Leakage current monitoring system and method
AssigneeContinental Engineering B.V.
InventorJames B. Briggs
Life of this patent
Estimating the term…
Abstract
A device is disclosed herein for monitoring a power system for the presence of faults thereon which cause leakage currents to ground. The device includes a test impedance and bridge switching means for connecting the test impedance in different combinations to a pair of power lines. A singe test impedance is connected in four different configurations to the power lines in sequence, and this cycle is continuously repeated. Currents are measured for each connection to determine whether or not a leakage or hazard current exists which results from a fault load on one or both power lines. The device includes control means for operating the test impedance switching means, and includes current level detecting means for providing an alarm indication in the event a predetermined hazard current exists.
Claims18
A system for monitoring leakage current to ground in a power system having a pair of power lines, comprising
- impedance means for connection to said power lines, said impedance means having first and second terminals and a third intermediate terminal,
- switching means coupled to said power lines and to the first and second terminals of said impedance means for connecting said impedance means in predetermined configurations to one or both of said power lines,
- control means coupled to said switching means for providing four sampling periods and for causing said switching means to each assume a given state in sequence for, in turn, causing said impedance means to be connected in four different configurations to said power lines wherein (a) the first and second terminals are connected to the first of said power lines, (b) the first and second terminals are connected in one orientation across said power lines, (c) the first and second terminals are connected to the second of said power lines, and (d) the first and second terminals are connected in another orientation across said power lines, and said control means causing said sequence to occur repetitively, and
- measuring circuit means connected to said third terminal of said impedance means for measuring leakage current therethrough to ground and for providing an indication of leakage current.
A system for monitoring leakage current to ground in a power system having a pair of power lines, comprising
- a single impedance means comprising resistive and capacitive reactance components with which said power lines can be loaded for enabling sampling of leakage current to ground, said impedance means having first, second and third terminals,
- switching means coupled to said power lines and to the first and second terminals of said impedance means for connecting said impedance means in predetermined different configurations to one or both of said power lines,
- control means coupled to said switching means for providing sampling periods and for causing each of said switching means to assume a given state in sequence for, in turn, causing said impedance means to be connected in plural different configurations to said power lines wherein (a) the first and second terminals are connected to the first of said power lines, (b) the first and second terminals are connected across said power lines, and (c) the first and second terminals are connected to the second of said power lines, and said control means causing said sequence to occur repetitively, and
- measuring circuit means connected to said third terminal of said impedance means for measuring leakage current therethrough to ground.
A system for monitoring leakage current to ground in a power system having a pair of power lines, comprising
- impedance means comprising a single circuit having resistive and capacitive reactance components and having first, second and third terminals,
- switching means coupled to said power lines and to the first and second terminals of said impedance means for connecting said impedance means in four predetermined configurations to one or both of said power lines,
- control means coupled to said switching means for providing plural sampling periods and for causing each said switching means to assume a given state in sequence for, in turn, causing said impedance means to be connected in said four different configurations to said power lines wherein (a) the first and second terminals are connected to the first of said power lines, (b) the first and second terminals are connected in one orientation across said power lines, (c) the first and second terminals are connected to the second of said power lines, and (d) the first and second terminals are connected in another orientation across said power lines, and said control means causing said sequence to occur repetitively, and
- measuring circuit means connected to said third terminal of said impedance means for measuring leakage current therethrough.
A test impedance and switching circuit for use in a system monitoring leakage current to ground in a power system having a pair of power lines, comprising
- impedance means comprising a single circuit having resistive and capacitive reactance components and having first, second and third terminals, and
- switching means for connection to said power lines connected to the first and second terminals of said impedance means for causing said impedance means to be connected in four predetermined configurations to said power lines wherein (a) the first and second terminals are connected to the first of said power lines, (b) the first and second terminals are connected in one orientation across said power lines, (c) the first and second terminals are connected to the second of said power lines, and (d) the first and second terminals are connected in another orientation across said power lines, said switching means comprising four switches each operable to a given state in sequence for causing said impedance means to be connected in said four different configurations to said power lines.
A method of monitoring leakage current to ground in a power system having a pair of power lines, comprising the steps of
- connecting an impedance means comprising a single circuit having resistive and capacitive reactance components and having first, second and third terminals in an ordered sequence of configurations to said power lines in four sampling periods, said impedance configurations for said sampling periods including said first and second terminals of said impedance means being (a) connected to one of said power lines, (b) connected across said power lines in a first orientation, (c) connected to the other of said power lines, and (d) connected across said power lines in another orientation,
- repeating said four period sampling of said power lines, and
- measuring the leakage current from said third terminal of said impedance means to ground.
Dependencies are inferred from the claim text.