A Guide To Power Problems

There are essentially two groups of power problems.

  • power problems or disturbances occurring within the mains power supply when it is present. Here the focus is on the quality of power being supplied in terms of stability, purity, wave shape and reliability.
  • breaks in the mains power supply and how to ensure business continuity and keep critical systems running.

Power Supply Problems

Power problems can be generated by many sources including: distribution network faults, system switching, environmental and weather conditions, faulty hardware, heavy local plant, terrorism, high power demands or accidental routing or cable cutting. The principal terms used for power problems include:

  • Sags: short durations reductions in the mains power supply voltage available, lasting several cycles. This is a common type of power disturbance, most commonly seen when there is a high power demand and the local distribution network is placed under strain. Sags can cause system lock, data loss and system reboots.
  • Surges: short duration increases in the mains power supply voltage, lasting several cycles. Surges present high voltages to connected power supplies, which can result in their malfunction, general component degradation and premature failure. A higher than normal heat output is good indicator of this phenomenon.
  • Transients or Spikes: are very fast high energy surges lasting only a few milliseconds. Transients or spikes as they are also know can lead to system lock up, hanging, crash and eventual power supply damage. Large transients can lead to nuisance circuit breaker tripping and the sudden failure of network equipment. Large transients can result from nearby or direct lightning strike.
  • Electrical Noise: is a high frequency noise, which can be one of two forms: common mode or normal mode. Of the two common mode is the more serious to ICT equipment and both can cause disruption and circuit damage.
  • Frequency Drift: results in a supply that is either fluctuating between 50, 60 or even 400Hz. ICT power supplies have a pre-set input window inside which they will deliver a specified output frequency tolerance. When the frequency drifts outside this input voltage window, their performance is affected.
  • Harmonic Pollution: is a growing concern for large sites and is governed by regulations such as G5/4. Harmonics are currents or voltages with frequencies that are integer multiples of the fundamental power frequency (50/60Hz) which can lead to overheating of conductors and component failure.
  • Brownouts: are similar to sags but over a longer time frame, lasting several minutes, hours or even days. During brownouts, systems can reboot or shutdown completely and a continuous brownout condition will lead to power supplies being forced to work harder to deliver the required power.
  • Blackouts, Power Outages Mains Power Supply Failures: a mains power supply failure or blackout is a sudden complete loss of power of several milliseconds or longer. Even a short break of 30ms can be enough to crash modern ICT systems without built-in capacitance and ride-through capabilities.

Switch Model Power Supplies

Most ICT systems are connected to the local mains power supply through their built-in Switched Mode Power Supplies (SMPS). This converts the incoming alternating current (AC) into the various levels of direct current (DC) required to power internal circuits including: motherboards, drives, communications or USB devices.

Modern switch mode power supplies are more robust devices but they require a clean, stable, and regulated sinewave supply to perform to specification, over their working life. The presence of power problems can and will affect their overall performance when the mains power supply is present but an actual break in power will result in their crashing.

Solving Power Problems

At Critical Power Supplies our Site Survey offers a process of risk assessment and method statement generation. Many organisations we work with are concerned more than ever with the environmental impact of their systems, energy usage and operating efficiency. Our review process is multi-staged and designed to achieve the first time, clean install of a system that will solve your power problems, whilst balancing the Total Cost of Ownership (TCO), resilience and operating efficiency equation. General review topics include:

  • Risk Assessment: mains power supply failures are an increasing phenomenon with data recorded and reported on the regional electricity companies. For any given potential site it is important to assess the risks created by a mains power supply failure to local ICT systems, people, process, security, and business performance. If your systems ‘go down’ what is the cost to the organisation in terms of service and performance?
  • System Investment: most organisations have invested thousands of pounds in their local systems in terms of hardware and software. The cost of installing a power protection device can represent a very small percentage of the overall cost of your systems.
  • Power Quality Assessment: whether you are running a single file server or multi-sever rack datacentre, power problems can disrupt your operation. Most organisations only become aware of power problems when they suffer a power break. Often however, pollution of the local mains power supply can be the cause of sporadic system failures. Power quality can be assessed using our mains monitoring software, which uses sophisticated data loggers to record significant events (to preset tolerances). This data can then help to define your power continuity plan and select the right level of power protection.
  • Protection Level Assessment: there are many types of power solution including uninterruptible power supplies, power conditioners, filters, voltage stabilisers, spike suppressors and generators. If a UPS is selected as the right solution, the question of which technology (standby, line interactive or on-line) arises. If an on-line UPS is selected, it may offer various operating modes as well as battery runtime and remote monitoring software options. The principal areas to consider include: hot swap modules, scalability, resilience, N+1 parallel architecture, UPS operating modes (ECO, emergency, standby), load sharing, removal of single points of failure, hot synchronising, hot-swaps, cold-swaps, redundancy, reliability, communications bus, operating systems, bypass arrangements, centralised or distributed power.
  • Method Statement: with the above in place a potential method statement can be generated. No matter whether you are installing UPS for a mini datacentre, enterprise wide solution or single file server, health and safety issues need to be covered including logistics, handling, electrical works – installation, power distribution, onsite permits, and access control.

There are a range of power solutions and uninterruptible power supplies represent provide the ultimate solution. However care must be taken to select and install the right UPS system in order for it to fulfill its role in your business continuity plan. Assessment by a Critical Power specialist will ensure that the design of your power solution is optimised, for your site, your budget and your system needs.

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