CN1195775A - Method and device for distinguishing transmission line fault direction - Google Patents

Abstract

A method and device for judging the fault direction of a transmission line, which is characterized in that the fault components of current and voltage are measured, and the fault components of current and voltage are multiplied and then integrated to obtain the fault energy of the measurement point. When the energy is negative, The fault occurs in the positive direction. When the energy is positive, the fault occurs in the reverse direction. The corresponding device can be a static type or a digital type. Compared with the existing technology, the advantages of this scheme are: the speed of discrimination is fast, it is free from fault transient harmonic interference, the discrimination result is accurate and reliable, and it is suitable for the discrimination of single-phase grounding, Fault direction of generator single phase to ground etc.

Description

Method and device for judging transmission line fault direction

The present invention relates to an emergency protection circuit device specially used for special electrical machinery or electric equipment or for section protection of cable or line system, in particular to a method and device for judging the fault direction of transmission lines.

In the 1970s, Sweden's ABB company successfully developed a traveling wave direction relay. It uses a comparison of the polarity of the initial current traveling wave and voltage traveling wave generated by a fault in the transmission line to determine the fault direction. This relay does not need to filter out the fault transient state. The harmonic component has the advantage of fast action, but its defect is that it can only maintain the correct directionality in a short time after the fault. After the reflected wave of the fault point and other wave impedance discontinuities in the system arrives, the relay The correct directionality cannot be maintained, so the traveling wave relay is susceptible to interference, has poor security, and has not been widely used. Chinese patent ZL86106756 (CN1007857A) provides a power frequency variation direction relay, which uses the phase angle of the comprehensive power frequency variation of the current and voltage circuits to determine the direction of various faults in the power system. The three-phase current and voltage are respectively The integrated quantity of current and voltage is obtained through the integrated filter, and then its power frequency variation component is formed respectively, and finally the phase angle between these two quantities is measured to determine the fault direction. Its defect is that the harmonic component generated by the distributed capacitance of the transmission line after the fault will affect the correct action of the relay. For this reason, the fault current and voltage must be filtered. The transient process of the filter prolongs the action time of the relay. For ultra-high voltage 1. The main frequency of fault transient harmonics of long-distance transmission lines is closer to the power frequency, and the filter delay is longer. This kind of line has higher requirements for the action time of the protective relay, and the contradiction is more prominent.

The purpose of the present invention is to provide a method and device for discriminating the fault direction of a transmission line, by measuring the fault component energy formed by the current fault component and the voltage fault component to judge the fault direction, and provide a corresponding detection device, using this The first scheme has the advantages of not needing to filter out transient harmonic components, fast action, and not being interfered by various fault transient harmonics of transmission lines.

A method for judging the fault direction of a transmission line, characterized in that: measure the fault component of current and voltage, multiply the current fault component and the voltage fault component and then integrate to obtain the fault energy of the measurement point. When the energy is negative, the fault occurs in the positive direction, when the energy is positive, the fault occurs in the reverse direction.

A device for implementing the above method is characterized in that the device consists of a casing, synthesizers 1 and 1', memory devices 2 and 2', subtractors 3 and 3', multipliers 4, overcurrent relays 5, overcurrent Pressure relay 5', OR gate 6, electronic switch K, given integrator 7, inverter 8, comparators 9 and 9', time relays T ₁ , T ₂ , T ₃ , OR gates 10 and 10', and Gates 11 and 11', wherein the input terminals of the synthesizer 1 are respectively connected to the three-phase currents ia, ib, ic, and its output terminals are respectively connected to the memory 2 and one input terminal of the subtractor 3, and the other of the subtractor 3 The input end is connected to the output end of the memory device 2, and its output end is respectively connected to an input end of the multiplier 4 and the input end of the overcurrent relay 5; the input end of the synthesizer 1' is respectively connected to the three-phase voltage ua, ub, uc , its output terminal is respectively connected to an input terminal of the memory device 2' and the subtractor 3', the other input terminal of the subtractor 3' is connected to the output terminal of the memory device 2', and its output terminal is respectively connected to the output terminal of the multiplier 4 The other input terminal is connected to the input terminal of the overvoltage relay 5', the multiplier 4 is connected to the input terminal of the given integrator 7 after passing through the electronic switch K, and the electronic switch K is passed through by the output of the overcurrent relay 5 and the overvoltage relay 5' Controlled by OR gate 6, one output of the given integrator 7 is connected to the positive terminal of comparator 9 through inverter 8, the other is connected to the positive terminal of comparator 9', and the negative terminals of comparator 9 and 9' are externally connected to the setting threshold D for comparison The output of the device 9 gives the fault signal F in the forward direction through the time relay T ₁ , the OR gate 10, and the AND gate 11. At the same time, the signal is sent to the OR gate 10 for maintenance, and sent to the AND gate 11' to block the reverse fault signal output; compare The output of the device 9' gives the fault signal F' in the reverse direction through the time relay _T2 , the OR gate 10', and the gate 11', and at the same time sends the signal to the OR gate 10' to hold, and sends it to the AND gate 11 to block the forward fault Signal output; after the fault current disappears, the signals of OR gates 10, 10' and AND gates 11, 11' are delayed and reset by overcurrent relay 5 and time relay _T3 .

According to the principle of superposition in electrotechnical science, the power system after the transmission line fault can be decomposed into normal system and fault component system. Figure 1 shows the fault component system when the line is short-circuited in the positive direction, F is the fault point, and Pm and Pn are the system Equivalent passive network, Δi is the line fault current component, Δu is the line fault voltage component, the detection point is m, the fault component system is a single excitation network, the initial value of the system is zero before the fault, and when the fault occurs (t=0) at A hypothetical power supply -u _F (0) and resistance R _F are suddenly added to the fault point F, so that the fault energy is S, then $S={\∫}_0^t\mathrm{\Δi\Δudt}$ Since it is a passive network with an initial value of zero, it is obvious that the fault energy S is the energy supplied to Pm by the imaginary power supply -u _F (0), and Spm is the energy absorbed by Pm after the fault, considering the reference of the fault current component Δi direction, then there is S=-Spm.

Figure 2 shows the fault component system when the transmission line is faulted in the opposite direction. At this time, S=Sx+Spn, where Sx and Spn are the energy absorbed by the line and Pn respectively from the system. Since Pm, Pn and the line can only absorb energy , so Spm, Spn, Sx are all greater than zero. To sum up, when the energy of the fault component at the measurement point is negative, the fault occurs in the positive direction, and when the energy is positive, the fault occurs in the reverse direction.

Compared with the prior art, the present invention has the following prominent advantages: the direction of the fault is judged by detecting the fault energy, no need to filter out the fault transient harmonic component, the discrimination speed is fast, and it is not interfered by the fault transient harmonic, especially The directionality of the fault energy exists for a long time after the fault, and the judgment result is accurate and reliable.

Figure 1 is a schematic diagram of positive direction fault discrimination.

Figure 2 is a schematic diagram of fault discrimination in the reverse direction.

Fig. 3 is a block diagram of the circuit structure of the detection device for judging the fault direction of the transmission line.

Example:

A device for discriminating the fault direction of a transmission line adopts the structure shown in Figure 3, wherein a wave trap is used as the memory device 2 and the subtractor 3, and as the memory device 2' and the subtractor 3', and the threshold D is set as 0.34×10 ^-9 kWh, the device is used to detect the fault direction of the three-phase 220 kV high-voltage transmission line, and the result is accurate and reliable.

Claims (2)

1. method of differentiating transmission line fault direction, it is characterized in that: the fault component of measuring electric current, voltage, with current failure component and the voltage failure component back integration that multiplies each other, obtain measurement point fault energy, when this energy is negative value, fault appears at positive dirction, energy be on the occasion of the time, fault appears in the other direction.

2. device of implementing claim 1 method is characterized in that: this device is by casing, compositor (1) (1 '), memory (2) (2 '), subtraction device (3) (3 '), multiplier (4), overcurrent relay (5), overvoltage relay (5 ') or door (6), electronic switch (K), reference integrator (7), phase inverter (8), comparer (9) (9) ', the time relay (T ₁) (T ₂) (T ₃) or door (10) (10 '), constitute with door (11) (11 '), wherein the input end of compositor (1) meets three-phase current ia, ib, ic respectively, its output terminal connects an input end of memory (2) and subtraction device (3) respectively, another input end of subtraction device (3) is connected with the output terminal of memory (2), and its output terminal is connected with the input end of multiplier (4) and the input end of overcurrent relay (5) respectively; The input end of compositor (1 ') meets three-phase voltage ua respectively, ub, uc, its output terminal connects an input end of memory 2 ' and subtraction device (3 ') respectively, another input end of subtraction device (3 ') is connected with the output terminal of memory (2 '), its output terminal is connected with overvoltage relay (5 ') input end with another input end of multiplier (4) respectively, multiplier (4) is connected with reference integrator (7) input end by electronic switch (K) back, this electronic switch (K) is passed through or door (6) control by the output of overcurrent relay (5) and overvoltage relay (5 '), it leads up to the output of reference integrator (7) phase inverter (8) and connects comparer (9) anode, another road connects comparer (9 ') anode, the external threshold level of adjusting of comparer (9) and (9 ') negative terminal (D), the output of comparer (9) is through the time relay (T ₁) or door (10), provide positive dirction fault-signal (F) with door (11), simultaneously this signal is sent or door (10) keeps, and deliver to door (11 ') locking reverse fault signal and export; The output of comparer (9 ') is through the time relay (T ₂) or door (10 '), provide reverse direction failure signal (F ') with door (11 '), simultaneously this signal is sent or door (10 ') keeps, and deliver to door (11) locking positive dirction fault-signal and export; After fault current disappears, by overcurrent relay (5) and the time relay (T ₃) make or the door (10) (10 ') and with door (11) (11 ') signal lag involution.

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