JPH0767233B2 - Digital ground fault bus protection relay - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital ground fault bus protection relay device for protecting a bus of a high resistance ground power system, and more particularly to prevention of ground fault accident detection error and external The present invention relates to a digital ground fault bus protection relay device that realizes reliable operation control against a ground fault accident.

[Prior Art] FIG. 7 is a block diagram showing a conventional ground fault bus protection relay device described in, for example, Japanese Patent Publication No. 50-27574.

In the figure, (1) is a bus of the electric power system, which is shown as a single line for convenience, but is actually a three-phase line. (2m) (m
= 1 to n) are n lines connected to the bus (1), (3
m) is a current transformer (hereinafter referred to as CT) installed on each line (2 m), and (4) is a voltage transformer (hereinafter referred to as PT) such as an instrument transformer connected to the busbar (1). is there.

(5m) is connected to the secondary side of each CT (3m) and each line (2m)
Which are input devices for detecting the zero-phase current Im of the transformer, and the resistors (8) and the rectifier circuit connected to the secondary side of the transformers (6) and (7), respectively, which are arranged in series. (9) and are provided.

(10) is a busbar protection relay that derives a relay operation signal S based on the zero-phase voltage V of the busbar (1) obtained from the tertiary side of PT (4) and the output of each input device (5m), An effective component differential amount deriving circuit (11) for deriving the effective breakdown differential amount E _D based on the phase voltage V and the zero phase current differential amount from each transformer (6), and the zero phase voltage V and rectification. a circuit effective inhibiting amount deriving circuit for deriving an effective inhibiting amount E _R based on the zero-phase current suppression amount from the transformer (7) through (9) (12), the active component differential amount E _D and the effective suppression And a level detection circuit (13) for deriving the relay operation signal S based on the ratio differential of the quantity E _R.

Next, the operation of the conventional ground fault bus protection relay device shown in FIG. 7 will be described.

An input device (5 with each zero-phase current Im (m = 1 to n) introduced
m) derives the differential amount for relay operation via the transformer (6) and the suppression amount for relay operation suppression via the transformer (7), the resistor (8) and the rectifier circuit (9). To do.

Generally, the effective component differential amount derivation circuit (11) in the busbar protection relay (10) vector-synthesizes the zero-phase current differential amounts for all lines (2 ₁ ) to (2n) into a differential amount. The effective suppression derivation circuit (12) connects the outputs of the rectifier circuits (9) in parallel, and sets the maximum value of the zero-phase current suppression amounts proportional to the zero-phase current Im of each line as the suppression amount.

Therefore, in the case of an external ground fault on bus (1), the differential amount is 0.
Or, it becomes a very small amount proportional to the CT (3m) error, and the suppression amount becomes an amount proportional to the fault current.

In the case of an internal ground fault on the bus (1), the differential amount is proportional to the fault current, and the suppression amount is proportional to the maximum value of the fault current of each line (2m) flowing into the bus (1). It will be the amount.

The level detection circuit (13) in the busbar protection relay (10) uses the ratio differential principle, and detects the ground fault accident of the busbar (1) by comparing the levels of the differential amount and suppression amount by ratio differential. To do.

At this time, if the power transmission line connected to the bus bar (1) has a cable system, the normal ratio differential relay may not be able to reliably operate in the event of an internal ground fault.

FIG. 8 is a block diagram showing an ordinary ratio differential relay,
(2a) to (2c) are lines connected to the bus (1), (3a)
~ (3c) is the CT installed in each line (2a) ~ (2c), (1
4) the cable charging capacitance between the ground and the line (2a) and (2b), jI _C is a charging current flowing through the line (2a) and (2b).

(15) and (16) are a neutral point ground resistance (hereinafter referred to as NGR) and a neutral point grounded reactor (hereinafter referred to as NGL) that are inserted between the line (2c) and the ground, and are connected in parallel with each other. Has been done. NGL (16) is provided for compensation when the charge capacity (14) is large.

(17) is a differential amount derivation circuit corresponding to the output circuit of the transformer (6) in FIG. 7, (18) is a suppression amount derivation circuit corresponding to the output circuit of the rectifier circuit (9), and (1) are A ratio differential relay corresponding to the level detection circuit (13).

In power system of Figure 8, when the bus (1) in 1FaiG (1 Senchi絡) Accident A is fault current I _N flows generated, the line (2a) and CT (3a) of (2b) and ( charging current jI _C flows through the 3b), the CT (3c) of the line (2c), NGR (1
Fault current flowing in 5) _{I N} and (reactor current flowing through the 16) (combined current and _{-jI L (I N -jI L)} NGL flows.

Here, suppression amount derivation circuit (18), so to derive the maximum value of the charging current jI _C and the resultant current _(I N _{-jI L)} as inhibiting amount _{I R,} inhibiting amount _{I R} is _I R = I _N -jI _L becomes, the amount proportional to the combined current _(I N _{-jI L).}

Further, the differential amount deriving circuit (17) derives the total value of the input currents as the differential amount I _D , so that the differential amount I _D becomes I _D = I _N −jI _L + 2jI _C If I _L = 2I _C , then I _D = I _N.

Ratio differential relay (19), for example, to determine the _{I D -ηI R> K S ...} , it derives the relay operation signal S satisfies the equation. However, in the formula, η is a ratio differential constant, and K
_S is a criterion constant serving as a criterion.

As is apparent from the equation, the suppression quantity I _R by the charging current jI _C and the reactor current (-jI _L) reactive current, such as (current having a vector phase difference of [pi / 2 with respect to fault current I _N)
As the ratio becomes larger, the ratio differential relay (19) is connected to the bus bar (1).
Even if an internal ground fault occurs, the relay operation signal S is not derived and the operation becomes inoperative.

As a countermeasure against such a reactive current, the conventional device of FIG. 7 uses the ratio differential principle by the effective component differential amount derivation circuit (11) and the effective component suppression amount derivation circuit (12).

That is, the effective differential amount derivation circuit (11) in the busbar protection relay (10) is connected to the zero phase current differential amount from each input device (5m) and the PT
Based on the zero-phase voltage V from (4), the effective component differential amount E _D in phase with the zero-phase voltage V is derived, and similarly, the effective component suppression amount derivation circuit (12) controls each zero-phase current suppression. Based on the amount and the zero-phase voltage V, the effective component suppression amount E _R in phase with the zero-phase voltage V is derived.

Then, the level detection circuit (13), based on the active component differential amount _{E D} and the active component inhibiting amount _{E R, E D -η R ·} E R ≧ Ko ... However, eta _R: inhibition ratio constant Ko: determining If the reference constant is judged and the formula is satisfied, the relay operating signal S for bus protection is derived.

[Problems to be Solved by the Invention] As described above, the conventional ground fault bus protection relay device has an effective component differential amount which is proportional to the effective component sum of the zero-phase current Im for each line (2 m). and (operation amount) E _D, also the amount proportional to the active component of the zero-phase current Im of each line (2m) as the active component inhibiting amount E _R, with the use of the ratio differential principle, reactive current ( thereby preventing erroneous non-operation internal ground fault due to unnecessary suppression amount due to charging current jI _C, or the reactor current (-jI _L)).

However, the external ground fault accident occurs, as the active component inhibiting amount E _R can be obtained an amount proportional to the NGR current (fault current) I _N, for transient DC component current is generated by the NGL (16) CT (3m) may transiently cause DC saturation, and if the transient DC component current is large and the duration is long,
There is a problem in that it may not be suppressed and may malfunction.

Further, when an external ground fault, when only reactive current is passed through the bus (1) is not the amount of active component suppression obtained E _R, there is a problem that malfunction becomes uninhibited state It was

The present invention has been made to solve the above problems, and uses a digital relay using a microprocessor to prevent a ground fault accident detection error due to the transient DC saturation of CT. The purpose is to obtain a relay device.

Another object of the present invention is to provide a digital ground fault busbar protection device capable of suppressing the operation even if only the reactive current penetrates the busbar in the event of an external ground fault.

[Means for Solving the Problem] A digital ground fault bus protection relay device according to the present invention provides a zero-phase voltage of a bus line derived from a voltage transformer and a zero-phase current of each line derived from a current transformer. Based on the voltage data and the current data, the sample-and-hold device that samples at the same time and the same interval, the AD converter that converts the sampled zero-phase voltage and zero-phase current into digital data and current data, respectively. And an arithmetic processing means for deriving a relay operation signal for busbar protection, and as the arithmetic processing means, a time integration means for deriving a time integral value by adding a product value of voltage data and current data for a predetermined time. , Differential amount calculation means for deriving the differential amount by adding all the time integrated values for each line, suppression amount calculation means for deriving the suppression amount based on the absolute value of the time integrated value, differential amount and Suppression The ratio differential operation amounts is provided with a the ratio differential operation means for deriving a relay operation signal.

Further, a digital ground fault bus protection relay device according to another invention of the present invention further comprises, as an arithmetic processing means, a phase shift means for deriving phase shift voltage data by phase shifting voltage data by a predetermined phase angle. Is provided and the product value of the phase shift voltage data and the current data is added for a predetermined time.

[Operation] In the present invention, the product value corresponding to the ground fault accident power of each line is integrated for a predetermined time (one cycle), and the ratio differential operation is performed based on this time integrated value, thereby performing the cable system. It is possible to prevent the generation of unnecessary suppression amount due to the reactive current of and to reduce the ground fault detection error due to the transient DC saturation of CT.

In another invention of the present invention, after the voltage data is phase-shifted by an appropriate phase angle (for example, π / 12 to π / 6), the product value with the current data is obtained, and the ratio is calculated based on this product value. By performing a differential operation, the amount of suppression due to the reactive current in the cable system is limited to an appropriate amount, and it operates reliably in the case of an internal ground fault, and the amount of suppression is generated by the reactive current in the case of an external ground fault. To prevent malfunction.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a block diagram showing an embodiment of the present invention.
(2m), (3m) and (4) are the same as described above.

Tm (m = 1 to n) is CT (3m) installed in each line (2m)
Is an input transformer for introducing the zero-phase current Im from PT, and To is an input transformer for introducing the zero-phase voltage V from PT (4) installed on the bus bar (1).

(20) is a digital relay that introduces the zero-phase voltage V and the zero-phase current Im through the input transformers To and Tm to derive the relay operation signal S, and detects the harmonics contained in the zero-phase voltage V and the current Im. A filter (21) to be removed and a sample-hold device (hereinafter, SH) that samples the zero-phase voltage V and the zero-phase current Im through the filter (21) at the same time and at the same interval.
(22) and a multiplexer (23) for selecting the sampled zero-phase voltage V and zero-phase current Im in time series.
And an AD converter (24) for converting the zero-phase voltage V and the zero-phase current Im through the multiplexer (23) into digital voltage data DV and current data DIm, respectively, and voltage data DV and current data DIm are stored. A memory (25), an arithmetic processing means (hereinafter, referred to as a CPU) (26) for arithmetically operating the voltage data DV and the current data DIm according to a predetermined program, and C
An output device (27) for deriving a calculation result of the PU (26), that is, a relay operation signal S is provided.

FIG. 2 is a functional block diagram showing the contents of the arithmetic processing of the CPU (26) as the arithmetic processing means, and (31) is the voltage data DV.
The product value DPm of the current data DIm and the current data DIm for a predetermined time (for example, ω
Time integration means for deriving the time integration value Pm by adding only one cycle corresponding to t = 0 to 2π), and (32) is the difference by adding the time integration value Pm for all lines (m = 1 to n). It is a differential amount calculation means for deriving the movement amount P _D.

(33) is inhibiting amount calculating means for deriving an inhibitory amount P _R based on the absolute value of the time integral value Pm, the maximum value of the absolute values of the time integral value Pm, or all (m = 1 to n) The scalar sum is derived as the suppression amount P _R.

(34) is a ratio differential calculation means for deriving the relay operation signal S ₁ by ratio differential calculation of the differential amount P _D and the suppression amount P _R , (3
5) differential level determining means for detecting the level of the zero-phase current amplitude value from the ratio of the differential amount P _D and the voltage data DV deriving a relay operation S _2, (36) each relay operation signals S ₁ and It is an AND gate for deriving the final relay operation signal S by taking the logical product of S ₂ .

Next, the operation of the embodiment of the present invention shown in FIGS. 1 and 2 will be described.

Zero-phase voltage V and CT of bus (1) derived from PT (4)
The zero-phase current Im of each line (2m) derived from (3m) is introduced into the digital relay (20) via the input transformers To to Tn, and the filter (21), SH (22) and multiplexer (23). Is introduced into the AD converter (24) via the, and digital data, that is, voltage data DV at each sampling time of SH (22).
And the current data DIm are stored in the memory (25).

The CPU (26) reads out the voltage data DV and the current data DIm from the memory (25), and first uses the time integration means (31) based on the product value DPm of the voltage data DV and the current data DIm for each line. Time integration value equivalent to (2m) ground fault power
Find Pm.

Generally, the angular frequency of the power system is ω, and the amplitude of the zero-phase voltage V is
Vo, amplitude of zero-phase current Im is Iom, zero-phase voltage V and zero-phase current Im
If the phase angle between and is θm, the zero-phase voltage V and the zero-phase current Im at a certain time t are functions of the time t: V (t) = Vo · sinωt ... Im (t) = Iom · It is represented by sin (ωt + θm). Therefore, the product value of both at time t is V (t) · Im (t) = Vo · Iom · sinωt · sin (ωt + θm) = Vo · Iom {cosθm-cos (2ωt + θm)} / 2 ... The time integrated value obtained by integrating only one cycle (ωt = 0 to 2π) is ∫ [Vo.Iom {cosθm-cos (2ωt + θm)} / 2] dt = π ・ Vo ・ Iom ・ cosθm .... . From the equation, it can be seen that the time integral value is represented by the product of the zero-phase voltage amplitude value Vo and the effective component amplitude value Iom · cos θm of the zero-phase current Im, and is independent of the time t.

In this case, since the digital data actually calculated by the CPU (26), that is, the voltage data DV and the current data DIm, are values obtained at the sampling time t _K at regular intervals, the time integration value Pm corresponds to one cycle. It is represented by the sum of the product values of the sampling times t _K.

For example, when the sampling frequency is 12 times ω, the sampling time interval corresponds to 1/12 of one cycle (2π), that is, π / 6, and 12 of the sampled digital data
If one product value is added, it means that one cycle of integration has been performed. Therefore, the time integration value Pm calculated at time t ₁₂ is the sum of the voltage data DV (t _K ) and the current data DIm (t _K ) at each sampling time t _K from K = 0 to K = 11. Pm = ΣDPm (t _K ) = Σ {DV (t _K ) · DIm (t _K )} = K · Vo · Iom · cos θm, where K is a constant.

Next, the differential amount calculation means (32) adds the time integrated value Pm for all lines (m = 1 to n), and derives the differential amount P _D from P _D = ΣPm.

On the other hand, the suppression amount calculation means (33) takes the absolute value of the time integration value Pm for each line (2m), of which the maximum value Max | Pm
|, _{Or, | P 1 | ~ | Pn} | Pm | | look as inhibiting amount P _R, P _{R =} Max | scalar sum sigma of Pm | ... _{or, P R = Σ | Pm |} ... to derive. Suppression amount P _R of the formula or formula,
The effect of the present invention can be obtained regardless of which is selected.

Next, the ratio differential operation means (34) receives the introduced differential amount P.
_{Based on D} and the suppression amount P _R , using the ratio differential principle, P _D −η _R · P _R > O, where η _{R is a} ratio differential constant, and if the formula is satisfied, the relay operation is performed. Derive the signal S ₁ .

Further, the differential level determining means (35) is a differential given by | Io _D | = | P _D | / | DV | ... Based on the ratio of the absolute values of the differential amount P _D and the voltage data DV. Current | Io _D |
_D | is compared with the tap value constant K _T , and if | Io _D |> K _T is satisfied, the relay operation signal S ₂ is derived.

Incidentally, the absolute value of the voltage data calculated in the certain time t _J | DV | is based on the time t _J voltage data DV (t _J) to correspond to the [pi / 2 3 Sampling before time t _J-3 of Te, | DV | = [{DV (t J)} 2 + {DV (t J-3)} 2] 1/2 = {{Vo · sinωt J) 2 (Vo · cosωt J) 2} 1/2 Required from.

Also, the equation is | Io _D | = | P _D | / | DV | ＝ | K ・ Vo ・ Σ (Iom ・ cosθm) | / | Vo | ＝ | K ・ Σ (Iom ・ cosθm) |, And the differential current | Io _D | becomes an amount proportional to the absolute value of the differential amount P _D.

The AND gate (36) is provided with the relay operation signals S ₁ and S ₂ from the ratio differential operation means (34) and the differential level determination means (35).
And the final relay operation S is derived.

As a result, the following effects can be obtained.

(I) Since it is not affected by the reactive current, it does not become inoperable due to an excessive control of the charging current and NGL current due to an internal bus fault, and the circuit breaker that responds reliably can be opened.

(Ii) It is possible to prevent malfunction due to transient DC saturation of CT (3 m).

Among these effects, (i) is apparent from the description based on the above formulas, and hence the effect (ii) will be specifically described below with reference to FIGS. 3 to 5.

In FIG. 3 (a), (2 _X ) to (2 _Z ) are lines connected to the bus (1), and (3 _X ) to (3 _Z are installed in each line (2 _X ) to (2 _Z ). The computed CT, in this case,
NGR (15) is connected to the line (2 _X), cable charge capacity to the line (2 _{Y) (14)} and NGL (16) is connected.

Assuming that the line (2 _Z) external ground fault A of 1φG occurs, NGR (15) the fault current I _N flows through the cable charging capacity (14) and each of the NGL (16) charge current Ic and the reactor current I _L flow.

At this time, the zero-phase voltage V detected from PT (4) (see FIG. 1) has a sinusoidal waveform according to the equation, as shown in FIG.

In addition, as described above, the charging current Ic and the reactor current I _L
If the relation of | Ic | = | I _L | is satisfied and the time constant of the transient DC component current generated by the reactor of the power system is T, the primary current at each CT (3 _X ) to (3 _Z ) I _X , I
_Y and -I _Z are _{each, I X = I N · sinωt} I Y = I L · exp (-t / T) + (Ic-I L) cosωt = I L · exp (-t / T) -I _{Z = I X + I Y =} I L · exp (-t / T) + a _{I N} · _sinωt. Therefore, Ix is a waveform in the same phase as the zero-phase voltage V, I _Y is a waveform corresponding to the transient DC component current I _L exp (−t / T), −I
_Z has a waveform obtained by combining I _X and I _Y. From Fig. 3 (b) showing these waveforms, CT (3
It can be seen that _{Z 2} ) is easily saturated.

FIG. 4 (a) shows a typical example installed on the line (2).
FIG. 4 (b) is a schematic diagram conceptually showing the CT (3), and FIG. 4 (b) is a waveform diagram for each current. I ^[1] and I ^[2] are primary and secondary currents in the CT (3), Iex Is the exciting current corresponding to the error, and I _DE is the transient DC component error contained in the exciting current Iex.

From FIG. 4 (b), when a primary current I ^[1] (solid line) containing a transient DC component current (for example, exp (−t / T)) is applied to the primary side of CT (3), CT (3) It can be seen that is easily saturated. Also, the exciting current Iex generated at this time (dashed line)
Is an AC current delayed by about π / 2 from the phase of the primary current I ^[1] (phase of the zero-phase voltage V), and the transient DC component error I _DE (2
It can be seen that it contains many dotted lines.

For simplification, the transient DC component error I _DE is set to I _DE = exp (−t / T), and the difference between the transient DC component error I _DE is set to only one line (2). Explain that the momentum P _D is hardly affected. From the above equations (1) to (6), the differential amount error ΔP _D due to the transient DC component error I _DE is ΔP _D = ∫ {exp (-t / T) ・ Vo ・ sinωt} dt = Γ {[-(t) cosωt]- [(t) sinωt] / ωT} = Γ {1 / ω- (t _Q )}…. However, Γ = 1 / {1+ (1 / ωT) ² } ≈1 ... = exp (-t / T) / ω ... and [-(t) cosωt] and [(t) sinω
t] is the value obtained by subtracting the value obtained by substituting t = 0 from the value obtained by substituting t = t _Q , and t _Q indicates the time corresponding to ωt = 2π. By substituting the equation and the equation into the equation, ΔP _D = {1-exp (-t _Q / T)} / ω {1+ (1 / ωt) ² } ≈ {1-exp (-t _Q / T)} Therefore, it can be seen that the differential amount error ΔP _D becomes almost zero and is significantly reduced, considering that / ω 2 is sufficiently large. The alternating current component of the exciting current is delayed by about π / 2, and as shown in the above formulas, it is almost removed as an ineffective component.

FIG. 5 (a) is a circuit diagram corresponding to FIG. 3 (a), FIG. 5 (b) is a waveform diagram, and FIG. 5 (c) is a waveform showing the operation output corresponding to FIG. 5 (b). a _diagram, I X '~I _Z' each CT
The secondary currents detected from (3 _X ) to (3 _Z ) are shown.

As is clear from Fig. 5, it becomes the inflow end of the ground fault current.
The sum (I _X ′ + I _Y ′) of the secondary currents _IX ′ and I _Y ′ of CT (3 _X ) and (3 _Y ) has a waveform including a transient DC component current, and CT (3) which is an outflow end. _The secondary current I _Z ′ of _Z ) has a waveform almost opposite in polarity to the secondary current (I _X ′ −I _Y ′),
The sum of all secondary currents (I _X ′ + I _Y ′ + I _Z ′) becomes the error differential current I _D ′.

Also, the calculation outputs | I _R12 | and | I _R3 | obtained by calculating the absolute values of the secondary currents (I _X ′ + I _Y ′) and I _Z ′ are the time integral value Pm used in the suppression amount calculation means (33). The calculation output I _RD of the error differential current I _D ′ corresponds to the absolute value waveform and corresponds to the error of the differential amount P _D derived from the differential amount calculating means (32).

It can be seen from FIG. 5 that the operation output I _RD (differential amount error ΔP _D ) can be remarkably reduced even when the transient DC component current is included in the secondary current.

Next, an embodiment of another invention of the present invention will be described with reference to FIG.

In FIG. 6, (31) to (36) are the same as those described above, and each operation output is associated with the same seal with a “′”.

(37) shows the voltage data DV as a predetermined phase angle θo (for example, π
/ 12 to π / 6)), and is adapted to derive the phase shift voltage data DV _θ to the time integration means (31).

In this case, the phase shift zero-phase voltage V _θ (t) at time t is
From the equation, V _θ (t) = Vo · sin (ωt + θo), and the product value with zero-phase current Im (t) is V _θ (t) · Im (t) = Vo · Iom · sin (ωt + θo) · sin ( ωt + θm) = Vo · IoM {cos (θm-θo) -cos (2ωt + θm + θo)} / 2 , and the time integration value, the equation, ∫V _theta (t ) · Im (t) dt = π · Vo · Iom · cos (θm−θo).

Therefore, at each sampling time t _K , the phase shift voltage data DV _θ (t _K is derived from the phase shift means (37) is DV _θ (t _K ) = Vo · sin (ωt _K + θo) = K ₁ Vo · sin ωt _K + K ₂ Vo · cosωt _K = K ₁ Vo (t _K ) + K ₂ {−Vo (t _K−3 )} = K ₁ Vo (t _K ) −K ₂ Vo (t _{K + 3} ), where K ₁ = cos θo, K ₂ = sin θo, and t
_K-3 represents the time three samplings before, which corresponds to π / 2.

Further, the time integral value Pm ′ derived from the differential amount calculating means (32) at the time t ₁₂ is the phase shift voltage data DV _{θ at the} time t _K.
The product value of (t _K ) and the current data DIm (t _K ) is _K = 0.
Since it is obtained by summing up _K = t ₁ from the equation and _{equation, Pm '= Σ {DV θ} (t K) · DIm (t K)} = K · Vo · Iom · cos (θm-θo) ... Becomes

Based on this time integrated value Pm ′, differential amount calculation means (32)
And the suppression amount calculation means (33) derives the differential amount P _D ′ and the suppression amount P _R ′ as described above, and the ratio differential calculation means (34) derives the relay operation signal S ₁ ′.

Further, the differential level determination means (35) obtains the differential current | Io _D ′ | based on the formula, compares it with the tap value constant K _T, and
When Io _D ′ |> K _K is satisfied, the relay operation signal S ₂ ′ is derived, and the differential current | Io _D ′ | at this time is | Ic _D | = | P _D ′ | / | DV | = | K · VoΣ {Iom · cos (θm−θo)} / | Vo | = | KΣ {Iom · cos (θm−θo)} |

Finally, the AND gate (36) ANDs the relay operation signals S ₁ ′ and S ₂ ′ to derive the final relay operation signal S.

According to the configuration shown in FIG. 6, the control amount P _R ′ derived based on the time integration value Pm ′ is, as is clear from the equation, the | cos (θm−θo) | of the zero-phase current Im. It is a proportional amount. Further, reduction through reactive current (Ic or I _L) passing through the bus (I) when an internal or external ground fault is that the reactive current has a phase difference of [pi / 2 relative to the zero-phase voltage V Therefore, | cos (−θo ± π / 2) | = sinθo | holds, so the amount is proportional to | sinθo |.

Therefore, if the phase angle | θo in the phase shift means (37) is set to an appropriate value (for example, about π / 12 to π / 6), the malfunction due to excessive suppression during an internal ground fault and the external ground fault will occur. It is possible to prevent malfunctions due to unrestrained accidents.

[Effects of the Invention] As described above, according to the present invention, the zero-phase voltage of the bus bar derived from the voltage transformer and the zero-phase current of each line derived from the current transformer are sampled at the same time and at the same interval. A sample and hold device, an AD converter that converts the sampled zero-phase voltage and zero-phase current into digital voltage data and current data, respectively, and a relay operation signal for busbar protection based on the voltage data and current data. The calculation processing means for deriving is provided, and the calculation processing means includes a time integration means for adding a product value of the voltage data and the current data for a predetermined time to derive a time integration value, and a time integration value for each line. Differential amount calculating means for deriving the differential amount by adding all the numbers,
Since it is composed of the suppression amount calculation means for deriving the suppression amount based on the absolute value of the time integration value and the ratio differential calculation means for deriving the relay operation signal by the ratio differential calculation of the differential amount and the suppression amount, it is invalid. It is possible to derive a highly reliable relay operation signal without being affected by the branch current and to obtain a digital ground fault bus protection relay device that prevents a ground fault accident detection error due to transient DC saturation of the current transformer. is there.

In another invention of the present invention, the arithmetic processing means includes:
Furthermore, a phase shift means for deriving the phase shift voltage data by shifting the voltage data by a predetermined phase angle is provided so that the operation can be suppressed even if only the reactive current penetrates the bus in the event of an external ground fault. So, it works reliably in the event of an internal ground fault, and
There is an effect that a digital ground fault busbar protection device that can prevent malfunction in the event of an external ground fault is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a functional block diagram showing the configuration of the arithmetic processing means in FIG. 1, and FIG. 3 (a) is a circuit showing an example of an external ground fault. Fig. 3 (b) is a waveform diagram showing the zero-phase voltage and the primary current of the current transformer at the time of an external ground fault, and Fig. 4 (a) is a conceptual configuration diagram showing the current transformer. Figure (b) is a waveform diagram showing the primary current, secondary current, and exciting current in the current transformer, Figure 5 (a) is a circuit diagram showing an example of an external ground fault, and Figure 5 (b) is an external ground fault. Waveform diagram showing the secondary current of the current transformer at the time of accident, Figure 5 (c) is
FIG. 6 is a waveform diagram showing an arithmetic output obtained by the present invention corresponding to FIG. 6B, FIG. 6 is a functional block diagram showing an arithmetic processing means according to another embodiment of the present invention, and FIG. FIG. 8 is a configuration diagram showing a ground fault bus protection relay device, and FIG. 8 is a configuration diagram showing an example of an external ground fault accident for explaining the operation of FIG. (1) …… Bus, (2 ₁ ) to (2n) …… Line (3 ₁ ) to (3n) …… Current transformer (CT) (4) …… Voltage transformer (PT) (22) …… Sample-and-hold device (SH) (24) …… AD converter (26) …… Computation processing means (CPU) (31) …… Time integration means, (32) …… Differential amount calculation means (33) …… Suppression Quantity calculating means (34) …… Ratio differential calculating means (37) …… Phase shifting means, V …… Zero phase voltage I _{1 to} In …… Zero phase current, DV …… Voltage data DI _{1 to} DIn, DIm ... ... current data Pm, Pm '...... time integral value _{P D,} P _D' ...... differential _{amount, P R,} P R '...... inhibiting amount DV _theta ...... phase voltage data S, S _1, S _1' ...... Relay operation signal In the figures, the same symbols indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A voltage transformer installed on a bus of a power system, a current transformer installed on each line connected to the bus, a zero-phase voltage of the bus derived from the voltage transformer, and A sample-and-hold device for sampling the zero-phase current of each of the lines derived from the current transformer at the same time and at the same interval, and the sampled zero-phase voltage and the zero-phase current, respectively, as digital voltage data and An AD converter for converting into current data, and an arithmetic processing means for deriving the relay operation signal for protecting the bus based on the voltage data and the current data, the arithmetic processing means, the voltage data and the current A time integrating means for adding a product value with data for a predetermined time to derive a time integrated value, and a differential amount calculator for adding the time integrated value for all of the lines to derive a differential amount. A suppression amount calculation means for deriving a suppression amount based on the absolute value of the time integration value; and a ratio differential calculation means for deriving the relay operation signal by a ratio differential calculation of the differential amount and the suppression amount. A digital type ground fault bus protection relay device characterized by including. 2. The arithmetic processing means includes a phase shift means for deriving the phase shift voltage data by shifting the phase of the voltage data by a predetermined phase angle, and the time integrating means includes the phase shift voltage data and the current data. The digital ground fault bus protective relay device according to claim 1, wherein product values are added for a predetermined time.