Method and apparatus for monitoring line voltage in a polyphase

Details Method and apparatus for monitoring line voltage in a polyphase Method and apparatus for monitoring line voltage in a polyphase

1978-06-15

1980-07-01

Moose, Jr., Harry E.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With phase sequence network analyzer

324 86, 361 85, H02H 332

Patent

active

042109485

ABSTRACT:
A method of monitoring open phase, phase reversal and voltage unbalance conditions in a polyphase source includes shifting the phase of signals which are proportional to the line voltages in a three-phase A.C. power source by 180.degree., +60.degree., and -60.degree., respectively, and summing the phase-shifted signals to generate a signal which is proportional to the negative-sequence component of the three-phase line voltage. This signal is rectified and compared with a reference signal. If a net negative-sequence signal is generated over a sufficient time period a positive output signal decreases until it crosses a switching threshold to disconnect a load from the source. The output signal will not rise again to the switching threshold, thereby allowing reconnection of the load, until the negative-sequence signal subsides and is less than the reference signal. A circuit is disclosed with three operational amplifiers and two passive filters to carry out the invented method.

REFERENCES:
patent: 3736470 (1973-05-01), Ford et al.
patent: 3743889 (1973-07-01), Lopez-Batiz
patent: 3848160 (1974-11-01), Boothman et al.
patent: 3875463 (1975-04-01), Reuter et al.
patent: 3938006 (1976-02-01), Gadwal et al.
patent: 3947728 (1976-03-01), Smith
patent: 4023075 (1977-05-01), Reuter
"Generator Protection with a New Static Negative Sequence Relay" IEEE Transactions on Power Apparatus and Systems, vol. PAS-94, No. 4, pp. 1208-1213, Jul./Aug. 1975.
"A Negative Sequence Voltage Relay", Hatch Inc. Tech. paper-62874-Kersting.
"Alternating-Current Circuits", Kerchner & Corcoran, 4th Ed., John Wiley & Sons, Inc., 1962, pp. 489-496.

Affiliated with

Also associated with

Rating

Method and apparatus for monitoring line voltage 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 Method and apparatus for monitoring line voltage in a polyphase , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for monitoring line voltage in a polyphase will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-301773