JPS5854574B2 - Protective relay device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protective relay device that protects a multi-terminal power transmission line by focusing on the propagation of traveling waves in the power transmission line.

Current differential methods and phase comparison methods have been proposed as fault detection methods for protective relay devices that protect power transmission lines, but these are all based on the theory of fundamental waves of voltage and current, and the theory that power transmission lines The idea was based on the premise that it would be expressed as a lumped constant circuit.

Therefore, when a transient phenomenon occurs due to a system fault or the operation of a switch, conventional protective relay devices malfunction or malfunction during the transition from the transient state to the steady state. The drawback was that there was a high possibility that it would work.

For this reason, conventional protective relay devices have been provided with time delay characteristics and sacrificed high-speed operation characteristics to prevent the above-mentioned malfunctions and malfunctions.

This invention abandons both of the two premises of conventional protection methods, and considers traveling waves such as voltage traveling waves, current traveling waves, or energy traveling waves on the transmission line by considering the power transmission line as a distributed constant circuit. , attempts to detect faults by focusing on the fact that the propagation of these traveling waves across multi-terminal power transmission lines changes due to faults in the transmission line. This was done for the purpose of detecting difficult high-speed accidents.

The present invention will be described below with reference to a lossless power transmission line.

FIG. 1 shows a two-terminal power transmission line for introducing the basic principle of this invention.

In Figure 1, the power transmission line is shown as a distributed constant circuit with inductance and capacitance of Aye per unit length, and ei(t), 1t(t), ex(t), 1x(t
), e2(t), and 12(t) are the voltage and current of terminal 1 at time t and the voltage and current at a point at distance X from terminal 1, respectively.
These are the current and the voltage/current at terminal 2, and d is the distance between both ends.

Combined by distribution.

The solutions of equations (1) and (2) are already known and are given by.

F(t--) is a traveling wave from terminal 1 to terminal 2, f(t
+-) is a traveling wave traveling from terminal 2 to terminal 1.

The following equation is obtained from equations (3) and (4).

Equation 5) gives the following equation.

For il and i2, the direction of inflow from each terminal is positive.

From soul 6), the following formula can be obtained.

11y12 assumes that the direction of inflow from each terminal is positive.

Therefore, from equations (7), (8), (9), and (10), a relational expression regarding the voltage and current of terminals 1 and 2 is established.

(11), (12)7) The relational expression always holds true unless an abnormality such as an accident occurs inside the power transmission line, and it does not hold only when an accident occurs inside the transmission line, so it is useful for determining internal accidents for the purpose of protection. It is valid.

That is, if we define the quantity using equation (11), when there is an internal fault within terminal 1 and terminal 2, ε1(t) y' O(14) When terminal 1 and terminal 2 are healthy, ε□ (t) = 0 (1
5) There is a relationship.

The presence or absence of an internal accident can be determined using 61(t) of equation (13).

Equation (13) is given as a quantity with dimensions of current, but
By doubling both sides, it can also be given as a quantity having the dimension of voltage.

In other words, it is possible to determine whether there is an internal accident by using ε2(t) given by ε2(t).

FIG. 2 is a block diagram showing an example of a protective relay device based on this principle.

In FIG. 2, 1 and 2 are terminals 1A and 2, respectively. B, , B2 are the busbars connected to terminals 1 and 2,
CT is an instrument current transformer that measures system current, PT is an instrument transformer that measures system voltage, 4 is a current voltage input device, 5
is a delay circuit having a delay time τ, 6 is an arithmetic unit, 7 is a transmitter, and 8 is a receiver.

Next, the operation of this protective relay device will be explained.

At the terminal 1, the currents i1 (t-τ) and el (-τ) measured by CT and PT with time equal to τ are outputted to the current-voltage input device 4.

The current/voltage input device 4 actually has an analog-to-digital conversion circuit, converts the input signal into a digital signal, and outputs the digital signal to the delay circuit 5.

The delay circuit 5 delays the input signal by a time τ and outputs the delayed signal to the arithmetic unit 6.

On the other hand, at terminal 2, the current 12 (0, voltage
e2(t) is measured, and these measured values are sent to the receiving device 8 of the terminal 1 using the transmitting device 7.

The calculation device 6 executes the calculation of equation (13) on the current and voltage at its own end inputted from the delay circuit 5 and the current and voltage inputted at the other end via the receiving device 8, and calculates the calculated value. When the relationship expressed by equation (14) is met, a trip command signal is output to the breaker.

Let us now explain the physical meaning of equations (11) and (12), which are the basic equations for determining internal accidents on which this invention is based.

The left side of equation (11) expresses the traveling wave that enters the power transmission line from terminal 1 at a time of 1 τ in terms of voltage.

On the other hand, the right side of equation (11) expresses the traveling wave flowing out from the terminal 2 at time t in the voltage dimension.

Therefore, comparing both sides of equation (11), the time is 1τ
It is understood that the following shows that the traveling wave traveling from terminal 1 to terminal 2 reaches terminal 2 after time τ.

τ is the propagation time of the traveling wave, and is determined by the distance d between both terminals, %−, and the surge propagation speed V as τ=d/v.

Similarly, equation (12) shows that a traveling wave traveling from terminal 2 to terminal 1 with time τ multiplied by τ reaches terminal 1 after time τ.
This shows that it reaches .

Of course, such traveling wave propagation is realized when there is no internal accident between terminal 1 and terminal 2. When an internal accident occurs, the propagation form of the traveling wave changes and the equation (U↓(12)
will no longer hold true.

This invention aims to protect power transmission lines by focusing on the propagation form of such traveling waves.

The example shown in FIG. 2 uses the above formula (11), and the delay circuit 5 is provided at the terminal 1, but the formula (1)
2), the delay circuit 5 is provided at the terminal 2.

The delay time of the delay circuit 6 is set in consideration of the signal transmission time from the transmitting device 7 to the receiving device 81.

The delay time of the delay circuit shown in FIGS. 4 and 6, which will be described later, is similarly set in consideration of the signal transmission time between terminals.

Furthermore, when the arithmetic unit 6 has a storage function, the delay circuit 5 can be omitted.

Next, the application of the above principle to a multi-terminal power transmission line will be explained.

In the case of multi-terminal transmission lines, Kirchhoff's first law at branch points is utilized.

FIG. 3 shows a two-terminal power transmission line to illustrate the relationship between traveling waves and Kirchhoff's first law.

In FIG. 3, O is a branch point, τ1 is a surge propagation time between terminal 1 and branch point 0, and τ2 is a surge propagation time between terminal 2 and branch point 0.

dl. d2 is the distance from terminals 1 and 2 to branch point 0 and 1, respectively.

Therefore, the surge propagation time τ1pτ2 is 71 = d1
/VyF2=d2/V.

The current flowing from branch point O toward terminals 1 and 2 for a time of 1 m is i.

1(t), 1o2(0, the voltage at branch point 0 is e.

(1), then the equations (8), (1
0), holds true.

Here, Fl is a traveling wave from terminal 1 to branch point O, F2 is a traveling wave from terminal 2 to branch point O, and fl is a traveling wave from branch point O to terminal 1. f2 is a traveling wave from branch point O to terminal 2. It is a traveling wave.

From equations (17), (18), (19), and (20), the current i at the branch point O at time t.

1(t) and 1o2(t) are obtained as follows.

According to Kirchhoff's first law 1 ol(j)+162(t)=0 Therefore, the following identity relation is finally derived.

Equation (23) is based on the time t-τ1. Terminal 1 across j−τ2
, 2 into the transmission line F1 (-τ1) F2
(t-τ2) at time t+τ1. Traveling wave f1 (t+τ1) flowing out from terminals 1 and 2 at j+τ2,
, F2 (t+τ2).

Here, since the surge impedances of both transmission lines are equal, no reflection occurs at the branch point, and Fl(t-τ1)=f2(t
+τ2 ), F2 (−τ2 )=ft(t+τ1
).

Since equation (23) always holds true as long as there is no internal fault between terminals 1 and 2, it is possible to determine whether or not there is an internal fault in the two-terminal power transmission line with equal surge impedance depending on whether this relationship holds.

FIG. 7 is an explanatory diagram of reflection and transmission of a traveling wave applied to point 00 when three power transmission lines with different surge impedances are connected to branch point O.

Figure 7A shows the traveling wave F1 (-τ1) that entered from terminal 1.
) is an explanatory diagram showing reflection and transmission at the 0 point of
As shown in the figure, the transmitted wave to terminal 2°3 is as follows.

Figure 7 shows the traveling wave F2 (t-τ2) entering from terminal 2.
) is an explanatory diagram showing reflection and transmission at the 00 point, and the reflection and transmission as shown are performed.

Regarding the traveling wave F3 (-τ3) entering from the terminal 3, reflection and transmission as shown in FIG. 7 occur at the zero point.

Traveling wave F1 (t-τ
1) Traveling wave F2 entering from terminal 2 at time t-τ2
(t-τ2), the traveling wave F3 (t-τ3) entering from terminal 3 at time 1τ3 is transmitted and reflected at point 0 at time t, and then enters terminal 1 at time t+τ1 at time t+
It reaches terminal 2 at time τ2, reaches terminal 3 at time t+τ3, and flows out from the respective power transmission lines.

A traveling wave f flows out from terminal 1 at time t+τ1.

(t + rl) is the reflected wave of Fl (t - rl), F2 (-τ2) and F3 (t-τ3)
It is a combination of the transmitted waves of , and can be obtained from FIG.

Similarly, traveling wave f2 (
t+τ2) is also the traveling wave f3(
t+τ3) is therefore, the time is 1τ1 t-τ2ttr3jt+τ1
．． t+τ2. For the traveling wave measured at t+τ3, calculate the difference between the left and right sides of equations (26), (24), and (25) above, and if the calculated value is below a certain value, there is no failure, and above the certain value. If so, it can be determined that there is a failure and whether there is a failure in the power transmission line.

When the branch point OVcn transmission lines are connected, the traveling wave FK (t-
τK) is reflected and transmitted at the 0 point as follows.

However, Z K p τ is the surge impedance and surge propagation time of the second transmission line.

Based on the above-mentioned transmitted waves and reflected waves, if three or more power transmission lines with different surge impedances are connected to a branch point and are in a protected area, from the kth transmission line to the time t.
+τ, the traveling wave fK (t+τK) that flows out and the traveling wave Fi (- τi) is obtained.

This equation holds true as long as there is no failure inside the multi-terminal power transmission line.

Therefore, if ε is the difference between both sides of equation (29) (7), it can be determined that there is an internal failure when ε is greater than the set value, and that there is no internal failure when it is smaller than the set value.

It is well known from the theory of transient phenomena that transmission and reflection occur as shown in FIG. 7 and equations (28) and (27).

The principle of the present invention, which protects a multi-terminal power transmission line by focusing on the propagation of traveling waves, has been described above, and the present invention will be explained in detail below.

FIG. 4 is a block diagram showing an embodiment of the protective relay device according to the present invention applied to three-terminal power transmission lines with equal surge impedance.

In Figure 4, 3 is the terminal 3, B3 is the bus bar of the terminal 3,
11, 12, 13 are traveling wave detection devices 21 for detecting traveling waves flowing into the power transmission line from the terminal 1.2.3; 22, 23 are devices for detecting traveling waves flowing out from the terminal 1.2.3;
1, 32, and 33 have delay times T+τ1 and T+, respectively.
Delay circuits 41, 42, and 43 each have a delay time of T-τ1. T-τ2. T-τ3 is a delay circuit, and 9 is a determination circuit.

τ1 is the surge propagation time between terminal 1 and branch point 0, τ2
is the surge propagation time between terminal 2 and branch point 0, and τ3 is terminal 3
and the surge propagation time between branch point 0, T is τ1. τ2. τ3
is a constant that is sufficiently larger than .

Next, the operation of the protective relay device shown in FIG. 4 will be explained.

The traveling wave detectors IL 12, 13 change the time t-τ□ to -τ2. Traveling wave F1 flowing into the transmission line at t-τ3
(-τ1), F2 (t-τ2), F3 (t-τ3)
Detect.

The detection of this traveling wave is carried out by the instrument current transformer CT, the instrument transformer P.
This can be done by introducing the output of T.

On the other hand, the traveling wave detector 21°22.23 detects the time t+τ1
．． t+τ2. Traveling waves fl(t+τ,) f2(t+τ2), f3(t+τ3) flowing out from the transmission line at t+τ3
) is detected.

By substituting the PT output, CT output output, and surge impedance into the left sides of equations (5) and (6), the traveling wave F
, (t-τ1)(1='L2,3)A, and a traveling wave f, (t+τ,)(1=1t2.3) are obtained.

These traveling wave detection devices 11. 12. 13,212
2.23 output is delay circuit 3L 32,33°41.4
2,43.

These delay circuits have different times: -τ1yj−τ2°, −τ3. The detection values detected at t+τ□ and t+τ2tt+τ3 are respectively expressed as T+τ1yT+τ2°T+τ3. T
-τ1. T-τ2? By delaying T-τ3,
It is provided to compare each detection value at the same time t+TKh.

The sum of the outputs of the delay circuits 3132.33, that is, F, (
−τ□) 1F2 (−τ2) 1F3 (t−τ3) are input to the determination circuit 9.

Similarly, the output of the delay circuit 4L 42, 43, that is, f
l(t+τ,), f2(t+τ2) f3(t+τ3) are input to the determination circuit 9.

Since the embodiment shown in FIG. 4 is a three-terminal power transmission line with equal surge impedance as described above, the determination circuit 9 uses the above equations (30), (31),
Calculate the difference between both sides of (32), or each of the above equations (30),
(31).

The difference between both sides of the equation (32) is calculated, and if the calculated value is greater than or equal to the set value, it is determined that there is an internal fault in the power transmission line.

When there is no internal failure in the transmission line, formula (32), (30)
, (31) holds, the verbal expressions (26), (24)
, can be easily understood from (25).

It is clear that a protective relay device for protecting a multi-terminal power transmission line having four or more terminals can also be obtained in the same manner as shown in FIG.

In the above, the present invention has been described in detail with respect to a power transmission line with a constant surge impedance, but protection joints can also be applied to power transmission lines where power transmission lines having different surge impedances are connected to a branch point by focusing on the propagation of traveling waves. electrical equipment can be obtained.

Figure 5 shows the transmission of traveling waves in transmission lines with different surge impedances and two diagrams to illustrate the opposite principle.
This shows a terminal transmission line.

In Fig. 5, Zi j τ1 is between terminal 1 and branch point 0.
Z2 p τ2 is the surge impedance and surge propagation time of the transmission line between terminal 2 and branch point 0, Fl(t-τ
1) is a traveling wave that flows into the power transmission line from terminal 1 at time t-τ1, and F2 (t-τ2) is a traveling wave that flows into the power transmission line from terminal 2 at time t-τ2.

These traveling waves F1 (t-τ1). F2(t-τ2) produces a reflected wave component and a transmitted wave component at branch point 0.

According to equations (28) and (27), the traveling wave F1(t-τ
The transmitted wave components of □) are Fl (−τ1) and 2z2Z2−
Zl z 1 + z 2 ″ product/reflected wave component is F・(trx
) z1+z2.

Similarly, the transmitted wave component of the traveling wave F2 (-.tau.2) and the traveling wave f1 (t+.tau.1) flowing out from the terminal 1 at time t+.tau.1 can be determined by the following equation.

Similarly, the traveling wave f2 (t+τ2) flowing out from the terminal 2 at time t+τ2 is as follows.

Since the above equations (34) and (33) always hold true when there is no internal fault between terminals 1 and 2, they can be used to determine an internal fault in the power transmission line.

FIG. 6 is a block diagram showing an embodiment of a protective relay device according to the present invention that protects a power transmission line using the above relational expression (33).

As shown in Figure 6, 11, 12, 21, 31, 3241
．． 6, 7, and 8 are the same as those shown in FIGS. 2 and 4.

The traveling wave detection device 11 detects the traveling wave F1 (-τ1) flowing into the power transmission line from the terminal 1 at a time of τ1.

The traveling wave detection device 21 detects the traveling wave f1(t+τ□) flowing out from the terminal 1 at time t+τ1, and the traveling wave detecting device 12 detects the traveling wave F2(t+τ□) flowing from the terminal 2 into the power transmission line at time 1τ2. t-F2) is detected.

The delay circuits 31, 32, and 41 are connected to each of the traveling wave detection devices 11 described above.
, 12, 21 respectively as T+τ1. T+τ2t
The output is delayed by T-τ1.

The transmitting device 7 transmits the output of the delay circuit 32 at the terminal 2 to the receiving device 8 at the terminal 1.

The arithmetic unit 6 outputs the output F1 (−τ1) of the delay circuits 31 and 41.
), f.

(t+τ2) and the output F2 of the receiving device 8 (t-τ2)
The calculation of equation (33) is executed based on the time t+Tlc>.

The arithmetic device 6 determines that the power transmission line is healthy if the relationship expressed by equation (33) holds, and determines that an internal accident occurs when the relationship expressed by equation (33) does not hold.

Surge impedance Z1 required for calculation of equation (33)
The value of y Z2 is set in advance in the arithmetic unit 6 as the traveling wave F□ (-τ1) on the right side of equation (33).

The value of F2 (-τ2) can be derived by substituting the output values of the potential transformer PT, the potential current transformer CT, and the surge impedance value into the left side of equation (5).

Similarly, the traveling wave fl(t+τ1) on the left side of equation (33)
is determined by equation (6).

Although Fig. 6 shows a protective relay device that uses equation (33), a protective relay device that uses equation (34) to determine internal faults in power transmission lines can also be configured in the same way as shown in Fig. 6. I can do it.

! Additionally, the device shown in Fig. 6 is intended for a device in which two power transmission lines with different surge impedances are connected to branch point O, but it is also applicable when three or more power transmission lines with different surge impedances are connected to branch point O. A protective relay device that is intended for use with

In other words, when n transmission lines with different surge impedances are connected to a branch point, the difference between both sides of equation (29) is assumed to be ε, and if ε is larger than the set value, an internal failure is set. If it is smaller than the value, it may be determined that there is no internal failure.

As mentioned above, this invention protects power lines by detecting changes in the propagation form of traveling waves due to internal faults in the power line, so the original waveforms of the voltage and current of the grid are used for the first time. It is characterized by what it can do.

The formula (
29), (24), (25), (26), (27), (
28) does not hold for internal faults in the multi-terminal protection section, but always holds for external faults, so it is a perfect method for detecting internal faults in multi-terminal systems.

Therefore, according to the present invention, it is possible to completely prevent malfunctions or malfunctions of the multi-terminal protective relay device due to the effects of surges accompanying the opening and closing of a switch or transient phenomena at the time of an internal accident.

As a result, the drawbacks of conventional protective relay devices can be overcome, and operation can be judged using instantaneous values, making it even better than conventional protective relay devices in terms of high-speed operation performance. A protective relay device is realized.

[Brief explanation of the drawing]

Figure 1 shows a power transmission line using a distributed constant circuit, Figure 2 is a block diagram showing an example of a protective relay device that is the basis of this invention, and Figure 3 explains the propagation form of traveling waves in a two-terminal power transmission line. 4 is a block diagram showing an embodiment of the protective relay device according to the present invention applied to a three-terminal power transmission line, and FIG. 5 is an explanation of reflection and transmission of traveling waves in power transmission lines having different surge impedances. 6 is a block diagram showing an embodiment of a protective relay device according to the present invention that protects power transmission lines having different surge impedances, and FIG. It is an explanatory diagram of transmission and reflection. In the figure, 1, 2.3 are power transmission line terminals, 4 is a voltage/current input device, 5, 31, 32, 33, 41°42.43 is a delay circuit, 6 is an arithmetic device, 9 is a judgment circuit, 11, 12,
13, 21, 22, 23 are traveling wave detection devices, CT is a voltage transformer, PT is a voltage transformer, 0 is a branch point, Fl (-τ, ), F2 (-τ2) are power transmission lines The traveling wave flowing into the transmission line, f, (10τ1), f2(t+τ2) is the traveling wave flowing out from the transmission line, e1(t). e Jt), i 1 (t), and i 2 (t) are the terminal voltage p and terminal current, Zl and z2 are the surge impedance of the power transmission line, and τ1゜τ2 is the surge propagation time of the power transmission line. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. It is detected that the propagation form of a traveling wave propagating through a multi-terminal protected section in which n (n is plural) transmission lines are connected to a branch point X is changed due to an accident in the protected section. In the protective relay device that protects the protection zone, each terminal constituting the boundary of the multi-terminal protection zone is k (k = 1.2...n), and the surge propagation time and surge of each zone kX are The impedances are TK (k=1y 2”n) and ZK (
k = 1 p 2 ""n), set the time at each terminal above one τ, and press the button t + τ, the traveling wave is FK (t - τK),
When fK(t+τK), the protection relay device is characterized in that it calculates six quantities, detects that the calculated value changes due to an accident in the protection area, and protects the protection area.