Monitoring device and method for insulation monitoring of an ungrounded electric subsystem having a liquid cooling operated to ground

Patent metadata

Field	Value
Publication number	US-2021263093-A1
Application number	US-202117183445-A
Country	US
Kind code	A1
Filing date	Feb 24, 2021
Priority date	Feb 26, 2020
Publication date	Aug 26, 2021
Grant date	—

Abstract

A monitoring device and a method for monitoring an insulation resistance for an ungrounded electric system includes a liquid cooling operated to ground and having refrigerant flowing in tubes. For this purpose, the measuring signal is supplied in series in the tube system via the refrigerant resistance. The monitoring device is realized having a current measurement or a voltage measurement at the tube sections in order to detect the insulation resistance and can be enhanced for monitoring a shared insulation resistance of several ungrounded electric subsystems fed by a shared transformer.

First claim

1 . A monitoring device ( 100 , 101 , 102 ) for monitoring an insulation resistance (R f ) for an ungrounded electric system ( 2 ) which comprises a liquid cooling which is operated to ground using a refrigerant ( 3 ) and has a supply line ( 6 ) and a return line ( 8 ), the supply line ( 6 ) and the return line ( 8 ) each being realized as a tube section ( 10 ) which is connected to a ground potential (PE) in an electrically conductive manner and to which an electrically insulated tube section ( 12 ) is connected which has a tube length (l i ) and is connected to the electric system ( 2 ),
characterized by one or two low-impedance measuring signal sources ( 30 ) each configured for generating a measuring signal having a measuring voltage (U m ), each comprising a ground-potential connection ( 31 ) connected to the electrically conductive tube section ( 10 ), and each comprising a coupling connection ( 32 ), a coupling-current measuring sensor ( 40 ) for measuring a coupling current (I AK ) which flows in the refrigerant ( 3 ) flowing through the electrically insulated tube section ( 12 ), a fault-current measuring sensor ( 42 ) which is switched downstream of the coupling-current measuring sensor ( 40 ) in the direction of the electric system ( 2 ) and is configured for measuring a fault current (I Ri ) which flows in the refrigerant ( 3 ) flowing through the electrically insulated tube section ( 12 ), a conductive coupling tube element ( 50 ) which contacts the refrigerant ( 3 ) and is electrically connected to the coupling connection ( 32 ) of the measuring signal source ( 30 ) for coupling the measuring signal, the coupling tube element ( 50 ) being disposed in such a manner on the electrically insulated tube section ( 12 ) between the coupling-current measuring sensor ( 40 ) and the fault-current measuring sensor ( 42 ) that the tube length (l i ) of the electrically insulated tube section ( 12 ) is divided into a coupling length (l AK ) extending between the electrically conductive tube section ( 10 ) and the coupling tube element ( 50 ) and a resistance length (l Ri ) extending from the coupling tube element ( 50 ) to the electric system ( 2 ), a computing unit ( 60 ) which is configured for computing the insulation resistance (R f ) from the measuring voltage (U m ), the detected coupling current (I AK ), the detected fault current (I Ri ), the coupling length (l AK ) and the resistance length (l Ri ).

2 . The monitoring device ( 100 , 102 ) according to claim 1 , characterized in that
the fault-current measuring sensor ( 42 ) comprises a fault-current measuring current transformer which encircles both the supply line ( 6 ) and the return line ( 8 ), and the coupling-current measuring sensor ( 40 ) comprises a coupling-current measuring current transformer which encircles both the supply line ( 6 ) and the return line ( 8 ), and the coupling tube element ( 50 ) is realized in one part and is connected to the measuring signal source ( 30 ) and the measuring signal is synchronously coupled both into the supply line ( 6 ) and the return line ( 8 ) in common mode, or the coupling tube element ( 50 ) is divided into two parts in a supply-line coupling tube element ( 52 ) and a return-line coupling tube element ( 54 ) which are each connected to one of the measuring signal sources ( 30 ) and synchronously couple the corresponding measuring signals into the supply line ( 6 ) or the return line ( 8 ) on one side in common mode.

3 . The monitoring device ( 101 ) according to claim 1 , characterized in that
the fault-current measuring sensor ( 42 ) comprises a fault-current measuring current transformer and the coupling-current measuring sensor ( 42 ) comprises a coupling-current measuring current transformer, the fault-current measuring current transformer and the coupling-current measuring current transformer both encircle the supply line ( 6 ) on one side and the return line ( 8 ) on one side, and the coupling tube element ( 50 ) is realized in one part and is connected to the measuring signal source ( 30 ) and the measuring signal is synchronously coupled together into the supply line ( 6 ) and the return line ( 8 ) in common mode, or the coupling tube element ( 50 ) is divided into two parts in a supply-line coupling tube element ( 52 ) and a return-line coupling tube element ( 54 ) which are each connected to one of the measuring signal sources ( 30 ) and synchronously couple the corresponding measuring signals into the supply line ( 6 ) or the return line ( 8 ) on one side in common mode.

4 . The monitoring device according to claim 1 ,
wherein the ungrounded electric system ( 2 ) comprises an ungrounded power converter system.

5 . A monitoring device ( 103 ) for monitoring an insulation resistance (R f ) for an ungrounded electric system ( 2 ) which comprises a liquid cooling which is operated to ground using a refrigerant ( 3 ) and comprises a supply line ( 6 ) and a return line ( 8 ), the supply line ( 6 ) and the return line ( 8 ) each being realized as an electrically conductive tube section ( 10 ) which is connected to a ground potential (PE) and to which an electrically insulated tube section ( 12 ) is connected which has a tube length (l i ) and is connected to the electric system ( 2 ),
characterized by a low-impedance measuring signal source ( 30 ) configured for generating a measuring signal having a measuring voltage (U m ), the measuring signal source ( 30 ) comprising a ground-potential connection ( 31 ) connected to the electrically conductive tube section ( 10 ) and comprising a coupling connection ( 32 ), a voltage meter ( 70 ) for measuring a partial voltage (U i ), the voltage meter ( 70 ) comprising a first voltage-meter input ( 72 ) connected to the coupling connection ( 32 ) of the measuring signal source ( 30 ), and the voltage meter comprising a second voltage-meter input ( 74 ), a conductive coupling tube element ( 50 ) which contacts the refrigerant ( 3 ) and is electrically connected to the coupling connection ( 32 ) of the measuring signal source ( 30 ) for synchronously coupling the measuring signal into the supply line ( 6 ) and the return line ( 8 ) in common mode, a conductive voltage-meter tube element ( 76 ) which contacts the refrigerant ( 3 ) and is connected to the second voltage-meter input ( 74 ) of the voltage meter ( 70 ), the coupling tube element ( 50 ) being disposed in such a manner on the electrically insulated tube section ( 12 ) that a coupling length (l AK1 ) is yielded between the system-sided end of the electrically conductive tube section ( 10 ) and the coupling tube element ( 50 ), and the voltage-meter tube element ( 76 ) being disposed in such a manner adjacent to the electrically insulated tube section ( 12 ) that a voltage-meter length (l AK2 ) is yielded between the coupling tube element ( 50 ) and the voltage-meter tube element ( 76 ) and a resistance length (l Ri ) is yielded between the voltage-meter tube element and the electric system, a computing unit which is configured for computing the insulation resistance from the measuring voltage (U m ) of the measuring signal, a supplied measuring current (I m ), the partial voltage (U i ), the coupling length (l AK1 ), the voltage-meter length (l AK2 ) and the resistance length (l Ri ).

6 . The monitoring device according to claim 5 ,
wherein the ungrounded electric system ( 2 ) comprises an ungrounded power converter system.

7 . An enhanced monitoring device ( 110 ) for monitoring a shared insulation resistance (R f ) of several ungrounded electric subsystems ( 16 ) which are fed by a shared transformer ( 15 ) and each comprise a liquid cooling operated to ground using a refrigerant ( 3 ) and comprising a supply line ( 6 ) and a return line ( 8 ), the supply

Assignees

• Bender Gmbh & Co Kg

Inventors

• Hackl Dieter

Classifications

• G01R27/025 Primary

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

• G01R31/1272 Primary

  of cable, line or wire insulation, e.g. using partial discharge measurements (locating faults in cables G01R31/083) · CPC title

• G01R31/1281

  of liquids or gases · CPC title

• G01R31/52

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

• H05K7/20927

  Liquid coolant without phase change · CPC title