JPS5930014B2 - Phase comparison transport protection relay system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection system for multiple faults across both four lines of a phase comparison relay device.

As a protective relay device for an important power transmission line such as the so-called main power transmission line of an electric power system, a high-speed operation, highly reliable carrier protection relay device with excellent protection performance is generally employed.

In particular, for ultra-high-voltage and ultra-super-high-voltage power transmission lines, a general transmission protection device that compares the phases of each phase is used, which can apply a multiphase reclosing method that selectively cuts off only the faulty phase and recloses the circuit at high speed.

This phase comparison carrier protection relay device correctly responds to and eliminates accidents between the terminals of the line in which it is installed, and conventional devices were able to respond correctly to various accidents within their protection responsibilities.

However, it was newly discovered that the system was malfunctioning due to an accident on an adjacent line, which was not originally under its protection responsibilities.

This phenomenon will be explained.

This is a parallel two-line power transmission line in which a phase-comparison, protection relay device for each phase is installed at each terminal, and it became a problem when an accident occurred on both lines at the same time.

At this time, the phase comparison relay device operates, and the circuit breaker of only the fault phase is tripped for all four terminals, the fault is removed from the system, and after the re-closing no-voltage period, the circuit breaker that was tripped is closed again. .

At this time, if Line 1 is in an arc accident and Line 2 is in a permanent accident, the fault in Line 2 will continue due to reclosing, so the phase comparison relay will detect this and issue an output. The circuit breakers at both terminals are then tripped again for all three phases, regardless of the fault phase, to remove the fault from the system.

However, Line 1 was cut off by the phase comparison relay due to an arcing accident, and the accident disappeared and the circuit was successfully reclosed.
It should be possible to continue stable operation.

However, as will be explained in detail later, conventionally, a continuous trip permission signal (hereinafter referred to as continuous F2 signal) is sent to the other end during the breaker open period, so the phase comparison relay device has not yet recovered when the breaker is reclosed. I haven't.

Then, because the voltage has dropped due to a permanent fault on the adjacent line, the undervoltage relay is also in operation, and the re-closing failure detection condition for line 1 is met, and at the same time as line 1 is reclosed, it is cut off again like line 2. become.

In other words, originally two-line operation becomes one-line operation, but the grid connection between both terminals is maintained and power supply is supposed to continue, but an accident occurs on both lines at the same time, causing a single-line arc accident. In the case of a permanent single-line fault, as long as the conventional phase comparison carrier protection relay device is installed, both circuits will be cut off and the system will be unnecessarily divided, resulting in a significant drop in system reliability.

The present invention was made in view of these newly discovered problems, and an object of the present invention is to solve the problem by allowing the phase comparison relay to be restored more quickly than the circuit breaker has to be turned on again.

Specifically, the above-mentioned time relationship is satisfied by controlling the carrier from the power source side to the F1 signal and determining the time corresponding to the opening of the circuit breaker.

An embodiment of the present invention will be described below.Prior to that, the operating principle of the phase comparison transport protection relay system for each phase will be explained with reference to FIGS. 1 and 2, and the conventional continuous F2 signal control circuit with reference to FIG. I will explain.

FIG. 1 shows a power system in which a phase comparison relay 7 is installed, and the phase comparison relays are installed at an electric station A and an electric station B.

Items common to both electrical stations are designated by the same reference numerals.

Reference numeral 1 indicates a busbar, and reference numeral 2 indicates a generator behind the power station. When a fault occurs on the power transmission line, the fault current is supplied from this generator.

The busbars 1 of electric stations A and B are interconnected by a power transmission line 5 via a circuit breaker 4, respectively.

When an accident occurs on the power transmission line 5, the relay side current 6 proportional to the fault current flowing through the power transmission line 5 is guided by the current transformer 3 installed at both electric stations to the phase comparison relay 7, and the output circuit 11 of 7 The circuit breaker 4 is opened.

The current 6 guided to the phase comparison relay 7 is converted from a sinusoidal alternating current into a rectangular wave by a rectangular wave shaping circuit 8 inside the phase comparison relay.

The relay side currents 6A and 6B detected at both electric stations have the same polarity when a passing current occurs in the event of an external fault as shown in FIG. 2a.

In the phase comparison relay that is treated as the power supply end of electric station A, the rectangular wave made of a positive half wave that exceeds level LH becomes a trip-permissible phase signal (hereinafter referred to as F2 signal), and the other sections are tripped. This becomes a lock phase signal (hereinafter referred to as F1 signal).

In addition, in the phase comparison relay that is treated as a variable power supply terminal at electric station B, the rectangular wave created by the current on the side that includes zero from level LL becomes the F2 signal, contrary to the power supply terminal, and the other sections are F1. It becomes a signal.

The phase signal generated by the rectangular wave shaping circuit 8 is guided to the matching circuit 9 (actually, it passes through a circuit that compensates for the transmission delay time until the phase signal transmitted from the other end reaches the matching circuit 9 at the other end). is omitted here for the sake of brevity), and is simultaneously transmitted to the transmitter 13 of the information transmission device 12, and generally further transmitted to the receiver 14 of the other end information transmission device 12 via the microwave line 15. Ru.

On the other hand, in the same way, the other end phase signal sent from the transmitter 13 of the other end information transmission device 12 through the microwave line 15 passes through the receiver 14 of the information transmission device 12 at the other end, and then passes through the phase comparison relay 7. It is introduced into another input of the matching circuit 9.

In the matching circuit 9, an AND signal of the F2 signals at both ends is created,
If this magnitude is measured by the next integrating circuit 10 and is large enough to be determined as an internal accident to be protected (generally 60 degrees) or more, the output circuit 11 issues a command to trip the circuit breaker 4.

Although only one set of phase comparison relays is shown in FIG. 1, it is actually A.

It is installed for each of the B and C phases, and the above-mentioned operation is performed independently for each phase.

Next, referring to FIG. 2, the response of the device shown in FIG. 1 to a system accident will be explained.

Components in FIG. 2 that are the same as those in FIG. 1 are designated by the same reference numerals.

Figure 2a shows the response to an accident outside the protected area, and as shown, the accident point F is outside the electrical station B.

Therefore, the current on the relay side of the transformer 3 is A terminal 6A and B terminal 6B.
Then, both the size and the phase will be the same.

The A terminal current, which is treated as the power supply terminal, is converted into a rectangular wave by the slice level LH in the rectangular wave shaping circuit 8 as shown in 8A, and then F2
The other sections are F1 signals.

The B-terminal current, which is treated as a variable power supply terminal, is converted into a rectangular wave by the slice level LL in the rectangular wave shaping circuit 8, and is converted into an F2 signal as shown in 8B, contrary to the electrical station A, which is treated as a power supply terminal, and the other section is an F1 signal. become.

The coincidence circuit 9 ANDs the F2 signals of 8A and 8B, but as shown in 9 (A, B), there is no AND output of 9, so the integrator circuit 10 and the output circuit 11 have 10 (A, B), respectively. B), 11 As there is no signal at all as shown in (A, B), no breaker trip signal is issued.

It is a well-known fact that the slice level LH at the power source end and the slice level LL at the variable power source end are configured such that LH>LL so that the F2 signals at both ends do not overlap due to an external accident.

Figure 2 shows the case of an internal accident when power is supplied at both ends, and as shown, there is an accident point F on the power transmission line 5 connecting electric station A and electric station B.

Due to an internal accident in the section, contrary to Figure 2a, the currents on the relay side of transformer 3 A terminal 6A and B terminal 6B are almost in opposite phase 8
As shown in A and 8B, phase signals are generated at each terminal station, and the F1 signal and F2 signal are generated, so the coincidence circuit 9 at both ends
At (A, B), a coincidence output as shown appears, and when this is measured (integrated) by the integrating circuit 10, it reaches the slice level SL of the integrating circuit as shown at 10 (A, B), and the output circuit 11 (A, B), and this signal opens the circuit breaker and eliminates accident F.

In Figure 2 C, the accident point is inside the protected area as in Figure 2, but unlike in Figure 2, there is no power source behind electric station B at the variable power source end (there is no generator 2), so B This is the case where no fault current is supplied from the end.

Therefore, 6A and 8A are exactly the same as in figure b.

However, as shown in 6B, the current at the B end is not completely heated, so it is always below the LL level, and as shown in 8B, it is F over the entire section.
2, that is, it becomes a phase signal that allows continuous tripping.

Therefore, the F2 signal of 8A appears as it is in the double-end matching circuit 9 (A, B), and the F2 signal of 10 (A) appears as it is.

B), 11 (A, B) clearly generate a breaker trip signal.

In other words, if it is treated as a variable power supply terminal, the breaker can be tripped even if no fault current flows.

Using Figure 3, Figure 4, Figure 6, and Figure 7, in the case of the simultaneous accident on both circuits as described earlier, with an arcing accident on Line 1 and a permanent accident on Line 2, the circuit was successfully reclosed and stable operation continued. 1 that should be possible
We will explain in detail the defects that cause the line to be cut off again due to permanent accidents.

Of the components shown in these figures, those that are the same as those in FIG. 1 are denoted by the same reference numerals, and it is clearly stated here that this concept is followed in the drawings that appear below.

First, Figure 3a shows the power system in which the phase comparison relay is installed, similar to Figure 1, but unlike Figure 1, electric station A and electric station B are connected by a two-circuit power transmission line, that is, a single-blade line 5. -1L is interconnected with bisecting line 5-2L.

It is assumed that the accident point on Line 1 is FA, and an arc accident has occurred.

Therefore, if the circuit breakers 4 at both ends of 5-1L are opened, the fault FA will disappear, so if the circuit breakers 4 at both ends of 5-1L are turned on again after a no-voltage period, the system should return to its original stable state. be.

It is assumed that the accident point on Line 2 is FP and a permanent accident has occurred.

Therefore, even if the circuit breaker 4 at both ends of 5-2L is opened and then reclosed, the accident continues and the circuit is shut off again, and the circuit breaker 4 at both ends of 5-2L remains open.

Figure 3 shows the concept of a breaker circuit, where 7-a is a normally open contact that closes when the phase comparison relay operates, and 16 is a normally open contact of an undervoltage relay for fault detection, which is used to detect faults in the system. , it operates and closes when undervoltage is detected.

Therefore, if an accident occurs inside the protected area in the system, contact 7
- Since a and 16 are closed, a cutoff command is issued from the operating bus P to the cutoff coil of a breaker (not shown), and the breaker is opened.

FIG. 4 shows a transfer control circuit for sending Fl and F2 signals formed from the currents at each end to the other end.

17 is a contact of a coil that is energized by a pallet switch when the breaker contact is opened, and is closed when the breaker is opened.

18-1 is a contact of a coil (described later) which is energized by the excitation signal of the closing coil for re-closing the breaker, and is opened when the closing coil is excited.

OR represents an OR gate, and PT represents a signal power supply.

In this circuit, when the breaker is closed, the contact 17 is open, and when there is a signal from the rectangular wave shaping circuit 8 of the phase comparison relay 7 to the transmitter 13 of the information transmission device 12, the F2 signal is transmitted to the transmitter 13. If there is no signal to F, a signal is sent to the other end.

Then, when a cutoff command is issued and the breaker opens, contact 17
Since the circuit is closed, a signal is continuously supplied to the transmitter 13 from the power supply PT, so a continuous F2 signal is transmitted to the other end, and this continues until the breaker is turned on again.

Here, the reason why the continuous F2 signal is forcibly generated when the circuit breaker is open is explained. One of the reasons is to facilitate the circuit breaker, especially at the end of the variable power supply.

In other words, a) if the breaker at the power end side opens in advance for some reason when an accident occurs, or b) an internal accident occurs when only the breaker at the power end side is opened and the line is being charged from the variable power end side. Considering that, the carrier signal sent by the phase comparison relay at the power supply end is a continuous F1 (trip prevention) signal because the current detected by it is zero due to the opening of the breaker, and the carrier signal sent by the phase comparison relay at the power supply end is a continuous F1 (trip prevention) signal. Regardless of the situation, the breaker array cannot be removed at the variable power source end.

The second reason is that one of the conditions for allowing reclosing is that there is a total of two or more phases of interconnection between two circuits.

” can be given.

This is to confirm that the power supplies at both ends of a two-line power transmission line are synchronized. For example, in the first line, the human phase and B phase are open due to an accident, and in the second line, the B phase and C phase are open. Assuming that the phase is open, two phases (A, C) are interconnected between both ends.

On the other hand, if the A phase and B phase of both the first and second lines are open, only the C phase is interconnected.

In the former case, it is considered that the remaining one phase is also in a synchronous state, but in the latter case, where one phase among the three phases is not interconnected, there is no guarantee that they are synchronized.

Needless to say, reclosing without confirming synchronization is not allowed, and the easiest and most reliable way to confirm two-phase interconnection at the other terminal at the own terminal is to detect the continuous F2 signal when the breaker is opened. It depends.

In order to determine whether the accident continues after the breaker is turned on again, contact 18-1 is opened at the same time as the closing coil is energized to cancel the continuous F2 signal.

Figure 6 shows the re-closing circuit of the breaker, and Figure 7 shows the signal waveforms at various parts after the occurrence of an accident until the breaker is re-closed (I is on the variable power supply end, ■ is on the power supply end) It shows.

To explain the functions of FIG. 3 b1 and FIG. 4 up to the accident removal using this FIG. 7, the accident occurrence time t.

In the previous state, the response was similar to the external accident shown in Figure 2a, and the carrier signal 15 sent from one electric station was F
1 signal, the other is the F2 signal.

Due to the occurrence of an accident, the carrier signals sent from both ends become almost in the same phase, and the F2 signals match.

As a result, both the Ct undervoltage relay 16 and the phase comparison relay 7 are in a non-operating state before to, and when an internal fault occurs, they are activated and open the circuit breaker 4 at time t0.

However, t is the time when the F2 signal matches the delayed phase signal from the own end and the phase signal from the opposite end, and this state continues for a predetermined period of time and the phase comparison relay 7 enters the operating state.

Set to 1. The contact 17 in FIG. 4 is closed when the circuit breaker 4 is opened, and thereafter the carrier signal 15 transmitted from its own end becomes a continuous F2 signal as shown by the solid line.

The operation up to this point is exactly the same at the power supply terminal and the variable power supply terminal.

By opening this breaker, the voltage is restored and the undervoltage relay 1
6 is inoperative at either terminal, but when looking at phase comparison relay 7, it is inoperable at the power supply end (a continuous F2 signal is obtained from the other end, but since the current is zero at the own end, it is at a level equivalent to a continuous F1 signal). It's a signal.

), the variable power source terminal operates (a continuous F2 signal is obtained from the other end, and since the current is zero at the own end, the signal is at a level equivalent to the continuous F2 signal).

) continues.

FIG. 7I shows the variable power supply end, and it is also the variable power supply end that causes malfunction in the event of an accident spanning both lines.

The reclosing circuit of FIG. 6 is at the time t when this accident is detected.

Start operation from 1.

In FIG. 6, 97 is the trip circuit of the circuit breaker 4 (the third
This is a contact that closes when a cutoff command is issued from Figure b), thereby exciting the auxiliary relay 34.

34-1 is the contact point of 34.

Reference numeral 26 is a contact that is closed only when re-closing is performed. For example, during single-end line charging operation in which one breaker is opened and the line is charged only from one end, re-closing is not performed, so contact 26 is closed. It remains as it was.

23 is a timer for measuring no-voltage time;
7 and 27-1 are auxiliary relays and their contacts for self-maintaining the operation of the timer 23.

Timer 23 closes contact 2 at time t2 after the no-voltage time has elapsed.
3-1 is closed.

18, 20.21 is the auxiliary relay coil, 20-1.2
0-2 is the normally open contact of the coil 20, 21-1.21-2 is the normally open contact of the coil 21, 22 is the normally closed contact of the auxiliary relay that is energized when the breaker is re-closed, and 23-1 is the normally open contact of the auxiliary relay. The normally open contact of the timer 23 that counts the no-voltage time from the fault removal time t1, 24-1 is the auxiliary relay that operates if the re-closing condition (for example, there is interconnection of two or more phases in two circuits) is established. The normally open contact 25 is the normally closed contact of the auxiliary relay that is energized in the event of a system fault.

Further, 19 is a closing coil of the breaker, 96 is a pneumatic contact that closes when the operating air pressure of the breaker is normal, and PIN is a DC operating bus bar.

In this Figure 6, the circuit section that determines the operation of contact 23-1 (consisting of auxiliary relays 34, 23, etc.) measures the no-voltage time from the time corresponding to the tripping of the circuit breaker. Although a tripping command signal is used here as the trigger condition, a tripping signal of the contact 17 may be used instead of the contact 97.

The auxiliary relay 18' is added according to the present invention, and its function will be described later.

The operation of FIG. 6 will be explained with reference to FIG. 7 as follows.

Contact 23-1 closes at time t2 when the voltage-free time has elapsed from fault removal time t1.

At this time, if there is no accident in the system and the reclosing conditions are satisfied,
Contacts 24-L25 are both closed, so auxiliary relay 2
0 is energized and self-held by the contact 20-1, and the auxiliary relay 21 is energized by the contact 20-2.

The auxiliary relay 21 is self-held by the contact 21-2, and at the same time, the closing coil 19 is turned on by the contact 21-1 at time t21.
is excited, and if the air pressure is normal, the contact 96 is closed, so the circuit breaker is closed at time t4.

Further, the contact 21-1 excites the auxiliary relay 18 in parallel with the closing coil 19 at time t2□, and opens the normally closed contact 18-1 (FIG. 4) of the auxiliary relay 18 at time t3.

At the time of this opening, the phase comparison relay 7 on the power supply end side is not outputting (the current at its own end is zero until time t4 when the breaker 4 is turned on again, and the current is at the "0" level corresponding to the continuous F1 signal). Output.

) Therefore, the carrier transmitted from the power supply end immediately becomes a continuous F1 signal and is received by the variable power supply end at time 131 after the transmission delay time Td.

Upon reception of this F1 signal, the phase comparison relay 7 at the variable power supply end shifts to the recovery state and becomes completely inoperable at time t.

Regarding the carrier sent out from the variable power supply terminal, the fourth contact 18-H is connected until time t4 when the circuit breaker 4 is turned on.
It is a continuous F2 signal regardless of whether the circuit breaker is opened (Fig.
Outputs 1” level.

). After time t4, it is determined by the input current.

In the above description of FIG. 7, it is assumed that all other operations except for the operation of the phase comparison relay 7 are substantially the same at both terminals, and that the sequences at both terminals proceed substantially simultaneously.

As is clear from this figure, on the variable power supply end side (Fig. 7 ■), the recovery time 15 of the phase comparison relay (time T1 after time t2 after the no-voltage time has elapsed) is the time 1 when the breaker is turned on. (From time t2 to T.

hours later).

By the way, the operating time of the auxiliary relays 18, 20, and 21 is approximately 15 (m5ec), the operating time of the closing coil 19 is approximately 30 to 40 (m5ec), and the transmission delay time is approximately 5 (m5ec).
m5ec), the recovery time of phase comparison relay 7 is approximately 20
(m5ec), so To and T1 are each 60 to 70
(mSeC), about 70 (m5ec).

This did not pose any problem in the conventional phase comparison relay device described above.

In other words, in the first case, if there is no internal fault when the breaker is turned on at time t4, the undervoltage relay in the tripping circuit shown in Figure 3 is inoperable and contact 16 is open. Because there is, it will not be cut off again.

In the second case, if there is an internal fault at time t4, a tripping signal can be instantaneously provided by the operation of the undervoltage relay, which is rather convenient for high-speed operation.

As a third case, when an external accident occurs at time t4, it is possible that the circuit will be erroneously cut off and the re-closing will fail, but this is almost impossible in practice.

That is, in FIG. 6, the excitation of the closing coil 19 of the breaker is caused by the contact 25 without any accident (the contact 25 is that of an undervoltage relay).

) is confirmed,
It is impossible as an accident phenomenon that there is no accident at time t2 and an external accident occurs by t4 immediately thereafter.

In this way, follow-up accidents like the third case (two or more accidents occur in succession), and the time of the second occurrence is a very limited and short time in the relay sequence, etc. Since this phenomenon never occurs, it was thought that the conventional phase comparison relay device was completely reliable in terms of reclosing operation.

However, this is the first time that it has been revealed that a third case like this occurs.

This is the one-blade line erroneous disconnection during the single-dose line arc accident and Line 2 permanent fault mentioned above, and the line 1 re-closing failure occurred due to voltage drop due to the permanent fault occurring during the second-dose line reclosing. Become.

Such a case is virtually unprecedented, and it was impossible to imagine that there would be a case where the problem would surface by reclosing the circuit.

The present invention aims to take measures against this problem, and the seventh
As is clear from the time diagram in the figure, in the conventional method, T1>To
Therefore, the arc fault line will be shut off again.

From the above explanation, it would be better to restore the phase comparison relay, which operates at the LL level and is treated as a variable power supply terminal, a little earlier.

To this end, the breaker on the phase comparison relay side, which operates at the LH level and is treated as a power supply end, should be turned on early.

For example, if the no-voltage time on the power supply end is set shorter than that on the variable power supply end, the phase comparison relay 7 on the variable power supply end can be reset before the breaker on the variable power supply end is turned on. good.

However, in recent years, phase comparison relays installed in ultra-high voltage systems or ultra-super high voltage systems often have two series as shown in Figure 5, and in series A, electric station A is treated as the power source end, and electric station B is treated as the variable power source. In the B series, unlike the A series, electric station A is treated as the variable power source end, and electric station B is treated as the power source end, so phase comparison relays that operate at the LL level are installed at both electric stations. Therefore, it is no longer possible to take measures by making a difference in the no-voltage time.

Therefore, in the present invention, T1<T
.

It has been devised so that. In FIG. 6, the dotted line added in parallel with the auxiliary relay 20 is according to the present invention, and the auxiliary relays 18 and 18' are in the relationship of a primary coil and a secondary coil, respectively, wound on the same iron core.

The operation of this 18' and other contacts that change accordingly is shown by dotted lines in FIG.
' is 7 due to the closing of timer contact 23-1 at time t2.
Contact 1 of the transport control circuit (Fig. 4) at one end, respectively.
Open 8-1.

As a result, the transmission AJ clear continuous F at the power supply terminal (Fig. 7 ■)
1 signal (because the current is zero, the rectangular wave shaping circuit 8 outputs the fIO14 level, which corresponds to the F1 signal).

), this is received at the variable power supply terminal, and as a result, the phase comparison relay 7 at the variable power supply terminal is restored.

In this case, the recovery time is t6, which is 12 hours after time t2.

If this time T2 is shown in the above example, the auxiliary relay 18'
operation time (approximately 15 v7Lsec) and transmission delay time (approx.
(approximately 5 m5ec) and recovery time of phase comparison relay 7 (approximately 2
0 m5ec) (approximately 40 m5ec) and time T.

(approximately 60 to 70 m5ec).

As is clear from this figure, the restoration time of the phase comparison relay can be brought earlier than the re-opening time of the breaker.

This prevents malfunctions from occurring in the case of the third case.

At the variable power supply end, the transmission carrier does not change due to the operation of the auxiliary relay 18' (because the current is zero, the output of the rectangular wave shaping circuit 8 is at the "1" level, which corresponds to the t2 signal).

), does not change the situation at the power supply end. The countermeasure shown by the dotted line in Figure 6 is the easiest way to solve the problem by making use of conventional equipment. <To, the continuous F2 signal may be canceled under the operating condition of this timer, which is shorter than the no-voltage time.

If the present invention is applied, it will not only be extremely effective in a two-series phase comparison relay system as shown in Figure 5, but also in a single-series phase comparison relay system, it will not be necessary to differentiate the reclosing no-voltage time. Since there is no such system, this is a very favorable advantage in terms of system operation.

From the above explanation, the problems posed by the present invention can be solved by temporarily turning off the operating output 11 of the phase comparison relay of LL level operation at the time of re-closing.
Such a method is not a preferable method because it may unnecessarily interfere with normal protective operation.

As described in detail in the present invention, it is a feature of the present invention that a malfunctioning phase comparison relay is solved and implemented from the other end using the conveyance control circuit which is the root cause of the malfunction.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the principle of the phase comparison transport protection relay system, Figure 2
Figure 3 is a diagram explaining the response under various conditions of the same system, Figure 3 is a diagram explaining problems in the conventional system, Figure 4 is a conveyance control circuit diagram, Figure 5 is a diagram of two-sequence phased comparison conveyance protection relay power formula, 6th
7 is a circuit example and a time diagram of the phase comparison conveyance protection relay system according to the present invention. 7...Phase comparison relay, 17...Contact that closes between circuit breakers, 18-1...Contact that opens upon re-closing command.

Claims (1)

[Claims] Applied to a power transmission line with a 12-line configuration, the current of the transmission line is detected for each phase at each terminal of the transmission line, and when the current passing through the transmission line is viewed as having the same polarity at each terminal, phase comparison is performed as if it were treated as a power supply terminal. The relay sends a phase signal to the other end that allows tripping during a period when the current is above a predetermined current level and does not include zero current, and prohibits tripping during other periods, and a phase comparison relay that is treated as a variable power supply terminal is used when the current level is below a predetermined current level. and sends to the other end a phase signal that allows tripping during a period including zero current and prohibits tripping during other periods, and sends a continuous phase signal that allows tripping at the open terminal of the breaker to the other end, At each terminal, the phase comparison relay at its own end determines whether the phase signal at its own end matches the trip permissible portion of the phase signal at the other end and outputs it, when it detects a drop in the line voltage at its own end and detects an undervoltage. In the phase comparison relay method, which opens the circuit breaker at its own end when the relay is also outputting, the phase comparison relay, which is treated as a power supply terminal, uses the phase signal that allows tripping between the above-mentioned circuit breakers to be opened at the circuit breaker at its own terminal. The time of this stop corresponds to the time when this phase signal is received at the variable power supply terminal and the first time point at which the phase comparison relay is restored is the time at which the variable power supply terminal A phase comparison transfer protection relay system characterized in that the time point is selected to be earlier than the second time point at which the circuit breaker is turned on.