JPS5923166B2 - Protective relay device - Google Patents

Description

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

Focusing on voltage or current traveling waves that propagate at a finite propagation speed on the protected transmission line, we detect and protect power transmission line accidents by confirming the normal propagation and passage of the traveling wave between both ends of the protected transmission line. Protection schemes have already been proposed.

FIG. 1 shows a two-terminal power transmission line for deriving the traveling wave propagation equation, which is the basic principle of this invention.

In Figure 1, the power transmission line is shown as a distributed constant circuit with an inductance and capacitance of lc per unit length, and el(t), 11(t), ex(t), i1)1e2(t) , 12(t) are the voltage at terminal 1 at time t, the voltage at a point at distance X from voltage terminal 1,
The current and the voltage at terminal 2 are the current, and d is the distance between both ends.

According to the theory of distribution systems, ex(t) and 1x(t) are is combined with

The solutions to equations (1) and (2) are already known and are given by the surge propagation velocity and surge impedance.

is from terminal 1 to terminal 2 A traveling wave heading towards is from terminal 2 to terminal 1 It is a traveling wave heading towards.

is obtained.

The following equation can be obtained from equation (5).

el(t r) +Ztl(t r)"2F(t-
τ) (7) e2(t)-Zi2(t)-2F (t-r)
(8) τ2d/v Surge propagation time 11.12 assumes that the direction flowing from each terminal is positive.

The following equation can be obtained from equation (6).

el(t) Zit(t)=2f(t)
(9) e2(t-r)+Zi2(t-r
)=2f(t) αO)i, ti2 are positive in the direction of inflow from each terminal.

Therefore, the equation (force, (8) , (9) , (10)
Regarding the voltage and current of terminals 1 and 2 from
(t)-Z12(t) αυ et(t)zil(t)=e2(t-r)+zi2
The relational expression (tr) (12) holds true.

The relational expression Uυ, (12+) 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 not effective for determining internal accidents for the purpose of protection. be.

In other words, if we define the quantity using the formula qυ, when there is an internal fault within terminal 1 and terminal 2, et(t)'=O(14) when terminal 1 and terminal 2 are healthy, et(t) −〇 There is the relationship shown in (15).

The presence or absence of an internal accident can be determined using ε1(t) in 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.

That is, ε2(t)””et (t r ) +Ztl (t
Tl )-(e2(t)-Z12(t))
The presence or absence of an internal accident can also be determined using ε2(tK) given by (16).

In this section, we will explain the physical meaning of 2αυ and a, which are the basic formulas for internal accident determination in this invention.

The left side of the equation ←D represents the traveling wave that enters the power transmission line from the terminal 1 at time t-τ in terms of voltage.

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

Therefore, if we compare both sides of 2〇〇, the traveling wave traveling from terminal 1 to terminal 2 on one side is time τ
It is understood that this indicates that terminal 2 will be reached later.

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)' indicates that the traveling wave traveling from terminal 2 to terminal 1 at time t-τ reaches terminal 1 after time τ.

Of course, such propagation of the traveling wave is realized when there is no internal accident between terminals 1 and 2, and when an internal accident occurs, the propagation form of the traveling wave changes and the equation (11) is expressed.
(12+ no longer holds true.

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

By the way, protection devices based on such a principle have so far been mainly considered as digital relays.

This protection method, which originally focuses on the propagation of traveling waves, was proposed in the process of searching for a relational expression that holds true for each instantaneous value under any conditions, such as the presence of charging currents in power transmission lines and the weight of distorted wave components. This is because it was considered to be the optimal principle for digital relays that make fault judgments based on sample values of instantaneous values such as current and voltage.

The formula ←υ holds true as long as there is no internal fault on the protected transmission line, and after acknowledging the existence of appropriate errors such as hardware errors and line constant measurement errors, the judgment is made by setting a corresponding dead band. If implemented, there is no risk of malfunction due to external accidents.

In the case of an accident inside the protected power transmission line, the normal propagation of traveling waves from one end to the other end is interrupted, so the formula ←υ
, 02) no longer holds true.

However, this does not mean that in the case of an internal accident, at any time t, eI Ct −r )+Z il (t −r )＼e
2(t)-Z 12(t)el(t)-z i 1(t
)'+e2 (t-r)+Zi2(-τ).

In other words, for a certain instantaneous value, even in the event of an internal fault, the 2αυ side can be established instantaneously.Therefore, in a digital relay that judges a fault based on a sample value of the instantaneous value, 2〇〇, ( It is necessary to judge an accident based on whether or not the relationship 12) holds true for not only one sample value but many sample values.
If the instantaneous establishment of 2) occurs in synchronization with each sample value for determination, there is a drawback that an internal accident cannot be detected no matter how many times the sample values are determined.

This is an essential problem associated with judgment based on sample values, and since equations (11) and (12) do not necessarily hold true in the event of an internal accident, we monitor the holding of 200 and α2 continuously over time. If you do, you can avoid these problems.

The present invention has been made in view of this point, and proposes an analog traveling wave differential protection relay.

The present invention will be explained below based on the above matters.

FIG. 2 is a block diagram showing an embodiment of the protective relay device according to the present invention, which eliminates the need for delay circuits when the speed of the traveling wave propagating on the power transmission line and the propagation speed of the information transmission path can be made equal. This is an analog traveling wave differential protection device.

In Fig. 2, 3 is a traveling wave detection device, 4 is an information transmission device, 5 is a transmission line, 6 is a traveling wave regeneration circuit, 7 is a subtraction judgment circuit, 8 is a timer, 9 is a power transmission line, and CT is a power transmission line PT is a voltage transformer that derives the voltage of the power transmission line 9.

The traveling wave that leaves terminal 2 at time t-τ propagates on the power transmission line and reaches terminal 1 after a certain time τ.

At the terminal 2, the traveling wave detection device 3 generates the amount of traveling wave from the amount of current and the amount of voltage based on equation (10), and sends it to the terminal 1 via the information transmission device 4 and the transmission line 5.

As such a transmission line 5, an analog optical transmission line such as an optical fiber is used, and the detected value of the traveling wave is transmitted as an optical signal.

At this time, assuming that the time required for converting an electrical signal to an optical signal and its inverse conversion can be ignored, the traveling wave component extracted at terminal 2 propagates on the optical fiber transmission path for a certain propagation time and reaches terminal 1. reach.

In the case of an overhead power transmission line, the propagation speed of a traveling wave is almost equal to the speed of light, and the propagation speed of an optical signal propagating within an optical fiber is also close to the speed of light in a vacuum, so the signal reaches terminal 1 through the transmission line made of optical fiber. It is possible to directly compare the detected value of the traveling wave with the traveling wave propagated through the overhead wire extracted at the terminal 1 at that time without time adjustment.

Therefore, as shown in FIG. 2, the traveling wave component extracted at terminal 1 (propagated from terminal 2 to terminal 1) and the transmission line 5
By directly introducing the traveling wave component of the terminal 2 transmitted through the terminal 2 into the subtraction determination circuit 7 having a subtraction function, it is possible to test the propagation of the traveling wave in equation (13).

That is, if the difference between the traveling waves at both ends is below a certain set value level, the power transmission line is healthy, and if the set value is exceeded by the operating time of the timer 8 or more, it is determined that there is an internal fault in the power transmission line 9.

Judgment using such an analog circuit has higher reliability than judgment based on sample values, and has the effect of reliably detecting internal accidents.

Figure 3 shows the propagation time of the traveling wave and the transmission line 5 in Figure 2.
FIG. 3 is an explanatory diagram showing the transmission delay time.

In FIG. 3, the solid line is from terminal 2 to terminal 1 on power transmission line 9.
The broken line shows the information transmission on the transmission path 5.

The transmission delay time of the transmission path 5 is τ, which coincides with the propagation time of the traveling wave.

In Figure 2 above, the propagation time of the traveling wave is the same as the transmission delay time of the transmission line, but depending on the transmission line, the propagation speed of the traveling wave may be slow, and depending on the transmission line, the transmission delay time may be the same. Therefore, it may be necessary to time-coordinate the transmission delay time of the information transmission path between the terminals and the propagation time of the traveling wave.

For example, in the case of an underground power transmission line, the propagation speed of a traveling wave is about half to one-third of the speed of light, and the detected value of the traveling wave transmitted from terminal 2 to terminal 1 through the information transmission path as described above is It is possible that the traveling wave actually reaches the terminal 1 earlier than the traveling wave actually propagating through the wire.

On the other hand, in the case of overhead power transmission lines, traveling waves propagate at the speed of light, while if we consider that relay transmission is performed using a micro circuit as an information transmission line, the arrival of the traveling wave component transmitted through the information transmission line is slow. There may be delays.

In either case, when implementing traveling wave differential, time adjustment using a delay circuit or the like is required.

In this case, there are cases in which a delay circuit is required when transmitting information from one end of the eye to the other end, and there are cases in which a delay circuit is required for the traveling wave component transmitted from the other end.

FIG. 4 is a block diagram showing another embodiment of the protective relay device according to the present invention, in which the transmission delay time of the transmission path is shorter than the propagation time of the traveling wave.

In FIG. 4, 10 is a delay circuit.

Other symbols are the same as those in FIG.

The propagation time of the traveling wave between terminal 1 and terminal 2 is τ, and the propagation delay time of the transmission line 5 is t.

When , the delay time of the delay circuit 10 is τ-t.

is set to

The detected value of the traveling wave traveling from terminal 2 to terminal 1 detected at terminal 2 at one time is the transmission line 5 and the delay circuit 1.
The signal is delayed by 0 and input to the subtraction determination circuit 7 at terminal 1.

The time delay in the transmission line 5 and delay circuit 10 is t1+τ-
i,=τ, which coincides with the propagation time τ of the traveling wave.

On the other hand, the traveling wave detected at the terminal 1 at time t is also input to the subtraction determination circuit 7.

The subtraction determination circuit 7 determines whether the relationship of equation 02) holds for the traveling waves at both ends.

If the difference between the traveling waves at both ends exceeds a certain value and continues for longer than the operating time of the timer 8, it is determined that an internal accident has occurred between terminal 1 and terminal 2.

FIG. 5 is an explanatory diagram showing the relationship between the propagation time τ of the traveling wave and the transmission delay time t1 of the transmission line 5 in FIG.

In FIG. 5, a solid line indicates propagation of a traveling wave from terminal 2 to terminal 1, and a broken line indicates information transmission through transmission line 5. In FIG.

Since there is a difference between the transmission delay time t1 of the transmission path 5 and the propagation time τ of the traveling wave, the difference τ−t1 is set as the delay time of the delay circuit 10, thereby measuring time coordination.

In FIG. 4, if the transmission delay time t1 of the transmission path 5 and the propagation time τ of the traveling wave are equal, the delay circuit 10 is unnecessary, and the result is consistent with FIG.

In short, the protective relay device shown in FIG. This delay is the same as the wave propagation time τ.

Therefore, the delay circuit 10 may be provided anywhere between PT and CT of the terminal 2 and the subtraction determination circuit 7 of the terminal 1.

FIG. 6 is a block diagram showing another embodiment of the protective relay device according to the present invention.

4 shows the case where the transmission delay time of the transmission line 5 is shorter bA than the propagation time of the traveling wave, whereas FIG. 6 shows the case where the transmission delay time is longer than the propagation time of the traveling wave.

In this case, the delay circuit 10 is provided to delay the detected value of the traveling wave that has arrived from the terminal 2 to the terminal 1, and the delay time is determined by the transmission delay time t1 of the transmission path 5 and the propagation time τ of the traveling wave. The difference between t1 and τ is set to t1−τ.

Other points are the same as those in FIG. 4.

Figure 7 shows the propagation time of the traveling wave and the transmission line 5 in Figure 6.
FIG. 3 is an explanatory diagram showing the transmission delay time.

In FIG. 7, a solid line indicates propagation of a traveling wave from terminal 2 to terminal 1, and a broken line indicates information transmission through transmission line 5. In FIG.

Since there is a difference between the transmission delay time t1 of the transmission path 5 and the propagation time τ of the traveling wave, the difference t1−τ is set as the delay time of the delay circuit 10.

FIG. 8 is a block diagram showing another embodiment of the protective relay device according to the present invention.

The protective relay devices shown in Figs. 2, 4, and 6 convert the detected value at terminal 2 of the traveling wave from terminal 2 to terminal 1 to the other terminal 1.
In contrast, the one shown in Figure 8 is
The detection value at terminal 1 of the traveling wave that has arrived from terminal 2 to terminal 1 is transmitted to the other terminal 2.

The delay time of the delay circuit 10 in FIG. 8 is set to the sum τ+t1 of the propagation time τ of the traveling wave and the transmission delay time t1 of the transmission line 5.

The subtraction determination circuit 7 calculates the difference between the traveling waves at both ends.

When this difference is greater than a certain value and continues for longer than the operating time of the timer 8, it is determined that an internal accident has occurred between terminal 1 and terminal 2.

Figure 9 shows the propagation time of the traveling wave and the transmission line 5 in Figure 8.
FIG. 3 is an explanatory diagram showing the transmission delay time.

A solid line indicates propagation of a traveling wave from terminal 2 to terminal 1, and a broken line indicates information transmission through transmission line 5.

After the traveling wave reaches terminal 1 from terminal 2, the detected value of the traveling wave at terminal 1 is transmitted to the other terminal 2 and compared with the detected value at terminal 2.

Therefore, at terminal 2, it is necessary to delay the detected value of the traveling wave by τ+t1, and for this reason, the delay time is τ+t1.
A delay circuit 10 is provided.

In the explanation of FIGS. 2, 4, 6, and 8 above, time delays in the traveling wave detection device 3, information transmission device 4, and traveling wave regeneration circuit 6 were ignored, but these time delays are ignored. If this is not possible, the total delay time of the transmission line 5, traveling wave detection device 3, information transmission device 4, and traveling wave regeneration circuit 6 is newly set as the transmission delay time t1 in the above drawing, and the delay time of the delay circuit 10 is set. All you have to do is do it.

As described above, the protective relay device according to the present invention focuses on the fact that the traveling wave that propagates between the terminals of a power transmission line with a predetermined propagation time is preserved unless there is an internal accident between the terminals,
Continuously compare the value when the traveling wave passes its own end and the value when it reaches the other end, and if the difference between the detected values of the traveling wave at both ends is greater than or equal to a certain value for a predetermined period of time, an internal accident has occurred. Since it is determined that there is an accident, the reliability of accident determination is higher than the digital method that compares instantaneous sample values many times, and internal accidents can be detected reliably.

[Brief explanation of drawings]

FIG. 1 is a power transmission line shown by a distributed constant circuit, and FIG. 2 is a block diagram showing an embodiment of a protective relay device according to the present invention.
FIG. 3 is an explanatory diagram of the propagation time of the traveling wave and the information transmission time of the transmission line in FIG. 2, and FIG. 4 is a block diagram showing another embodiment of the protective relay device according to the present invention. 5 is an explanatory diagram of the propagation time of the traveling wave and the information transmission time of the transmission line in FIG. 4, and FIG. 6 is a block diagram showing another embodiment of the protective relay device according to the present invention. 7 is an explanatory diagram of the propagation time of the traveling wave and the information transmission time of the transmission line in FIG. 6, FIG. 8 is a block diagram showing another embodiment of the protective relay device according to the present invention, and FIG. FIG. 9 is an explanatory diagram of the propagation time of the traveling wave and the information transmission time of the transmission path in FIG. 8; In the figure, 1 and 2 are power transmission line terminals, 3 is a traveling wave detection device, 4 is an information transmission device, 5 is a transmission line, 7 is a subtraction judgment circuit, 8 is a timer, 9 is a power transmission line, and 10 is a delay circuit , CT is a potential current transformer, PT is a potential transformer, τ is a propagation time of a traveling wave, and tl is a transmission delay time. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a power transmission line in which the propagation time of a traveling wave from one end to the other end is τ, the analog waveform value of the traveling wave departing from the own end at a time of τ is defined as a first means for transmitting to the other end via a transmission line having a transmission delay time equal to the propagation time; and detecting an analog waveform value of the traveling wave at the other end at time t while propagating through the transmission line. a protective joint comprising a second means and a third means for comparing each output of the first and second means and determining an internal accident in the power transmission line if the deviation exceeds a set value for a predetermined time or more; Electrical equipment. 2 In protecting a power transmission line whose propagation time of a traveling wave from one end to the other end is τ, the analog waveform value of the traveling wave departing from its own end at time t-τ is converted to a transmission delay time tl.
a first means for transmitting to the other end via the transmission line, a second means for propagating the power transmission line and detecting the analog waveform value of the traveling wave at the other end at time t, and the propagation time and the first or second of the above transmission delay times, whichever is shorter.
A third means provided in the means for delaying the traveling wave by 1τ-111 hours, and each output of the first and second means is compared through the third means, and the deviation is determined from the set value by a predetermined time. and a fourth means for determining an internal accident in the power transmission line if the power transmission line is exceeded. 3. In a device for protecting a power transmission line in which the propagation time of a traveling wave from one end to the other end is τ, a first means for detecting an analog waveform value of the traveling wave departing from the own end at time t-τ; , a second means for propagating the power transmission line and transmitting the analog waveform value of the traveling wave at time t at the other end to the own end via a transmission line having a transmission delay time of 11; a third means provided in the means for delaying the traveling wave by τ+t1 time, and comparing the output of the second means and the output of the first means via the third means, and the deviation thereof determines a predetermined integer constant. and fourth means for determining an internal accident in the power transmission line if the time exceeds the time limit.