DE1116320B - Arrangement for measuring the leakage current flowing when testing electrical machines, electrical devices or electrical raw materials and electrical engineering installations with high-voltage alternating current - Google Patents

Description

GERMAN

PATENT OFFICE

E 17537 IXd / 21e

A N MELD E DAY: 25. A P R I L 1959

NOTICE
THE REGISTRATION
AND ISSUE OF THE
EDITORIAL: NOVEMBER 2, 1961

When testing electrical devices and components, in addition to testing with high voltage, the Measurement of the leakage current flowing during this high-voltage test is required. This is supposed to Insights into the state of the insulation can be obtained using the high-voltage test alone unable to give. Because the test also with a significantly higher voltage than the operational voltage (e.g. second or minute test) leaves open whether the examinee can repeat the test without Would endure damage. The measurement provides a perfect assessment of the insulation status of the leakage current.

In the case of direct current, this measurement is simple and either takes place with the help of the high-voltage circuit installed ammeter (overload protection necessary) or with so-called Coloumb meters, for example where the leakage current charges a capacitor that is periodically discharged via a glow lamp where the light flash sequence is a measure of the leakage current.

With alternating current, the detection of the leakage current is more difficult because only the ohmic component / · Cos ^ may be recorded. There are known methods in which by simultaneous measurement of current, voltage and active power, the ohmic component of the flowing through the test object Current can be determined. The disadvantage here is not only the great expense of measuring instruments, but also also the fact that the desired quantity can only be obtained by means of suitable methods of practical mathematics (Formula. Nomogram) must be determined.

Various methods are given for measuring the loss angle of insulating materials been. Common to all methods is a not inconsiderable outlay in terms of equipment, so that loss angle measurements usually only be carried out in the laboratory. In addition, should also be here after the Measurement first take place a conversion, with the help of which the ohmic Component of the leakage current can be determined. For measuring currents with a certain phase position vibrating contact rectifiers and tube circuits are known. With these known circuits However, the underlying task is not solvable.

One that is easy to handle, even for the unskilled layperson, is not laborious and is operationally reliable Device for the direct display of the ohmic component of the leakage current, as it is the operational one Practice demands, has not yet become known.

The object of the invention is to provide such an arrangement for operational practice.

Arrangement for measuring the when testing
of electrical machines, electrical

Appliances or electrical raw materials
and electrical engineering installation items with high-voltage alternating current
flowing leakage current

Applicant:

Electrotechn. laboratory

Dipl.-Ing. Richard Karl Baumann.

Stuttgart N, Mönchhaldenstr. 129

Dipl.-Ing. Albert Hang,

Holzheim (Kr. Neu-Ulm Donau).

has been named as the inventor

This is achieved with an arrangement for measuring the when testing electrical machines, electrical Devices or electrical raw materials and electrical engineering installations high voltage alternating current flowing by means of a controlled rectifier circuit, the active component through control with an auxiliary alternating voltage with the same frequency and phase of the leakage current makes available, according to the invention in that the leakage current in on known way via a ground side in the high-voltage test circuit lying measuring resistor: is. its voltage drop as input voltage one with extremely low-resistance semiconductor diodes, which are also known per se, in particular silicon area diodes or transistors, provided rectifier bridge is used.

The characteristic of the Glciefirichterbrücke shows the Character of bilateral limitation with linear operating range on followed by sharp Saturation kink to limit overload. The necessary Hilisspannuni is extremely low.

In combination with the characteristic curve of the diodes used, this results in a saturation voltage as maximum output voltage, which is once based on the linear range used for the measurement

Claims (6)

The bridge characteristic is closely connected and is still so low that a highly sensitive display device located in the bridge output can remain without special protective measures even with a higher input voltage. The rectifier bridge has balancing precision resistors for drooling adjustment. A selective circuit, in the simplest case a capacitor, is inserted in the input of the diode bridge (parallel to the measuring resistor) in such a way that current or voltage peaks contained in the arc are kept away from the bridge in the event of breakdown or flashover of the test object. The phase shift of the selective circuit must be negligibly small at the measuring frequency. Instead of the indicating instrument in the bridge output, a display device or a recorder, a switching or sorting device or a good-bad control can be connected, which z. B. stops defective test items, identifies them or rejects them. Overall, an extremely simple, precise and operationally reliable device for measuring the ohmic component of the leakage current is created, which corresponds to the requirements of operational testing practice, works without major expenditure on equipment and, after training, can also be used by laypeople. The device for measuring the leakage current is electrically connected to the associated high-voltage test device by means of known multiple plug devices. The mechanical connection of the two devices is made by means of large push buttons, which enable the two measuring devices to be connected and disconnected quickly. PATENT CLAIMS: 1. Arrangement for measuring the leakage current flowing when testing electrical machines, electrical devices or electrical raw materials and electrical installation items with high-voltage alternating current by means of a controlled rectifier circuit that makes the active component of the leakage current available through control with an auxiliary alternating voltage of the same frequency and phase. characterized in that the leakage current is conducted in a manner known per se via a measuring resistor located on the ground side in the high-voltage test circuit. its voltage drop as an input voltage with an extremely low resistance. also known semiconductor diodes, in particular silicon area diodes or transistors, provided rectifier bridge is used. 2. Arrangement according to claim 1, characterized in that the auxiliary AC voltage is a has a small amplitude corresponding to the semiconductor diodes. 3. Arrangement according to claim 1 and 2, characterized in that the rectifier bridge has balanced precision resistors. 4. Arrangement according to claim 1 to 3, characterized in that parallel to the measuring resistor a capacitor is connected. 5. Arrangement according to one of the preceding claims, characterized by releasable electrical Multiple couplings and mechanical push button connections to your electrical and mechanical coupling with the high voltage generator. 6. Arrangement according to one of the preceding claims, characterized by the connection the bridge output with a display, writing or warning device or a relay. Considered publications:
German Patent No. 833 079;
U.S. Patent No. 2,424,131;
»Archive for technical measurement«. V 339-6. September 1933, and Z 53-1, July 1949; »Telefunken-Zeitune«, 31st year (September 1958), H. 121, pp. 162 to 174; F. Koppelmann, "The measurement technology of the mechanical precision rectifier", 1948, p. 32.