System and method for ground fault detection in a transformer isolated communication channel of a network device

Patent metadata

Field	Value
Publication number	US-9319101-B2
Application number	US-201213631045-A
Country	US
Kind code	B2
Filing date	Sep 28, 2012
Priority date	Sep 28, 2012
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

A system and method for non-intrusive fault detection of a ground fault in a communication channel is provided. A bias voltage may be established on a first portion of the communication channel and a second portion of the communication channel. A first voltage may be detected across a first resistor electrically connected to the first and second portions of the communication channel. Data indicative of whether the ground fault exists in the first or second portions of the communication channel may be provided based on the detecting.

First claim

What is claimed is:

1. A ground fault detection system for detecting a ground fault in a system having a first node, a second node, and a communication channel between the first node and the second node, the ground fault detection system comprising:
a bias generator electrically connected to the communication channel system, the bias generator having a first connection to ground and a second connection for output of a non-ground voltage, and the bias generator configured to establish a bias voltage on a first portion of the communication channel and a second portion of the communication channel;
a first resistor electrically connected to the second connection of the bias generator to receive the non-ground voltage and electrically connected to the first and second portions of the communication channel, the first resistor being connected between the bias generator and the first and second portions of the communication channel; and
a first detector circuit configured to detect a first voltage across the first resistor and configured to output, based on the detection of the first voltage, a signal indicative of whether the ground fault exists in the communication channel system.

2. The ground fault detection system of claim 1 , wherein the communication channel comprises an Ethernet cable.

3. The ground fault detection system of claim 2 , wherein the communication channel further comprises first and second coupling transformers coupled to the Ethernet cable.

4. The ground fault detection system of claim 3 , wherein the first and second portions of the communication channel comprise first and second taps, respectively, on the respective first and second coupling transformers.

5. The ground fault detection system of claim 4 , wherein the first and second taps are center taps on the first and second coupling transformers.

6. The ground fault detection system of claim 1 , wherein when the first voltage across the first resistor is outside of a threshold window, the first detector circuit is configured to output a signal indicative of the ground fault in the communication channel.

7. The ground fault detection system of claim 1 , wherein when the first voltage across the first resistor is within a threshold window, the first detector circuit is configured to output a signal indicative of no ground fault in the communication channel.

8. The ground fault detection system of claim 1 , further comprising:
a power source configured to supply power to the second node.

9. A ground fault detection system for detecting a ground fault in a system having a first node, a second node, and a communication channel between the first node and the second node, the ground fault detection system comprising:
a bias generator electrically connected to the communication channel system and configured to establish a bias voltage on a first portion of the communication channel and a second portion of the communication channel;
a first resistor electrically connected to the bias generator and the first and second portions of the communication channel;
a first detector circuit configured to detect a first voltage across the first resistor and configured to output, based on the detection of the first voltage, a signal indicative of whether the ground fault exists in the communication channel system;
a second resistor electrically connected to the bias generator and the first and second portions of the communication channel; and
a second detector circuit configured to detect a second voltage across the second resistor and configured to output, based on the detection of the second voltage, a signal indicative of whether the ground fault exists in the second portion of the communication channel.

10. The ground fault detection system of claim 9 , wherein when the second voltage across the second resistor is non-zero or exceeds a threshold value, the second detector circuit is configured to output a signal indicative of the ground fault in the second portion of the communication channel.

11. The ground fault detection system of claim 9 , wherein when the second voltage across the second resistor is zero or less than a threshold value, the second detector circuit is configured to output a signal indicative of no ground fault in the second portion of the communication channel.

12. The ground fault detection system of claim 9 , wherein, when the first detector circuit outputs the signal indicative of the ground fault, the ground fault is in the first portion of the communication channel.

13. A method for detecting a ground fault in a communication channel between a first node and a second node, the method comprising:
establishing a bias voltage on a first portion of the communication channel and a second portion of the communication channel, the bias voltage being established with a bias voltage source having a non-ground output connected to the first and second portions through a resistor;
detecting a first voltage between the first and second portions of the communication channel; and
providing data indicative of whether the ground fault exists in the first or second portions of the communication channel, the providing based on a comparison of the bias voltage on the first or second portion of the communication channel to a voltage across the resistor.

14. The method of claim 13 , wherein providing comprises outputting data indicative of the ground fault in the first or second portions of the communication channel when the detected first voltage is outside of a threshold range relative to the bias voltage.

15. The method of claim 13 , wherein providing comprises outputting data indicative of no ground fault in the first or second portions of the communication channel when the detected first voltage is within a threshold range relative to the bias voltage.

16. The method of claim 13 , wherein the communication channel comprises an Ethernet cable coupled to first and second coupling transformers.

17. The method of claim 16 , wherein the first and second portions of the communication channel comprise first and second center taps, respectively, on the respective first and second coupling transformers.

18. A method for detecting a ground fault in a communication channel between a first node and a second node, the method comprising:
establishing a bias voltage on a first portion of the communication channel and a second portion of the communication channel;
detecting a first voltage between the first and second portions of the communication channel;
providing data indicative of whether the ground fault exists in the first or second portions of the communication channel, the providing based on the detecting;
detecting a second voltage developed across a second resistor electrically connected to the first and second portions of the communication channel; and
providing a signal indicative of whether the ground fault exists in the second portion of the communication channel, the providing based on the detection of the second voltage.

19. A fire safety system having a fire alarm control panel coupled to fire safety equipment via a communication channel, the fire safety system comprising:
a power supply configured to provide power over the communication channel;
a ground fault detection system configured to detect a ground fault on the communication channel, the ground fault detection system comprising:
a bias generator electrically connected to the communication channel and configured to establish a bias voltage on a first portion of the communication channel and a second portio

Assignees

• Siemens Industry Inc

Inventors

• Lontka Karen D

Classifications

• H04B3/46 Primary

  Monitoring; Testing · CPC title

• G01R31/025

  Physics · mapped topic

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title