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Voltage Surges: The Real World Of Power Quality Problems


VASI

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Most electronic equipment is designed to operate at voltage levels of 120 volts in North America or 230 volts in Europe.

Occasionally some very current hungry equipment might be powered from 208 volts in North America.

Regardless of the power line voltage, power supplies inside the electronic equipment convert this AC voltage into much smaller DC voltages that power the integrated circuits and transistors which in turn do the work inside the preamp, mixing console, graphic equalizer or amplifier.

Voltage surges are a commonly recognized but somewhat misunderstood power quality phenomenon. They are typically hundreds or even thousands of volts in amplitude, and may contain substantial amounts of energy.

Back in the days when electronics was largely based on vacuum tubes, a voltage surge of a thousand volts might not have’ been a big deal. It’s much more of a problem, however, for systems that use solid state components whose operating voltages are five volts or less.

The damage caused by a voltage surge may be either visible or invisible. If surge energy is large, destruction of an electronic device may occur, and damage will be tangible in the form of charred components.

Unfortunately, surges don’t always cause outright damage. Sometimes surges contain smaller energy amounts, and the damage they cause is invisible. That’s because smaller energy amounts merely erode semiconductor material at a microscopic level - a phenomenon sometimes called “electronic rust.”

The component gradually degrades, and damage accumulates with repeated exposure to smaller energy surges. Eventually the component fails and usually without visible damage. It’s difficult to associate cause with effect in such cases, and equipment failure may often not be attributed to voltage surges at all.

DEFINING THE PROBLEM

Voltage surges come in different shapes and sizes depending on where they occur in a facility. The Institute of Electrical and Electronic Engineers (IEEE), in its standard IEEE C62.41, classifies voltage surges as Category A, Category B, or Category C according to where they occur within a building’s electrical system. The figure at right illustrates the three general categories.

Category A surges are associated with long branch circuits, the type that typically power audio equipment. Category B surges are found near the service entrance to the building (short branch circuits), and Category C surges are those found at the service entrance or outside the building. Not surprisingly as one moves from Category A to Category C, the maximum voltage amplitude of the surge along with the maximum surge current and surge energy become greater.

Category A surges may measure up to 6,000 volts and 200 amps while Category B surges may measure up to 6,000 volts and 500 amps. In Category C locations, substantially larger voltages and currents are possible.

In addition to lightning, surges have a variety of causes.

Some are internal, some external, and some quite mundane.

Large loads like the motors used in elevators and air conditioners can cause voltage surges every time they start and stop.

When a power outage occurs, the rapid de-energization of electrical loads throughout the grid also generates substantial voltage surges.

In one documented case, a faulty light bulb socket in a refrigerator caused surges of as much as 5,000 volts whenever the refrigerator door was opened or closed.

APPROPRIATE SOLUTIONS

Surge energy is mitigated by using a surge diverter. As its name implies, this is a device that reacts to surge voltages over a certain threshold by diverting surge energy away from the power conductor to ground.

If the system is microprocessor based (such as an audio mixing console), this is undesirable because the diversion action will create a neutral to ground voltage that is likely to cause system upset.

If part of a larger, interconnected system, surge energy on ground is likely to circulate throughout the entire system on the grounding conductors. Surge protectors should never be installed at the end of a branch circuit for these reasons.

The most appropriate place for a surge diverter is at the service entrance of the building where it will divert surge energy directly to the building’s earth reference without causing a neutral to ground voltage or disruption to computer-based systems within the building.

At the point where the electronic system plugs into the branch circuit, a much higher level of protection is desirable. At this point, the goal is to eliminate both destruction and electronic rust and to do it without creating a neutral to ground voltage that will disrupt the system. The best way of accomplishing this is with a power protection solution that uses an isolation transformer.

Properly designed solutions can limit even catastrophic power disturbances to insignificant levels ensuring both the survivability and operability of the system.

http://www.prosoundweb.com/article/voltage_surges_the_real_world_of_power_quality_problems/P1/

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Hi Vasily,

And here we thought you were grounded in EE. Whole house surge suppressors-always. Never had to wrestle with the cart kit issue, though. What do the professionals employ, if anything. All sortsa spikes gotta be goin' on, during real world set recording.

Efharisto very much

Fury

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Hi Fury,

I think the "bomb" is in the hand for video / television / film industry and no so much for audio industry. If we are talking about audio industry the "problem" is in the hand for sound studios and not the field area. Because all of us we have the battery solution.

My pleasure

Vasileios

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