IEEE Std 1250:2011 pdf free download

IEEE Std 1250:2011 pdf free download.IEEE Guide for Identifying and Improving Voltage Quality in Power Systems.
3.3.4.1 Basic EMC concepts related to voltage fluctuations
The flicker levels in IEC standards and in IEEE Std 1453TM20O4 [B18] are characterized by the following two parameters:
— 10 mill “short-term flicker severity”—Pst: This value is obtained from a statistical analysis of the “instantaneous flicker value” in a way that models incandescent lamps and the observation of light intensity variations.
— 2 h “long-term flicker severity”—PJt: This is calculated by combining 12 successive Pst measurements using a cubic relationship.
fl(th of these parameters are defined along with the equipment to measure them in
IF( 61000-4-15:2010 [R7].
A human observer can tolerate a certain amount of light flicker before becoming annoyed. JEC 61000-2-2:2002 [84] defines this level of flicker as the compatibility level. It is important to note that compatibility levels are defined for LV systems only (IEC 61000-3-7:2008 [B51]) where the following is true:
— Short-term flicker level (Pst) is 1.0
— Long-term flicker level (Pit) is 0.8
Flicker planning levels are utilized so that the overall flicker level at MV, HV, and EHV buses because of all global flicker emissions does not result in an LV flicker level that is above the compatibility level, thereby greatly reducing the probability of having customer complaints. Suggested planning levels for flicker are provided in IEC 61000-3-7:2008 [B5] and IEEE Std 1453-2004 [B18]. To maintain proper coordination, it is suggested that flicker planning levels be based on 99th percentile values.
Note that individual step changes in the voltac, such as would he caused by a motor starting or switching a capacitor bank, are often limited separately from the continuous flicker limits. IEC 6 1000-2-2:2002 [84] specifies a compatibili level of 3% for the individual voltage variations. EN 50 160-1999 [B2] specifies a limit of 5% for these variations but mentions that more significant variations (up to 10%) can occur for some switching events. Specific recommendations arc not provided in IEEE standards, but individual utilities usually have their own guidelines in the range of 4% to 7%.
3.3.4.2 Survey results
Survey results for flicker are very limited. Most measurement campaigns evaluating flicker are performed when there is a specific problem, and the results are, therefore, not representative of the power system in general (most sites have very low flicker levels).
Survey results suggest that flicker levels in excess of the compatibility level have been measured at MV. HV, and EHV without corresponding customer complaints. Research (Horton and Haskew [B40], [B41]: Renner and Sakulin [B51]) has shown that when flicker is transferred from the point of emission (i.e., flicker source) to other parts of a network, the flicker level tends to be reduced when going from HV or EHV toward MV, which explains why EHV and HV flicker levels above 1 .0 do not necessarily correspond to customer complaints. Great care should be exercised whenever flicker planning levels in excess of those specified in fEC 61000-3-7:2008 [B5] are used. To determine such planning levels, the effects of flicker transfer coefficients should he carefully taken into account (Renner and Sakulin [B51] as well as Horton and Haskew [B4O]).
3.3.4.3 Recommended limits and assessment method
The recommended limit for flicker is Pst = 1.0 at the 95% probability level. This is consistent with the compatibili levels in IEC 61000-2-2:2002 1841 and is based on the actual design of the flicker meter. In other words, this flicker limit should prevent customer complaints associated with light flicker.