DE564811C - Protective circuit for cable sections, transformers or the like. - Google Patents

Description

GERMAN EMPIRE

ISSUED ON
November 23, 1932

REICH PATENT OFFICE

PATENT LETTERING

JVI-564811 CLASS 21c GROUP

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

Protective circuit for cable runs, transformers or the like,

Addition to patent 400

Patented in the German Empire on February 15, 1931 The main patent started on November 10, 1922.

The subject of patent 400 321 is a protective circuit for cable sections, transformers o. The like. In which the switches on both sides of the relevant line section with Overcurrent and directional relays are provided and between these protective relays a Auxiliary line is available. The overcurrent relays are designed as changeover relays and close one in their rest position

ίο Earthing contact, through which also when responding of the overcurrent relay and the direction relay at only one end of the line section to be protected End of line causing circuit is closed. To protect each phase line an auxiliary line is necessary, which of course makes such line protection much more expensive. The invention now shows an arrangement in which

ao only one auxiliary line is required for the protection of all phases, and it is based ensure that the common auxiliary line over all overcurrent relays designed as changeover relays is connected to earth in the rest position and when only one overcurrent relay is triggered the connection of the auxiliary line to earth via the other overcurrent relays is also opened. To this end are actuated by the overcurrent relay when responding double contacts, of which one then the auxiliary line via the control contacts of the direction relay to the " Control current source applies, while the other contact then the earth line via the control contacts of the other two changeover relays opens.

Fig. Ι schematically shows such a protection system, only the relays at the end of a line are drawn, α is the auxiliary line, the trip coil b opens the switch c when one of the directional relays> ^A -r ³ indicates a current flowing into the line and at the same time one of the overcurrent relays ni'-m ³ has responded. In this case, the auxiliary line α is connected to earth via the current source d. Speaks at-

*) The patent seeker stated as the inventor:

Peter Claus van der Sterr in The Hague.

For example, the overcurrent relay m ² on first, this opens the circuit that connects the auxiliary line via the changeover switches of the overcurrent relays m ¹ and m ^3. Earth, so that the state of the other phases is not taken into account for the shutdown.

Now it can happen that, for example, a double earth fault occurs in a line network, as Fig. 2 shows. The directions of the arrows on the lines R, S, T indicate the direction of the fault energy, which always flows towards the fault location. In the event of a double earth fault, only sections A and C, or better still only one of both sections, should switch off. With a single auxiliary line for all three phases, section B threatens to shut down, as can be seen from the line protection of this route, which is shown in Fig. 3; because the overcurrent relays bm ¹ , bm ⁵ , cm ¹ , cm ³ respond, furthermore the directional relays br ¹ , br ² , er ³ . There is a closed circuit from d ¹ to br ¹ , bm ¹ , e ¹ , e ² , cm ³ , er ³ , d? over earth to d \ The release coil e ¹ , e ^s switch off the line B (Fig. 2), which must be avoided. If an auxiliary line were available for each phase, this error could not occur.

According to the invention, adequate protection for double earth faults can nevertheless be obtained with an auxiliary line if the direction of the earth current flowing in the event of an earth fault is used to actuate the line section to be triggered. In Fig. 4, the current flowing in the earth through a two-phase earth fault is shown as line section E. The deflection of the relay depends on the selected type of connection of the voltage coil to the resulting earth fault voltage. So they will all point in the same direction with earth fault current, in the present case for example in the direction from section A to section C. In line section A , the earth current flows only at one end, the same in section C, while in section B at both Ends the earth current flows, in the same direction. The latter is the sign that the earth connection point cannot be in this section, i.e. the disconnection of this section must be prevented. The flow of an earth current and its direction can be determined in a known manner by the Holmgreen circuit. If the closing of the common auxiliary line, as shown schematically in Fig. 1, is made dependent at the same time by the position of a So directional and overcurrent relay operated by the earth current, a faulty circuit will not occur in the event of a double earth fault. Fig. 5 shows such a circuit diagram for line section B.

The earth current direction relays br *, er * and the earth current relays bm ¹ and cm * are fed based on the Holmgreen circuit shown in Fig. 6. In the event of an earth fault they respond and will work exactly like the phase relays, so that in the event of an earth fault in sections A and C in section B the overcurrent relays bm * and cm * respond. In addition, the direction relay br * will respond, since the error energy flows into section B ; the relay er * will not respond because the fault energy flows out of section B. As a result, the tripping circuit for coils b ¹ and b- remains open. A shutdown of section B does not occur. It does not matter which phase relays respond, as they remain ineffective due to the relays bm * and cvi *.

If the circuit diagram in Fig. 5 is used for line section A , the earth fault via current relay bm * will not respond, but relay cm * will. But since the error energy flows out of section ^, it does not respond. The tripping circuit for the coils b ^x , b ² remains open; section A also does not switch off.

The circuit diagram in Fig. 5, applied to section C , shows that the overcurrent relay bm * and the direction relay br * respond in the earth circuit. The overcurrent relay cm * does not respond, but on this side of the circuit diagram the phase ^{overcurrent relays cm 1} and c ??! ⁵ , furthermore the phase direction relays er ¹ and cr ^s , since the fault energy flows into section C. There is a closed circuit, from earth via rf ¹ , br *, bm *, via the tripping coils b ¹ , b-, via cm *, cm ¹ , er ¹ , d ² to earth. Section C is switched off from the line network; the two-phase earth fault is thus converted into a single-phase.

Claims (2)

Patent claims: i. Protective circuit for cable sections, transformers or the like, in which the two switches at the ends of the relevant line sections are provided with overcurrent and reverse current relays and an auxiliary line is provided between these protective relays, according to Patent 400 321, characterized in that the overcurrent relays are used as changeover relays (m) are designed with double contacts, of which, when an overcurrent relay responds, one contact carries the auxiliary line (α) common to all phases via the control contacts of the connects the corresponding direction relay (r) to the control current source (d) and the other contact opens the earth connection of the auxiliary line (α) via the control contacts of the other overcurrent relays (in). 2. Protection circuit according to claim ι against double earth fault, characterized in that the direction of the earth current flowing in the double earth fault through built into the line and the control circuit overcurrent (bm *, cm *) and directional relays (br *, er *) for the sole shutdown of the faulty line section is monitored. For this purpose ι sheet of drawings