DE956427C - Circuit arrangement for a single-system resistance measuring relay to protect three-phase cables - Google Patents

Description

The main patent 906126 describes a circuit arrangement for a single-system resistance measuring relay for protecting three-phase lines. The circuit arrangement according to the main patent works in such a way that four switching contacts are provided for the selection of the correct voltages and currents or current-proportional voltages for the resistance measuring relay both on the current side and on the voltage side, namely two switching contacts of the relay A ₀ in the phase Zero and one changeover contact each of the relays A _t and A _r in the preferred and the conditionally preferred phase T or B-.

The arrangement according to the main patent has the disadvantage that errors between phase 5 and the Neutral conductors are not recorded.

According to the invention, these deficiencies are eliminated by the fact that the changeover contacts of the overcurrent exciter relay are connected to one another in such a way that all short-circuits and earth faults occurring are correctly detected, the selection circuit on the current and voltage side only containing four changeover contacts each, namely two changeover contacts of the relay in each case phase zero (A ₀ ) and one changeover contact each of the relays in the two with trigger relays A _t and A ₇ . equipped phases JR and T.

The drawing shows the principle of the circuit arrangement according to the invention for a single-system resistance measuring relay. The left side of the drawing represents that part of the relay circuit through which the currents J ₀ , Jr, Js and Jt of the current transformers not shown here flow. In each of the conductors 0, R and T there is an overcurrent trigger relay A ₀ , A _r and A _t . The currents each flow through a calibrated resistor. The voltage drops occurring at these resistors are fed to the current side of the impedance measuring relay, not shown, via changeover contacts. The latter can be, for example, a quotient toggle relay in a rectifier circuit.

The right side of the circuit shows the voltage path through the voltage converter, not shown is fed.

The overcurrent exciter relay A _r actuates the changeover contacts al and af either directly or via auxiliary relays (not shown). Analogously, the relay A _t controls the changeover contacts af and af, while the relay A _{0 has} two changeover contacts A ₀ ¹ and «| Actuated in the .voltage path and two changeover contacts al and «0 ™ current path.

The switching contacts ^ ₀ ¹ or al are with their working contacts on the voltage U ₀ or on the voltage tap of the resistance of the neutral conductor and with their center contact on the impedance measuring relay. Your normally closed contact is connected to the center contact al or al of the start relay A _T. From here there is also a connection to the contact of the contact "0 or" o ⁴ · The break contact of al or atf Hegt at the voltage _s U or the voltage tap of the resistance of the conductor S. In addition, is the break contact of the contact or al a% at the voltage Us or at the voltage tap of the resistor in the conductor S. The working contact of the contact «/ or al is at the voltage Ur or at the voltage tap of the resistor in the conductor R. The center contact of al or« ₀ ⁴ is connected to the normally closed contact of the contact af or af . The center contact of the contact a _t ¹ or af is on the impedance measuring relay, while the normally open contact of the contact af or al is on the voltage Ut or on the voltage tap on the resistance of the conductor T.

In the event of a short circuit between the conductors R and S , only the start relay A _r responds and actuates the

Contacts al and a *. The impedance -γ ^ - is measured. If a short circuit occurs between the conductors S and T , the excitation relay A _t switches the

Contacts al and af um so that the impedance

is measured. In the event of a fault between R and T and with three-pole short circuits, the impedance -p ^ - is measured via the contacts al, al, al, af.

In the event of double earth faults in the conductors RS, ST and TR , the voltage side of the impedance relay receives the voltages Uso, Ut _O > and Uτο via the corresponding contacts, while the corresponding currents Jro, Jto and Jto are fed to the current side. The single-pole earth faults in solidly earthed systems are also correctly recorded. In the event of a ground fault in the conductor R , the voltage Ur 0 and the current J ro become effective in the impedance relay. Also, a ground fault of the conductor S is detected correctly because the Impedanzmeßrelais the voltage U is supplied _s0 by the switching of the contacts al and al, during al by the switching of the contacts and a% of the current J _S o acting on the measuring system. In the event of a ground fault in conductor T , the impedance is set in the impedance measuring relay by switching contacts al, af, al and al measured.

Jto.

Claims (2)

PATENT CLAIMS: 1. Circuit arrangement for a single-system resistance measuring relay for the protection of three-phase lines with double earth fault detection and acyclic conductor preference according to patent 906126, characterized in that the switching contacts of the overcurrent excitation relay are connected to one another in such a way that all short circuits and earth faults that occur are correctly detected, the selection circuit on the Current and voltage side only contains four changeover contacts each, namely two changeover contacts each of the relay in phase zero (^ ₀ ) and one changeover contact each of the relays in the two phases (R and T) equipped with excitation relays (A _t and A _r) contains. 2. Circuit arrangement according to claim 1, characterized in that the center contact of a changeover contact of phase zero («0 or # 0) leads to the resistance measuring relay, while the make contact of this changeover contact at phase zero and the break contact at the center contact of the relay to the conditionally preferred phase (R) belonging changeover contact (a1 or a%) and at the same time to the normally open contact of the second changeover contact of the phase. Zero (« ₀ ³ or« 0) leads and the normally closed contact of the changeover contact belonging to the relay of the conditionally preferred phase (R) is on the non-preferred phase (S) , while the normally open contact of this changeover contact is connected to the conditionally preferred conductor (R) is and also the Mittelkontäkt of the relay in the preferred phase (A _t ) belonging changeover contact (al or af) leads to the resistance measuring relay, while the make contact of this changeover contact is on the preferred phase (T) and its break contact via the center contact and the break contact of the second relay in the neutral (A ₀₎ associated with the changeover contact (al or a $) leads to the non-preferred phase (S). 1 sheet of drawings © 609 549/389 T. (609 756 1.57)