G - Physics – 01 – R
Patent
G - Physics
01
R
324/35
G01R 29/16 (2006.01) H02H 3/36 (2006.01) H02H 7/16 (2006.01)
Patent
CA 1086825
DEVICE FOR DETECTING UNBALANCED CONDITIONS IN A POLYPHASE EQUIPMENT BANK ABSTRACT: A sensing device is connected to an intermediate tap point on each phase leg of a poly- phase system such as a grounded wye-connected capacitor bank to detect faulted capacitor units and thereby control a switching device to isolate the capacitor bank. The intermediate tap point is selected in each phase leg such that the number of series units (such as parallel capacitor groups) above the tap point equals (or exceeds by one) the number of series units below the tap point. The outputs of these sensing devices are coupled through a calibration network to a summing amplifier which operates to add the three signals vec- torily to produce an AC output signal that is filtered by a 60 Hz band pass filter to attenuated unwanted harmonics and noise which might introduce error into the measurement. Initial balance is achieved by adjusting the magnitude of each phase to ground signal to equalize those signals from each of the intermediate tap points. Thus, an artificial neutral is created at the summing amplifier and filter output when the output is adjusted to a null. By this adjustment, the output signal of the summing amplifier and filter is then proportional to the per cent unbalanced among the three intermediate tap point voltages. The per cent un- balance output signal is directly related to the change in voltage occurring at the tap point due to faulted capacitor units. The output AC per cent unbalance signal is rectified to a proportional DC voltage and applied to a meter that is calibrated to read the capacitor bank tap-voltage percent unbalance due to loss of individual capacitor units. The DC voltage is also fed to a level detector which has an adjustable reference level setting means. This level detector can operate a control circuit when the tap-voltage per cent unbalance attains a corresponding level such that the voltage across the surviving units in a series group exceeds the recommended maximum working voltage. Avoidance of false operation due to transient voltages (caused by bank switching or system disturbances) is accomplislled by a timing circuit which requires the signal to persist for a selectable period of 4 to 30 seconds before an operation is initiated. When the unbalance persists at the preset level for the pre- selected time period, a latching relay is operated which can actuate an alarm or a switching device to isolate and protect the capacitor bank. The device also incorporates a gross overvoltage circuit which functionally bypasses the level detector and the timing circuit to achieve fast isolation of the polyphase system in the event of a massive fault. -2-
278041
Osler Hoskin & Harcourt Llp
S&c Electric Company
LandOfFree
Device for detecting unbalanced conditions in a polyphase... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for detecting unbalanced conditions in a polyphase..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for detecting unbalanced conditions in a polyphase... will most certainly appreciate the feedback.
Profile ID: LFCA-PAI-O-335329