditioners are employed. There are different levels of TVSS equipment. Their performance specifications vary widely and may depend on price. TVSS performance degrades in time as it suppresses high voltage spikes therefore, needs periodic replacement.


Voltage Regulators

Voltage regulators maintain voltage output within a desired limit during wide fluctuations in the input. They might provide protection against spikes or noise and limited or no protection from rapid voltage changes. Voltage regulators respond best to slow changes in voltage.


Isolation Transformers

Isolation transformers protect sensitive electronic equipment by buffering electrical noise. They effectively reject common mode line-to-ground noise, but are limited in their rejection to normal mode line-to-line or line-to-neutral noise. Isolation transformers do provide a "separately derived" power source and permit single point grounding.


Power Synthesizers

Power synthesizers are capable of not only enhancing the incoming power, but also providing auxiliary power during utility outages. Power synthesizers are more complex and costly than power enhancers. In addition, power synthesizers are usually less efficient and require more maintenance. Power Synthesizers include:

  • Motor Generators
  • Standby Power Supply
  • Uninterruptible Power Supply
  • Uninterruptible Power Supply with Auxiliary Generator

Motor Generators

Motor generators consist of an electric motor driving a generator. They convert incoming electrical energy into mechanical energy and back again into electrical energy. The mechanical shaft isolates the electrical load from incoming disturbances such as voltage impulses, surges and sags. The motor generator rides through many short "momentary interruptions" but will not protect against sustained outages. Typical ride-through capability is 10-30 seconds.


Standby Power Supply

For problems with power supply interruptions, use a standby power supply (SPS) or an off-line uninterruptible power supply (UPS). This device switches to a battery supply upon loss of utility power. Some designs include a transfer during certain power disturbances.
The SPS is effective only when the equipment being protected can withstand the transfer time, usually a number of milliseconds. When voltage is normal, the transfer switch returns to the normal utility feed. Standby power supplies are typically available for small loads such as personal computers.

Standby Power Supply

Uninterruptible Power Supply

Uninterruptible power supply (UPS) devices provide power to critical loads at all times. The two classifications of UPS systems are "rotary" and "static." A rotary UPS uses some form of a motor generator to provide uninterruptible power, while a static UPS has no moving parts and typically uses power semiconductors.

A static UPS system includes a rectifier/charger, a battery bank, a static inverter and an automatic transfer switch. Direct current power feeds an inverter from either the rectifier or battery and is converted to conditioned AC power that serves the sensitive electronic equipment. A direct utility feed powers the on-line UPS. A DC bus backed by a battery provides conditioned power. An on-line UPS typically has a solid-state transfer switch for switching directly to utility power if an internal element fails within the UPS.

Surge and transient or spike suppressors are the simplest, least expensive way to condition power. They reduce the size of spikes to levels that are safe for your electronics. High energy surge suppressors are installed at the service entrance. Transient voltage surge suppressors (TVSS) also are installed at the terminals of the sensitive electronic load. They provide protection against lower energy, high voltage spikes. The service entrance suppressor is considered a minimum protection level, even if other power conditioners are employed. There are different levels of TVSS equipment. Their performance specifications vary widely and may depend on price. TVSS performance degrades in time as it suppresses high voltage spikes therefore, needs periodic replacement.

Uninterruptible Power Supply

Uninterruptible Power Supply with Auxiliary Generator
An uninterruptible power supply plus an auxiliary generator provides an even better supply system. This kind of system allows computers, for instance, to operate during lengthy utility outages. The generator starts automatically upon loss of utility power, and the power source for the UPS will automatically transfer to the generator. Generators are available that utilize different fuels including gasoline, natural gas, propane or diesel.


For Motors and Other Electrical Equipment

Customers are advised that there are numerous manufacturers of protective devices for electrical equipment and more arrive on the market everyday. The following list is not exhaustive but provides a starting point for customers to purchase motor and equipment protective devices consistent with Rule 2 (Character of Service) of Hawaii Electric Light's tariff. You should factor in the cost of the motor or equipment you are protecting or the resultant cost of motor or equipment failure on your business, when selecting a specific product.

Industrial Motor Applications

Commercial Motor Applications

Local Consultants:

  • A-1 A-Lectricians, Inc. (Tel: 839-2771)
  • American Electric (Tel: 848-0751)
  • GE Industrial Systems (Tel: 852-6851)
  • Siemens Industrial Services (Tel: 833-6687)

This list of manufacturers, suppliers, and consultants is not comprehensive and Hawaii Electric Light does not, in any way, endorse or guarantee the performance or suitability of any of the products manufactured by these suppliers or information provided by consultants. Furthermore, all information contained herein is provided "as is" without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability, fitness for particular purpose, or non-infringement. Hawaii Electric Light assumes no responsibility for errors or omissions in this publication or other documents that are referenced by or linked to this publication. This list is intended solely as a guide to assist our customers. The customer is encouraged and must contact suppliers directly or through a sales agent or distributor for specific information about what products are suitable for their intended application as well the performance of these products. Hawaii Electric Light recommends that customers consult with a qualified consultant regarding preventive maintenance, power quality and motor and electrical equipment protection.