Power Problems

        Power problems can occur in two forms:

      · problems or disturbances that occur with a mains supply. Here we are concerned with Power Quality issues.

      · when the mains supply completely fails. Here we are concerned with how to keep systems running and business continuity.


        Power supply problems are caused by various sources, for example distribution network faults, system switching, weather and environmental conditions, heavy plant and equipment or simply just faulty hardware. Regardless of the cause of the problem, the result will include one or more of the following types of power problems:

        Sags: are short duration decreases in the mains supply voltage which generally last for several cycles. They are one of the more common forms of disturbances. When sags occur sensitive equipment can lock or hang causing data loss and system resets.

        Surges: are short duration increases in the mains supply voltage which generally last several cycles. When surges occur equipment can suffer from premature failure. The high voltage causes wear and tear and general component degradation. This may not be noticeable until failure, though heat out is a good sign.

        Transients and Spikes: these are very fast high energy surges lasting only a few milliseconds. When transients or spikes occur equipment can lock or hang, crash and even suffer damage which inevitably causes data loss and corruption. Large transients can occur from local or worst case a direct lightning strike.

         Electrical Noise: this is a high frequency noise either common or normal mode which can cause severe disruption and damage to circuits and equipment.

         Brownouts: are long term sags in the mains supply voltage which can last up to several days. During a brownout equipment can reset or even shutdown.

         Blackouts and Mains Failures: when the mains supply fails completely this is known as a total mains failure or blackout. A break in the mains supply of only several milliseconds is sufficient enough to crash, lock or reset many of the components that make up a typical data or voice processing IP network, such as PC, terminal, console, server, PBX, printer, modem, hub or router.A survey can be used to identify the types, duration and magnitude of power problems experienced on a site.

         Power problems cause voice and data processing errors, hardware damage and expensive downtime. When an Uninterruptible Power Supply (UPS) as your power protection solution it is important to consider two elements:
         · How clean is my mains supply when it is present ?
         · Does the application need to be kept running when the mains fluctuates wildly or fails and if so for how long?


         Power Quality without battery back-up
         Solutions vary in the power quality they provide and include:


         A filter will attenuate spikes and electrical noise down to predefined levels. A very basic economic form of power protection.


         Transient Voltage Surge Suppressors (TVSS)
          A TVSS will clamp and divert the excess electrical energy of transients away from downstream loads. A TVSS is superior to a filter and can cope with lightning strike surges in some instances. They are commonly used within heavy industrial complexes and mobile base stations. When placed before Uninterruptible Power Supplies a TVSS will provide protection for the Uninterruptible Power Supply itself from local transient surges.


         Voltage Stabilisers
          Smooth out sags, surges and brownouts in an attempt to provide a near stable supply and are typically used in combination with a filter. They provide a form of power protection used typically in third world countries for non-critical loads such as fridges and freezers. A voltage stabiliser (also known as an Automatic Voltage Stabiliser or AVR) can be electronic or electro-mechanical.


         Power Conditioners
         The ultimate power protection without battery back up. They can be either transformer or electronic based and provide conditioning in the form of filtering, stabilisation and regulation. Some power conditioners can also provide Galvanic isolation. This is more commonly associated with Constant Voltage Transformers (CVTs).

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