Powerware Surge/Power Filters

Selecting the correct protection equipment for commercial and industrial applications is vital.

POINT OF ENTRY - CATEGORY C

Basically all installations should at least be protected at the point of entry. The starting point for protection is the surge diverter. Surge diverters effectively clamp the incoming lines to neutral or earth protecting switchboards, contractors, transformers and motors from burnout due to extreme voltages. A properly installed surge diverter can limit surges to below 2000V.

If the main load in an installation is critical of high voltages (computers, communications systems, test equipment etc) or generates electrical noise (variable speed motor drives, high frequency welders etc) should be used. In a SPFi, surge diverters are utilised in conjunction with low-pass filtering to reduce the surge voltage and remove noise. In normal operation and SPFi can be expected to reduce surge potentials to less than 1000V whilst providing up to 40dB of noise attenuation.

Method
Firstly determine whether or not you require filtering or just surge diversion. If selecting a surge diverter select a device appropriate for the protection category. The PO-VSD1 and PW-VSD3 are suitable for category B & C whilst the PW-VSD120 is designed for exposed or critical sites. In extremely exposed situations multiple PW-VSD120's may be connected in parallel to increase surge lifetime. If the site requires filtering at the point of entry select a SPFi with appropriate current rating for the load then select the model appropriate for the protection category. SPF's are available to suit categories A to E depending upon current rating. Options available include alarms and extra shunt protection.

MINOR SUB MAINS AND SHORT FINAL SUB CIRCUITS - CATEGORY B

Once past the main board most protection involves both surge diversions and filtering. Non critical loads such as lighting and general-purpose power circuits don't necessarily require protection.

Method
For large 3-phase loads such as mainframe computers or computer controlled machinery select a SPFi appropriate for the load. In this case the protection level required is usually taken as 'one step' below the protection level applied to the point of entry. For single phase loads up to 63A, the DSFi and MSFi filter ranges are suitable (for current less than 25A, the CSFi filter also provides installation compatibility with modular switchboards). Generally filters should be mounted as close as possible to the equipment being protected.

LONG FINAL SUB CIRCUITS AND POWER OUTLETS - CATEGORY A

When protecting final sub circuits and power points there are two options. Either fit hard wired filters to the circuit or use plug in filters on the equipment to be protected. This choice will be determined by the load (Plug in filters are only rated up to 10A) and whether or not there is space for a plug in filter adjacent to the equipment. With large computer networks many administrators prefer not to use plug in filters as they can be accidentally unplugged by the operator's foot, causing network problems. For small servers however, a plug in filter provides extra protection at the computer for insurance.

While the key issues in selecting appropriate protectionequipment vary according to the specific needs of theinstallation the following:

Protect the point-of-entry
This protects the switchboards and building wiring from externally generated surges and also provides a degree of protection against internally generated surges and spiked from equipment at the site.

Protect sub mains
Protection at this level usually involves filtering and surge protection to further reduce surges and spikes to acceptable levels for medium sized non critical loads.

Protect equipment
This involves protecting individual items of equipment against surges, spikes and other electrical noise. In the case of operation critical equipment and security equipment, protection against power failure is usually required in the form of a UPS.

PROTECTION CATEGORIES

Powerware manufactures a complete range of power protection components. These components fall into a number of categories depending upon where they are utilised in an electrical installation. The three main categories are according to AS/NZS1768-1991.