Method for detecting ground faults in a LVDC electric line and an electronic device thereof

Patent metadata

Field	Value
Publication number	US-10352985-B2
Application number	US-201615228404-A
Country	US
Kind code	B2
Filing date	Aug 4, 2016
Priority date	Aug 5, 2015
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

In a further aspect, the invention relates to an electronic device (1) including processing means for carrying out said method.

First claim

What we claim is:

1. A method for detecting faults in a LVDC electric line, the line having first and second conductors, the method comprising: passing an excitation current through an excitation winding, the excitation winding being wound around a magnetic core, the magnetic core being enchained with the first and second conductors of the electric line; acquiring a first detection signal indicative of low-frequency components of an unbalancing current (IG) between, comprising; sending a current through the first conductor; obtaining a first measuring signal (VM 1 ) in response to the excitation current in the excitation winding;
low pass filtering the first measuring signal (VM 1 ) to output a first detection signal (VLOW); acquiring a second detection signal (VHIGH) indicative of high-frequency components of said unbalancing current (IG), comprising; sending a current through the second conductor; obtaining a second measuring signal (VM) in response to the excitation current in the excitation winding; high pass filtering the second measuring signal (VM 2 ) to output a second detection signal (VHIGH); obtaining a third detection signal (RT) by calculating the ratio between said first and second detection signals (VLOW, VHIGH); checking whether a DC current (IF) towards ground is present by comparing said third detection signal (RT) with a first threshold value (TH 1 ) (highlighted for emphasis).

2. An electronic device for detecting faults in a LVDC electric line, the line having first and second conductors, the device comprising:
sensing means for providing at least a measuring signal (VM 1 , VM 2 ) indicative of an unbalancing current (IG) between the conductors of said electric line;
filtering means for filtering the measuring signal (VM 1 , VM 2 ) and providing a first detection signal (VLOW) indicative of low-frequency components of said unbalancing current and a second detection signal (VHIGH) indicative of high-frequency components of said unbalancing current;
processing means for processing said first and second detection signals (VLOW, VHIGH), said processing means being programmed to perform operations comprising:
obtaining a third detection signal (RT) by calculating the ratio between said first and second detection signals (VLOW, VHIGH); and
checking whether a DC current (IF) towards ground is present by comparing said third detection signal (RT) with a first threshold value (TH 1 ).

3. A device, according to claim 2 , the operations further comprising, which comprises the following steps of: obtaining a fourth detection signal (VSUM) indicative of the an overall currents flowing towards ground by calculating the sum of said first and second detection signals (VLOW, VHIGH), if said third detection signal (RT) exceeds said first threshold value (TH 1 ); comparing said fourth detection signal (VSUM) with a third threshold value (TH 3 ); generating a trip signal (TRIP) to command the interruption of said electric line, if said fourth detection signal (VSUM) exceeds said third threshold value (TH 3 ).

4. A device according to claim 2 , the operations further comprising, which comprises the steps of: comparing said second detection signal (VHIGH) with a second threshold value (TH 2 ), if said third detection signal (RT) does not exceed said first threshold value (TH 1 ); generating an alarm signal (WARN) indicative of the presence of high-frequency leakage currents towards ground, if said second detection signal (VHIGH) exceeds said second threshold value (TH 2 ).

5. An electronic device, according to claim 2 , wherein said sensing means comprise at least a magnetic core configured to form a magnetic flux path enchained with the conductors of said electric line.

6. An electronic device, according to claim 5 , wherein said sensing means comprise an excitation circuit section comprising at least an excitation winding wound around said magnetic core and at least a power source electrically connected to said excitation winding to provide an excitation current circulating along said excitation winding, said excitation current having a frequency (fE) comprised in the interval 0<fE<fsw, where fsw is the switching frequency of a AC/DC conversion stage feeding said electric line.

7. An electronic device, according to claim 6 , wherein said sensing means comprise an output circuit section comprising at least a detection winding and at least a detection element (Rs 1 , Rs 2 ) electrically connected with said detection winding, said detection element detecting at least a detection current (IO 1 , IO 2 ) flowing along said detection winding and providing at least a measuring signal (VM 1 , VM 2 ) indicative of said unbalancing current (IG).

8. An electronic device, according to the claim 5 , wherein said sensing means comprise: said magnetic core; an excitation circuit section comprising an excitation winding wound around said magnetic core and a power source electrically connected to said excitation winding; an output circuit section comprising: a first detection winding wound around said magnetic core and a first detection element (Rs 1 ) electrically connected with said first detection winding, said first detection element detecting a first detection current (Io 1 ) flowing along said first detection winding and providing a first measuring signal (VM 1 ) indicative of said unbalancing current (IG); a second detection winding wound around said magnetic core and a second detection element (Rs 2 ) electrically connected with said second detection winding, said second detection winding detecting a second detection current (IO 2 ) flowing along said second detection winding and providing a second measuring signal (VM 2 ) indicative of said unbalancing current (IG).

9. An electronic device, according to claim 6 , wherein said sensing means comprise an output circuit section comprising at least a detection element (Rs 1 , Rs 2 ) electrically connected with said at least an excitation winding, said detection element detecting said excitation current (IE) flowing along said excitation winding and providing at least a measuring signal (VM 1 , VM 2 ) indicative of said unbalancing current (IG).

10. An electronic device, according to claim 5 , wherein said sensing means comprise: said magnetic core; an excitation circuit section comprising: a first excitation winding and a second excitation winding wound around said magnetic core; a power source electrically connected with said first and second excitation windings to provide said excitation current (IE) flowing along said first and second excitation windings; an output circuit section comprising: a first detection element (Rs 1 ) electrically connected with said first excitation winding, said first detection element detecting said excitation current (IE) flowing along said first detection winding and providing a first measuring signal (VM 1 ) indicative of said unbalancing current (IG); a second detection element (RS 2 ) electrically connected with said second excitation winding, said second detection element detecting said excitation current ( 1 E) flowing along said second detection winding and providing a second measuring signal (VM 2 ) indicative of said unbalancing current (IG).

11. An electronic arrangement for LVDC electric power distribution networks which comprises an electronic device, according to claim 2 .

12. A switching device for LVDC electric power distribution networks which comprises an electronic device, according to claim 2 .

13. A device, according to claim 4 , the operations further comprising: obtaining a fourth detection signal (VSUM) indicative of an overall currents flowing towards ground by calculating the sum o

Assignees

• Abb Spa

Inventors

• Ragaini Enrico
• Carminati Marco

Classifications

• G01R31/086 Primary

  in power transmission or distribution networks, i.e. with interconnected conductors · CPC title

• H01F38/40

  for DC · CPC title

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• G01R31/025

  Physics · mapped topic

• H02M7/04

  by static converters · CPC title