Apparatus and method for automatic ground fault location determination in high resistance grounded motor drive system

Patent metadata

Field	Value
Publication number	US-9684026-B2
Application number	US-201314048156-A
Country	US
Kind code	B2
Filing date	Oct 8, 2013
Priority date	Oct 8, 2013
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

A PLC or other industrial controller programmed to locate ground faults in a networked high resistance grounded multi-drive system through network communications messaging to automatically place networked motor drives in various operational states to isolate individual drives for ground fault identification testing and selectively identify individual drives as suspected ground fault locations.

First claim

The following is claimed:

1. An automated method for identifying candidate ground fault locations in a high resistance grounded multi-drive system with a multiphase AC source including a neutral connected to a system ground through a high resistance, the method comprising:
(i) using a controller with at least one processor operative to communicate with a plurality of motor drives via a communications network, selecting a first one of a plurality of motor drives as a single selected motor drive for testing;
(ia) using the controller, closing a system main circuit breaker to connect the multiphase AC source to the plurality of motor drives or to a shared rectifier;
(ii) using the controller, disabling all non-selected ones of the plurality of motor drives;
(iii) using the controller, enabling the single selected motor drive;
(iv) using the controller, determining whether a ground fault is detected while the single selected motor drive is enabled and all the non-selected motor drives are disabled;
(v) using the controller, selectively identifying the single selected motor drive as a candidate location of a ground fault if a ground fault is detected while the single selected motor drive is enabled and all the non-selected motor drives are disabled; and
(vi) using the controller, selecting at least one remaining untested motor drive of the plurality of motor drives for testing, and repeating steps (ii)-(v) to selectively identify one or more candidate locations of the ground fault or to eliminate further ones of the plurality of motor drives from consideration as ground fault locations.

2. The method of claim 1 , further comprising:
(vii) using the controller, disabling all of the plurality of motor drives;
(viii) using the controller, determining whether a ground fault is detected while all of the plurality of motor drives are disabled and the system main circuit breaker is closed; and
(ix) using the controller, selectively identifying a system input or common DC bus as a candidate location of a ground fault if a ground fault is detected while all of the plurality of motor drives are disabled and the system main circuit breaker is closed.

3. The method of claim 2 , wherein (iii) enabling the single selected motor drive and (iv) determining whether a ground fault is detected while the single selected motor drive is enabled comprises:
testing for DC side ground faults by:
(a) sending at least one command or message from the controller to cause the single selected motor drive to close an associated local drive disconnect switch to connect the single selected motor drive to an AC input power source while turning off all inverter switching devices of the single selected motor drive;
(b) using the controller, determining whether a ground fault is detected while the associated local drive disconnect switch is closed and all the inverter switching devices of the single selected motor drive are turned off; and
(c) using the controller, selectively identifying a DC side ground fault at the single selected motor drive as a candidate location of a ground fault if a ground fault is detected while the associated local drive disconnect switch is closed and all the inverter switching devices of the single selected motor drive are turned off.

4. The method of claim 3 , wherein (iii) enabling the single selected motor drive and (iv) determining whether a ground fault is detected while the single selected motor drive is enabled further comprises:
testing for motor side ground faults by:
(d) sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device of the single selected motor drive while the associated local drive disconnect switch is closed;
(e) using the controller, determining whether a ground fault is detected while at least one of the inverter switching devices of the single selected motor drive is turned on and the associated local drive disconnect switch is closed; and
(f) using the controller, selectively identifying a motor side ground fault at the single selected motor drive as a candidate location of a ground fault if a ground fault is detected while at least one of the inverter switching devices of the single selected motor drive is turned on and the associated local drive disconnect switch is closed.

5. The method of claim 4 , wherein (d) sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device of the single selected motor drive comprises sending at least one command or message from the controller to cause the single selected motor drive to rotate a connected motor.

6. The method of claim 4 , wherein (d) sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device of the single selected motor drive comprises sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device while preventing rotation of a connected motor.

7. The method of claim 2 , wherein (iii) enabling the single selected motor drive and (iv) determining whether a ground fault is detected while the single selected motor drive is enabled comprises:
testing for motor side ground faults by:
(d) sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device of the single selected motor drive while an associated local drive disconnect switch is closed;
(e) using the controller, determining whether a ground fault is detected while at least one of the inverter switching devices of the single selected motor drive is turned on and the associated local drive disconnect switch is closed; and
(f) using the controller, selectively identifying a motor side ground fault at the single selected motor drive as a candidate location of a ground fault if a ground fault is detected while at least one of the inverter switching devices of the single selected motor drive is turned on and the associated local drive disconnect switch is closed.

8. The method of claim 7 , wherein (d) sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device of the single selected motor drive comprises sending at least one command or message from the controller to cause the single selected motor drive to rotate a connected motor.

9. The method of claim 7 , wherein (d) sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device of the single selected motor drive comprises sending at least one command or message from the controller to cause the single selected motor drive to turn on at least one inverter switching device while preventing rotation of a connected motor.

10. The method of claim 1 , wherein (iii) enabling the single selected motor drive and (iv) determining whether a ground fault is detected while the single selected motor drive is enabled comprises:
testing for DC side ground faults by:
(a) sending at least one command or message from the controller to cause the single selected motor drive to close an associated local drive disconnect switch to connect the single selected motor drive to an AC input power source while turning off all inverter switching devices of the single selected motor drive;
(b) using the controller, determining whether a ground fault is detected while the associated local drive disconnect switch is closed and all the inverter sw

Assignees

• Wei Lixiang
• Mcguire Jeffrey D
• Hu Jiangang
• Liu Zhijun
• Rockwell Automation Tech Inc

Inventors

• Wei Lixiang
• Mcguire Jeffrey D
• Hu Jiangang
• Liu Zhijun

Classifications

• H02H3/16

  responsive to fault current to earth, frame or mass (with balanced or differential arrangement H02H3/26 {; monitoring earth connection H02H5/105}) · CPC title

• B60L2220/42

  with use of more than one motor · CPC title

• G01R31/086

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

• B60L3/0069

  relating to the isolation, e.g. ground fault or leak current · CPC title

• Y02T90/16

  Information or communication technologies improving the operation of electric vehicles · CPC title