DE590215C - Protective circuit for the disconnection of only a single diseased network section in the event of a double earth fault in three-phase networks - Google Patents

Description

GERMAN EMPIRE

ISSUED ON
DECEMBER 23, 1933

'REICH PATENT OFFICE

PATENT LETTERING

CLASS 21 c GROUP 6850

Voigt & Haeffner Akt.-Ges. in Frankfurt a. M. *)

Patented in the German Empire on November 14, 1931

In order to continue operation in larger networks in the event of a double earth fault. To maintain it, it has already been suggested to eliminate the short-ax double ground fault by switching off only the section in which the phase connection is located, but to continue working with the ground fault of a second section in the other phase so as not to let any intermediate station become dead. Whichever of the two diseased sections should be switched off in this case is in and of itself indifferent, ■ for example, a certain phase can always be preferred for the switch-off before the other two. With regard to the converter connections of wattmetric network seat relays, it may, however, under certain circumstances be more advantageous to carry out the phase preference in a cyclic sequence, for example by always preferring the lagging phase by means of a suitable auxiliary relay, i.e. phase S is preferred in the event of a ground fault in phases R and 5 , in the event of a ground fault in phases 5, T phase T and in the event of a ground fault in phases T and R, phase R. With the help of such an arrangement, the double earth fault can be eliminated perfectly and the network can then continue to operate with a single-phase earth fault.

In this known arrangement, however, the protection is in my dneiphase earth fault ineffective, because the lagging phases are always due to the cyclic phase preference the leading 'would block, so that no phase at all for the shutdown in Question might come up. In order to pull a phase here for disconnection at all in this case to be able to, is according to the invention on one of the phase preference monitoring! three auxiliary relays, one SCM measuring contact attached, the opening contact of an auxiliary relay bridges the other two phases, so that with a three-phase Earth fault a shutdown takes place.

The arrangement is shown schematically in the drawing, and only the auxiliary lines are drawn, a, b and c are overcurrent relays in the three phases of a station, which close the auxiliary relays d, e and / when responding. Each of these relays each has a closing contact g ¹ , g ² , £ ³ and an opening contact A ¹ , A ² , h ³ cause individual phases by each of them on the same trip coil of the with the overflow relays a, b, c and not shown.

*) Your patent seeker stated as the inventor:

Dipl.-Ing. Frits Alten in Frankfurt a. M. Ginnheini.

Neten converter equipped switch acts. Would z. B. the overcurrent relays. «, & Respond by a double earth fault in two mains phases, so the relays d and e were fed. The current flowing through the contacts g ¹ , h? to üem timing relay k flows, is open at h-. Switching off can therefore not take place through the relay k. The current that passes through contacts g ² , / z ³ to the timing relay /

ίο flows would -dagegen this relay I effect by feeding the cut-off, ie in the present FaE effected by the response of, the overcurrent relay α nuclear shutdown of the associated switch, but rather the timing relay is t gespieist b by the response of the overcurrent relay, whereby the average Phase contact, for disconnection there.

According to the invention, a further contact / is attached to the auxiliary relay / which closes when the relay / is activated. If all three overcurrent relays a, b, c respond in the event of a three-phase earth fault, all auxiliary relays ^, e, f close. Due to the contact / relay / additionally arranged according to the invention, however, the circuit in which contact g ¹ is located and which is used to feed relay k is closed despite the open contact A ² and a switch-off is brought about, so that even with three-phase Earth fault in the presence of the phase locking relays d, e, f required for double earth faults, the switch is released.

Claims (1)

Claim: Protective circuit "for the disconnection of only one, single larank rivet section in the event of a double earth fault in three-phase networks, in which in the event of a double earth fault by means of an overcurrent relay in each phase and by means of a special auxiliary relay assigned to each overcurrent relay. characterized in that, for the purpose of canceling the blocking in the event of a three-phase earth fault, a further closing contact (i) is arranged on one of the auxiliary relays (/), which cancels the blocking of the other auxiliary relay (e) in another phase. 1 sheet of drawings