This paper is written to raise awareness of an important problem in the area of transformers, reactive power and geomagnetically-induced currents. The problem is important because of the possibility of transformer failure leading to prolonged and widespread blackouts. An estimate by Lloyd's, an insurer, puts the risk of insurance losses at between 0.6and2.6 trillion in the event of a major geomagnetic storm. While the risk of this storm is low, the chances of our power system surviving it are simply not known. Those chances depend, to a large extent, on the definition and measurement of reactive power, a topic that has been the subject of a long and sometimes bitter debate. This paper contributes to a solution by explaining the definition problem and pointing a way to a solution. The solution relies on aspects of measurement theory that have been developed in the last half-century or so. Anyone concerned with GIC and reactive power, and in particular the impact on transformers, should not feel comfortable.

1 aKirkham, H.1 aWhite, D.R. uhttps://ieeexplore.ieee.org/document/8494870/01857nas a2200145 4500008004100000245007600041210006900117260003600186520129200222100002301514700001601537700001701553700001101570856013001581 2017 eng d00aEstimation of goodness of fit of synchrophasors during transient faults0 aEstimation of goodness of fit of synchrophasors during transient aChicago, IL, USAbIEEEc07/20173 aSynchrophasor measurements are a useful tool, in particular for understanding dynamic or transient phenomena on large electrical systems. However, synchrophasors are only truly valid when the system is time invariant, that being when the frequency and magnitude of the waveforms is cyclical and continuous from one cycle to the next. This paper considers a metric for determining the quality of synchrophasors, Goodness of Fit (GoF). This metric returns a single scalar value which indicates how closely the estimated synchrophasors compare with the sampled values from which they are computed. The GoF metric is applied to empirical data obtained during a transient event on the power system of the island of Ireland. It is found that the metric returns a value indicating that the synchrophasors are of good quality before the transient event commences, and correctly indicates when the synchrophasors are no longer a good match to the sampled values. The authors propose that this technique should be added to PMUs and can be immediately incorporated with existing PMU communications. Additionally, as the GoF metric indicates when the sampled data is not a good sinusoidal fit, GoF can itself be useful for triggering captures of sampled values for post analysis.

1 aLaverty, David, M.1 aKirkham, H.1 aMorrow, John1 aLiu, X uhttp://ieeexplore.ieee.org/document/8274707/http://xplorestaging.ieee.org/ielx7/8263544/8273724/08274707.pdf?arnumber=8274707