| 摘要 |
A demand response unit (DRU) interposed between a utility's electrical power line (PL) and at least one load (L1-Ln) to which power is supplied by the utility over the line. A detector (Fdet or Vdet) measures a characteristic (frequency F, voltage V) of an electrical waveform (W) by which power is transmitted by the utility to the load. The detector (Fdet or Vdet) determines both when the measured frequency (F) or voltage (V) exceeds a predetermined threshold for a first predetermined period of time; and, if the threshold is exceeded, when the frequency (F) or voltage (V) exceeds the second predetermined threshold for a second predetermined period of time. For this purpose, the detector (Fdet or Vdet) processes a predetermined number of intervals of the waveform and produces an average value of the characteristic which is compared to the threshold. This is done to reduce the effect of extraneous events which may temporarily change the value of the frequency or voltage. A power control (PC) is responsive to an output from the detector to, at least, partially interrupt flow of power to the load during the period of time when the measured frequency or voltage exceeds the threshold, thereby to reduce the load on the utility. |
