High impedance fault detector

A method for detecting the possible existence of a high impedance fault in an electrical distribution system conveying AC electricity of a fundamental frequency, comprising:

• monitoring electrical signals in said electrical distribution system during a plurality of data acquisition periods;
• isolating a plurality of predetermined frequency components from the monitored electrical signals during each of a plurality of respective data acquisition periods;
• sampling the plurality of predetermined frequency components during at least one data acquisition period;
• forming a first pattern which separately represents the respective magnitudes of the plurality of predetermined frequency component samples during said at least one data acquisition period;
• comparing said first pattern with a predetermined template pattern;
• and
• determining the possible existence of a high impedance fault on the basis of said comparison.

A high impedance fault or arcing phenomenon detector for use in an electrical distribution system including at least one electrical feeder line for conveying AC electricity of a fundamental frequency, said detector comprising:

• a. monitoring means for monitoring electrical signals on said at least one electrical feeder line during a plurality of data acquisition periods;
• b. filtering means for isolating a plurality of predetermined frequency components from the monitored electrical signals within each data acquisition period, wherein each predetermined frequency component has a respective magnitude;
• c. weighting means for individually scaling the respective magnitudes of said plurality of predetermined frequency components according to selected scaling factors, wherein each predetermined frequency component is associated with a respective scaling factor;
• d. comparison means for comparing said scaled magnitudes of said predetermined frequency components from a first data acquisition period with the scaled magnitudes of said predetermined frequency components from a preceding data acquisition period prior to the first data acquisition period;
• and
• e. detecting means for detecting the occurrence of a high impedance fault or arcing phenomenon on said electrical feeder line on the basis of said comparison.

An electrical isolation switch for use in an electrical distribution system including at least one electrical feeder line for conveying AC electricity of a fundamental frequency, comprising:

• a. monitoring means for monitoring electrical signals on said at least one electrical feeder line during a plurality of data acquisition periods;
• b. filtering means for isolating a plurality of predetermined frequency components from the monitored electrical signals within each data acquisition period, wherein each predetermined frequency component has a respective magnitude;
• c. weighting means for individually scaling the respective magnitudes of said plurality of predetermined frequency components according to selected scaling factors, wherein each predetermined frequency component is associated with a respective scaling factor;
• d. comparison means for comparing said scaled magnitudes of said predetermined frequency components from a first data acquisition period with the scaled magnitudes of said predetermined frequency components from a preceding data acquisition period prior to the first data acquisition period;
• e. detecting means to detect the possibility of a high impedance fault on said electrical feeder line on the basis of said comparison and to generate a trip signal if the possibility of a high impedance fault is so detected;
• and
• f. means for actuating a switch to electrically isolate said at least one electrical feeder line from a source of said AC electricity upon generation of said trip signal.

An electrical distribution system comprising:

• a source of AC electricity of a fundamental frequency;
• at least one electrical feeder line coupled to said source by way of switching means capable of electrically isolating said at least one electrical feeder line from said source upon receipt of a trip signal;
• monitoring means for monitoring electrical signals on said at least one electrical feeder line during a plurality of data acquisition periods;
• filtering means for isolating a plurality of predetermined frequency components from the monitored electrical signals within each data acquisition period, wherein each predetermined frequency component has a respective magnitude;
• weighting means for individually scaling the respective magnitudes of said plurality of predetermined frequency components according to selected scaling factors, wherein each predetermined frequency component is associated with a respective scaling factor;
• and
• comparison means for comparing said scaled magnitudes of said predetermined frequency components from a first data acquisition period with the scaled magnitudes of said predetermined frequency components from a preceding data acquisition period prior to the first data acquisition period, and for issuing the trip signal to said switching means if said comparison indicates the possibility of a high impedance fault on said at least one electrical feeder line.

A method for detecting an arcing phenomenon in an electrical distribution system comprising the steps of:

• monitoring a plurality of selected frequency components C.sub.n of the voltage and current at a point on the distribution system during each of a plurality of data acquisition periods j, wherein n designates respective ones of the plurality of selected frequency components during each of the plurality of data acquisition periods and wherein each selected frequency component has a respective magnitude M(C.sub.n);
• generating a first pattern M.sub.j (C.sub.n) representative of the respective magnitudes of the selected frequency components during data acquisition period j;
• comparing the first pattern with a pattern M.sub.j-1 (C.sub.n) generated based upon the respective magnitudes of the selected frequency components during a preceding data acquisition period (j-1) to determine whether the difference therebetween exceeds a pattern threshold M.sub.t (C.sub.n) such that
• .vertline.M.sub.j (C.sub.n)-M.sub.j-1 (C.sub.n)/>M.sub.t (C.sub.n) for each of the plurality of selected frequency components n;
• and
• determining an occurrence of an arcing phenomenon in the system on the basis of the comparison.