JPH05252645A - Protective relaying device for transmission line - Google Patents

Abstract

PURPOSE:To improve the protective performance of the title device upon normal time by a method wherein an intercepting command is outputted when the output of a high-sensitivity type current differential element is removed and the output of a low-sensitivity type current differential element as well as the output of a failure detecting element are established for a given period of time under a condition that the condition of generation of an excitation rush current for a transformer for a branch load substation is established. CONSTITUTION:A high-sensitivity type current differential element 4 is locked and the locking is continued until a time limit reset timer 3 is reset when either one of a breaker throwing command detecting element 1 or a system voltage increase detecting element 2 is outputted. The intercepting output for a breaker is outputted by the OR of the output and a low-sensitivity type current differential relay element 5 as well as the AND of the output and a failure detecting element 6. In this case, protection during the generating period of transformer exciting rush current is effected by the low-sensitivity type current differential element 5. According to this method, high-sensitivity protection can be effected without spoiling any protecting performance upon a normal time even in a system wherein branch load terminals which are not equipped with the relaying devices are existing in a protecting division.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line protection device for a power system, and more particularly to a current differential relay system when there is a terminal in which a relay device is not installed in the protection section.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. 8 and 9 are relay installation terminals, 10 and 11 are customers in the protection section, branch load substations such as distribution substations, and terminals 10 and
It is assumed that 11 has no relay installed. In this way, a system that has a terminal without a relay is configured in consideration of the fact that it does not operate in combination with two lines at that terminal, it does not serve as a source of fault current, and the economy of the system is taken into consideration. It is a relatively common case in low-order systems. Terminals 10 and 11 have power receiving transformers 12 and 13, respectively. At the terminals 8 and 9, current transformers 14a and 14b for measuring the current of the transmission line and transformers 15a and 15b for measuring the voltage of the system are respectively installed. The relay installed at terminal 8 has the above 14
a, 15a are the above 14 in the relay device installed in the terminal 9.
b and 15b are supplied, and when it is judged that each relay device has an internal accident, a break command is output to each breaker 17a and 17b. 17c and 17d are terminals 10 and 11, respectively
It is a circuit breaker. Note that FIG. 7 shows an example,
There is no substantial difference in the number of terminals and the number of transformers installed in terminals 10 and 11. Further, the relay devices 16a, 16b can mutually know the current information of the other end through the transmission system. FIG. 8 shows an outline of main constituent elements and protection sequences of the relay devices 16a and 16b. The main detection relay element 18 is a current differential method (also referred to as a ratio differential method), and the failure detection relay element has a principle different from that of the main detection relay element, and is a typical undervoltage relay method. .. A cutoff command is output by the logical product of the outputs of elements 18 and 19. In FIG. 7, the instrument transformer is connected to the bus bar, but it may be connected to the outside (the other end side) of the power line breaker. The current differential element 18, which is the main detection element, is generally expressed by the following operation equation, where I _{11 is} the current flowing in from the terminal 8 and I ₁₂ is the current flowing out from the terminal 9 in FIG. As shown in the figure.
In FIG. 9, the hatched portion indicates the operation area. I ₁₂ ≤K ₁ I ₁₁ -K ₂ (1) or I ₁₁ ≤K ₁ I ₁₂ -K ₂ (2)

(1) and (2) indicate that the sensitivity of the current differential element 18 is K ₂ / K ₁ . Further, in the characteristic diagram shown in FIG. 9, the sensitivity is the intersection of the vertical axis and the horizontal axis, and exhibits a so-called ratio characteristic in which the sensitivity decreases as the passing current increases. In the system having terminals without relay devices as shown in FIG. 7, it is necessary to consider the following points when determining the sensitivity K ₂ / K ₁ . (I) Current that always flows out from terminals 10 and 11 (terminals 10 and 11
Settle down that does not malfunction due to the sum of the currents. (Ii) Set the terminals 10 and 11 so that they will not malfunction due to a transformer secondary side accident. (Iii) Set the value so that it does not malfunction due to the excitation inrush current generated in the transformers at terminals 10 and 11.

The capacity of the transformers 12 and 13 is about several tens of MVA even if it is generally large in one substation total, and the transformer impedance is about 5 to 10% in self capacity basis. Two
In the secondary accident, the fault current decreases considerably, and the magnetizing inrush current tends to reach up to 10 times the transformer capacity at the peak value.Therefore, considering (iii) above is the worst case in most cases. Is. In order to satisfy the above (iii), it is necessary to consider the following three points. First is the terminal
This is an exciting inrush current that occurs when the circuit breaker 17c or 17d is turned on at 10 or 11, and it is unlikely that the two circuit breakers will be turned on at the same time, so the larger one is usually considered. For example, assuming that the system voltage is KV, the transformer capacity is MVA (three phases), and the peak value of the exciting inrush current is about n times the transformer capacity at maximum. Becomes It is well known that this exciting inrush current is maximum when the breaker closing phase is 0 and the waveform is similar to a half-wave rectified waveform. In determining the sensitivity of the current differential element 18 under such conditions, the relay is usually a fundamental wave (commercial frequency) responsive type, so The value is obtained by multiplying (the ratio of the fundamental wave component contained in the half-wave rectified waveform) by an appropriate margin. Since it is generally difficult to predict and detect the breakers at terminals 10 and 11 at terminals 8 and 9, the sensitivity values obtained here are obtained. Can be said to be a value that must always be lowered due to the first problem.

The second is the exciting inrush current when the breaker 17a or 17b of the relay installation terminal (generally with a back-up power source) is closed while the breakers 17c and 17d are closed. Exciting inrush currents of all the transformers (12 and 13 in FIG. 7) existing in the above state flow into the circuit breaker closing terminal as a sum, resulting in a considerably large current. So in this case the sensitivity of the current differential element to be reduced is generally Given in.

Thirdly, as shown in FIG. 10, the breaker 17a, 17b, 17c, 17d in the protection section is in a closed state and the terminal 8 is turned on.
Is an inrush current generated when the system voltage is once reduced and the system voltage is once recovered, and then the system voltage is recovered by fault elimination. In this case, since the system fault is removed at a point near the plus or minus peak of the voltage, the magnetizing inrush current is considered to be slightly smaller than in equation (4), but the worst value is equivalent to equation (4). There is no problem in thinking that the current will occur.

As described above, conventionally, the worst condition is to set the sensitivity of the current differential element as given by the equation (4) to prevent malfunction in any case. That is, by setting K ₂ / K ₁ in FIG. 9 to the value given by the equation (4) or more, the current differential element 18 in FIG. 8 does not malfunction due to the transformer inrush current of the branch load substation in the protection section. I was taking measures.

[0008]

In general, a transformer exciting inrush current has a peak value of about 10 times the transformer capacity, and moreover, it occurs simultaneously in a plurality of transformers. Therefore, the value of the equation (4) is However, there is a problem in that, as a result, the conventional method leads to the steady reduction in the protection performance against accidents inside the protection section. (For example, there is a problem of insufficient sensitivity for detecting internal accidents.)

In view of the above-mentioned problems, the present invention has a low sensitivity so that the sensitivity of the current differential element satisfies the above expression (4) when the inrush current is generated in the branch load substation transformer in the protection section. In other states, the sensitivity is set high to improve the protection performance in normal times. The high sensitivity means that the sensitivity satisfies the expression (3).

[0010]

SUMMARY OF THE INVENTION The present invention has a functional configuration newly provided in a relay installation terminal in order to solve the above-mentioned problems, and is means for detecting a condition under which an inrush current of excitation occurs in a branch load substation transformer. When this output is obtained, it is for locking the output of the high-sensitivity type current differential element.

[0011]

As described above, when the conditions for generating the inrush current for the branch load substation transformer are satisfied, the output of the high-sensitivity type current differential element is blocked and the low-sensitivity type current difference is maintained for a certain period of time. When the output of the moving element and the output of the failure detecting element are both established, the interruption command is output.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, reference numeral 1 is a circuit breaker at its own end (see FIG. 7).
17a or 17b) in FIG. 7, and 2 is an element for detecting a rise in the self-system voltage (output of the instrument transformer 15a or 15b in FIG. 7). Specifically, reference numeral 1 denotes an element to be inserted in the circuit breaker closing circuit as shown in FIG. 2, which may be a static element such as an auxiliary relay or thyristor as long as it can detect the flow of current. As shown in Fig. 3, 2 is an element to detect that there is a recovery of β% of the system voltage within Tα [ms] in order to detect the voltage rise at the time of accident recovery, and it is necessary to determine Tα so as to coordinate with the system phenomenon. However, in general, it may be about 10 to 20 ms. Further, β should be coordinated so that the current differential element (high-sensitivity type) is set to a voltage recovery level at which unnecessary response does not occur.

Reference numeral 3 is a time-limit reset type timer for coordinating with the decay time of the exciting inrush current. Note that the output of voltage rise detection at each relay installation terminal must always match, so if it is included in the transmission data and the voltage rise is detected at any terminal, other The terminal is also controlled as if rising was detected.

FIG. 4 shows a protection sequence using this embodiment. In FIG. 4, 4 is a high-sensitivity type differential element with a sensitivity that does not operate with respect to the exciting inrush current when the branch load end transformer is turned on, and 5 is a relay installation terminal (terminals in FIGS. 7, 8 and 9)
This is a low-sensitivity current differential element with a sensitivity that does not operate with the sum of the inrush currents of the branch load end transformer when the circuit breaker is turned on. When either the breaker closing command detection element 1 or the system voltage rise detection element 2 is output, the high-sensitivity current differential element 4 is locked, and the lock is continued until the time-limit reset timer 3 is reset. This output, the logical sum of the low-sensitivity type current differential relay element 5 and the logical product of the failure detection element 6 give a breaking output to the breaker. In other words, the protection during the transformer inrush current generation period is the low sensitivity type current differential element 5
Performed by. Reference numeral 7 is a timer of a time-delayed operation type, which is a timer for coordinating so that the high-sensitivity type current differential element output does not come out earlier than the operation time of the system voltage rise detection element 2, and actually has a protection performance of about 10 ms. Does not significantly reduce

That is, an element for detecting the breaker closing and an element for detecting the voltage rise of the system are provided at the relay installation terminal, and when either of them operates, the current differential element has a low sensitivity for a certain period of time. If it does not work (normal time), the current differential element can have high sensitivity.

Next, a second embodiment will be described with reference to FIGS. 5 and 6. In FIG. 5, reference numeral 1 is an element for detecting a closing command of the breaker at its own end (17a or 17b in FIG. 7), 20 is a high-sensitivity type current differential relay element, and 6 is a failure detection relay element. .. An external accident is judged by the logical product of the inhibit output of the element 20 and the output of the element 6, and the transformer inrush current is prepared for the subsequent voltage recovery after the accident is removed.

Further, as in the first embodiment, 3 is a time-reset timer for coordinating with the decay time of the exciting inrush current. Since the output of the external accident detection at each relay installation terminal must be the same, it must be included in the transmission data, and if an external accident is detected at any of the terminals, the other terminals will also be included. Control as if an external accident was detected.

FIG. 6 shows a protection sequence using this embodiment. In FIG. 6, 20 is a high-sensitivity type current differential relay element with a sensitivity that does not operate with respect to the excitation inrush current when the branch load end transformer is turned on, and 5 is a relay installation terminal (FIG. 7,
It is a low-sensitivity current differential element with a sensitivity that does not operate with the sum of the inrush currents of the branch load end transformer when the breaker is turned on at terminals 8 and 9. When any of the circuit breaker closing command detection element 1 and the final output of the logic shown in FIG. 5 is output, the high-sensitivity current differential element 20 is locked,
Time limit recovery type Lock continues until the timer 3 recovers.
Further, a logical sum of this output, the low-sensitivity type current differential relay element 5 and the logical product of the failure detection relay element 6 provides a breaking output to the breaker.

That is, for a certain period of time, the logical sum of the element for detecting the closing of the breaker at the relay installation terminal and the logical product output condition of the current differential relay element non-operation condition and the failure detection relay element operation condition Reduces the detection sensitivity of the current differential element, and can achieve high sensitivity (normal sensitivity) under normal conditions.

[0021]

As described above, according to the present invention, the output of the high-sensitivity type current differential element is locked for a certain period of time when a condition in which an exciting inrush current is generated in a branch load substation transformer is detected. Even in a system where there is a branch load terminal in which a relay device is not installed inside the protection section, high sensitivity protection can be performed without impairing the constant protection performance.

[Brief description of drawings]

FIG. 1 is a logical block configuration diagram of a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing a circuit breaker closing command detection element of the present invention.

FIG. 3 is a voltage waveform diagram of the power system before and after the accident is removed.

FIG. 4 is a protection sequence diagram to which the first embodiment is applied.

FIG. 5 is a logical block configuration diagram of a second embodiment of the present invention.

FIG. 6 is a protection sequence diagram to which the second embodiment is applied.

FIG. 7 is an electric power system diagram having a branch load terminal.

FIG. 8 is a protection sequence diagram of a conventional relay device.

FIG. 9 is an operating characteristic diagram of a current differential element.

FIG. 10 is a power system diagram having a branch load terminal.

[Explanation of symbols]

1 ... Breaker closing command detection element, 2 ... System voltage rise detection element, 3 ... Time-reset timer, 4, 20 ... High sensitivity type current differential element, 5 ... Low sensitivity type current differential element, 6 ... Failure detection Element, 7 ... Timed operation type timer.

Claims (3)

[Claims] 1. A current differential relay element that operates when current information of each terminal of a multi-terminal transmission system satisfies an operating condition in which a predetermined relationship is settled, and a fault detection relay based on a principle different from this current differential relay element. An element, a detection means for detecting a condition under which an exciting inrush current is generated in a branch load substation transformer of the power transmission system, and when the condition is satisfied by this detection means, the output of the current differential relay element is blocked for a certain period of time, And a logical product means for setting a logical product output of the output of the second differential current relay element settled to a sensitivity lower than that of the differential current relay element and the output of the failure detection relay element as a cutoff command. Transmission line protection relay device. 2. A high-sensitivity type current differential relay element which is set to high sensitivity for detecting that current information at each terminal of a multi-terminal transmission system satisfies a predetermined relationship, and low sensitivity which is set to low sensitivity. Type current differential relay element, a fault detection relay element based on a principle different from that of the current differential relay element, and a condition for either detection of the closing command of the self-end circuit breaker or detection of a rise in the self-end system voltage. Blocking means for blocking the output of the high-sensitivity type current differential relay element for a fixed time, logical OR means for outputting the logical sum of the output of this blocking means and the output of the low-sensitivity type current differential relay element, and this logic A transmission line protection relay device, comprising: a logical product means that outputs a cutoff command when both the output of the summing means and the output of the failure detection relay element are satisfied. 3. A high-sensitivity type current differential relay element which is set to high sensitivity for detecting that current information at each terminal of a multi-terminal transmission system satisfies a predetermined relationship, and low sensitivity which is set to low sensitivity. Type current differential relay element, failure detection based on a principle different from that of the current differential relay element, relay element, detection of closing command of self-end circuit breaker or high sensitivity type current differential relay element A blocking means for blocking the output of the high-sensitivity current differential relay element for a certain period of time when any condition of the relay element operation is satisfied, and an output of the blocking means and an output of the low-sensitivity current differential relay element. And a logical sum means for outputting a logical sum, and a logical product means for outputting a cutoff command when both the output of the logical sum means and the output of the failure detection relay element are established. Electric wire protection relay device.