What is the difference between a Surge Suppressor and a Surge Protective Device (SPD)?

    There is no difference.  Underwriters Laboratories uses the term "Surge Suppressor".  Other organizations, such as NEMA (National Electrical Manufacturers Association), IEC (International Electro-Technical Commission), and IEEE (Institute of Electronic and Electrical Engineers) use the term "Surge Protective Device".  The terms are interchangeable.

 

 

What is the difference between a "Surge Suppressor and a "Surge Arrestor"?

    The main differences are related to magnitude and capability.  An additional qualifier is usually the location where it is installed.  A surge arrester (also sometimes called a Secondary Surge Arrestor, or "SSA"), is designed to be installed on the "Service" side of your electrical installation and isn't protected by any of the components of your electrical system.

    A surge suppressor is designed to be installed on the load side of your electrical system.  As a result, it is protected by your own wiring and breakers.

    The advantage of our design is that it is sufficiently "stout" to be installed on the SERVICE side of your electrical system while being sufficiently "sensitive" to serve as an extremely responsive surge suppressor.

 

 

 

 

Why should I take care of surge suppression first?

    Surge suppression takes care of the lion's share of problems and it's easily the most cost effective method of improving power quality.  A study performed by Adams and Segall (IBM) indicated that fully 88% of all power problems are related to transient voltages.

    If you choose to take care of transient protection first, you provide protection that can't be provided by other means and don't create problems that need to be handled by additional equipment.

    If you choose to take care of power factor correction equ ipment first, you either have to settle with less than maximum efficiency by choosing systems that don't respond to current conditions, or you have to install surge suppression equipment to deal with the responding increase of high-level transient activity produced by systems that actively compensate for different load changes.

    Taking advantage of surge suppression first allows you to take care of most of your problems, and will most likely take care of problems you never knew you had...or were attributing to something else.  Then, you can take advantage of the savings produced by effective surge suppression to finance further increases in your electrical system's efficiency, by adding such things as power factor correction and harmonic filtering equipment.

 

 

What is Power Factor?

    Low power factor is corrected by the installation of capacitors.  You can control the amount of capacitance applied one of two ways:

     Power factor is the ratio between the KW (Kilo-Watts) and the KVA (Kilo-Volt Amperes) drawn by an electrical load where the KW is the actual load power and the KVA is the apparent load power. It is a measure of how effectively the current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system.

   It's far too complicated to explain in terms of a "frequently asked question".  If you need detailed information please see this.

 

 

How is low power factor corrected?

    Low power factor is corrected by the installation of capacitors.  You can control the amount of capacitance applied one of two ways:

1. You can "guess" (sometimes called by practitioners "monitor and calculate the requirements") by applying a fixed amount of capacitance.  This is done by monitoring the facility and determining the range of power factor correction that will be needed.  The problem with this approach is that if, for example, your system's power factor ranges between 80% and 90% you can only apply 5% of correction.  This means that your new "performance" will be between 85% and 95%.  This is necessary because if you apply much more correction you run the risk of producing an effect known as "leading power factor" and this is very undesirable.
2. The other solution is usually the installation of capacitor "banks" consisting of groups of capacitors.  You then apply a control system that reads your instantaneous needs for correction and applies (or removes) capacitors from your electrical system to provide correction.  The advantage to this method is that you can maintain very high levels of power factor.

    The disadvantages of this type of correction is that you now have an internal source of transients resulting from the switching of capacitors.  These aren't "small" transients...they are quite large.  Further, transient activity within the facility has an adverse affect on the life of your capacitors.

 

 

 

Can a surge suppressor improve power factor?  How much?

    Yes, but the amount is negligible.  First, you need to understand that Power Factor is the calculation of the ratio between True and Reactive Power.  In motors, "reactive" power is used to produce the magnetic field the motor needs to operate.  This power, however, doesn't do any real "work".  The "work" is produced by True Power.

  The amount of energy used to produce this magnetic field can range between 20 and 60% of a motor's "total" load.

   It is well-known that transient activity produces hysteresis losses in the iron cores of inductive devices.  This results in an inefficiency in building the "magnetic field" within the motor.

   Reducing transient activity increases this efficiency and will, therefore, increase power factor...to which the next logical question is "How much?"

   The amount is related to the amount of transient activity that is present to interact with this magnetic field.  It cannot be estimated.  If it is assumed that transient activity can produce up to a 10% loss in efficiency related to hysteresis losses, and the reactive loading of motors ranges between 20% and 60%, it could be inferred that it will increase power factor by a relatively small amount....2% to 6%.  What confuses many people is that this "2% to 6%" is only of the difference between the actual power factor and the theoretical "perfect" power factor of 1.0.  If you have a power factor of .86 and increase power factor by 6%, you've only gone from .86 to .87 (6% times the remaining 14% of power factor available is only 1 percent)

     The difference in our installation is that we distribute our equipment throughout your facility putting it closest to the equipment being measured.  Most power factor correction is done at the service entrance...to make the utility happy.

 

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Technical Support tech@tvss.net		Stedi-Power, Inc. 5044 B U Bowman Drive, Suite 102 Buford GA 30518
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Stedi-Power, Inc
5044 B U Bowman Drive #102
Buford, Georgia 30518
PHONE: (678) 546-6780

Last Updated: 07 Jun 2004
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