DE1956526B2 - IMPEDANCE PROTECTION DEVICE FOR AN ELECTRICAL SYSTEM - Google Patents

Description

The invention relates to an impedance protection device for an electrical system that has at least one voltage-dependent and two current-dependent Has excitation members, which are connected on the output side to a logic circuit are and downstream Mcldecinrichtungen or circuit breakers directly or via an or Influence additional protective devices.

no such by the German reading 1150439 known impedance protection device is the one current-dependent exciter a voltage tapped at a comparison resistor and proportional to the fault current and the other current-dependent excitation element a tapped at a comparison inductance, dor temporal Change in Feblerstronus proportional voltage supplied. The one from the opposite country of comparison comparison impedance formed and inductance is to the impedance of a line to be protected :, track coordinated. This ensures that the known impedance protection device only triggers in the event of a fault on a certain line section.

In order to obtain reverse protection in the case of the failure of individual protective devices in network protection technology, impedance protection devices are required that are capable of generally occurring detect a fault in an electrical system. For selective triggering of the switches in the System such impedance protection devices z. B. Impedance protection devices of the known Kind, which measure the exact location of the fault and the one adjacent to the location Trigger the 2 switch.

Particular problems arise with regard to the detection of faults in double-line systems and in high-voltage networks from 110 kV and above. In the case of a double line, for example, in the event of a failure or switching off one line system, except for twice as much electricity in the other line system Face value increase. An impedance protection device must handle such a rise in current from a distinguish the increase caused by an error. On the other hand, the protective device must also small, below the value of the NVnnstromcs of a pipeline system reliably detect lying fault currents. Such small fault currents can be at distant Short-circuits or when the machine is not used much during off-peak times. With the known In the impedance protection device, it is not possible to detect such faults

The invention is therefore based on the object of designing an impedance protection device so that through their response behavior a safe response is achieved with both large and small fault currents.

The problem posed is achieved with an impedance protection device of the type described at the beginning Kind in that the current-dependent excitation elements are set to different response values are that the current-dependent excitation element set to the low response value also does that voltage-dependent excitation element on the output side to the inputs of an »ANDw logic circuit are connected and the output of this »UNDo link circuit in a

“ORÄ linkage with the output of the current-dependent contact element set to the higher response value is connected.

The sensitivity of the impedance protection device can according to one embodiment of the invention when used in a polyphase alternating voltage system can be increased by the fact that the voltage-dependent A switching device is connected upstream of the excitation element, through which the value of the phase voltage, in which the voltage-dependent excitation element responds, is increased, and that the switching device in turn depending on the switching of

a current or the smallest phase voltage is included in the zero current path.

■ converter stands. "This selection circuit then operates the Umscnall-

The increase in sensitivity can also include setting up in the phase with the greatest current or

by crreicth that the enveloping device has the smallest tension, so that the contact

depending on the switching of a selection circuit 5 in that phase aiii greater sensitivity uin-

to AiK selection of the largest phase current and or is done, in which the presence of an Fe ¹

/ ur selection of the smallest phase voltage. lets most likely.

in such a way that only the encapsulation of the

The selected selection circuit is actuated, the or Ouolicntcnbildung work. For example kor, -

the phase conductor with the greatest phaseiistiom and. m newly polarized relays with two windings lur ei .. ·

or with the lowest phase voltage assigned. Line winding let; -: ch

is. ~ then in a DC circuit with one of the Oe-

On the basis of an accurate phase current shown in the drawing, current em-

Auslührungsbeispiels the opposing band of the Hrfin- switch, while the other winding in one

application is described in more detail below. l: s shows 15 direct current circuit, whose current is the summ, the

Fig. 1 is a block diagram of an impedance protection three phase currents is proportional.

device according to the invention. In the event of a- * short circuit in the secondary

Fig. 2 a response characterisnk of the in Fig.! Circuit of the voltage converter ^ is the Ubcr-

Impedance protection equipment shown. respond to current relay. FIie ^r through is the second

On the primary winding of a converter Wl there is 20 open circuit of the converter! F 2. s _O that there-

tine phase voltage U 1 of the system to be protected sp; dimension-dependent excitation element LG! no exit

stcnis. In the same way, more flows through the primary weighing signal. To prevent. YesI: ¹ .

development of a current transformer ΙΓ3 the / u of the same here by exceeding the im siromabhang-igeii

Phase associated current / 1. while the primary excitation element / Gl set Ubeistromwenes the

winding of a current transformer * H'1 from which zero 25 Bcfehlsgebcr B is switched on, there is a continuity

current JO of the system is flowing through. The seconds of the overcurrent release LVl in series with the output

The winding of the converter Wl is via a reversal of the NOR gate - "AND" logic!

switching device (■ 'and an (overcurrent release .Yl. If the secondary circuit of the

I am connected to a voltage * ablüinszi «es stimulating element (/ GI converter Wl can therefore only be the responsibility of the orderer

connected. This tension-dependent refinement even when crossing the Überslromweries door

element L'G 1 always emits an output signal. current-dependent excitation element I switched on wcr-

if a certain voltage value at the input.

is exceeded. The NOR gate - "AND <-V < knitting scarf

The secondary voltage of the current transformer * U '3 ment / Y 1 - thus receives signals at both inputs η in the N. r is in series with two current-dependent excitation general state signals. Only if neither on the Aiisdern / 1. 1 and ICi 2. Of these, the current-dependent uanü of the voltage-dependent excitation element LCi I gige excitation element / G 2 is set to a greater response even at the output of the current-dependent excitation value than the current-dependent excitation element / G 1 an output signal appears, so if / G 1. Both then emit an output signal when a certain limit voltage of the voltage ί 1 of the respective associated response value is undershot and a certain limit value of the output current is not exceeded. Current / 1 is exceeded, an output

The .output of the voltage-dependent excitation signal at the NOR gate -: .AND- \ er

member L'G 1 and the output of the current-dependent logic circuit Al. When exceeding a

The excitation element / G I are connected to a second sirom value, the signal at the sirom

N'OR-Gattcrs - »UNDK linkage sound 45 dependent excitation element / G2 disappear, so that

.V 1 - guided. The output of this NOR gate is a signal at the output signal of the NOR gate .V 2

via the contact of the overcurrent relay ÜA to which appears and regardless of the voltage-dependent

Input of a command generator B connected. External excitation element LGl switch on the command

this is the output of the current-dependent starter.

gliedes / G 2 with the greater demand over 50 The response characteristics of the in F i g. 1 dis-

a NOR gate Λ'2 also with the input of the Benen Sc'.altung is in F i g. 2 shown. Flier is there ^

Commander B connected. Ratio of the voltage L'l to the nominal voltage L.

The switching device L '. the liier is shown as a relay on the ordinate and the ratio of the current / i with changeover contact. isi _v displayed on the secondary to Nennstroni / on the abscissa. Fs is connected to the current transformer IF 1 :,:, Assuming that the response value of the stronutbvind will switch over when the inclined Aiiregiedercs IG 1. namely the ratio of zero current exceeds a certain value. At the current / 1 to ii nominal current / _v . in which the current of a changeover of the switching device by the dependent exciter / Gl just responds, a flowing zero current IO has the voltage value U.25, while the corresponding attached excitation element Ulli has a smaller ^span voltage of the current-dependent exciter l <! 2 nuug L'l faked, so that it is already at one to 2.2. The resulting response ringcrcn voltage drop in voltage L'I characteristic AT 1 is shown in I-i g. 2 shown. By corresponding and no more output signal to the subsequent selection of the response values for the activated NO ^. Gates - "AND" gates, the one represented by the point / '; V 1 - can always be emitted. A particular advantage - G5 was a critical load case for a double line, especially for more distant faults - arises when one part of the line has failed. lay in such a way that with the switching device U a selector switch safety no excitation takes place. Nevertheless, tunp results in the selection of the largest phase current and due to the low response value of the downstream

pending excitation element IG 1 is very sensitive to small fault currents, which are then present in the event of a fault when only a few generators are in operation on the network at a low load time.

In addition, the sole use of voltage and current-dependent regegiedercrn and the lack of any measuring circuit for quotient formation or to take into account de phase angle ensures that the excitation, ie the switching on of the command generator B, can take place immediately after the occurrence of the error.

1 sheet of drawings

Claims (4)

Patent claims: 1. Impedance protection device for an electrical system, di the current-dependent Aive elements (/ Cl. / G 2) are set to different response values that the current-dependent excitation element (/ Gl) set to the lower response value and the voltage-dependent excitation element (L'Gl) are output to the inputs one; ;) LJND «logic circuit (N 1) are connected and the output of this» UNDtf logic circuit (Nl) is connected in an »OR ^ logic circuit to the output of the current-dependent exciter (IG 2) set to the higher response value. 2. Impedance protection device according to claim 1 for multi-phase AC networks, characterized in that the voltage-dependent excitation '' .ed (L ¹ G 1) is preceded by a switching device (U) through which the value of the phase voltage (Ul). at uem the voltage-dependent excitation element (i ^.: Eq.) responds, is increased, and that the switching device (LQ is in turn dependent on a current transformer (UM) connected to the zero siromp path. 3. Impedance protection device according to claim 1 or 2, characterized in that with the voltage-dependent exciter (L'Gl) an overcurrent release (ÜA) in series business and a contact member actuated by this between the output of the "AND" -Verknüpf ungs circuit (ΛΊ) and The "OR" logic circuit is arranged so that when the overcurrent release is triggered, the connection between the "AND" and "OR" logic circuit is interrupted. 4. Impedance protection device according to claim 2, characterized in that the switching device (U) is dependent on a selection circuit for selecting the largest phase siromes and / or for selecting the smallest phase voltages, in such a way that only the switching device (U) is actuated by the upstream selection circuit which is assigned to the phase conductor with the largest phase current and / or with the smallest phase voltage.