What Are The Most Common Power Problems That Could Disrupt My Computer Loads?

The following is a list of the most commonly seen power problems, both in the UK and worldwide. In the UK we generally have a stable electrical supply who delivery is affected by several factors including demand on the grid a certain times of the day, our national grid electrical infrastructure which can see transformer and substation failures and weather conditions including storms and lightning. Inside the location where you run the loads to be protected, there can also be power problems created by local loads.

The most commonly seen power problems include the following:

• Spikes and Electrical Noise: are sudden surges in the electrical supply over a short-term period. They are caused by local lightning strikes and the switching of local loads. Fast transient spikes and long-term exposure to electrical noise can disrupt the operation of the power supplies within your connected loads, leading to processing errors, erratic operation and over term, component degradation and potential failure. Offline and Line Interactive UPS have built-in circuits to clamp or surpass spikes and electrical noise. Online UPS have similar but more sophisticated protection circuits, and digitally generated their output waveform which is not disrupted by the incoming mains power supply levels.
• Brownouts and Sags: brownouts are long duration low voltage levels (typically 10-15% below the nominal voltage) which can be just outside the operating input window of your connected loads. In the UK we expect the nominal mains power supply voltage we plug-into to be 230Vac 50Hz, single phase and 400Vac, 50Hz 3phase. Sags can be any momentary voltage lower than these levels whereas Brownouts will last for several minutes, hours or even days. When within the input voltage range of the power supply within your loads, these conditions simply cause the power supply to work harder to deliver the power required. When outside the input voltage window this will be seen as a power failure and your load can crash. Offline UPS will switch to battery power during brownouts and sags that fall outside their input voltage and frequency windows. Line Interactive UPS will typically have a built-in automatic voltage stabiliser which will boost the incoming mains supply level up before resorting to battery power for voltage and frequency levels outside their input window. Online UPS will be unaffected as their inverter section is constantly running, powered either from the rectified mains power supply or battery.
• Surges: surge conditions in electrical supply are the opposite to Sags. They are increases in the electrical supply voltage (typically above 10-15%) and are referred to as ‘high mains’ and can again be caused by sudden changes in the load on the local electrical grid or building where you operate. Surges will cause the power supply in your connected loads to work harder, and over time can lead to wear and tear and eventual component failure. For Offline, Line Interactive and Online UPS the operation is the same as for brownouts and sags. If the operating conditions for the local mains power supply are within the UPS operating parameters, the UPS will continue to operate without resorting to battery power. Outside of these they will use their connected batteries and discharge them until either exhausted or the mains power supply stabilises.
• Power Outages and Blackouts: power outages are momentary fluctuations in electrical supply voltage levels which are seen by connected loads a power breaks. The level of mains voltage available falls outside the input voltage window of your connected loads. Typical examples include local storms which can make the lights flicker and alarms to sound, and substation switches as the electricity utilities make automatic changes within the grid to power local supplies. Blackouts are longer duration power failures lasting minutes to several hours. Whilst less common than momentary power interruptions, their effect can be as severe for IT operations that cannot be interrupted and must continue to operate. Protection for these types of power problem are provided by a combination of Online UPS with battery extension packs and generators.

Frequency problems and harmonic distortion are not commonly seen within the UK and where they occur are local in nature, typically caused by local site electrical infrastructure and the systems being operated. See our guide to UK mains power supply voltages for more information on the voltage and frequency levels to be expected.