DE698699C - Device for determining the active component of the residual current to earth fault in networks with earth fault extinguishing devices - Google Patents

Description

Device for determining the active component of the residual earth fault current in networks with earth fault extinguishing devices E s is already a device for monitoring the coordination of earth fault extinguishing devices. electrical network with the help of line i earth fault resistance% between a network phase and earth has been proposed, in which the current flowing through the mixing device .and the resistance through the earth fault are fed to a quotient meter. A quotient meter is used. which indicates the real or active component of the ratio of the current in the earth fault resistance and the current in the extinguishing device and thus allows the reactive residual current to be recorded quantitatively. This mechanism is based on the knowledge that the mutual relationship between these two currents is: '1VIass @ - for the compensation relationships in the network.

To determine the active component of the residual current to earth in networks with earth fault extinguishing devices is now .a quotient meter according to the invention used, which is the imaginary or reactive component of the ratio of the earth leakage resistance current flowing through (earth leakage residual current) to the quenching coil current. In turn, the quenching coil current and the earth fault resistance are shown to the quotient meter flowing stream supplied. The = invention is illustrated in the drawing, for example.

Fig. I shows the three-phase network z to be compensated with a transformer z, the zero point of which is connected to earth via the quenching coil 3. Between its phase voltage of the three-phase system and the earth is a short circuit resistance q. arranged .. As a result the additional earthing of the system via the earth fault resistance q. becomes the zero point of the system relocated. The displacement voltage is the same as that at the quenching coil lying tension.

Fig. Z shows the vector diagram of the entire system. The residual earth fault current J4 results from the vectorial addition of the Lüs-chspu-lencurrent J3, the current J5 caused by the loss resistance 5 of the earth circuit and the capacitive current J6 caused by the network capacitance 6 and is with under- or over-compensation with the displacement voltage UV not in phase, but; shifted by the angle cp compared to this: The residual earth leakage current J4 can then be thought of as divided into two components, namely the reactive residual earth leakage current 1, # sin cp and the @ active residual earth leakage current J4 # cos cp.

According to. According to the invention, the active residual earth leakage current J4-cos cp is now to be determined by the quotient meter. For this purpose, a ratio meter, known per se, is used which indicates the imaginary or reactive component of the ratio of the two phase-different electrical quantities to be monitored (J4 and 13). The current J3 flowing through the quenching coil and the current I1 flowing in the earth fault resistor are thus fed to this quotient meter. The measuring instrument is thus, since it responds to two quantities shifted from one another by 90 electrical degrees; the ratio of the quenching coil current J3 to the active component J4. cos (p of the residual earth fault current J4, i.e. Show.

The determination of the active component of the residual current to earth in networks with ground fault extinguishing devices can also be done according to the invention in such a way that a simple - quotient meter is used, the phase position -between does not take into account the currents Ja undlJ_ 4 acting in its windings thus only the ratio of the absolute values of the current, J4 in the earth fault resistance q. and the current Yes in the quenching coil 3. indicates. As such a quotient meter For example, a simple DC ohmmeter can be used, which has a rectifier is influenced by the two currents J3 and J4 b @ e.

However, it is then. necessary, the coordination of the earth fault extinguishing coils still to be checked by other means, since only with precise or approximately precise coordination the determined absolute value of the ratio of the two currents with the active component of . Residual earth fault current is identical. To check the coordination of the network may use the proposed device of patent 661,331 or other known arrangements to serve. -

Claims (2)

PA'LRNIAN CLAIM: i. Device for determining the active component of the residual current to earth fault in networks with earth fault circuit devices with the aid of a Earth fault resistance between a mains phase and earth; whereby the by the extinguishing device and the current flowing through the earth fault resistance is fed to a quotient meter is characterized by the use of @ the imaginary component of the ratio the current (J4) of the earth leakage resistance (¢) and the current (J3) of the quenching coil (g) indicating quotient meter, which quantitatively determines the residual current allows to capture. 2. Device for determining the active component of the residual current to earth in networks with - earth fault extinguishing devices with the aid of an earth fault resistor between a mains phase and earth, where .der by the extinguishing device and the Current flowing through the earth leakage resistance: fed to a quotient meter is characterized by the use of only the absolute value of the ratio des-: Current (J4) of the earth fault. resistance (q :) and the current (J3) of the quenching coil (3) indicating quotient meter, the -bei. more precisely or at least approximately more precisely Voting also the active residual current. allows to capture.