JP4994140B2 - Ratio differential relay and ratio differential relay malfunction prevention method - Google Patents

Description

  The present invention relates to a ratio differential relay and a ratio differential relay malfunction prevention method, and more particularly, to a ratio differential relay and a ratio differential relay malfunction prevention method suitable for preventing malfunction due to human error of an operator.

Proportional differential relays for power system transformer protection will malfunction if an operator accidentally shorts or opens a current transformer circuit (CT circuit) for the proportional differential relay. Power out of the transformer.
As a countermeasure, when the test terminal (CTT) is inserted into the current transformer circuit and the work is performed, the current transformer circuit is momentarily interrupted (instantaneously interrupted) when the test terminal is inserted. An operator has locked the ratio differential relay. In addition, "there is a ratio differential relay" is displayed on the test terminal with a warning sticker, etc., so that the operator does not inadvertently insert the test terminal.
In this way, when working on the current transformer circuit for the ratio differential relay, it is necessary to lock the ratio differential relay, which lowers the protection reliability.
In addition, even when an operator disconnects the cable of the current transformer circuit for the ratio differential relay due to cable work or the like, the ratio differential relay malfunctions, causing a power failure of the transformer.

  Conventionally, as a countermeasure for preventing malfunction of the ratio differential relay, there is a method of preventing malfunction by detecting an inrush current (second harmonic component) when charging the transformer. As a measure for improving the reliability of the ratio differential relay, there is a method with an overcurrent element for detecting an accident. Further, in the case of a digital relay, there are a method of monitoring a three-phase current imbalance, a method of monitoring a difference current, and a method of monitoring a current input circuit by a current change.

  In Patent Document 1 below, a relay element and an analog input unit do not have to be duplicated in a differential relay that outputs a trip signal by calculating a difference between a primary current and a secondary current of a transformer by a relay calculation unit. In order to prevent the occurrence of mistripping, a ΔI relay that locks the relay operation unit when any one of the primary current and the secondary current decreases by a certain value or more, and a ΔI relay that locks the relay current when the primary current increases by a certain value or more. The ratio differential relay which provided the AC overcurrent relay for the main transformer primary which locks the operation | movement of this is disclosed.

In addition, in Patent Document 2 below, in order to prevent a factor that hinders the stable supply of power unnecessarily by preventing an abnormality even though the monitoring target to be originally protected is normal, the monitoring target is not included. An input unit that receives a signal detected by a current detection unit that detects a flowing three-phase AC current, an input conversion unit that converts the detected signal into a digital signal, and processes the digital signal to determine an abnormality to be monitored In the digital protection relay device having the calculation unit and the output unit for outputting the determination result to the outside, the calculation unit determines that the current detection unit is normal when the vector sum of currents for three phases is zero, When it is not zero, the current detection unit has a detection unit abnormality determination means that determines that the current detection unit is abnormal, and when the output unit detects an abnormality of the current detection unit, the determination result that the monitoring target is determined to be abnormal is output to the outside. Digital protective relay device is disclosed in which the odd.
Japanese Utility Model Publication No. 5-39138 JP-A-5-161249

However, in the conventional method described above, when the current transformer circuit for the ratio differential relay in operation is short-circuited or disconnected in 1 to 3 phases due to human error, from the following problems, All cases cannot be judged instantaneously to prevent the malfunction of the ratio differential relay.
(1) In the method with an overcurrent element, the overcurrent element operates when the settling tap value is small or the load current is large.
(2) In the method of monitoring the three-phase current imbalance and the method of monitoring the difference current, it is necessary to discriminate from an actual accident. Therefore, a certain amount of detection time is required. It cannot be locked.
(3) Since the ratio differential relay described in Patent Document 1 is a method of detecting by reducing ΔI of the current of any one of all the circuits, it cannot detect when the two-phase or three-phase abnormality occurs.
(4) Since the digital protective relay device described in Patent Document 2 detects a combination of the method for monitoring the three-phase current imbalance and the method for monitoring the difference current, detection at the time of three-phase abnormality is possible. Can not.

  An object of the present invention is to provide a ratio differential relay and a ratio difference in which a current transformer circuit for a ratio differential relay in operation does not malfunction even if it is short-circuited or disconnected in one to three phases due to human error or the like. The object is to provide a method for preventing malfunction of a relay.

The ratio differential relay of the present invention is provided with a trip signal (T _{1X to} T _3X ) that respectively shuts off a transformer (1) protective circuit breaker (3 _{1X to} 3 _3X ) installed for each phase of a plurality of busbars. A ratio differential relay (10) for output, which is input from a current transformer (2 _1X to 2 _3X ) installed in the vicinity of the transformer via a current transformer circuit (5 _{1X to} 5 _3X ). A ratio differential relay circuit (11) that outputs the trip signal when an accident relating to the transformer is detected based on a secondary current (i _{1X to} i _3X ) of the current transformer, and a scalar current of the secondary current Current value / change rate calculation circuit (12) for calculating the value (| i _1X | ˜ | i _3X |) and the change rate (Δ | i _1X | ˜Δ | i _3X |) of the scalar current value of the secondary current On the basis of the scalar current value and the change rate of the secondary current input from the current value / change rate calculation circuit. Characterized by comprising a locking circuit (13) for generating a lock signal for trip signal to lock the said ratio differential relay circuit so as not to output (L).
In this case, the lock circuit is configured such that the secondary current instantaneously becomes “0” or the rate of change is equal to or greater than the own circuit current no change detection value (β) and corresponds to the corresponding phase of the own circuit. When the circuit breaker installed in the phase of the bus is in the on state and the rate of change in the corresponding phase of the other circuit is equal to or less than the other circuit current no change detection value (α), the corresponding phase of the own circuit Generating the lock signal for not outputting the trip signal for interrupting the circuit breaker installed in the phase of the bus corresponding to the output, and outputting the generated lock signal to the ratio differential relay circuit May be.
The other circuit current no change detection value is a value of 20% of the pre-scalar current value, the own circuit current no change detection value is a value of 50% of the pre-scalar current value, and the pre-scalar current value However, when the secondary current is sampled, it may be a scalar current value of 0.5 period or 1 period before the sampling.
When the secondary current is sampled, the change detection amount of 1 bit may be less than 20% and the secondary current may be handled as “0”.
And further comprising a short-circuit device (20 _{1 to} 20 ₃ ) provided in the vicinity of the current transformer of the current transformer circuit and for short-circuiting the secondary side of the current transformer for each phase, When the lock circuit detects an abnormality with respect to the phase of the current transformer circuit based on the scalar current value and the rate of change of the secondary current, the current transformer of the current transformer corresponding to the phase of the current transformer circuit that has detected the abnormality is detected. A short-circuit command signal (S) for short-circuiting the secondary side of the phase may be generated, and the generated short-circuit command signal may be output to the short-circuit device.
The short-circuit device may include a switch (21 _{1X to} 21 _3X ) that is turned on / off in response to the short-circuit command signal input from the lock circuit.
When the lock circuit detects an abnormality in the phase of the current transformer circuit based on the scalar current value and change rate of the secondary current, an alarm signal (ALM) to be output to the outside may be further generated.

The ratio differential relay malfunction prevention method according to the present invention includes a trip signal (T _{1X to} T) that respectively shuts off a transformer (1) protective circuit breaker (3 _{1X to} 3 _3X ) installed for each phase of a plurality of buses. _3X ) is a ratio differential relay malfunction prevention method for preventing malfunction of the ratio differential relay circuit (11), wherein the lock circuit (13) is installed in the vicinity of the transformer. Secondary current scalar current value (| i _1X | ˜ | i _3X |) and the change rate (Δ | i _1X | ˜Δ | i _3X ) of the secondary current scalar current value of the secondary current (2 _{1X to} 2 _3X ) |), Monitoring whether the secondary current instantaneously becomes “0” and whether the rate of change is equal to or greater than the own circuit current no-change detection value (β) (S11), Whether the secondary current instantaneously becomes “0” or the rate of change does not change the current of the own circuit. If the detected value is greater than or equal to the detected value, the step (S12) of checking whether or not the circuit breaker installed in the phase of the bus corresponding to the corresponding phase of the own circuit is in the on state, and the lock circuit, When the circuit breaker installed in the phase of the bus corresponding to the corresponding phase of the own circuit is in the on state, the change rate in the corresponding phase of the other circuit is equal to or less than the other circuit current no change detection value (α). A step (S13) for checking whether or not the current phase of the lock circuit is equal to or less than the detected value of the other circuit current unchanged when the rate of change in the phase of the other circuit And generating a lock signal (L) for preventing the trip signal output from the circuit breaker installed in the phase of the bus corresponding to the output from being output, and using the generated lock signal as the ratio differential relay Output to the circuit (S Characterized by comprising 4) and the.
Here, the other circuit current no change detection value is a value of 20% of the pre-scalar current value, the own circuit current no change detection value is a value of 50% of the pre-scalar current value, When the secondary current is sampled as the scalar current value, it may be the scalar current value of 0.5 period or 1 period before the sampling.
When the lock circuit detects an abnormality in the corresponding phase of the own circuit based on the scalar current value and change rate of the secondary current, it generates an alarm signal (ALM) to be output to the outside and generating a short-circuit command signal to be output the short circuit device for short-circuiting the secondary side of the phase of the current transformer (20 ₁ to 20 ₃₎ corresponding to the phase (S) (S14, S15) further comprises a May be.

The ratio differential relay and the ratio differential relay malfunction prevention method of the present invention have the following effects.
(1) Even if the current transformer circuit for the ratio differential relay in operation becomes short-circuited or disconnected from 1 to 3 due to human error, the ratio differential relay is instantly locked. Therefore, malfunction of the ratio differential relay can be prevented.
(2) It is also effective as a new monitoring means for the current input circuit.

  Based on the scalar current value and change rate of the secondary current input from the current value / change rate calculating circuit, the lock signal for locking the ratio differential relay circuit so that the trip signal is not output is provided for the above purpose. Realized by generating

Hereinafter, embodiments of the ratio differential relay and the ratio differential relay malfunction prevention method of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the proportional differential relay 10 according to an embodiment of the present invention includes a proportional differential relay circuit 11, a current value / change rate calculation circuit 12, and a lock circuit 13.
Further, as shown in FIG. 2, the ratio differential relay 10 includes a primary side to a tertiary side current transformers 2 ₁ to 2 ₃ installed in the vicinity of the transformer 1 of the primary to tertiary bus, and primary to tertiary. The current transformer circuits 5 _{1 to} 5 ₃ are connected to each other.

Here, the primary current transformer 2 _1, R-phase of the primary bus, R-phase are respectively installed in the S-phase and T-phase, S-phase and T-phase primary current transformer 2 _1R, 2 _1S, 2 _1T (hereinafter, Collectively referred to as “each phase primary current transformer 2 _1X ”), and the secondary current transformer 2 ₂ is installed in the R phase, S phase and T phase of the secondary bus, respectively. And T-phase secondary current transformers 2 _2R , 2 _2S , 2 _2T (hereinafter collectively referred to as “each phase secondary current transformer 2 _2X ”) (see FIG. 3), and tertiary current transformer 2 ₃ Are the R-phase, S-phase, and T-phase tertiary current transformers 2 _3R , 2 _3S , 2 _3T (hereinafter collectively referred to as “three-phase current transformers for each phase” respectively installed in the R-phase, S-phase, and T-phase of the tertiary bus. 2 _3X ").
The primary current transformer circuit 5 _1, each phase primary current transformer 2 _1X secondary side and the ratio differential relay 10 and the connecting respectively R phase, S phase and T-phase primary current transformer circuit 5 _1R, 5 _1S, 5 _1T made (hereinafter collectively also referred to as "phase primary current transformer circuit 5 _1X".), the secondary current transformer circuit 5 _2, 2-order phase secondary current transformer 2 _2X R-phase, S-phase, and T-phase secondary current transformer circuits 5 _2R , 5 _2S , 5 _2T (hereinafter collectively referred to as “each phase secondary current transformer circuit 5 _2X "and also referred to.) a three-the primary current transformer circuit 5 _3, R-phase phase tertiary current transformer 2 _3X the secondary side and the ratio differential relay 10 and the connecting respectively, S-phase and T-phase tertiary strange It consists of a current transformer circuit 5 _3R , 5 _3S , 5 _3T (hereinafter collectively referred to as “each phase tertiary current transformer circuit 5 _3X ”).

First R-phase, S-phase, and T-phase primary currents I _1R , I _1S , I _1T flowing through the R-phase, S-phase, and T-phase of the primary bus (hereinafter collectively referred to as “first-phase primary current I also referred to as _1X. "), after being inputted to the primary side of each phase primary current transformer 2 _1X is converted at a predetermined current transformer ratio, first from the secondary side of each phase primary current transformer 2 _1X R-phase, S-phase, and T-phase secondary currents i _1R , i _1S , i _1T (hereinafter collectively referred to as “first phase secondary current i _1X ”). Second R-phase, S-phase, and T-phase primary currents I _2R , I _2S , I _2T flowing through the R-phase, S-phase, and T-phase of the secondary bus (hereinafter collectively referred to as “second-phase primary currents”) I _2X ”) is input to the primary side of each phase secondary current transformer 2 _2X , and then converted at a predetermined current transformation ratio to obtain the secondary side of each phase secondary current transformer 2 _2X. To R-phase, S-phase, and T-phase secondary currents i _2R , i _2S , i _2T (hereinafter collectively referred to as “second phase secondary current i _2X ”). Third R-phase, S-phase, and T-phase primary currents I _3R , I _3S , I _3T flowing through the R-phase, S-phase, and T-phase of the tertiary bus (hereinafter collectively referred to as “third-phase primary current I also referred to as _3X. "), after being inputted to the primary side of each phase tertiary current transformer 2 _3X is converted at a predetermined current transformer ratio, the third from the secondary side of each phase tertiary current transformer 2 _3X R phase, S phase, and T phase secondary currents i _3R , i _3S , i _3T (hereinafter collectively referred to as “third phase secondary current i _3X ”).

In the vicinity of the primary to tertiary current transformer circuits 5 ₁ to 5 ₃ of primary or tertiary current transformers 2 ₁ to 2 _3, the secondary side of the primary to tertiary current transformers 2 ₁ to 2 ₃ for each phase at the time of abnormality First to third short-circuit devices 20 _{1 to} 20 ₃ for short-circuiting are provided, respectively.

Here, as shown for ₂ second short device 20 in FIG. 3 (a), the first short device 20 _1, the primary current transformer 2 ₁ secondary side R-phase, each S-phase and T-phase R-phase, S-phase, and T-phase primary switches 21 _1R , 21 _1S , 21 _1T (hereinafter collectively referred to as “each phase primary switch 21 _1X ”), and a second short-circuit device 20 _2. , the secondary current transformer 2 ₂ on the secondary side of the R-phase, R-phase for short-circuiting each S-phase and T-phase, S-phase and T-phase secondary switch _{21 2R, 21 2S, 21 2T} ( hereinafter, collectively also referred to as "phase secondary switch 21 _2X".) comprises a third short circuit device 20 ₃ is shorting the secondary of tertiary current transformer 2 ₃ R-phase, for each S-phase and T-phase R phase for, S-phase and T-phase tertiary switch _{21 3R, 21 3S, 21 3T} ( hereinafter, collectively "phase tertiary switch 21 _3X" Provided with the also referred to.).
Incidentally, FIG. 3 (a) shows a second shorting device 20 ₂ in the structure when the primary to tertiary current transformer circuits 5 ₁ to 5 ₃ are Y-connected, FIG. 3 (b), a primary or tertiary current transformer circuits 51 _to indicate a second shorting device 20 ₂ in the structure in case of a Δ connection.

Each phase primary to tertiary switch 21 _{1X to} 21 _3X is turned on / off in response to a short-circuit command signal S (described later) input from the lock circuit 13 of the ratio differential relay 10.

In the vicinity of the transformer 1 of the primary to tertiary buses, primary to tertiary circuit breakers 3 ₁ to ₃ 3 for protecting the transformer 1 are installed, respectively. Here, the primary circuit breaker 3 _1, R-phase of the primary bus, S-phase and T the installed R phase for each phase, S-phase and T-phase primary circuit breaker 3 _1R, 3 _1S, 3 _1T (hereinafter collectively also referred to as "phase primary breaker 3 _1X".) equipped with a secondary breaker 3 _2, R-phase of the secondary bus, R-phase, which is installed in each S-phase and T-phase, S-phase and T-phase to two Secondary circuit breakers 3 _2R , 3 _2S , 3 _2T (hereinafter also referred to as “each phase secondary circuit breaker 3 _2X ”), and the tertiary circuit breaker 3 ₃ includes the R phase, S phase and T of the tertiary bus. R phase, S phase, and T phase tertiary circuit breakers 3 _3R , 3 _3S , 3 _3T (hereinafter collectively referred to as “each phase tertiary circuit breaker 3 _3X ”) provided for each phase.
Each phase primary circuit breaker 3 _1X has a first R-phase, S-phase, and T-phase trip signal T _1R , T _1S , T _1T (hereinafter collectively referred to as “first output”) input from the ratio differential relay circuit 11. also referred to as phase trip signal T _1X ".) is blocked respectively by respective phase secondary breaker 3 _2X, the second R-phase inputted from the ratio differential relay circuit 11, S-phase and T-phase trip signal T _2R , T _2S , T _2T (hereinafter collectively referred to as “second phase trip signal T _2X ”) are respectively disconnected, and each phase tertiary circuit breaker _{33 X} is connected to the ratio differential relay circuit 11. They are blocked by the inputted third R-phase, S-phase and T-phase trip signals T _3R , T _3S , T _3T (hereinafter collectively referred to as “third phase trip signal T _3X ”).

The ratio differential relay circuit 11 performs the same operation as that of the conventional ratio differential relay based on the first to third phase secondary currents i _{1X to} i _3X . That is, the vector sum i _dX (X = R, S, T) of the first to third phase secondary currents i _{1X to} i _3X is always “0” (i _dR = i _1R + i _2R + i _3R = 0, i _dS = i _1S + i _2S + i _3S = 0, i _dT = i _1T + i _2T + i _3T = 0) However, since it is not “0” in the case of an internal fault of the transformer 1, the ratio differential relay circuit 11 is When the vector sums i _dR , i _dS , i _{dT of} the first to third phase secondary currents i _{1X to} i _3X are equal to or higher than a predetermined operation set value k, it is determined that an internal fault has occurred in the transformer 1. Thus, the first to third phase trip signals T _1X , T _2X , T _3X are output to block the phase primary to tertiary circuit breakers 3 _{1X to} 3 _3X , respectively. Further, the ratio differential relay circuit 11 operates when the ratio between the operating current and the transformer passing current becomes a certain value or more in order to prevent malfunction due to an error of the transformer 1 or the like in the event of an external accident. Designed to be

Current / change rate calculating circuit 12, first to the scalar current value of the third phase secondary current _{i 1X ~i 3X | i 1X |} ~ | i 3X | a, first to third phases 2 A change rate Δ | i _1X | ˜Δ | i _3X | of the scalar current values | i _1X | ˜ | i _3X | of the secondary currents i _{1X to} i _3X is calculated.

The lock circuit 13 includes scalar current values | i _1X | ˜ | i _3X | and change rates Δ of the first to third phase secondary currents i _{1X to} i _3X input from the current value / change rate calculation circuit 12. Lock signal for locking the ratio differential relay circuit 11 so that the first to third phase trip signals T _1X , T _2X , T _3X are not output based on | i _1X | ˜Δ | i _3X | L is generated.
The lock circuit 13 also includes scalar current values | i _1X | ˜ | i _3X | and change rates Δ | i _1X | ˜Δ | i _3X | of the first to third phase secondary currents i _{1X to} i _3X. When an abnormality such as a short circuit or disconnection of the R-phase, S-phase, and T-phase of the primary to tertiary current transformer circuits 5 _{1 to} 5 ₃ is detected based on the above, an alarm is always displayed at the monitoring point and an alarm is sounded locally. Alarm signal ALM for the primary, secondary or tertiary phase current transformers 2 _1X to 2 _3X installed in the phase of the primary, secondary or tertiary bus corresponding to the phase of the current transformer circuit which detected the abnormality A short-circuit command signal S for short-circuiting the secondary side is generated.

Next, an abnormality detection method in the lock circuit 13 of the ratio differential relay 10 will be described with reference to a flowchart shown in FIG.
The lock circuit 13 includes scalar current values | i _1X | ˜ | i _3X | and change rates Δ of the first to third phase secondary currents i _{1X to} i _3X input from the current value / change rate calculation circuit 12. Based on | i _1X | ˜Δ | i _3X |, the secondary currents i _{1X to} i _{3X of} the first to third phases instantaneously become “0”, and the rate of change Δ | i _1X | ˜ It is monitored whether Δ | i _3X | is equal to or greater than the own circuit current no change detection value β (step S11).

As a result, the secondary currents i _{1X to} i _3X of each of the first to third phases instantaneously become “0”, or the change rate Δ | i _1X | to Δ | i _3X | When β is greater than or equal to β, the lock circuit 13 is connected to a circuit breaker installed in the R phase, S phase, or T phase of the primary, secondary, or tertiary bus corresponding to the corresponding phase of the circuit (primary to tertiary for each phase). It is checked whether one of the circuit breakers 3 _{1X to} 3 _3X is in the on state (step S12).
Here, the corresponding phase of the own circuit is the change rate Δ | i _1X | ˜Δ | i _3X | of whether the first to third phase secondary currents i _{1X to} i _3X instantaneously become “0”. primary became more self circuit current non-change detection value beta, secondary or tertiary current transformer circuits 5 ₁ to 5 ₃ R-phase refers to the S phase or T phase.

As a result, when the circuit breaker installed in the R phase, S phase, or T phase of the primary, secondary, or tertiary bus corresponding to the corresponding phase of the own circuit is in the on state, the lock circuit 13 It is checked whether or not the change rate Δ | i _1X | ˜Δ | i _3X | in the corresponding phase is equal to or less than the other circuit current no change detection value α (step S13).
Here, the corresponding phase of the other circuit is the change rate Δ | i _1X | ˜Δ | i _3X | that the secondary currents i _{1X to} i _{3X of} the first to third phases instantaneously become “0”. primary became more β own circuit current unchanged detection value, secondary or tertiary current transformer circuits 5 ₁ to 5 ₃ other than the primary, secondary or tertiary current transformer circuits 5 ₁ to 5 ₃ of R phase, S phase Or the T phase.

As a result, when the change rate Δ | i _1X | ˜Δ | i _3X | in the corresponding phase of the other circuit is equal to or less than the other circuit current no-change detection value α, the lock circuit 13 corresponds to the corresponding phase of the own circuit. Trip signal (one of the first to third phase trip signals T _{1X to} T _3X ) that shuts off the circuit breaker installed in the R phase, S phase, or T phase of the primary, secondary, or tertiary bus Is generated, and the generated lock signal L is output to the ratio differential relay circuit 11 (step S14). Thereby, it can prevent that the circuit breaker of the applicable phase of the transformer 1 is interrupted | blocked unnecessarily.

  Further, the lock circuit 13 generates an alarm signal ALM that notifies an alarm that “an abnormality has occurred in the corresponding phase of its own circuit”, and outputs the generated alarm signal ALM to the outside (step S14). As a result, an alarm stating that “an abnormality has occurred in the corresponding phase of the own circuit” is always displayed on the monitoring point to notify the monitoring person, or an alarm sound can be sounded at the work site to notify the worker. .

Further, the lock circuit 13 is a current transformer installed in the R phase, S phase or T phase of the primary, secondary or tertiary bus corresponding to the corresponding phase of its own circuit (each phase primary to tertiary current transformer 2 _1X- A short-circuit command signal S for short-circuiting the secondary side of 2 _3X is generated, and the generated short-circuit command signal S is output to the _{first to third} short-circuit devices 201 to 203 (step S15). ). Thus, the first to be one is closed the corresponding one of the third short circuit devices 20 ₁ to 20 ₃ of each phase primary to tertiary switch 21 _1X through 21 _3X, one corresponding to the relevant phase of the self-circuit primary, the secondary The secondary side of the current transformer installed in the R phase, S phase or T phase of the next or tertiary bus is short-circuited.

The other circuit current no change detection value α is a pre-scalar current value (in the case where the first to third phase secondary currents i _{1X to} i _3X are sampled, 0.5 sampling period or The value of 20% of the scalar current value 1 cycle before) is assumed, and the self-circuit current no-change detection value β is 50% of the previous scalar current value.
Further, if the full scale when sampling the first to third phase secondary currents i _{1X to} i _3X is 163.84A, the scalar current value (LSB) per bit is 50 mA. For example, in order to make the change detection amount of 1 bit less than 20%, it is necessary to detect a current value of 0.03 A or more. Therefore, when an abnormality is detected, the first to third are set to be less than 0.03 A as a dead zone. Each phase secondary current i _{1X to} i _3X is treated as “0”.

Next, as an example of the operation of the ratio differential relay 10 according to the present embodiment, a case where a disconnection or a short circuit occurs due to human error at time t ₀ in the R-phase secondary current transformer circuit _{52 R} is taken as an example. , Scalar current values | i _1R | to | i _3R | and first to third R-phase secondary currents i _{1R to} i _3R flowing through the R-phase primary to tertiary current transformer circuits 5 _{1R to} 5 _3R. A description will be given with reference to FIG. 5 showing the temporal change of the scalar value | i _dR | of the vector sum i _dR (= i _1R + i _2R + i _3R ) of the third R-phase secondary currents i _{1R to} i _3R .

The lock circuit 13 of the ratio differential relay 10 is based on the scalar current value | i _2R | of the second R-phase secondary current i _2R input from the current value / change rate calculation circuit 12 at time t ₀ . When it is detected that the second R-phase secondary current i _2R flowing through the R-phase secondary current transformer circuit 5 _2R instantaneously becomes “0”, the R-phase secondary installed in the R-phase of the secondary bus Check whether the breaker 3 _2R is in the on state.

As a result, when the R-phase secondary circuit breaker 3 _2R is in the on state, the lock circuit 13 causes the first and third _Rs to flow through the R-phase primary and tertiary current transformer circuits 5 _1R and 5 _3R (other circuits). Whether the change rates Δ | i _1R |, Δ | i _3R | of the scalar current values | i _1R |, | i _3R | of the phase secondary currents i _1R , i _3R are less than the other circuit current no-change detection value α Check for no.

As a result, if these change rates Δ | i _1R |, Δ | i _3R | are both equal to or less than the other circuit current no-change detection value α, the lock circuit 13 sends the lock signal L to the ratio differential relay circuit 11. The second R-phase trip signal T _2R that outputs and shuts off the R-phase secondary circuit breaker 3 _2R is not output, and the alarm signal ALM is output to the outside to output the “R-phase secondary current transformer circuit”. 5 _2R is disconnected or short-circuited. As a result, it is possible to prevent the R-phase secondary circuit breaker 3 _2R from being interrupted unnecessarily, and to constantly monitor the fact that the R-phase secondary current transformer circuit _{52 R} has a break or short circuit. An alarm can be displayed on the monitor to notify the monitoring staff, or an alarm sound can be sounded at the work site to notify the worker.

The lock circuit 13, short-circuit command signal to short the secondary side of the R-phase secondary current transformer circuit 5 of the corresponding secondary bus to _2R R phase to the installed R-phase secondary current transformer 2 _2R S Is output to the second short-circuit device 20 ₂ . As a result, the R-phase secondary switch 21 _{2R of the} second short-circuit device 20 ₂ is closed and the secondary side of the R-phase secondary current transformer 2 _2R is short-circuited.

It is a figure which shows the structure of the ratio differential relay 10 by one Example of this invention. It is a figure for demonstrating the connection relation of the ratio differential relay 10 shown in FIG. 1, and primary thru | or the tertiary current transformers 2 ₁ to 2 ₃ . Is a diagram showing the first through third short devices 20 ₁ to 20 ₃ of the configuration shown in FIG. It is a flowchart for demonstrating operation | movement of the ratio differential relay 10 shown in FIG. Is a graph for explaining the operation of the ratio differential relay 10 when the disconnection or short-circuited by human error of the worker in the R-phase secondary current transformer circuits 5 ₂ at time t ₀ has occurred as shown in FIG. 2 .

Explanation of symbols

1 transformer 2 _{1 to} 2 ₃ primary to tertiary current transformer 2 _1R , 2 _1S , 2 _1T R phase, S phase and T phase primary current transformer 2 _2R , 2 _2S , 2 _2T R phase, S phase and T phase Secondary current transformers 2 _3R , 2 _3S , 2 _3T R-phase, S-phase and T-phase tertiary current transformers 2 _1X to 2 _3X primary to tertiary current transformers 3 _{1 to} 3 ₃ primary to tertiary circuit breakers 3 _1R , 3 _1S , 3 _1T R phase, S phase and T phase primary circuit breakers 3 _2R , 3 _2S , 3 _2T R phase, S phase and T phase secondary circuit breakers 3 _3R , 3 _3S , 3 _3T R phase, S phase And T-phase tertiary circuit breakers 3 _{1X to} 3 _3X primary to tertiary circuit breakers 5 _{1 to} 5 ₃ primary to tertiary current transformer circuits 5 _1R , 5 _1S , 5 _1T R-phase, S-phase and T-phase primary current transformers Circuits 3 _2R , 3 _2S , 3 _2T R-phase, S-phase and T-phase secondary current transformer circuits 3 _3R , 3 _3S , 3 _3T R-phase, S-phase and T-phase tertiary current transformer circuits 5 _{1X to} 5 _3X each Phase primary to tertiary current transformer circuit 10 ratio differential relay 11 ratio SadoTsugi conductive circuit 12 current / change rate calculating circuit 13 lock circuit 20 ₁ to 20 ₃ first through third short device _{21 1R, 21 1S, 21 1T} R phase, S phase and T-phase primary switch 21 _2R, 21 _2S , 21 _2T R-phase, S-phase and T-phase secondary switches 21 _3R , 21 _3S , 21 _3T R-phase, S-phase and T-phase tertiary switches 21 _{1X to} 21 _3X primary to tertiary switches I _1R , I _{1S for} each phase , I _1T first R phase, S phase and T phase primary currents I _2R , I _2S , I _2T second R phase, S phase and T phase primary currents I _3R , I _3S , I _3T R-phase, S-phase and T-phase primary currents I _{1X to} I _3X first to third phase primary currents i _1R , i _1S and i _1T first R-phase, S-phase and T-phase secondary currents i _2R, i _2S, i _2T second R phase, S phase and T-phase secondary current i _3R, i _3S, i _3T third R phase, S phase and T-phase secondary current i _{1 X} ~i _3X first 1st to 3rd Secondary current i _RX vector sum | i _1X | ˜ | i _3X | Scalar current value Δ | i _1X | ˜Δ | i _3X | Rate of change | i _dR | Scalar value k Operation set value ALM Alarm signal L Lock signal S short-circuit command signals T _1R , T _1S , T _1T first R phase, S phase and T phase trip signals T _2R , T _2S , T _2T second R phase, S phase and T phase trip signals T _3R , T _3S , T _3T Third R-phase, S-phase and T-phase trip signals T _{1X to} T _3X First to third phase trip signals S11 to S15 Step t ₀ Time

Claims (10)

A plurality of transformers installed in each phase of the bus (1) breaker for protection (3 _1X to 3 _3X) a trip signal for interrupting the respective (T _1X through T _3X) ratio differential relay for outputting (10) Because
The secondary current (i _{1X to} i) of the current transformer input from the current transformer (2 _1X to 2 _3X ) installed in the vicinity of the transformer via the current transformer circuit (5 _{1X to} 5 _3X ). _3X ), the ratio differential relay circuit (11) that outputs the trip signal when an accident relating to the transformer is detected,
Current value // to calculate the scalar current value (| i _1X | ˜ | i _3X |) of the secondary current and the rate of change (Δ | i _1X | ˜Δ | i _3X |) of the scalar current value of the secondary current Change rate calculation circuit (12);
Based on the scalar current value and change rate of the secondary current input from the current value / change rate calculating circuit, a lock signal (for locking the ratio differential relay circuit so that the trip signal is not output) L) generating a lock circuit (13);
A ratio differential relay comprising:   The lock circuit is configured such that the secondary current instantaneously becomes “0” or the rate of change is equal to or greater than the own circuit current no change detection value (β) and the phase of the bus corresponding to the corresponding phase of the own circuit. Corresponds to the corresponding phase of the own circuit when the circuit breaker installed in the circuit is in the on state and the rate of change in the corresponding phase of the other circuit is equal to or less than the other circuit current no change detection value (α). Generating the lock signal not to output the trip signal that interrupts the circuit breaker installed in the phase of the bus, and outputting the generated lock signal to the ratio differential relay circuit The ratio differential relay according to claim 1, wherein: The other circuit current no change detection value is a value of 20% of the previous scalar current value,
The self-circuit current no change detection value is a value of 50% of the prior scalar current value;
When the pre-scalar current value is sampling the secondary current, it is a scalar current value of 0.5 cycle or 1 cycle before the sampling,
The ratio differential relay according to claim 2, wherein:   4. The ratio differential relay according to claim 3, wherein when the secondary current is sampled, a change detection amount of one bit is less than 20% and the secondary current is treated as “0”. . A short-circuit device (20 _{1 to} 20 ₃ ) provided in the vicinity of the current transformer of the current transformer circuit and for short-circuiting the secondary side of the current transformer for each phase;
When the lock circuit detects an abnormality in the phase of the current transformer circuit based on the scalar current value and change rate of the secondary current, the current transformer corresponding to the phase of the current transformer circuit that detected the abnormality Generating a short-circuit command signal (S) for short-circuiting the secondary side of the phase of the phase, and outputting the generated short-circuit command signal to the short-circuit device,
The ratio differential relay according to any one of claims 1 to 4, wherein The ratio differential relay according to claim 5, wherein the short-circuit device includes a switch (21 _{1X to} 21 _3X ) that is turned on / off in response to the short-circuit command signal input from the lock circuit.   When the lock circuit detects an abnormality in the phase of the current transformer circuit based on a scalar current value and a change rate of the secondary current, the lock circuit further generates an alarm signal (ALM) to be output to the outside. The ratio differential relay according to claim 5 or 6. A plurality of transformers installed in each phase of the bus (1) breaker (3 _1X to 3 _3X) a trip signal for interrupting the respective (T _1X through T _3X) and outputs the ratio differential relay circuit for protecting ( 11) a ratio differential relay malfunction prevention method for preventing malfunction of 11),
The lock circuit (13) includes a scalar current value (| i _1X | to | i _3X |) of the secondary current of the current transformer (2 _1X to 2 _3X ) installed in the vicinity of the transformer and the secondary current. Based on the change rate (Δ | i _1X | ˜Δ | i _3X |) of the scalar current value, whether the secondary current instantaneously became “0”, or the change rate was detected as no change in the own circuit current Monitoring whether it is greater than or equal to the value (β) (S11);
When the secondary current instantaneously becomes “0” or the rate of change is equal to or greater than the detected value of no change in the own circuit current, the lock circuit causes the phase of the bus corresponding to the corresponding phase of the own circuit. A step (S12) of checking whether the circuit breaker installed in the battery is in an on state;
When the circuit breaker installed in the phase of the bus corresponding to the corresponding phase of the own circuit is in the on state, the change rate in the corresponding phase of the other circuit is detected as no change in other circuit current. A step (S13) of checking whether or not the value (α) or less;
When the rate of change in the corresponding phase of the other circuit is equal to or less than the detected value of no change in other circuit current, the lock circuit is installed in the phase of the bus corresponding to the corresponding phase of the own circuit. Generating a lock signal (L) not to output the trip signal for shutting off the device, and outputting the generated lock signal to the ratio differential relay circuit (S14);
A ratio differential relay malfunction prevention method comprising: The other circuit current no change detection value is a value of 20% of the previous scalar current value,
The self-circuit current no change detection value is a value of 50% of the prior scalar current value;
When the pre-scalar current value is sampling the secondary current, it is a scalar current value of 0.5 cycle or 1 cycle before the sampling,
The ratio differential relay malfunction prevention method according to claim 8, wherein: When the lock circuit detects an abnormality in the corresponding phase of the own circuit based on the scalar current value and change rate of the secondary current, it generates an alarm signal (ALM) to be output to the outside and generating a short-circuit command signal to be output the short circuit device for short-circuiting the secondary side of the phase of the current transformer (20 ₁ to 20 ₃₎ corresponding to the phase (S) (S14, S15) further comprising 10. The ratio differential relay malfunction prevention method according to claim 8 or 9, wherein:

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