US 4,364,007 AGranted

Unintentional impedance detection system

AssigneeGeneral Electric Company

InventorsJohn H. Cutler, Willard B. Jarvinen, Loren H. Walker

Life of this patent

Estimating the term…

Loading patent…

Abstract

A detection system for detecting unintentional impedances between the power conductors and a first node of either a power conversion circuit or a load, the first node typically being an earth ground. The circuit has power level lines utilizing a wye-connected line filter network which has equal impedance values for each leg of the line filter and which defines a first node at the common connection thereof. A different impedance network is also connected in wye-fashion to the power level lines and defines a second node at the common connection thereof. Each impedance leg of the impedance network is also equal in impedance value whereby the second node normally has the same potential as the first node. The potential difference between the first and second nodes is frequency compensated to produce a system output signal indicative of a predetermined value of current in unintentional impedance between any of the power conductors and the first node.

Claims20

Dependent claims

A system for detecting unintentional impedances between the power conductors and a first node in a network including a power conversion circuit, a plurality of power level lines for connecting said power conversion circuit to an alternating current power source, a static power converter included in said power conversion circuit, and a load supplied by said power conversion circuit, comprising:

(a) a first plurality of impedances equal in number to said power level lines, each being substantially equal in value and having first and second terminals, all of said first terminals being connected to said first node, and each of said second terminals being connected to a respective different one of said power level lines;
(b) a second plurality of impedances, distinct from said first plurality, equal in number to said power level lines, each being substantially equal in value and having first and second terminals, said first terminals being interconnected and defining a second node, and each of said second terminals being connected to a respective different point within said network having a potential which is representative of the potential on a respective different one of said power lines;
and
(c) sensing means, responsive to frequencies including that of the source and lower order harmonics thereof, for monitoring the potential difference between said first and second nodes, and effective for providing a system output signal in reaction to said unintentional impedance when said potential difference exceeds a preselected value.

1 more element

(a) a first plurality of impedances equal in number to said power level lines, each being substantially equal in value and having first and second terminals, all of said first terminals being connected to said first node, each of said second terminals being connected to a respective different one of said power level lines, and each impedance of said first plurality of impedances comprising a capacitance having a magnitude of impedance at a power frequency which is small relative to the magnitude of impedance at the same frequency of any unintentional capacitance between said first node and the power level line connected to the second terminal thereof;
(b) a second plurality of impedances, distinct from said first plurality, equal in number to said power level lines, each being substantially equal in value and having first and second terminals, said first terminals being interconnected and defining a second node, and each of said second terminals being connected to a respective different point within said network having a potential which is representative of the potential on a respective different one of said power level lines;
(c) frequency selective means, responsive to frequencies including that of the source and lower order harmonics thereof, comprising an amplifier, having the potential difference between said first and second nodes as an input thereof, and effective for providing an output characterized by a gain which is a function of frequency of the potential difference between said first and second nodes and representing the level of current in said unintentional impedance;
(d) a full-wave rectifier having said output of said frequency selective means as an input thereof and effective for providing a rectified output voltage;
(e) means generating a reference voltage representing a preselected value of said unintentional impedance;
and
(f) means effective for comparing said rectified output voltage with said reference voltage and producing a system output signal when said rectified output voltage exceeds said reference voltage.

4 more elements

Dependencies are inferred from the claim text.