Mobile high-voltage tester

1. A mobile tester ( 2 , 2 ′) for very low frequency (VLF) testing of a measurement object ( 3 ), especially a high-voltage or medium-voltage cable, comprising

a voltage generator for generating an a.c. voltage, used as the test voltage, with rms amplitude greater than or equal to 1 kV and a frequency in the range between 0.01 and 1 Hz,

a terminal element ( 9 ) for connection of the measurement object ( 3 ) to be subjected to the test voltage and

circuitry for measurement and evaluation of the test voltage present at the measurement object and of the test current caused hereby,

wherein the tester ( 2 , 2 ′) is set up in a first mode of operation for autonomous performance of a VLF test with the test voltage generated by it,

wherein the tester ( 2 , 2 ′) additionally has a communications interface ( 17 ) for transmitting a synchronization signal (S) or for receiving an externally generated synchronization signal (S) and

wherein the tester ( 2 , 2 ′) is set up in a second mode of operation (parallel mode) to synchronize the generated test voltage as a function of the synchronization signal (S) with the test voltage generated by at least one further tester ( 2 , 2 ′) of the same type, such that the generated test voltage of the tester and the test voltage of the at least one further tester are additive.

2. A system ( 1 , 1 ′) for VLF testing of a measurement object ( 3 ), which system comprises at least two mobile testers ( 2 , 2 ′) of claim 1 ,

wherein the system ( 1 , 1 ′) is set up, during operation of all testers ( 2 , 2 ′) in parallel mode and suitable connection of the measurement object ( 3 ) to all testers ( 2 , 2 ′), to ensure that the testers ( 2 , 2 ′) interact with one another through synchronization of the a.c. voltage generated respectively by them for the VLF test of the measurement object ( 3 ) in such a way that the measurement object ( 3 ) is subjected simultaneously to the synchronized a.c. voltages of all testers ( 2 , 2 ′).

3. The system of claim 2 , wherein at least one of the testers ( 2 , 2 ′) operated in parallel mode is set up for measurement of the test voltage present at the measurement object and

in that, in parallel mode of operation, all testers ( 2 , 2 ′) are set up for measurement of the test current flowing in the tester ( 2 , 2 ′) in question due to the test voltage.

4. The system of claim 2 , wherein the system ( 1 , 1 ′) has a control unit ( 14 ) that generates and transmits the synchronization signal.

5. The system of claim 4 , wherein all testers ( 2 , 2 ′) operated in parallel mode can be controlled via the control unit ( 14 ).

6. The system of claim 2 , wherein the system has a central evaluation unit ( 18 ), to which all voltage and/or current values needed for evaluation of the VLF test and measured by the various testers ( 2 , 2 ′) in parallel mode are transmitted.

7. The system of claim 4 , wherein the control unit ( 14 ) or the central evaluation unit ( 18 ) is integrated into one of the testers ( 2 ′) or into an external device ( 15 ).

8. The system of claim 2 , wherein the synchronization signal (S) is transmitted in wireless form.

9. The system of claim 2 , wherein, starting from the specified number of at least two mobile testers ( 2 , 2 ′), the system ( 1 , 1 ′) can be expanded respectively by additional mobile testers ( 2 ) up to a given maximum number of testers ( 2 , 2 ′).

10. The system of claim 2 , wherein the system ( 1 , 1 ′) is provided with a distributor structure ( 13 ), which has a specified maximum number of testers ( 2 , 2 ′) capable of being connected thereto and which connects the terminal elements ( 9 ) provided for the measurement object ( 3 ) on the at least two testers ( 2 , 2 ′) and the measurement object ( 3 ) to be tested in the manner of a parallel circuit.

11. The system of claim 2 , wherein the at least two testers ( 2 , 2 ′) are connected to a common ground potential ( 11 ).

12. The system of claim 2 , wherein each tester ( 2 , 2 ′) is set up for simultaneous VLF testing of three phases ( 4 , 5 , 6 ) of a high-voltage or medium-voltage cable ( 3 ) with the same test voltage.

13. A method for VLF testing of a measurement object ( 3 ) using at least two mobile testers ( 2 , 2 ′) according to claim 1 comprising the following steps:

A) connecting the measurement object ( 3 ) to the respective terminal elements ( 9 ) of all testers ( 2 , 2 ′) by means of a parallel circuit;

B) activating the parallel mode in all testers ( 2 , 2 ′);

C) generating and transmitting a synchronization signal (S);

D) simultaneously generating, with all testers ( 2 , 2 ′), a test voltage synchronized on the basis of the synchronization signal (S);

E) measuring and evaluating the test voltage present at the measurement object ( 3 ) and the test current caused hereby in the measurement object ( 3 ) or in the individual testers ( 2 ).