DC ground fault detection
First Claim
1. A method of detecting low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising the steps of connecting a resistor across the DC power supply, connecting an indicator between a tapping point relative to the resistor and a ground point such that a ground leakage current in the system closes a ground circuit to activate the indicator means, periodically interrupting said circuit by opening and closing the ground circuit effectively to generate a DC pulse interrupted ground fault signal being substantially a square wave to produce proportional periodic changes in a magnetic field associated with the system while the ungrounded DC system remains substantially operational, and magnetically sensing in a location relative the DC system said magnetic field changes related to said pulse interrupted ground fault signal whereby said magnetic field changes provide the necessary signal for low level ground fault current detection, the pulse interruption rate being between about 2 to about 1/6 cycles per second.
1 Assignment
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Accused Products
Abstract
Apparatus for the detection of ground leakage in a normally ungrounded DC system includes a DC power supply and conductors from the supply for supplying power to a load connected to the DC system. There is an indicator connected between the DC system and a ground point such that a ground leakage in the system closes a circuit to activate the indicator. With such activation, a pulser periodically interrupts the circuit to effectively generate an interrupted ground fault signal. Such signal is detected by a sensor located relative to the DC system such that an interrupted ground signal detected by the sensor locates the ground fault. Noise introduced into the pulse signal by the periodic interruption of the circuit during the ground fault occurrence is suppressed by the sensor means.
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Citations
70 Claims
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1. A method of detecting low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising the steps of connecting a resistor across the DC power supply, connecting an indicator between a tapping point relative to the resistor and a ground point such that a ground leakage current in the system closes a ground circuit to activate the indicator means, periodically interrupting said circuit by opening and closing the ground circuit effectively to generate a DC pulse interrupted ground fault signal being substantially a square wave to produce proportional periodic changes in a magnetic field associated with the system while the ungrounded DC system remains substantially operational, and magnetically sensing in a location relative the DC system said magnetic field changes related to said pulse interrupted ground fault signal whereby said magnetic field changes provide the necessary signal for low level ground fault current detection, the pulse interruption rate being between about 2 to about 1/6 cycles per second.
- 2. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a connector between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit, a relay between the tapping point and ground, a pulser for periodically opening and closing said relay while the ungrounded DC system remains substantially closed and operational, the opening and closing of said relay interrupting said ground circuit effectively thereby to generate a DC pulse interrupted ground fault signal and a magnetic sensor for location relative to the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal and thereby providing for detecting the location of the low level ground leakage current in the relatively high capacitive reactance system, said DC system remaining substantially closed and operational during the ground leakage current detection, the pulse interruption rate being between about 1/6 to about 1/11 cycles per second.
- 15. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a connector between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit, a relay between the tapping point and ground, a pulser for periodically opening and closing said relay while the ungrounded DC system remains substantially closed and operational, the opening and closing of said relay interrupting said ground circuit effectively thereby to generate a DC pulse interrupted ground fault signal and a magnetic sensor for location relative to the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal and thereby providing for detecting the location of the low level ground leakage current in the relatively high capacitive reactance system, said DC system remaining substantially closed and operational during the ground leakage current detection, the pulse interruption rate being less than about 2 times per second.
- 24. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a distribution system having a relatively high capacitive reactance, including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a responsive element connected between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit to activate the responsive element, a relay between the responsive element and ground pulser for periodically opening and closing said relay, while the ungrounded DC system remains operational, the opening and closing of said relay interrupting said ground circuit effectively to generate a DC pulse interrupted ground fault signal to produce proportional periodic changes in a magnetic field associated with the system, said pulser being incorporated in a circuit with a normally open switch, whereby on the occurrence of a ground fault condition, said pulser operates said relay, and a magnetic sensor for location relative the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal whereby solely said interrupted ground fault signal provides the necessary signal for the low level ground fault current in the relatively high capacitive reactance system detection, and including electronic signal and conditioning means for reducing noise generated by the pulser and relay wherein said conditioning means includes an amplifier and filter for the noise, the pulse interruption rate being less than about 2 times per second.
- 25. A method of detecting low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising the steps of connecting a resistor across the DC power supply, connecting an indicator between a tapping point relative to the resistor and a ground point such that a ground leakage current in the system closes a ground circuit to activate the indicator means, periodically interrupting said circuit by opening and closing the ground circuit effectively to generate a DC pulse interrupted ground fault signal to produce proportional periodic changes in a magnetic field associated with the system while the ungrounded DC system remains substantially operational, and magnetically sensing in a location relative the DC system said magnetic field changes related to said pulse interrupted ground fault signal whereby said magnetic field changes provide the necessary signal for low level ground fault current detection, the pulse interruption rate being less than about 2 times per second.
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28. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a connector between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit, a relay between the tapping point and ground, a pulser for periodically opening and closing said relay while the ungrounded DC system remains substantially closed and operational, the opening and closing of said relay interrupting said ground circuit effectively thereby to generate a DC pulse interrupted ground fault signal being substantially a square wave, and a magnetic sensor for location relative to the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal and thereby providing for detecting the location of the low level ground leakage current in the relatively high capacitive reactance system, said DC system remaining substantially closed and operational during the ground leakage current detection, the pulse interruption rate being less than about 2 times per second.
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29. A method of detecting low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising the steps of connecting a resistor across the DC power supply, connecting an indicator between a tapping point relative to the resistor and a ground point such that a ground leakage current in the system closes a ground circuit to activate the indicator means, periodically interrupting said circuit by opening and closing the ground circuit effectively to generate a DC pulse interrupted ground fault signal being substantially a square wave to produce proportional periodic changes in a magnetic field associated with the system while the ungrounded DC system remains substantially operational, and magnetically sensing in a location relative the DC system said magnetic field changes related to said pulse interrupted ground fault signal whereby said magnetic field changes provide the necessary signal for low level ground fault current detection, the pulse interruption rate being less than about 2 times per second.
- 38. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a connector between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit, a relay between the tapping point and ground, a pulser for periodically opening and closing said relay while the ungrounded DC system remains substantially closed and operational, the opening and closing of said relay interrupting said ground circuit effectively thereby to generate a DC pulse interrupted ground fault signal and a magnetic sensor for location relative to the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal and thereby providing for detecting the location of the low level ground leakage current in the relatively high capacitive reactance system, said DC system remaining substantially closed and operational during the ground leakage current detection, the pulse interruption rate being between about 2 to about 1/6 cycles per second.
- 47. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a distribution system having a relatively high capacitive reactance, including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a responsive element connected between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit to activate the responsive element, a relay between the responsive element and ground pulser for periodically opening and closing said relay, while the ungrounded DC system remains operational, the opening and closing of said relay interrupting said ground circuit effectively to generate a DC pulse interrupted ground fault signal to produce proportional periodic changes in a magnetic field associated with the system, said pulser being incorporated in a circuit with a normally open switch, whereby on the occurrence of a ground fault condition, said pulser operates said relay, and a magnetic sensor for location relative the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal whereby solely said interrupted ground fault signal provides the necessary signal for the low level ground fault current in the relatively high capacitive reactance system detection, and including electronic signal and conditioning means for reducing noise generated by the pulser and relay wherein said conditioning means includes an amplifier and filter for the noise, the pulse interruption rate being between about 2 to about 1/6 cycles per second.
- 49. A method of detecting low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising the steps of connecting a resistor across the DC power supply, connecting an indicator between a tapping point relative to the resistor and a ground point such that a ground leakage current in the system closes a ground circuit to activate the indicator means, periodically interrupting said circuit by opening and closing the ground circuit effectively to generate a DC pulse interrupted ground fault signal to produce proportional periodic changes in a magnetic field associated with the system while the ungrounded DC system remains substantially operational, and magnetically sensing in a location relative the DC system said magnetic field changes related to said pulse interrupted ground fault signal whereby said magnetic field changes provide the necessary signal for low level ground fault current detection, the pulse interruption rate being between about 2 to about 1/6 cycles per second.
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60. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a connector between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit, a relay between the tapping point and ground, a pulser for periodically opening and closing said relay while the ungrounded DC system remains substantially closed and operational, the opening and closing of said relay interrupting said ground circuit effectively thereby to generate a DC pulse interrupted ground fault signal being substantially a square wave, and a magnetic sensor for location relative to the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal and thereby providing for detecting the location of the low level ground leakage current in the relatively high capacitive reactance system, said DC system remaining substantially closed and operational during the ground leakage current detection, the pulse interruption rate being between about 2 to about 1/6 cycles per second.
- 61. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a distribution system having a relatively high capacitive reactance, including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a responsive element connected between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit to activate the responsive element, a relay between the responsive element and ground pulser for periodically opening and closing said relay, while the ungrounded DC system remains operational, the opening and closing of said relay interrupting said ground circuit effectively to generate a DC pulse interrupted ground fault signal to produce proportional periodic changes in a magnetic field associated with the system, said pulser being incorporated in a circuit with a normally open switch, whereby on the occurrence of a ground fault condition, said pulser operates said relay, and a magnetic sensor for location relative the Dc system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal whereby solely said interrupted ground fault signal provides the necessary signal for the low level ground fault current in the relatively high capacitive reactance system detection, and including electronic signal and conditioning means for reducing noise generated by the pulser and relay wherein said conditioning means includes an amplifier and filter for the noise, the pulse interruption rate being between about 1/6 to about 1/11 cycles per second.
- 63. A method of detecting low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising the steps of connecting a resistor across the DC power supply, connecting an indicator between a tapping point relative to the resistor and a ground point such that a ground leakage current in the system closes a ground circuit to activate the indicator means, periodically interrupting said circuit by opening and closing the ground circuit effectively to generate a DC pulse interrupted ground fault signal to produce proportional periodic changes in a magnetic field associated with the system while the ungrounded DC system remains substantially operational, and magnetically sensing in a location relative the DC system said magnetic field changes related to said pulse interrupted ground fault signal whereby said magnetic field changes provide the necessary signal for low level ground fault current detection, the pulse interruption rate being between about 1/6 to about 1/11 cycles per second.
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65. Apparatus for the detection of low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising a resistor element for connection across the DC power supply, a tapping point to the resistor element, a connector between the tapping point and a ground point such that a ground leakage current in the system completes a ground circuit, a relay between the tapping point and ground, a pulser for periodically opening and closing said relay while the ungrounded DC system remains substantially closed and operational, the opening and closing of said relay interrupting said ground circuit effectively thereby to generate a DC pulse interrupted ground fault signal being substantially a square wave, and a magnetic sensor for location relative to the DC system for sensing said magnetic field changes and thereby said DC pulse interrupted ground fault signal and thereby providing for detecting the location of the low level ground leakage current in the relatively high capacitive reactance system, said DC system remaining substantially closed and operational during the ground leakage current detection, the pulse interruption rate being between about 1/6 to about 1/11 cycles per second.
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66. A method of detecting low level ground leakage current in a normally ungrounded DC system in a multifeeder distribution system having a relatively high capacitive reactance and being associated with a relatively strong electromagnetic and electrostatic field, said system including a DC power supply, conductors from the supply for supplying power to a load connected in the DC system comprising the steps of connecting a resistor across the DC power supply, connecting an indicator between a tapping point relative to the resistor and a ground point such that a ground leakage current in the system closes a ground circuit to activate the indicator means, periodically interrupting said circuit by opening and closing the ground circuit effectively to generate a DC pulse interrupted ground fault signal being substantially a square wave to produce proportional periodic changes in a magnetic field associated with the system while the ungrounded DC system remains substantially operational, and magnetically sensing in a location relative the DC system said magnetic field changes related to said pulse interrupted ground fault signal whereby said magnetic field changes provide the necessary signal for low level ground fault current detection, the pulse interruption rate being between about 1/6 to about 1/11 cycles per second.
Specification