METHODS AND DEVICES FOR TESTING THE FUNCTION OF AN INSULATION MONITORING DEVICE

Abstract

Methods and devices are provided for testing the function of a standard insulation monitoring device, installed in an ungrounded power supply system, during operation. The basic concept of the invention rests upon adding a testing apparatus to the ungrounded power supply system, which is being monitored using an insulation monitoring device according to regulations, between the active conductors of an ungrounded power supply system and ground, said testing apparatus systematically changing an insulation resistance of the ungrounded power supply system and observing the reaction of the insulation monitoring device in a fully automated manner in perpetually repetitive testing cycles. The power supply system is monitored perpetually during its operation. In the method, the current operating state (insulation level, load state) of the power supply system is detected via network parameters, such as insulation resistance and system leakage capacity, and consulted for assessing the functionality of the insulation monitoring device.

Claims

1. A method for testing the function of a standard insulation monitoring device (10), installed in an ungrounded power supply system, during operation characterized by a fully automated, perpetually running testing cycle, comprising the method steps: (a) measuring a first insulation resistance (Riso1) of the ungrounded power supply system via the insulation monitoring device (10), (b) transmitting the first insulation resistance value (Riso1) to a testing apparatus (20) and saving the first insulation resistance value (Riso1) in the testing apparatus (20), (c) calculating an uncritical test fault resistance value (Rf) via the testing apparatus, (d) adding the test fault resistance (Rf) between at least one of the active conductors of the ungrounded power supply system and ground via the testing apparatus (20), (e) measuring a second insulation resistance (Riso2) of the ungrounded power supply system via the insulation monitoring device (20), said second insulation resistance (Riso2) resulting from the first insulation resistance (Riso1) and the test fault resistance (Rf) added parallel thereto, (f) transmitting the second insulation fault resistance (Riso2) to the testing apparatus (20) and saving the second insulation fault resistance in the testing apparatus (20), (g) calculating a comparative insulation fault value (Rref), via the testing apparatus (20), from the first insulation resistance value (Riso1) and the test fault resistance value (Rf) added parallel thereto, (h) comparing the second insulation resistance (Riso2) measured by the insulation monitoring device (10) to the comparative insulation resistance value (Rref) calculated by the testing apparatus (20) in the testing apparatus (20) and generating a result log, (i) activating an alarm message via the testing apparatus (20), should the comparison result in the second insulation resistance (Riso2) measured by the insulation monitoring device (10) deviating from the calculated comparative insulation resistance value (Rref), said deviation indicating a faulty function of the insulation monitoring device (10), (j) removing the test fault resistance (Rf) via the testing apparatus (20).

2. The method according to claim 1, characterized in that should the testing apparatus (20) be a functional component of a further insulation monitoring device (10), this insulation monitoring device (10) takes over the task of insulation monitoring in the ungrounded power supply system when a faulty function occurs in the already installed insulation monitoring device (10).

3. The method according to claim 1, characterized in that should the testing apparatus (20) be a functional component of a further insulation monitoring device (10) and should the already installed insulation monitoring device (10) comprise a further testing apparatus as a functional component, the already installed insulation monitoring device (10) and the further insulation monitoring device (10) alternately take over the task of monitoring the insulation and the task of testing the function of the other insulation monitoring device (10).

4. A method for testing the function of a standard insulation monitoring device (10), installed in an ungrounded power supply system, during operation, characterized by (a) depositing the following in the testing apparatus (20): an internal resistance value (Ri) of the insulation monitoring device (10), a response value (Rres) set in the insulation monitoring device (10) and a maximum permissible response time (Tresmax) set in the insulation monitoring device (10), and by a fully automated, perpetually running testing cycle, comprising the method steps: (b) measuring an effective insulation resistance (Reff) via the testing apparatus (20), said effective insulation resistance (Reff) resulting from the internal resistance (Ri) of the active insulation monitoring device (10) and an insulation resistance (Riso) of the ungrounded power supply system arranged parallel thereto (c) calculating an insulation resistance value (Rca1) of the ungrounded power supply system via the testing apparatus (20) from the measured effective insulation resistance value (Reff) and the deposited internal resistance value (Ri) of the insulation monitoring device (10), (d) calculating a critical test fault resistance value Rf via the testing apparatus (20) while considering the calculated insulation resistance value (Rca1) of the ungrounded power supply system, (e) adding the test fault resistance (Rf) between at least one of the active conductors of the ungrounded power supply system and ground via the testing apparatus (20) and simultaneously starting a time measuring device in the testing apparatus (20) for measuring a response time (Tres) of the insulation monitoring device (10), (f) monitoring a system alarm output (12) of the insulation monitoring device (10) and measuring the response time (Tres) via the testing apparatus (20), (g) starting a fault treatment via the testing apparatus (20), should the measured response time (Tres) exceed the maximum permissible response time (Tresmax), (h) generating a result log and/or transmitting the test results to a management system, should the measured response time (Tres) not exceed the maximum permissible response time (Tresmax), (i) removing the test fault resistance Rf via the testing apparatus (20).

5. The method according to claim 4, characterized in that one or more of the following actions can be executed by the testing apparatus (20) as a fault treatment: logging the fault; transmitting a fault message to a superordinate management system; dispatching a function alarm message; shutting down the power supply system.

6. The method according to claim 4, characterized in that by uncoupling the system alarm output (12) of the insulation monitoring device for providing an effective system alarm, a difference is made between an actual system alarm of the insulation monitoring device (10) and a test-related system alarm of the insulation monitoring device (10) in such a manner that the system alarm triggered by the insulation monitoring device (10) only becomes effective if the system alarm triggered by the insulation monitoring device (10) was not triggered by a testing cycle.

7. A testing apparatus (20) for testing the function of a standard insulation monitoring device (10), installed in an ungrounded power supply system, during operation, implementing a method according to claim 1, comprising: a controlling and a computing unit having a storage device for implementing the fully automated, perpetually running testing cycle; a communication device for transmitting data; a switching device for adding the test fault resistance between at least one active conductor of the ungrounded power supply system and ground; and a test alarm device.

8. A testing apparatus (20) for testing the function of a standard insulation monitoring device (10), installed in an ungrounded power supply system, during operation, implementing a method according to claim 4, comprising: a controlling and computing unit having a storage device for implementing the fully automated, perpetually running testing cycle; a measuring device for measuring the insulation resistance effective in the ungrounded power supply system; a communication device for transmitting data; a switching device for adding the test fault resistance between at least one active conductor of the ungrounded power supply system and ground; and a monitoring input (22) for monitoring a system alarm output (12) of the insulation monitoring device.

9. An insulation monitoring device (10) for monitoring an insulation resistance of an ungrounded power supply system, characterized by a testing apparatus (20) according to claim 7.

10. An insulation monitoring device (10) for monitoring an insulation resistance of an ungrounded power supply system, characterized by a testing apparatus (20) according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0066] Further advantageous embodiments can be taken from the following description and the drawing, which describe preferred embodiments of the invention by way of examples. In the figures,

[0067] FIGS. 1a, 1b show a flow chart of the first method according to the invention,

[0068] FIGS. 2a, 2b show a flow chart of the second method according to the invention and

[0069] FIGS. 3a, 3b and 3c show arrangements of the uncoupling of the system alarm output of the insulation monitoring device.

DETAILED DESCRIPTION

[0070] FIGS. 1a and 1b show a flow chart of the first method according to the invention, said method being characterized by data being transmitted between the insulation monitoring device 10 (FIGS. 3a to 3c) to be tested and the testing apparatus 20 (FIGS. 3a to 3c) controlling the insulation monitoring device.

[0071] Each method step is described individually:

[0072] (a) measuring a first insulation resistance Riso1 of the ungrounded power supply system via the insulation monitoring device 10,

[0073] (b) transmitting the first insulation fault resistance value to the testing apparatus and saving the first insulation resistance value Riso1 in the testing apparatus 20,

[0074] (c) calculating an uncritical test fault resistance value Rf via the testing apparatus 20,

[0075] (d) adding the uncritical test fault resistance Rf between at least one of the active conductors of the ungrounded power supply system and ground via the testing apparatus 20,

[0076] (e) measuring a second insulation resistance Riso2 of the ungrounded power supply system via the insulation monitoring device 10, said second insulation resistance Riso2 resulting from the first insulation resistance Riso1 and test fault resistance Rf added parallel thereto,

[0077] (f) transmitting the second insulation fault value Riso2 to the testing apparatus 20 and saving the second insulation resistance value Riso2 in the testing apparatus 20,

[0078] (g) calculating a comparative insulation resistance value Rref via the testing apparatus 20 from the first insulation fault value Riso1 and the test fault resistance value Rf added parallel thereto,

[0079] (h) comparing the insulation resistance Riso2 measured by the insulation monitoring device 20 to the comparative insulation resistance value Rref calculated by the testing apparatus 20 in the testing apparatus 20 and generating a result log,

[0080] (i) activating an alarm message via the testing apparatus 20, should the comparison result in the second insulation resistance Riso2 measured by the insulation monitoring device 10 deviating from the calculated comparative insulation resistance value Rref, said deviation indicating a faulty function of the insulation monitoring device 10,

[0081] (j) removing the test fault resistance Rf via the testing apparatus 20.

[0082] In an amended embodiment, it is presupposed that two insulation monitoring devices (10) are provided with the testing function—for testing the function of the other insulation monitoring device (10)—so that the following additional step can be conducted when reliability requirements are heightened:

[0083] (k) switching the device function after a timer, which runs in sync in both insulation monitoring devices, has run out.

[0084] FIGS. 2a and 2b show a flow chart of the second method according to the invention, in which data, when compared to the first method, is not directly transmitted between the insulation monitoring device 10 (FIGS. 3a to 3c) to be tested and the testing apparatus 20 (FIGS. 3a to 3c) controlling the insulation monitoring device.

[0085] In an initializing step, the following takes place:

[0086] (a) depositing the following in the testing apparatus 20: an internal resistance value Ri of the insulation monitoring device 10, a response value Rres set in the insulation monitoring device 10 and a maximum permissible response time Tresmax set in the insulation monitoring device 10

[0087] if the insulation monitoring device is supposed to be tested, the following method steps will subsequently take place in a perpetually running testing cycle:

[0088] (b) measuring an effective insulation resistance Reff via the testing apparatus, said effective insulation resistance Reff resulting from the internal resistance Ri of the active insulation monitoring device and an insulation resistance Riso of the ungrounded power supply system arranged parallel thereto,

[0089] (c) calculating an insulation resistance value Rca1 of the ungrounded power supply system via the testing apparatus from the effective measured insulation resistance value Reff and the deposited internal resistance value Ri of the insulation monitoring device,

[0090] (d) calculating a critical test fault resistance value Rf via the testing apparatus 20 while considering the calculated insulation resistance value Rca1 of the ungrounded power supply system,

[0091] (e) adding the test fault resistance Rf via the testing apparatus between one of the active conductors of the ungrounded power supply system and ground and simultaneously starting a time measuring device in the testing apparatus 20 for measuring a response time Tres of the insulation monitoring device 10,

[0092] (f) monitoring a system alarm output of the insulation monitoring device and measuring the response time Tres via the testing apparatus,

[0093] (g) starting a fault treatment via the testing apparatus, should the measured response time Tres exceed the maximum permissible response time Tresmax,

[0094] (h) generating a result log and/or transmitting the test result to a management system, should the measured response time Tres not exceed the maximum permissible response time Tresmax, meaning an alarm was triggered according to the function,

[0095] (i) removing the test fault resistance Rf via the testing apparatus 20.

[0096] FIGS. 3a to 3c show different possibilities of uncoupling the system alarm output 12 of the insulation monitoring device 10 in order to be able to ensure that the system alarm triggered by the insulation monitoring device 10 only becomes effective if the triggered system alarm was not triggered by a testing cycle.

[0097] For this purpose, the testing apparatus 20 comprises a monitoring input 22 for monitoring the system alarm output 12 of the insulation monitoring device 10.

[0098] In a first embodiment according to FIG. 3a, the insulation monitoring device 10 is serially connected to the testing apparatus 20 via the system alarm output 12 of the insulation monitoring device 10 and via the monitoring input 22 of the testing apparatus 20. An alarm message queueing at the system alarm output 12 of the insulation monitoring device 10 is only passed on as an effective system alarm by the testing apparatus 20 if this alarm message was not triggered as a reaction in the scope of a function testing.

[0099] In the embodiment according to FIG. 3b, the alarm contacts of the system alarm output 12 of the insulation monitoring device 10 are added in series having alarm contacts 24 of the testing apparatus so that an open alarm contact 24 of the testing apparatus 20 can suppress a system alarm message of the insulation monitoring device 10, which was triggered by closing a “normally open” alarm contact 12.

[0100] In the embodiment according to FIG. 3c, the alarm contacts of the system alarm output 12 of the insulation monitoring device 10 are added parallel to the alarm contacts 24 of the testing apparatus so that a closed alarm contact 24 of the testing device 20 can suppress a system alarm message of the insulation monitoring device 10, which was triggered by opening a “normally closed” alarm contact 12.