DE409957C - Circuit of earth fault relays - Google Patents

Description

GERMAN EMPIRE

ISSUED
AIH FEBRUARY 14, 1925

REICH PATENT OFFICE

PATENT LETTERING

- JVl 409957 - CLASS 21c GROUP

(A 41670 VIII / sic *)

General Electricity Society in Berlin *).

Circuit of earth fault relays. Patented in the German Empire on February 27, 1924.

Earth fault relays, which react to the earth fault current extracted from the operating current of the network, of course also respond when the earth fault becomes a short circuit due to simultaneous earth faults in several phases. The currents that occur are a multiple of those that occur in a single-phase earth fault. This completely overturns the time graduation intended for a completely different order of magnitude of the current, ie all relays trigger practically at the same moment and put a far too large part of the network out of operation. In addition, under the action of the short-circuit current, the earth-fault relays can swing in the wrong direction and thus switch off other routes that are not affected by the earth-fault. Since the overcurrent relay does not respond with a single-phase earth fault, these disadvantages can also be eliminated according to the invention by providing the overcurrent relays with a device which makes the earth fault relay ineffective at the moment these relays respond. You can z. B. run the trip circuit of the earth-fault via a normally closed contact that during start

* J The following has been indicated by the patent seeker as the inventor:

Josef Biermanns in Karlshorst.

speak of the overcurrent relay is opened, or one of the working windings of the Open or short-circuit the earth fault relay through such a contact. It is also possible directly in series with the current winding of the mostly asymmetrical circuit Ground fault relays special overcurrent relays have to be built in, which block or enable the ground fault relays.

ίο An exemplary embodiment is shown in the drawing. In the phases u, ν a ground fault relay α and an overcurrent time relay b are installed in a known manner. The former actuates contact c, the latter actuates the normally open contact d via a timer and also the normally closed contact e without delay. The contacts c and d work in parallel on the release magnet / the oil switch g. If the overcurrent relay responds, the contact is opened first and the tripping magnet is thereby removed from the influence of the earth fault relay. After a while, this tripping magnet is actuated by contact d. The contact e can also be placed in the circuit of the voltage coil of the earth-fault relay or it can be designed as a working contact and short-circuit the current coil of the earth-fault relay with it.

Claims (1)

Patent claim: Circuit of earth fault relays, characterized by a device on the in of the system already existing or on specially built-in overcurrent relays, which when these relays respond makes the earth fault relays belonging to the same line section ineffective.