Method and devices for extended insulation-fault search using a multifunctional test current

Patent metadata

Field	Value
Publication number	US-10067517-B2
Application number	US-201615219060-A
Country	US
Kind code	B2
Filing date	Jul 25, 2016
Priority date	Jul 31, 2015
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

The invention relates to a method and to devices for extended insulation-fault search in an IT power supply system using a multifunctional test current, wherein, selectively and depending on the application, the test current functions as a voltage compensation current so as to compensate a voltage increase in an active conductor of the IT power supply system, as a tripping current so as to trip a residual current protection device arranged in a subsystem of the IT power supply system and/or as a leakage-capacitance compensation current so as to compensate a capacitive leakage current. The test current can fulfil more than one of the cited functions simultaneously.

First claim

The invention claimed is:

1. A method for extended insulation-fault search in an IT power supply system ( 4 ), comprising the following method steps:
feeding a test current (IL) functioning as a locating current into at least one active conductor of the IT power supply system ( 4 ),
registering a test-current portion in a subsystem ( 8 a , 8 b ) of the IT power supply system ( 4 ),
evaluating the registered test-current portion to locate an insulation fault (Rf),
characterized in that
selectively and depending on the application, the test current (IL), when functioning
as a voltage compensation current, compensates a voltage increase in an active conductor of the IT power supply system ( 4 ),
as a tripping current, trips a residual current protection device ( 22 a , 22 b ) arranged in a subsystem ( 8 a , 8 b ) of the IT power supply system ( 4 ),
as a leakage-capacitance compensation current, compensates a capacitive leakage current,
the test current (IL) being capable of fulfilling more than one of the cited functions simultaneously.

2. The method according to claim 1 ,
characterized in that
as a voltage compensation current, the test current (IL) effects a compensation of an excess voltage caused by a low-resistance insulation fault.

3. The method according to claim 1 ,
characterized in that
as a voltage compensation current, the test current (IL) effects a compensation of a displacement direct voltage.

4. The method according to claim 1 ,
characterized in that
when the test current (IL) functions as a voltage compensation current and as a leakage-capacitance compensation current, at least one of the test-current parameters test-current amplitude, test-current frequency and test-current phase is determined by control.

5. The method according to claim 1 ,
characterized in that
a maximum test-current value is predefined by a factory setting or directly by the user.

6. The method according to claim 5 ,
characterized in that
the maximum test-current value is derived from at least one electrical system parameter of the IT power supply system ( 4 ), the electrical system parameter being configured statically or determined dynamically.

7. The method according to claim 1 ,
characterized in that
the feeding of the test current (IL) as a voltage compensation current starts when a critical voltage-increase limit value is exceeded.

8. The method according to claim 1 ,
characterized in that
the feeding of the test current (IL) as a tripping current starts when the insulation resistance falls below an insulation-resistance limit value or when a critical voltage-increase limit value is exceeded.

9. The method according to claim 1 ,
characterized in that
a duration of the test-current feeding is limited.

10. The method according to claim 5 ,
characterized in that
a duration of the test-current feeding at maximum test-current value is limited.

11. A test-current generator ( 20 ) for extended insulation-fault search in an IT power supply system,
characterized by
being configured as a multifunction test-current generator ( 20 ) comprising circuitry-related and programming-related devices that generate not only a test current (IL) for locating the insulation fault (Rf), but also, selectively and depending on the application, a voltage compensation current for compensating a voltage increase in an active conductor of the IT power supply system ( 4 ), a tripping current for tripping a residual current protection device ( 22 a , 22 b ) arranged in a subsystem ( 8 a , 8 b ) of the IT power supply system ( 4 ) and a leakage-capacitance compensation current for compensating a capacitive leakage current.

12. The test-current generator ( 20 ) according to claim 11 ,
characterized in that
the circuitry-related and programming-related devices comprise a control device for setting a test-current parameter.

13. The test-current generator ( 20 ) according to claim 11 ,
characterized in that
the circuitry-related and programming-related devices comprise a checking device for controlling the sequence of test-current generation and feeding.

14. An insulation-fault search system for extended insulation-fault search in an IT power supply system ( 4 ), comprising a test-current generator ( 20 ) for generating and feeding a test current (IL), a test-current registering device ( 12 a , 12 b ) and an insulation-fault evaluating device ( 14 ),
characterized in that
the test-current generator ( 20 ) is configured as a multifunction test-current generator ( 20 ) according to claim 11 .

Assignees

• Bender Gmbh & Co Kg

Inventors

• Hackl Dieter
• Schaefer Oliver

Classifications

• H02H3/17

  by means of an auxiliary voltage injected into the installation to be protected {(using summation current transformers H02H3/33)} · CPC title

• G01R31/083

  in cables, e.g. underground · CPC title

• G05F1/10 Primary

  Regulating voltage or current  (G05F1/02 takes precedence) · CPC title

• H02H3/34

  of a three-phase system · CPC title

• 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