JPH09215177A - Method for determining phase and calculating impedance when system power failure occurs - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably calculated the impedance of a power system when a failure occurs in the system by improving the phase determining accuracy. SOLUTION: When a one-line ground fault is not detectable with the conventional detection logic composed of undervoltage relays 1A-1C, ground fault directional relays 2A-2C, and AND gates AN1-AN6, ground fault directional distance relays 5A-5C and AND gates AN7-AN9 confirm the operations of the relays 5A-5C in order of phase impedance from the smallest one to the largest one and determinine the phase having the smallest impedance as a failed phase. Therefore, the failed phase of a power system can be determined accurately even when the large fault current of the system is large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection control and a fault point locating method for detecting or protecting a phase of a fault point or a fault phase of a power transmission line in a power system to perform protection or control.

[0002]

2. Description of the Related Art Conventionally, in the case of failure of a transmission line, first of all,
There is a method of obtaining a failure phase and a failure point by using general protection relays individually or in combination. That is, the operation phase of the overcurrent relay and the undervoltage relay is set as the failure phase, and the distance relay operation phase is set as the failure phase. Furthermore, since the distance relay determines whether or not the impedance at the time of failure is in a certain fixed area, the area of the failure point can be specified by the zone. Similarly, a differential relay that focuses on the difference between the currents at each end of the power transmission line can calculate the failure point in the zone.

On the other hand, a fault point locator (fault locator: abbreviated as FL) for focusing on impedance and calculating a fault point is based on the hardware of a protection relay and has a PCT (transformer, current transformer) installation point. Focusing on the fact that the distance to the fault point is almost proportional to the impedance of the transmission line, the distance to the fault point is calculated not as a zone but as an absolute value. The calculation error is from several hundred meters to several K.
It is about m.

[0004]

[Problems to be Solved by the Invention]

(1) In recent years, the constant power flow of the system is increasing due to the expansion of capacity. Also, due to the expansion of the scale of the system, transmission lines have become longer and meshed, making it difficult to detect voltage drops and fault currents when a fault occurs. This prevents the undervoltage relay from detecting the correct fault phase. (2) In addition, although the recent increase in the speed of circuit breakers realizes high-speed interruption of system failures, on the contrary, FL that detects a failure point by focusing on voltage and current at the time of failure has a detectable time. The problem of shortening has arisen. That is, the current at the time of failure,
Accurately grasp the voltage, and discard the current and voltage during the delay phenomenon (transient change) of the analog input circuit filter built in the hardware (of the protection relay) that realizes the fault location ( The correct value cannot be obtained using the data of this period), the current for a limited stable period,
Must be located using voltage. Therefore, an object of the present invention is to improve the accuracy of phase determination at the time of system failure,
It is to enable stable impedance calculation.

[0005]

In order to solve such a problem, in carrying out protection control and fault location for a fault occurring in a transmission line of a power system, (1) the impedance of each phase of the transmission line is obtained, The presence or absence of the operation of the ground fault direction distance relay is checked in the order of the phase having the smallest impedance, and the minimum impedance phase is set as the ground fault occurrence phase (the invention of claim 1). (2) The impedance between each line of the power transmission line is obtained, and the presence or absence of the operation of the short-circuit direction distance relay is confirmed in the order of the smallest line-to-line impedance, and the minimum impedance phase is defined as the short-circuit occurrence phase, and the one-wire ground fault is detected. At this time, the short circuit determination is locked (the invention of claim 1).

(3) The impedance of each phase of the power transmission line is obtained, and the presence or absence of the operation of the ground fault direction distance relay is confirmed in the order of the phase impedance, and the smallest impedance phase is the ground fault occurrence phase. Failure determination and impedance between each line of the transmission line are obtained, and the presence or absence of the operation of the short-circuit direction distance relay is confirmed in the order of the impedance between the lines, and the minimum impedance phase is defined as the short-circuit occurrence phase, and a one-wire ground fault is detected. In such a case, which of the second failure determination that locks the short-circuit determination is performed is selected depending on whether it is a short-circuit failure or multiple failures (invention of claim 3).

(4) The one-line ground fault is detected when at least the distance relay in the ground fault direction operates and the line current does not change (the invention of claim 4). (5) The impedance between each line of the power transmission line is calculated for a plurality of times to obtain a tentative convergence value, and by taking an arithmetic mean of a set of values within a certain period within a certain range with respect to this convergence value, The convergence is determined and the impedance is calculated (the invention of claim 5). (6) In the invention of claim 5, the fixed period can be determined from the rise and fall of the failure detection relay (invention of claim 6).

[0008]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a system to which the present invention is applied. Although FIG. 1 shows a hardware image, as shown in FIG. 2, the insulating transformer 6, analog filters 7A and 7B, A / D converter 8, memory 9 and CP are shown.
CPU1 of a device such as U10 (central processing unit)
Needless to say, the soft processing may be performed with 0.

In FIG. 1, 1A, 1B and 1C are undervoltage relays (also referred to as 27 relays) corresponding to each phase, 2A and 2A.
B, 2C and 5A, 5B, 5C are ground fault direction distance relays (also referred to as 44G relays) corresponding to each phase, AN1 to AN9.
Is an AND gate, and NR1 is a NOR gate. here,
Regarding ground fault direction distance relays 5A, 5B, 5C, Ymin phase = phase with minimum absolute value of phase impedance Ymdl phase = phase with intermediate absolute value of phase impedance Ymax phase = phase with maximum absolute value of phase impedance . For example, A, B, with respect to three-phase _{C, | Z B (·)} | (= | V B (·) | / | I B (·) |)
_{<| Z A (·) |} <| Z C (·) | When, Ymin phase = B phase, Ymdl phase = A phase, Yma
x phase = C phase. In addition, the vector amount is shown by adding (•) to each symbol.

In other words, by using three 27 relay blocks and AND logic (AN1 to AN3), 27
When the relay operates only one phase, the operating phase can be specified.
There is a high possibility of a one-line ground fault due to the output of any of N1 to AN3. In addition, AND (AN4 ~ A
By adding in N6), it is possible to judge the failure inside or outside. The logic using 1, 2 and AN1 to AN6 is conventional as a one-line ground fault logic.

However, depending on the system conditions (such as the load end in a system with a large fault current in a long-distance transmission line), the 27 relays may operate in two or more phases due to the induced voltage due to the fault current, or conversely, the 27 relays may be 1 In some cases, the phase does not work. At this time, the conventional logic cannot correctly detect. Therefore, in the present invention, the NOR gate NR1, the ground fault direction distance relays 5A, 5B, 5C and the AND gate AN.
7 to AN9 are provided to detect a ground fault. That is, if there is a failure (even if the voltage is high and the 27 relay cannot operate), the impedance of the failure phase becomes small, and the impedance angle is close to the impedance angle of the transmission line. Operate. Therefore, the operation phase of the 44G relay may be regarded as the failure phase.

However, even if there is a one-line ground fault, the influence of heavy power flow,
Depending on the setting of the relay, a 44G relay with two or more phases may operate. Therefore, the presence or absence of the operation of the 44G relay is confirmed in the order of the phases with the smallest phase impedance (Ymin, Ymdl, Ymax), and the failure phase is specified as one phase. This is based on the fact that the fault phase impedance is generally smaller than the load impedance. According to this logic, not only the one-wire ground fault can be accurately detected, but also the failure phase can be specified even in the multiple failure across two lines.

Conventionally, for a two-phase or three-phase failure (short circuit, ground fault), AND condition of 27 relay operations of two or more phases and short circuit direction distance relay (also referred to as 44S relay) operation of 27 relay operating phases. The fault phase is specified by or the fault phase is specified by the minimum line voltage phase or the maximum line current phase.
The failure phase may not be accurately identified due to the influence of induced voltage and the settling of the relay. Therefore, in this invention, FIG.
44S relays 3A, 3B, 3C and AND gates AN10 to AN12, etc. are provided, and the presence or absence of the short-circuit direction distance relay is checked in the order of the smallest line impedance, and the minimum impedance phase is determined as the short-circuit occurrence phase. I am trying to do it. However, in order to prevent erroneous detection of short circuit due to 44S relay operation at the time of 1-wire ground fault, NOR gate N
When a one-line ground fault is detected by R1, the above-mentioned short circuit determination is locked so as not to be performed.

At this time, regarding the short-circuit direction distance relays 3A, 3B, 3C corresponding to each phase, Δmin phase = phase with minimum absolute value of line impedance Δmdl phase = phase with intermediate absolute value of line impedance Δmax phase = The phase in which the absolute value of the line impedance is the maximum. For example, for three phases A, B and C, | Z _AB (•) | (= | V _AB (•) | / | I _AB (•) |)
<| Z _BC (•) | <| Z _CA (•) |, Δmin phase = AB phase, Δmdl phase = BC phase, Δ
max phase = CA phase.

In general, in the method of locating the FL focusing on the impedance, in the case of a short-circuit fault or a two-phase ground fault, it is expected that a better accuracy can be expected by calculating the impedance between the lines and locating it. , The phase impedance consists of positive, zero, and negative phase impedances, and the line impedance has only positive and negative phases. Therefore, the line impedance is advantageous because there is no influence of zero phase.) That is, when a short circuit is detected by FL (and gate AN
10 to AN12 output), the line impedance is used for orientation, and the phase impedance for ground fault detection is desired to be locked.

FIG. 4 is a circuit diagram showing an embodiment in such a case, which is a combination of FIG. 1 and FIG. Reference numeral 4 in FIG.
Is a multi-fault detection block that determines whether or not the system is a multi-fault over two or more lines (“1” output when there is a multi-fault). AN13 to AN15 and AN19 are AND gates.
NR2 is a NOR gate. That is, as shown in FIG. 4, a NOR gate NR2 is provided to give priority to short circuit detection, and the ground fault detection logic of FIG. 1 is locked. However, in the case of multiple faults, the correct orientation cannot be expected with the line impedance (because the influence of the zero phase becomes large). Therefore, when multiple faults are detected by the multiple fault detection block 4, the short circuit is detected in reverse to the above. Are locked by AND gates AN13 to AN15, and the ground fault detection of FIG. 1 is executed via the AND gate AN19.

FIG. 5 shows another example of the one-line ground fault detection. For example, in the 1-line ground fault of the A phase, the load current and the A
The induced current induced by the fault current flowing in the phase flows. Since this induced current is almost zero phase, the BC phase line current has almost no induced current component. That is, A
In the (B, C) phase failure, the line current of the BC (CA, AB) phase hardly changes. The logic 12A to 12C of FIG.
This is to detect no change in the BC (CA, AB) phase current. K1 in the logic 12A to 12C is a constant, and is temporarily B phase or C phase (C phase or A phase, A phase or C phase).
12A (12B, 12C) is surely "0" by the failure including
This is the output value. 13A to 13C are overcurrent relays for locking the output when the 44G relay operates due to a distant external failure for convenience of settling of the 44G relay, and may be omitted in some cases. In addition, 13A ~ 1
3C may detect not only the overcurrent detection but also the current change before and after the occurrence of the failure. K2 is a constant, A
It is a value that reliably outputs "1" due to a phase failure, and 13A to 13C do not output "1" when the load current changes due to load tap switching or the like. In addition, 44G relay 1
1A to 11C are for making an internal / external determination of a one-line ground fault. AN16 to AN18 are AND gates.

FIG. 6 is a waveform for explaining various amounts of electricity when a system failure occurs. Here, a failure occurs at time t1 and V (•) and I (•) change suddenly, a start relay (failure detection relay) operates at time t2, and the circuit breaker (CB) is opened at time t3. Then, the case where the current is removed is shown.
At this time, the hardware to which the present invention is applied includes the hardware shown in FIG.
Since the analog filters 7A and 7B are included as shown in FIG. 5, a transient change occurs due to the filter characteristic, which causes the | V (•) | and | I (•) | characteristics, especially at times t0 and t2.
The vibration (attenuated depending on the filter) as seen around occurs, and naturally the calculated impedance | Z (•) | at the time of failure also changes as shown in the figure.

The impedance stabilizes after some time has elapsed after the occurrence of the failure. However, if the failure is quickly shut down, the time period during which stable impedance can be obtained is limited accordingly. Times t2 to t3 indicated by reference symbol R in FIG. 6 are the limited time zones, but when this portion R is viewed in detail, minute vibrations remain as shown in FIG. Therefore, the following processes (a) and (b) are executed.

(B) Please refer to FIG. The detector 15 detects the operation start-up time t2 of the start relay 14, and the time determination unit 16A determines the time Δt1 before that (see FIGS. 6 and 7) as the start time t1, and from this time t1, the start relay return time t4. The impedance stabilization period is the time period up to and the impedance during this period is calculated.
The result is output after averaging or convergence determination of. When the relay operation is for a long time (t4 is after a long time), the monostable multivibrator (also simply referred to as a timer) 18 terminates with a fixed time tint. It should be noted that Δt1 is smaller than the time delay (t2-t0) from the occurrence of a failure until the relay operates, and the tint is about the time during which the transient phenomenon of the filter is in principle settled, or the longest failure determined in system operation. It is the duration. In this way, the detector 17A detects the fall of the start relay 14 or determines the start relay return time t4 after a lapse of tint from the rise of the start relay 14. By using this period t1 to t4, stable impedance can be obtained.

(B) If the impedance does not fall within the permissible error (± ε) with respect to the true value as shown in FIG. Arithmetic average (D1 to D10 / 1 in FIG. 7)
0 = A value), the convergence judgment shown by the following equation, a value that takes the minimum ε value at | (x−1) − (x) | + | (x) − (x + 1) | <ε, or (x -1), (x),
There is a method of taking an intermediate value of (x + 1) or taking an average of three (see B1 and B2 shown in FIG. 7). The comparison data is not limited to three points. Among these, those taking the arithmetic mean are D1, D3 to D5, D shown in FIG.
It will be affected by data outside the allowable error such as 9, D10. Further, in the case of the convergence determination, when a good result such as D6 to D8 is obtained as in B2 of FIG.
As described above, there is a case where the allowable error such as D3 to D5 cannot be set, and it is uncertain which one.

Therefore, in the present invention, while taking advantage of the convergence determination, the above-mentioned drawbacks are eliminated as shown in FIG. That is, in the conventional convergence determination, FIG.
The case of B1 is a problem, but this is that the data D3 to D5 used as B1 are out of the error range. However, the data D3 to D5 are all close to the convergence value,
Data close to the true value (D2, D6 to D8 in FIG. 7) exist in the near time zone before and after this time. Therefore, in FIG. 8, the provisional convergence value {y} (y = 1 to 10) is obtained in the same manner as in the conventional case (step S1), and ± is calculated from the provisional convergence value {y}.
A set of values within η (η: constant, indicated by ε in FIG. 5) is obtained (step S2), and the arithmetic mean thereof is taken as the result (output) (step S3). For example, if {y} = D4 in FIG. 5, the set is D3, D4,
If D5, D6, D7, D9 and {y} = D7,
The set is D2, D6, D7, D8. In this way, the value is not a true value but can be kept within a certain tolerance.

[0023]

According to the present invention, the failure phase at the time of a system failure is determined based on the magnitude judgment of the impedance and the operation of the corresponding relay, and the one-line ground is based on the no change in the line current and the operation of the corresponding relay. The detection of the junction has the advantage that more accurate detection is possible. Further, even if the failure occurs for a short time, the impedance of the data can be accurately calculated by improving the data collection timing and the convergence determination, and the reliability is improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a power system to which the present invention is applied.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention.

FIG. 5 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 6 is a waveform diagram for explaining various electric quantities at the time of system failure.

FIG. 7 is a partially enlarged view of FIG.

FIG. 8 is a block diagram showing a period determining method according to the present invention.

FIG. 9 is a flow chart for explaining the fifth embodiment of the present invention.

[Explanation of symbols]

1A, 1B, 1C ... Undervoltage relay, 2A, 2B, 2
C, 5A, 5B, 5C, 11A, 11B, 11C ... Ground fault direction distance relay, 3A, 3B, 3C ... Short circuit direction distance relay, 4 ... Multiple fault detection block, 6 ... Insulation transformer, 7
A, 7B ... Analog filter, 8 ... A / D converter, 9 ...
Memory, 10 ... CPU (central processing unit), 12A, 12
B, 12C ... Line current determination block, 13A, 13B,
13C ... Phase current determination block, AN1 to AN19 ... AND gate, NR1, NR2 ... NOR gate, OR1 ... OR gate, 14 ... Start relay, 15 ... Rise detector, 16
A, 16B ... Time determination unit, 17A, 17B ... Fall detector, 18 ... Timer (monostable multivibrator).

Claims (6)

[Claims] 1. When performing protection control and fault location for a fault that has occurred in a power transmission line of a power system, the impedance of each phase of the transmission line is obtained, and the operation of the ground fault direction distance relay is performed in order of the phase impedance having the smallest phase impedance. A phase determination method at the time of a system failure, characterized by confirming the presence or absence and setting the minimum impedance phase as the ground fault occurrence phase. 2. When performing protection control for a fault that has occurred in a transmission line of a power system and fault location, the impedance between each line of the transmission line is obtained, and the presence or absence of the operation of the short-circuit direction distance relay in order of decreasing line impedance. And a minimum impedance phase as a short circuit generation phase, and further, when a one-line ground fault is detected, the short circuit judgment is locked. 3. When performing protection control and fault location for a fault that has occurred in a transmission line of an electric power system, the impedance of each phase of the transmission line is obtained, and the operation of the ground fault direction distance relay is performed in order of the phase impedance having the smallest phase impedance. The presence / absence is checked, the first failure determination in which the minimum impedance phase is the ground fault occurrence phase, the impedance between the lines of the transmission line is obtained, and the presence or absence of the operation of the short-circuit direction distance relay is confirmed in the order of the impedance between the lines However, when the minimum impedance phase is set as the short-circuit generation phase, and when a one-line ground fault is detected, which of the second failure determination that locks the short-circuit determination is the short-circuit failure or the multiple failure is determined. A method for determining a phase at the time of a system failure, which is characterized by selecting whether or not 4. A one-line ground fault is detected when at least a ground fault direction distance relay operates and a line-to-line current does not change when performing protection control and fault location for a fault that has occurred in a transmission line of a power system. A method for determining a phase at the time of a system failure, which is characterized by: 5. When performing protection control and fault location for a fault that has occurred in a power transmission line of an electric power system, impedance between each line of the power transmission line is calculated for a plurality of times to obtain a tentative convergence value, and this convergence value is set to this convergence value. On the other hand, a method of calculating an impedance at the time of a system failure, characterized by calculating an impedance by performing a convergence determination by taking an arithmetic mean of a set of values within a certain period within a certain range. 6. The impedance calculation method at the time of a system failure according to claim 5, wherein the fixed period is determined from the rise and fall of the failure detection relay.