JP2001359235A - Ground protective relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a controlled variable of a relay from being affected by zero-phase circulating current. SOLUTION: Ground protective relays G1, G2 conduct operation output, when a value obtained by subtracting the controlled variable from an operating amount is equal to or higher than a prescribed value, where differential current between a power source side terminal A of each of parallel two lines 3L, 4L fitted in parallel with parallel liens 1L, 2L and a load side terminal C is defined as an operating amount, and (k) (sum of the currents of the respective terminals) is defined as the controlled variable. A zero-phase circulating current IOth, prior to the occurrence of an accident by several cycles, is stored as a vector amount, and conventionally the vector amount of IOth stored from the current of the respective terminals (vector sum IOF3+IOth at a terminal A) is subtracted from the controlled variable including IOth, to obtain a controlled variable excluding IOth, thereby preventing malfunctions due to variation in IOth based on induction from the line 1L or 2L.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault protection relay for a transmission line, a ground fault protection relay in a high resistance grounding system (60 kV to 145 kV system), and in particular, the influence of a zero-phase circulating current on a parallel transmission line cannot be ignored. It relates to a ground fault protection relay of a system.

[0002]

2. Description of the Related Art Ground fault protection of an overhead transmission line will be described with reference to FIG. The transmission lines 1L and 2L and the transmission lines 3L and 4L are respectively two parallel lines, and the lines 1L, 2L and 3L and 4L are mounted on the same steel tower. Such transmission lines 3L and 4L
As for the earth fault protection relay, the zero phase difference current of the lines 3L and 4L is obtained at the substation (terminal) A or C, and depending on the direction of the zero phase difference current, which of the lines 3L and 4L has a ground fault has occurred. Or a ground fault line selection relay (not shown) for determining whether or not, as shown in FIG. 5, the D / A converters 1a and 1c convert the zero-phase currents of the terminals A and C into D / A converters 1a and 1c. ground fault differential relay 2c via the optical fiber oF _1, oF ₂ transmits to the transmission device 2c, 2a of the other terminal side by, protected to determine each circuit internal fault performs differential operation microprocessor 3a, the 3b The above-mentioned ground fault line selection relay employing G _a and G _c can be protected by data (information) only at its own end, and requires no transmission device or transmission cable. Many are adopted.

Further, since the above-mentioned ground fault differential relays G _a and G _c are of a differential current protection type of transmission lines, transmission cables such as cables and optical fibers are required, which is expensive. It does not include zero-phase circulating current I _O th within the differential current in the lines generated complex such as a phase circulating current I _O th. (Zero-phase circulating current I _O th inflow current and outgoing current for a current circulating between the lines can be removed by obtaining equally be differential current.) Therefore earth in併架system and multi-terminal system It is more often used than a line selection relay.

[0004]

The configuration of the ground fault differential relays G _a and G _{c provided at} the terminals A and C as digital relays is shown in FIG. 1 (configuration of the ground fault protection relay of the present invention). The ground fault protection relays G ₁ and G ₂ installed at the terminals A and C of the two lines 3L and 4L are the same (however, the operation amount,
The calculation method of the suppression amount is different). Further, the input of the relay is the same, and the operation equation of the ground fault protection relays G ₁ and G ₂ shown in Table 1 is expressed by equation (1).

[0005]

[Table 1]

[0006]

(Equation 1)

[0007] Operation of internal fault F ₁ at the relay G ₁ is the fault current I _F becomes, the fault current itself becomes the input relay G ₁ becomes operating current, suppressing the amount of the sum of the respective terminal current absolute value zero-phase circulation current I _o th itself is input becomes suppression quantity since there.

[0008] zero-phase circulating current I _O th is line 1L being併架, 2L Ninen rack state of the load current I _L1, I _L2 (FIG. 5), varies with conditions such as 1 line stop, during normal May change during an internal accident.

[0009] become most problematic in ground protection relay with current differential, the nature of the relay shown in FIG. 6, by a change in inhibiting amount due to a change in the zero-phase circulation current I _o th, many suppression quantity When this happens, the operating point x, which was in the operating area as shown in FIG. 6A, moves out of the operating area as shown in FIG. 6B, and the relay becomes inactive despite an internal accident. It is becoming.

[0010] For example, in FIG. 5, if a ground fault occurs simultaneously in the lines 2L and 3L and the line 2L is cut off first,
The overhead line is only 1L, and 3 lines from lines 1L and 2L
Since the induction M to the L and 4L sides becomes unbalanced, 3
L, the zero-phase circulation current I _O th of 4L increases during accident 3L. As a result, the operating point x in FIG.
As shown in the above, the relay becomes inoperative.

[0011] As described above, since the zero-phase circulating current I _O th come included in the suppression of the relay operation (1), the magnitude of the zero-phase circulating current I _O th, the operating point is constant not become, it is difficult to determine the (1) inhibition rate K ₁ of the formula.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a ground fault protection relay in which the amount of suppression of the relay is not affected by the zero-phase circulating current. It is in.

[0013]

According to the present invention, the difference between each terminal current of each line is set as an operation amount and the sum of each terminal current of each line is multiplied by a suppression rate. In the ground fault protection relay that outputs an operation when the value obtained by subtracting the amount of suppression from this amount of operation becomes a predetermined value or more, the zero-phase circulating current several cycles earlier is referenced to the line voltage. Is stored in a memory as a vector amount, and the stored zero-phase circulating current vector amount is subtracted from the zero-phase current of each terminal to remove the zero-phase circulating current included in the suppression amount.

Alternatively, each terminal is provided with a ground fault detecting element which operates when the current flowing toward the inside of both lines is equal to or greater than a predetermined value by the vector sum of the zero-phase currents of both lines. The suppression amount is controlled by calculating the logical product of the operation output of the ground fault detection element and the inverted operation output of the ground fault detection element at the load side terminal.

[0015]

FIG. 1 shows the configuration of a ground fault protection relay according to a first embodiment.
You. Ground fault protection relay G ₁, G_TwoIs the ground fault protection
Leh G_a(G_c) Voltage, current, etc. of own terminal detected in the same way
A / D converter for converting digital data into digital data, optical fiber
Data exchange with other terminal side ground fault protection relay via bar
Transmission device, ground fault using data of own terminal and other terminal
It consists of a microprocessor that performs dynamic relay operation
I have. FIG. 5 shows a conventional ground fault protection relay according to the first embodiment.
Ground fault protection relay G_a(G_c) Is different from the differential width method
The point is that.

A ground fault protection relay according to the first embodiment.
G₁, G_TwoThe change width differential method will be described with reference to FIGS.
You. In the description, voltage and current are vector quantities.
The kutle symbol is omitted. The transmission line is parallel 2 shown in FIG.
Lines 1L and 2L and 3L and 4L, accident line 3L
Then, the R, S, T phase voltage on the terminal A side of this fault line is
E_aR, E _aS, E_aT, ST phase voltage to E_aTSAnd

The earth fault F ₁ generation zero-phase circulation current I _O th line voltage not to change one line ground as shown in FIG. 2 the preexisting, for example, zero-phase E _ATS based the circulating current I _O th stored in the memory as a vector quantity. Also, detected by detecting the zero-phase voltage V _O generate ground fault F ₁ generation, stored in memory several cycles before the current I _O th as a vector quantity from the time of detection, for suppressing the amount of calculation terminal current input, the terminal A I _F1 + I _O
The vector quantity I _O th that the memory from th removing I _O th contained amount suppression by subtracting.

[0018]

(Equation 2)

[0019] Always accident before flowing and zero-phase circulating current I _O th is as shown in FIG. 2 (b), stored as a vector quantity with respect to a certain reference (magnitude and phase angle theta) in the memory.
This storage method is also to store the instantaneous value of the current as it is in the memory for a fixed number of samples, and to subtract the instantaneous value of the current data from the stored data at the same time when the zero-phase voltage V _{O is} generated (the occurrence of a ground fault). (2) can be removed I _O th from suppression amount as expression. However, in the method of storing the instantaneous value, when a time difference (difference) occurs between the stored value several cycles before and the current data, the difference becomes a phase shift as it is, but shortly after the zero-phase voltage V _{O is} generated. Time (2
(3 cycles), there is not much problem when the protection is shut off.

However, in a high-resistance grounding system or the like, a short-circuit relay is often given priority in the event of an out-of-phase ground fault or the like. For this reason, the ground fault protection relay is operated with a certain delay. In such a case, the method of storing the instantaneous value may cause a malfunction or a malfunction due to the influence of the time lag. This time lag occurs when the frequency of the system changes even if it is very small after a ground fault.

Embodiment 2 In Embodiment 1 described above, the zero-phase circulating current before the occurrence of the ground fault is stored as a vector quantity, and the zero-phase current during the fault (sum of the fault current and the zero-phase circulating current) is stored. it is intended to eliminate the zero-phase circulation current I _O th included in the zero-phase current by subtracting the stored value. However, this alone has a zero-phase circulating current I
There is a problem can not be completely removed the effects of _O th.

Now, consider the simultaneous accident of the overhead transmission lines 1L and 3L in FIG. In particular, when the lines 1L and 2L are separate systems and have a very high voltage (direct grounding system), it is general that the accident of the line 1L is generally removed first, and the 1L is cut off.

In such a case, simultaneously generated 1L
3L The side ground fault current of the zero phase circulation current between 4L I _O t
h changes. In addition, the 1L cut-off causes the 1L-side load current to become zero and shifts to the 2L side. As a result, 3
L, I _O th among 4L may change significantly. This occurs when it is impossible to remove the effects of the accident before the zero-phase circulating current I _O th even zero-phase circulation is stored in the memory to a vector quantity of current I _O th as in the first embodiment.

[0024]

[Table 2]

This is because when the internal fault F _{1 in} Table 2 (accident F _{1 in} FIG. ₁ ) occurs, the ground fault protection relays G ₁ and G _{2 of the} differential current protection method are used.
Equation for the amount of suppression

[0026]

(Equation 3)

[0027] Since the zero-phase circulation current I _O th contained in changes during the accident, in the above (2) shows that it is difficult to completely remove the I _O th, FIG 6 (b )
It is inevitably shifted operating point × by I _O th as.

[0028] Embodiment 2, to prevent the zero-phase circulation current I _O th change during the accident differential relay G _1, G ₂ becomes inoperative, as shown in FIG. 3, the line The terminals A and C of 3L and 4L are connected to the terminals 3L and 4L, respectively, as viewed from the zero-phase power source by the vector sum of the zero-phase currents of 3L and 4L.
A ground fault detection element that operates when the current flowing toward the inside of L (with respect to the zero-phase voltage V _O ) is equal to or greater than a certain value.
I and ΣO are provided, and as shown in FIG. 4, a logical product of the operation output of the ground fault detection element ΣI and the inverted operation output of ΣO is taken by an AND circuit A ₁ and the signal is used as a control amount control signal. The amount of suppression of the relays G ₁ and G ₂ is controlled.

[0029] The ground fault detection element ΣI, ΣO, as shown in Table 2, the zero-phase circulating current I _O th in any of the system state does not come entered exactly as input. (For I _O th is circulating current, the direction of the current of 3L and 4L is opposite, is completely erased by taking the vector sum.).

Therefore, in the case of an internal accident, the ground fault detecting element ΔI
Is 0, 2I _F2 is input to the ground fault detection element ΣO, ΣI operates, and ΣO does not operate. The element ΣI out ground fault in the external accident _{I F / 2 + I F /} 2 = I F next,
It works like an internal accident. However, although the ground fault detecting elements ΣO the same in the I _F input, does not work because the phase is opposite to the internal fault with respect to the zero-phase voltage V _O. Therefore, as shown in FIG. 4, by controlling the suppression amounts of the relays G ₁ and G ₂ by the suppression amount control signal which is the logical product of the operation outputs of the ground fault detection elements ΣI and 検 出 O, as shown in FIG. It is possible to prevent a significant shift of the operating point, and the relays G ₁ and G ₂ can operate correctly.

The suppression of the control constant of the system (I _F of magnitude, the maximum value of I _O th, etc.) in advance settling by.
For example inhibition of the time of I _O th is 0 | I _F1 | + | I _F2
Since | ≒ | I _F |, the suppression amount equal to or greater than | I _F | is cut. If there is no problem such as CT saturation or the like in the current due to an external failure, the setting is made such that the suppression amount is set to zero.

[0032]

Since the ground fault protection relay of the present invention is constructed as described above, the ground fault protection can be performed without being affected by the zero-phase circulating current in a transmission line parallel system. Further, the present invention can be applied to a transmission line having any system configuration, such as an overhead transmission line with a different power source (ultra high voltage) system or the like, or a high resistance grounding overhead transmission line connected to the same power source.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a variable-width differential ground fault protection relay according to a first embodiment;

FIG. 2 is a voltage and current vector diagram for explaining the operation of the relay.

FIG. 3 is a configuration diagram of a ground fault protection relay according to a second embodiment;

FIG. 4 is a block diagram of a suppression amount control of the relay.

FIG. 5 is a configuration diagram of a ground fault differential relay according to a conventional example.

FIG. 6 is an explanatory diagram of an operation point movement of a ground fault protection relay.

[Explanation of symbols]

_{G 1, G 2, G a} , G c ... ground fault protection relay .SIGMA.I, MO ... ground detection element I _O th ... zero-phase circulation current I _F ... internal fault current

Claims (2)

[Claims] 1. A terminal provided for two parallel lines,
The difference between the terminal currents of each line is set as the operation amount, and the value obtained by multiplying the sum of the terminal currents of each line by the suppression rate is set as the suppression amount, and the value obtained by subtracting the suppression amount from this operation amount is equal to or greater than a predetermined value. In a ground fault protection relay that outputs an operation when the power supply becomes zero, the zero-phase circulating current several cycles ago is stored in a memory as a vector amount with reference to the line voltage, and stored in the memory from the zero-phase current of each terminal. A ground fault protection relay, wherein a vector amount of a zero-phase circulating current is subtracted to remove a zero-phase circulating current included in the suppression amount. 2. A terminal provided for each of two parallel lines,
The difference between the terminal currents of the respective lines is used as the operation amount, and the value obtained by multiplying the sum of the respective terminal currents of the respective lines by the suppression ratio is used as the suppression amount. A ground fault protection relay that operates and outputs in the event of a fault, a ground fault detection element that operates when the current flowing toward the inside of both lines is equal to or greater than a predetermined value due to the vector sum of the zero-phase currents of both lines at each terminal. And controlling the suppression amount by taking the logical product of the operation output of the ground fault detection element of the power supply terminal and the inverted operation output of the ground fault detection element of the load side terminal. Fault protection relay.