Method and insulation monitoring arrangement for a functionally grounded electric installation operated using a supply direct voltage

Patent metadata

Field	Value
Publication number	US-12553930-B2
Application number	US-202418959086-A
Country	US
Kind code	B2
Filing date	Nov 25, 2024
Priority date	Nov 24, 2023
Publication date	Feb 17, 2026
Grant date	Feb 17, 2026

Abstract

A method and insulation monitoring arrangement for insulation monitoring of an electric installation operated using a supply direct voltage and has a first insulation resistance between the positive active conductor and ground and a second insulation resistance between the negative active conductor and ground as well as a functional grounding between the negative active conductor and ground by a ground resistance. The method involves measuring a ground current, which flows in the path of the functional grounding, by means of a DC measuring device; measuring the supply direct voltage by means of a voltage measuring device; computing the first insulation resistance from the supply direct voltage divided by the ground current by means of a computing unit; the condition is valid during operation of the electric installation that the second insulation resistance being at least 100 times greater than the ground resistance.

First claim

The invention claimed is:

1 . A method for insulation monitoring of an electric installation ( 2 ) which is operated using a supply direct voltage (U DC ) and has a first insulation resistance (R iso1 ) between the positive active conductor (L+) and ground (PE) and a second insulation resistance (R iso2 ) between the negative active conductor (L−) and ground (PE) as well as a functional grounding between the negative active conductor (L−) and ground (PE) by means of a ground resistance (R E ),
the method comprising the following steps:
measuring a ground current (I E ), which flows in the path of the functional grounding, by means of a DC measuring device ( 14 ),
measuring the supply direct voltage (U DC ) by means of a voltage measuring device ( 12 ),
computing the first insulation resistance (R iso1 ) from the supply direct voltage (U DC ) divided by the ground current (I E ) by means of a computing unit ( 20 ),
the condition being valid during operation of the electric installation ( 2 ) that the second insulation resistance (R iso2 ) is at least 100 times greater than the ground resistance (R E ).

2 . The method according to claim 1 , wherein an antiparallel diode circuit ( 16 ) having a bypass switch ( 18 ) switched parallel to the antiparallel diode circuit ( 16 ) is disposed in series to the ground resistance (R E ) in the path of the functional grounding, the bypass switch ( 18 ) cyclically alternating between a high-impedance open state and a low-impedance closed state,
a diode voltage (U D ) being measured by means of another voltage measuring device ( 12 ), the first insulation resistance (R iso1 ) being computed in the closed state from the supply direct voltage (U DC ) divided by the ground current (I E ), and the second insulation resistance (R iso2 ) being computed by dividing a diode voltage change (ΔU D ) between the two states and a ground current change (ΔI E ) between the two states by means of the computing unit ( 20 ).

3 . The method according to claim 1 , wherein an antiparallel diode circuit ( 16 ) without a bypass switch ( 18 ) switched parallel thereto is disposed in series to the ground resistance (R E ) in the path of the functional grounding, the first insulation resistance (R iso1 ) being computed from the supply direct voltage (U DC ) divided by the ground current (I E ) by means of the computing unit ( 20 ).

4 . The method according to claim 1 , wherein the ground current (I E ) measured by means of the DC measuring device ( 14 ) is detected in a range less than 100 mA.

5 . The method according to claim 1 , wherein a DC residual current (I F ) is detected by means of DC residual-current measuring device ( 30 ) installed in the path of the functional grounding.

6 . The method according to claim 5 , wherein the DC residual current (I F ) is detected by means of a DC residual-current measuring device ( 30 ) configured as a modular residual current device.

7 . An application of the method for insulation monitoring according to claim 1 , wherein the electric installation ( 2 ) operated using the supply direct voltage (U DC ) is a hydrogen electrolysis installation.

8 . An insulation monitoring arrangement ( 10 ) for an electric installation which is operated using a supply direct voltage (U DC ) and has a first insulation resistance (R iso1 ) between the positive active conductor (L+) and ground (PE) and a second insulation resistance (R iso2 ) between the negative active conductor (L−) and ground (PE) and a functional grounding between the negative active conductor (L−) and ground (PE) by means of a ground resistance (R E ), the insulation monitoring arrangement ( 10 ) having a DC measuring device ( 14 ) for measuring a ground current (I E ) flowing in the path of the functional grounding, a voltage measuring device ( 12 ) for measuring the supply direct voltage (U DC ), a computing unit ( 20 ), which is configured for computing the first insulation resistance (R iso1 ) from the supply direct voltage (U DC ) divided by the ground current (I E ), the condition being valid during operation of the electric installation ( 2 ) that the second insulation resistance (R iso2 ) is at least 100 times greater than the ground resistance (R E ).

9 . The insulation monitoring arrangement ( 10 ) according to claim 8 , wherein an antiparallel diode circuit ( 16 ) having a bypass switch ( 18 ) switched parallel to the antiparallel diode circuit ( 16 ) is disposed in series to the ground resistance (R E ) in the path of the functional grounding, the bypass switch ( 18 ) cyclically alternating between a high-impedance open state and a low-impedance closed state, the computing unit ( 20 ) being configured for computing the first insulation resistance (R iso1 ) from the supply direct voltage (U DC ) divided by the ground current (I E ) in the closed state and for computing the second insulation resistance (R iso2 ) by dividing the voltage change (ΔU D ) between the two states and the current change (ΔI D ) between the two states.

10 . The insulation monitoring arrangement ( 10 ) according to claim 8 , wherein an antiparallel diode circuit ( 16 ) is disposed in series to the ground resistance (R E ) in the path of the functional grounding, the computing unit ( 20 ) being configured for computing the first insulation resistance (R iso1 ) from the supply direct voltage (U DC ) divided by the ground current (I E ).

11 . The insulation monitoring arrangement ( 10 ) according to claim 8 , wherein the DC measuring device ( 14 ) is designed to be highly sensitive for detecting the ground current (I E ) in the range of less than 100 mA.

12 . The insulation monitoring arrangement ( 10 ) according to claim 8 , further including a DC residual-current measuring device ( 30 ) installed in the path of the functional grounding and configured for detecting a DC residual current (I F ).

13 . The insulation monitoring arrangement ( 10 ) according to claim 12 , wherein the DC residual-current measuring device is configured as a modular residual current device.

14 . A usage of the insulation monitoring arrangement ( 10 ) according to claim 8 , wherein the electric installation ( 2 ) is a hydrogen electrolysis installation.

Assignees

• Bender Gmbh & Co Kg

Inventors

• Hackl Dieter

Classifications

• G01R27/08

  Measuring resistance by measuring both voltage and current · CPC title

• G01R27/025 Primary

  Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters · CPC title

• C25B15/06

  Detection or inhibition of short circuits in the cell · CPC title

• G01R31/52

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

• G01R27/18 Primary

  Measuring resistance to earth {, i.e. line to ground} · CPC title