JP3396496B2 - DC power transmission protection relay - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay device for a DC power transmission line.

[0002]

2. Description of the Related Art Conventionally, for example, the one disclosed in Japanese Examined Patent Publication No. 63-14564 (Patent No. 1469929) has been used to protect a DC transmission line. This is a phenomenon peculiar to DC transmission lines.At the time of an internal fault in the transmission line, the current at the terminal on the forward converter side increases and the current on the terminal on the inverse converter side decreases, and this is detected to increase the speed. It protects power lines. In addition,
Differential protection is also used, which sends out a protection output when the magnitude of the current difference between both terminals exceeds a certain value.
This avoids unauthorized response due to transient phenomena immediately after the accident, and therefore high-speed operation cannot be expected.

[0003]

[Problems to be Solved by the Invention] That is, the conventional protection of a DC transmission line is a device that quickly responds to a transient phenomenon after an accident (such as the one described in Japanese Patent Publication No. 63-14564) and after the transient phenomenon stabilizes. It is implemented complementarily by two combinations with a differential protection device for protection. However, this is not preferable because the protection device becomes complicated.

The present invention has been made in view of the above circumstances, and an object thereof is to realize a protection operation, which has been conventionally complemented by two protection apparatuses, with a simple apparatus and highly accurately by a newly proposed protection algorithm. To do.

[0005]

According to the present invention, a protection interlocking signal is transmitted when the operation amount I _d is larger than the suppression amount I _r (strictly, when it is larger than the relay sensitivity k ₀ ). The relay device has the following features.

[0006] [1] Operation amount Id are electric quantity derived by the following equation from the pair land potential VL of the current Ia, Ib and DC transmission lines of the protected DC transmission line Ryotanshi (or operation amount).

[0007]

[Equation 1] Here the third term is a counter locations charging current of the DC transmission line, short transmission lines and Ke - this third term so negligible if without the table section is not required. [2] The suppression amount Ir is the current I of both terminals of the protected DC transmission line.
It is the amount of electricity (or amount of calculation) derived from a and Ib by the following equation.

[0008]

## EQU2 ## I _r = max {ΔI _a , ΔI _b } (2)

Here, ΔI _a is _a change current of the terminal current I _a , and represents, for example, the amount of change in current for 10 ms (corresponding to a half cycle in a 50 Hz system). Similarly, ΔI _b is a change current of the terminal current I _b . Therefore, the larger the change in current, the larger the suppression amount, and the smaller the change, the smaller the suppression amount. Further, max {ΔI _a , ΔI _b } is the amount of suppression which is larger of the two change currents ΔI _a and ΔI _b .

[0010]

Next, the operation of the present invention will be described. In such a protective relay device, it is most important to distinguish between internal accidents and external accidents. This identification is made mainly by the magnitude of the motion amount Id. Below are the relational expressions for external and internal accidents.
Indicates.

That is, formula (A) shows an external accident,
Equation (B) shows an internal accident.

[Equation 3]

I f ≠ 0 (I f is the fault current),
The identification is made by the size of Id. However, when an actual accident occurs, vibration occurs due to the inductance of the transmission line itself and the capacitance between the transmission line and the ground, and under the influence of these harmonic components, it transiently (decays with time) despite an external accident. Error difference current I
dε occurs. Since the error difference current Idε becomes the operation amount as it is, it tends to be an unnecessary operation as it is.

In the present invention, unnecessary operation is avoided by using the following suppression amount, and the above error difference current I _d ε is due to electric vibration of the transmission line at the time of accident. In this case, the currents I _a and I _b at both terminals oscillate simultaneously. In addition, the magnitude of this vibration depends on the error difference current I
_It can be said that it has the same tendency as the magnitude of _d ε. Therefore, it is possible to cancel the above error difference current I _d ε by making the magnitudes of the currents ΔI _a and ΔI _{b corresponding} to the changes in both terminals / currents participate in the suppression amount.

Specifically, the maximum values max {ΔI of the changes ΔIa, ΔIb of the currents Ia, Ib at both terminals are set.
By setting a, ΔIb} as the suppression amount Ir, a suppression amount that cancels the error difference current Id ε due to the vibration after the accident occurs is generated. Here, the reason why the maximum value is taken is to obtain a certain amount of suppression and the same operation when the operation determination is performed by different devices installed at both ends of the power transmission line. From the above, it becomes possible to satisfy Idε <Ir, and the relay does not operate at the time of an external accident. On the other hand, in an internal accident, Id ≈ If, which is large, and the above-mentioned suppression amount Ir does not hinder the operation. Note that the ≅ marks are symbols that mean that they are almost equal.

[0015]

EXAMPLES Next, examples of the present invention will be described.

FIG. 1 shows an embodiment of the present invention.
Are DC transmission lines, 3A and 3B are DC reactors, 4A and 4
B is a forward and reverse converter, 5A and 5B are AC systems linked to a DC power transmission system, 6A and 6B are DC current transformers, 7A and
Reference numeral 7B is an input converter, 8A and 8B are transmission devices that transmit the amount of electricity proportional to the terminals of their own terminals to the other terminal, and 9A and 9B are transmission devices that receive the amount of electricity that is proportional to the terminal current of the other terminals. , 10A, 10B are relays for making an operation determination with the outputs of 7A and 9A or 7B and 9B as inputs, and are connected as shown in the figure. Although not shown, the ground potential V _L of the DC transmission line is introduced into 10A and 10B from the DC transformer, respectively.

FIG. 2 is a block diagram of the relay shown by the above 10A of the present invention. In the figure, 11A is an operation amount synthesizing unit, 12A is a suppression amount synthesizing unit, 13A is a judging unit, and k ₀ is a relay sensitivity. . Ten
The configuration of B is similar, but is omitted here. Next, the operation of the embodiment of the present invention will be described.

The current I _{A at the} A terminal is transmitted to the relay 10B at the B terminal through the input converter 7A, the transmission device 8A, and the transmission device 9B, and at the same time is transmitted to the relay 10A at the self terminal (A terminal). Similarly current I _B is also input transducer 7B terminal B, the transmission apparatus 8B, are transmitted to the relay 10A of the terminal A through a transmission device 9A, it is also transmitted to the relay 10B of the own terminal (B terminal) at the same time. Therefore, the relays 10A and 10B are always introduced with the current values of the self-end and the mating terminal. When an accident (internal accident) occurs in the power transmission line 1 in such a state, a relatively large damped oscillating current is generated in addition to a large difference current. FIG. 3A shows the tendency of the envelope of the oscillating current in this case with respect to the operation amount I _d and the suppression amount I _r . In this case, I _d >> I _r , and the relay can operate stably. Is. The >> mark is a symbol that means that I _d is much larger than I _r . Further, the suppression amount I _r is due to the oscillating current, and if the protection interlocking does not work and the internal accident continues for some reason, I _r → 0 and the relay I _d > k ₀ (k ₀ is the sensitivity of the relay), that is, the differential current is equal to or higher than the sensitivity of the relay (generally, there is a so-called differential current for the current margin), and the operation continues continuously.

When an accident (external accident) occurs outside the power transmission line 1, a difference current is generated in this case, but it is small. In addition, a relatively large damped oscillating current is simultaneously generated.
FIG. 3B shows the tendency of the envelope curve of the oscillating current in this case with respect to the operation amount I _d and the suppression amount I _r . In this case, I _d <I _r , and the relay is stably positive and negative. Become.

As described above, according to the above embodiment, the internal / external accident of the DC transmission line is correctly identified, and the high speed protection is performed. Even if it continues, it is possible to continuously output the operation output even after the transient phenomenon disappears.

The present invention is not limited to the above-mentioned embodiment, and can be applied not only to the two-terminal power transmission line but also to the protection of a multi-terminal power transmission line having three or more terminals. For example, in the protection of the three-terminal power transmission line. , Processing of the third terminal instead of the equation (1) I
_{with c}

[0022]

[Equation 4] Instead of the equation (2), the conversion component ΔI _c of the current at the third terminal is used.

[0023]

## EQU5 ## Needless to say, I _r = max {ΔI _a , ΔI _b , ΔI _c } (2) ′ can be easily expanded to n terminals. Further, the charging current compensation may be performed by another known method instead of the equation (1) and the equation (1) ′.

Next, a second embodiment will be described with reference to FIGS. 4 and 5. In addition to the previous embodiment, this embodiment further includes
A means is provided for forcibly switching the suppression amount I _r to zero when it is judged that an internal accident has occurred. FIG. 4 is a flowchart of the determination process in the relay of this embodiment.

As shown in the flowchart of FIG. 4, first,
14 blocks fetch the self-end current, voltage and other end current into the calculation processing unit, 15 blocks calculate the difference current, and 16 blocks calculate the charging current compensation amount. In block 17, the operation amount I _d is calculated using the charge current compensation amount with the difference current calculated in 15 and 16. Next, in this embodiment, it is determined in 18 blocks whether or not the relay is operating at the present time, and when the relay is not operating normally or at the time of an external accident, the suppression amount I _R is calculated in 19 blocks. When it is determined that the relay has operated once during an internal accident, the routine proceeds to a routine in which the suppression amount I _R is forcibly set to zero in 20 blocks. When the suppression amount I _R is obtained at 19 or 20, the judgment calculation is performed in the block at 21 by the above judgment formula, and as a result, the relay operation or the reset is set. FIG. 5 shows the changes over time in the operation amount I _d and the suppression amount I _{R at} the time of an internal accident.

Even if the fault current oscillates immediately after the occurrence of the internal accident as shown in FIG. 5B, in the present embodiment, the relay is temporarily operated with a sufficient operation amount I _d at the time of the internal accident as shown in FIG. 5A. When operated, the suppression amount I _R is controlled to zero, so that the suppression amount I _R is suppressed even if a transient vibration of the operation amount I _d immediately after that occurs.
Does not exceed the operation amount I _d , and stable relay operation can be obtained. Further, in the event of an external accident, a large suppression amount I _R is obtained as before, and the relay does not malfunction.

Also, in the present embodiment, the two-terminal power transmission line having the charging current compensation has been described, but the presence or absence of the charging current compensation is not the essence of the present invention, and the calculation of the charging current compensation is performed by another known method. You may implement. Regarding the number of terminals,
Of course, it can be applied to protection of a multi-terminal transmission line having three or more terminals. 6 and 7 for the third embodiment.
Will be described with reference to.

[0028] This example, relay - focused on sensitivity k _0, i.e. relay - current becomes Moto select the sensitivity k ₀ Ma - gin Noting that vary by the DC line voltage, relay - DC sensitivity It changes according to the line voltage.

FIG. 6 is a diagram showing the control characteristics of DC power transmission. The characteristic a shows the characteristic of the rectifier (REC) operation, and the characteristic b shows the characteristic of the inverse converter (INV) operation. The intersection of these two characteristics shows the operating point of DC power transmission at that time.

In the case of a ground fault of the DC line, the line voltage becomes almost zero, so the operation of DC power transmission is RE
Since the C operation is operated at the operating point c and the INV operation is performed at the operating point d, the current difference Id = ia + ib has a large current fluctuation transiently, but is finally called a current margin ΔI. Become ₁ . (Conventionally, the minimum sensitivity of the current differential relay in this case was set to ΔI _1/2 .) By the way, this ΔI obviously changes depending on the DC line voltage V _L , that is, ΔI is Function of DC line voltage, ΔI =
f ( _VL ).

Therefore, in this embodiment, as shown in FIG. 7, a sensitivity setting section for inputting a DC line voltage and changing the relay sensitivity.
24 is provided. Thus, for example, in the case of a high resistance ground fault, the DC line voltage V _L does not drop so much. Therefore, the time of V _L sensitivity from ΔI for k ₀₂ = f (V
_L2 ) = ΔI / 2 is calculated. That is, from the relationship of ΔI ₂ <ΔI ₁ , k ₀₂ <k _{01 and the} accident detection becomes high.

[0032]

As described above, according to the present invention, the protection operation which has conventionally been complemented by the two protection devices,
It is possible to realize with high accuracy and high sensitivity with one simple device.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a protection device for a DC power transmission line of the present invention.

FIG. 2 is a configuration diagram of a current differential relay of the present invention.

FIG. 3 is a diagram showing changes over time in the envelopes of the movement amount and the suppression amount at the time of internal / external accident.

FIG. 4 is a flowchart of a determination process of a protection device for a DC power transmission line according to a second embodiment.

FIG. 5 is a diagram showing temporal changes in the operation amount and the suppression amount at the time of an internal accident of the second embodiment.

FIG. 6 is a diagram showing a relationship between control characteristics and relay sensitivity of DC power transmission according to a third embodiment.

FIG. 7 is a configuration diagram of a current differential relay according to a third embodiment.

[Explanation of symbols]

1, 2 ... DC power transmission lines 3A, 3B ... DC reactors 4A, 4B ... Forward / inverse conversion devices 5A, 5B ... AC systems 6A, 6B ... DC converters 7A, 7B ... Input converters 8A, 8B ... Transmission device (transmission) ) 9A, 9B ... transmission device (reception) 10A, 10B ... relay 11A ... operation amount combining unit 12A ... suppression quantity synthesis section 13A ... determining unit 24 ... sensitivity setting unit k ₀ ... relay - sensitivity

─────────────────────────────────────────────────── --- Continuation of front page (72) Inventor Hideo Takeda 1-1-1 Shibaura, Minato-ku, Tokyo Inside Toshiba Headquarters office (56) Reference JP-A-59-70118 (JP, A) JP JP-A-55-131229 (JP, A) JP-A-60-2016 (JP, A) JP-A-59-149718 (JP, A) JP-A-59-149719 (JP, A) JP-A-59-149720 (JP , A) JP-B 1-18645 (JP, B2) JP-B 1-21683 (JP, B2) JP-B 1-13292 (JP, B2) JP-B 63-61854 (JP, B1) JP-B Sho 63-66131 (JP, B1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02H 3/26-3/30 H02J 1/00

Claims (5)

(57) [Claims] 1. A DC power transmission line protection system for a DC power transmission system, comprising: a forward conversion device for converting AC power to DC power; and a reverse conversion device for transmitting the DC power to a power receiving end through a DC power transmission line and converting it to AC power. In the relay device, the direct current
A transmitter that mutually transmits the current of each terminal of the power transmission line to the other end
Stage and the difference current between the currents at each terminal of the DC transmission line
The amount of movement composition means and the predetermined time of the current at each terminal
Suppression amount that is obtained by obtaining a value proportional to the amount of change in
Synthesizing means, and the operation amount is provided in the suppression amount and the terminal
When it is larger than the sum of the relay sensitivity of the relay
A determination means for determining a DC transmission line accident;
If the means determines an accident, the forward conversion device and the reverse conversion device
Control signal output that outputs a control signal to stop the device
Protective relay device of the DC transmission line, characterized by comprising a force means. 2. The suppression amount according to claim 1,
The maximum value among the changes calculated from the current of
A protective relay device for a DC power transmission line, which is characterized in that 3. The calculation of the suppression amount according to claim 1,
When it is judged that the accident is within the section, the suppression amount is forced to zero.
And zero control means for switching to
Protective relay for DC transmission lines. 4. A forward conversion device for converting AC power into DC power.
And transmit this DC power to the receiving end through the DC transmission line.
DC transmission system equipped with an inverse converter that converts the AC power to AC power.
Stem DC transmission line protection relay device,
A transmitter that mutually transmits the current of each terminal of the power transmission line to the other end
Stage and the difference current between the currents at each terminal of the DC transmission line
The amount of movement composition means and the predetermined time of the current at each terminal
Suppression amount that is obtained by obtaining a value proportional to the amount of change in
Synthetic means and relay feeling of relays provided at each terminal
Sensitivity setting means for changing the degree according to the DC line voltage,
A protective relay for a DC power transmission line, comprising: a determination unit that determines and outputs an internal accident when a value obtained by subtracting the suppression amount from the operation amount is larger than the relay sensitivity set by the sensitivity setting unit. apparatus. 5. The protective relay device for a DC power transmission line according to claim 4, wherein the sensitivity setting means reduces the sensitivity when the DC line voltage is high.