JPH0638354A - Bus protective relay unit - Google Patents

Abstract

PURPOSE:To stabilize relay unit by determining a ratio between a differential current obtained from vector sum of zero-phase currents at respective terminals and a restraining current obtained from maximum values of zero-phase currents at respective terminals, and locking the output from a ratio operating means upon detection of an eddy current when the restraining current is higher than a predetermined level. CONSTITUTION:A difference derivation means 21 determines a differential current ID from vector sum of zero-phase currents at respective terminals. A restrain derivation means 22 determines a restrain current IR from maximum values or scalar sum of zero-phase currents at respective terminals. A ratio operating means 23 determines the ratio between the currents ID and IR and produces an output if ID>IR. An eddy current detecting means 24 outputs an eddy current signal if the restrain current IR is higher than a value KV0 which is proportional to a zero-phase voltage V0. Upon receiving the eddy current signal, a lock means 25 locks output from the ratio operating means 23. Output is delivered from the ratio operating means 23 on condition that no output is delivered from the eddy current detecting means 24. This constitution enhances safety, accuracy, and coordination in setting of the relay unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a busbar protective relay device in a high resistance grounding system.

[0002]

2. Description of the Related Art In order to protect a ground fault in a high resistance grounding system, it is necessary to improve the detection sensitivity, but on the other hand, an error in a current transformer (hereinafter referred to as CT) due to an increase in power flow in the system increases, and line charging occurs when a ground fault occurs. Existence of current other than ground fault current due to ground resistance, such as the current of the current discharge and charging current compensating reactor (from the relationship with the zero-phase voltage when a ground fault occurs, the ground fault current due to ground resistance is used as an effective component current, line There is a contradictory need to lower the detection sensitivity due to charging current, reactor current, etc. (generally referred to as reactive current), etc., and various methods have been proposed in the past (Japanese Patent Publication Nos. 50-27475 and 53-53).
18090).

Another problem is that at the time of a ground fault involving a short circuit, especially a zero-phase current similar to a short-circuit current flows into the protective relay device due to an external different-phase ground fault accident, an internal-external different-phase ground fault accident, or the like. That is.

FIG. 5 shows this state in an external out-of-phase ground fault. That is, in the figure, 1 is a protected bus, 2 is a power supply side line, 3 and 4 are load side lines, and F is a load side line 3.
_An a-phase ground fault occurs at _one point, and a b-phase ground fault occurs at the F ₂ point on the load side line 4.

Further, reference numerals 5, 6 and 7 are CTs, and the input to the ground fault relay is generally a residual circuit of three-phase CT (I ₀ = I
_a + I _b + I _c: Symmetric coordinate method _{I a + I b + I c} = 3
I _0, but since this current is input to the relay device, it is generally referred to as I ₀ ).
It is assumed that T derives a zero-phase current. 8 is a power source, 9
Is a power supply side ground resistance (hereinafter referred to as NGR), and 10 is a differential relay device. Where I _NGR is the NGR current.

Next, considering the zero-phase current output of each CT 5 to 7 in FIG. 5, the current of CT 5 is I ₀₁ = I
The current of _NGR and CT6 is I ₀₂ = I _a , and the current of CT7 is I ₀₃
= I _b , and generally, if there is no CT error, I ₀₁ + I ₀₂
+ I ₀₃ = 0.

Considering that this system is a high resistance grounding system, I _a ≈I _b and I _a >> I _NGR . And in the busbar ground fault protection relay, I _NGR
Since the sensitivity is increased in order to detect, the input transformer may be saturated when an input current equal to the short-circuit current is applied. The accuracy of the outputs of CT5 to CT7 in the large current region becomes a problem, and the error becomes large.

As a countermeasure against this, for example, Japanese Patent Laid-Open No. 50-61.
646 and JP-A-55-86321. These are those in which the operation amount is suppressed in the large input range, and the outline is as shown in FIG. In the figure, 16 is a rectifier circuit, 11 is a differential current input circuit, 12 is a resistor, 13 is a suppression current input circuit, 14 is a ratio calculation circuit,
Reference numeral 15 is a Zener diode.

FIG. 7 shows the characteristics of this busbar protective relay device, where I ₁ and I ₂ are inflow and outflow currents. Although the derivation of the differential current and the suppression current is not shown in FIG. 5, the differential current I _D = | I ₁ −I ₂ |, the suppression current I
_R = | I ₁ | + | I ₂ |, and this derivation may be either input transformer primary synthesis or input transformer secondary synthesis.

In FIG. 7, when _ID becomes larger than point P, the differential amount does not increase any more due to the Zener diode 15, and the calculation result of the ratio calculation circuit 14 becomes apparently inoperative (as shown in FIG. 7). If you write it like this, the ratio becomes very large). Depending on how the Zener diode 15 is operated, the ratio changes as shown by. However, there is a failure point on the I _NGR line indicated by the alternate long and _short dash line in FIG. 7, and if the 100% ground fault I _NGR is large, it will be difficult to set the P point.

[0011]

Since the conventional busbar protective relay device is constructed as described above, the avalanche action of the Zener diode 15 is controlled by the ground resistance value so as to suppress the operation amount in the large input region. Since it has to be manufactured in consideration of hardware cooperation such as use, it is difficult to manufacture a general-purpose device, and there is a problem that the device cannot be inexpensive.

The invention of claim 1 is made in order to solve the above-mentioned problems, and it is easy to coordinate with external specifications (ground resistance current, etc.), and it is possible to detect continuous external failures depending on failure conditions. It is an object of the present invention to obtain a busbar protection relay device that can change the discrimination ability.

Further, according to the invention of claim 2, stable operation can be achieved against an error differential current at the time of an external accident, coordination with external specifications can be facilitated, and continuous external failures can be identified according to failure conditions. The purpose is to obtain a busbar protection relay device whose ability can be changed.

[0014]

According to a first aspect of the present invention, there is provided a busbar protective relay device, wherein differential deriving means for calculating a vector sum of zero-phase currents at respective terminals and maximum or scalar sum of currents at each terminal are obtained. Suppression derivation means, a ratio calculation means for performing a ratio calculation based on the differential current from the differential derivation means and the suppression current from the suppression derivation means, and when the suppression current is equal to or greater than a predetermined value proportional to the zero-phase voltage An overcurrent detecting unit that outputs a signal is provided, and the lock unit locks the output of the ratio calculating unit when the overcurrent detecting unit outputs a signal.

According to a second aspect of the present invention, there is provided a busbar protective relay apparatus in which differential derivation means for taking a vector sum of zero-phase currents at respective terminals, and effective differential differential from the differential current from the differential derivation means. Effective component differential deriving means for deriving current, active component suppression deriving component for deriving effective component suppression amount from each terminal zero-phase current and zero-phase voltage, and effective component differential current from the effective component differential deriving device. And a ratio calculation means for performing a ratio calculation based on the effective component suppression amount from the effective component suppression derivation means, and an overcurrent which outputs a signal when the output of the effective component suppression derivation means is equal to or greater than a predetermined value proportional to the zero-phase voltage. And a lock means for locking the output of the ratio calculation means when the overcurrent detection means outputs a signal.

[0016]

The busbar protection relay device according to the invention of claim 1 is
By the zero-phase voltage, which has a property proportional to the degree of ground fault,
A predetermined value for detecting the suppression current is linked, and the ratio differential operation output is locked by this detection.

Further, in the busbar protection relay device according to the invention of claim 2, the active differential of the differential current and the suppression current is obtained to prevent oversuppression due to the reactive current, and the error differential current in the event of an external accident. With respect to the above, the ratio calculation output can be locked when the signal of the overcurrent detection means is output while improving the external failure stability.

[0018]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 21 is a differential derivation means for taking the vector sum of the zero-phase current of each terminal, 22 is a suppression derivation means for taking the maximum value or a scalar sum of the zero-phase current of each terminal, and 23.
Is a ratio calculation means for performing a ratio calculation using the output of the differential derivation means 21 (referred to as differential current) and the output of the suppression derivation means (referred to as suppression current).

Further, 24 is an overcurrent detecting means for outputting when the suppression current is a predetermined value proportional to the zero phase voltage or more, and 25 is an output of the ratio calculating means 23 is locked when there is an output of the overcurrent detecting means 24. It is a logical product means as a lock means.

FIG. 2 is a characteristic diagram of the busbar protective relay device according to the present invention. In the figure, the symbols I _R100 and I _R50 are detected by the overcurrent detecting means 24 when the zero-phase voltage is 100% and 50%, respectively. Indicates a value. In addition, FIGS. 3A and 3B are one-line ground faults (1ΦG) for explaining the relationship between the zero-phase current and the zero-phase voltage.
And a symmetric coordinate method equivalent circuit at the time of two-line ground fault (2ΦG).

Next, the operation will be described. In FIG. 3, the zero-phase current is represented by I ₀ = V ₀ / R _N , and the zero-phase voltage is V ₀ = E · R _N / (2Z ₁ + R _F + in a _one -line ground fault.
R _N ), where R _N >> Z ₁ is taken into account, V ₀ = E · R _N / (R _F + R _N ), and when R _F is 0, there is a 100% ground fault.

At this time, I ₀ becomes maximum, and the value of I ₀ is used as the nominal value of the grounding system in the high resistance grounding system. In the case of a two-wire ground fault, V ₀ = E · R _N / 2 / (R _F + R
_N ). This means that V ₀ = E / even when R _F is 0.
It shows that it is only 2. Of course, I _{0 is} also ½ of the value at the one-line ground fault.

As described in the description of the conventional example, the systematic zero-phase current is as described above at the time of an external different-phase ground fault, but the relay input current is similar to the short-circuit current, and some measure is required. Has become. At the time of external out-of-phase ground fault, originally,
Since the zero-phase current is ½ or less, the present invention has been made with a focus on relay locking at a lower level. FIG. 2 shows this relationship.

In the case of 100% ground fault, the relay characteristics include the internal fault current corresponding to this in the protection range.
The protection range changes corresponding to (proportional to the magnitude of V ₀ ). That is, the detection sensitivity of the overcurrent detection means 24 is K *.
It is represented by V ₀ , and the detection sensitivity of the overcurrent detection means 24 becomes 1/2 in the case of an external phase ground fault.

As a result, the relay deriving current, which is similar to the short-circuit current at the time of the external ground fault, is applied to the overcurrent detecting means 24 by the suppression deriving means 22 as the suppression current. Since the CT saturation or the like occurs due to the relay input current similar to the short-circuit current at the time of the external different-phase ground fault, the output of the differential deriving means 21 becomes large and the ratio calculating means 23 may operate, but the overcurrent detecting means is present. By the logical product means 25 with the output of 24, the stability is maintained.

Example 2. FIG. 4 shows another embodiment of the present invention. In the figure, 26 is an effective differential deriving means, 27
Is an effective component suppression derivation unit, and 28 is an output of the effective component differential derivation unit 26 (referred to as an effective component differential current) and an effective component control amount that is an output of the effective component suppression derivation unit 27 (referred to as an effective component suppression current). It is a ratio calculation means for performing a ratio calculation.

Further, 29 is an overcurrent detecting means for outputting when the suppression current is a predetermined value or more proportional to the zero-phase voltage, and 30 is a logic for locking the output of the ratio calculating means 28 when there is an output to the overcurrent detecting means 29. It is a product means.

Next, the operation will be described. The usefulness of the ground fault bus protection by the calculation of the effective differential amount and the suppression amount is not related to the present invention, and therefore the description thereof is omitted here. In this embodiment, by taking the effective differential, the stability due to an external fault is increased, but the systematic zero-phase current is as described above when an external phase-to-ground fault occurs, but the relay input current is similar to the short-circuit current. And some measures are needed.

At the time of an external phase-to-ground fault, the zero-phase current is originally 1
Since it is / 2 or less, relay lock may be performed at a lower level as described in the above embodiment. That is, the detection sensitivity of the overcurrent detection means 29 is K * V.
It is represented by ₀ , and the detection sensitivity of the overcurrent detection means 29 is 1/2 in the case of an external different-phase ground fault.

As a result, the relay input current equivalent to the short-circuit current at the time of the external different-phase ground fault is given to the overcurrent detection means 29 by the effective component suppression derivation means 27 as the suppression current. Since CT saturation or the like occurs due to the relay input current at the time of the external different-phase ground fault, the output of the effective component differential deriving means 26 becomes large and the ratio calculating means 28 may operate, but the overcurrent detecting means 29 does not operate. Stability is maintained by the logical product means 30 with the output.

In this embodiment, since the suppression current also takes an effective part, it becomes easier to set the full scale in the digital relay and the sensitivity of the overcurrent detection element as compared with the embodiment shown in FIG. In other words, there are no restrictions on system conditions,
Therefore, the external out-of-phase ground fault can be easily detected.

This means that the relay inflow current at the time of a simple internal failure is I _NGR + I _C + I _L , so that in the embodiment of FIG. 1, the overcurrent detection sensitivity is I _C , I as a system condition.
_Although it is necessary to assume _L , in this embodiment, I _C and I _L
Is an invalid part, so that only I _{NG R} need be considered.

In the above embodiment, the effective component suppression derivation means 2
7 is not described in detail, the present invention may be applied to either the scalar sum suppression method or the maximum suppression method that is generally adopted, and the same effect as that of the above-described embodiment is obtained. In addition, in the scalar sum method, the currents of all terminals are added regardless of the polarity, so the scalar sum becomes twice the failure current in the event of an external accident. Therefore, in the scalar sum, the detected value of the overcurrent detection means is the maximum value. If the suppression method is twice as large as the suppression method, it becomes easier to achieve cooperation.

Further, in FIGS. 1 and 4, 100%
The detection values of the overcurrent detection means 24 and 29 at the time of the ground fault are arbitrary as long as they are equal to or more than the suppression current corresponding to the maximum zero-phase current.
The ground resistance should be the maximum value.

Further, the detection value of the overcurrent detection means 24, 29 at the time of 100% ground fault is arbitrary as long as it is equal to or higher than the suppression current corresponding to the maximum zero-phase current. Since the full-scale value is designed corresponding to the maximum zero-phase current, it may be matched with this value.

[0036]

As described above, according to the invention of claim 1, the differential deriving means for taking the vector sum of the zero-phase currents at each terminal and the suppression deriving means for taking the maximum value or the scalar sum of the terminal currents. A ratio calculation means for performing a ratio calculation based on the differential current from the differential derivation means and the suppression current from the suppression derivation means, and a signal when the suppression current is equal to or larger than a predetermined value proportional to the zero-phase voltage. The overcurrent detection means is provided, and the lock means is configured to lock the output of the ratio calculation means when the overcurrent detection means outputs a signal. By making the condition that there is no output of the detection means, and by making the detection value of the overcurrent detection means proportional to the zero-phase voltage, the stability of the device is increased, and it becomes easier to coordinate the settling. Also, you can get high precision There is an effect.

According to the second aspect of the invention, the differential deriving means for taking the vector sum of the zero-phase current of each terminal, and the effective differential current deriving from the differential current from the differential deriving means. Differential differential deriving means, effective component suppression deriving means for deriving an effective component suppression amount from each terminal zero-phase current and zero-phase voltage, effective component differential current from the effective component differential deriving means and the effective component suppression A ratio calculation means for performing a ratio calculation based on the effective component suppression amount from the derivation means, and an overcurrent detection means for outputting a signal when the output of the effective component suppression derivation means is equal to or greater than a predetermined value proportional to the zero-phase voltage. Since the lock means is configured to lock the output of the ratio calculation means when the overcurrent detection means outputs a signal, the excess current due to the reactive current is obtained by obtaining each effective component of the differential current and the suppression current. Preventing suppression and making mistakes during external accidents While also achieving stabilized against differential current, so as to be a lock to the ratio calculation output when the output signal of the overcurrent detecting unit, the effect of which can improve the external fault stability.

[Brief description of drawings]

FIG. 1 is a block diagram showing a busbar protective relay device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the differential current and the suppression current of the busbar protective relay device according to the embodiment of the present invention.

FIG. 3 is a circuit diagram showing a symmetrical coordinate method equivalent circuit for explaining the present invention.

FIG. 4 is a block diagram showing a busbar protective relay device according to another embodiment of the present invention.

FIG. 5 is a circuit diagram showing a system to be protected by the busbar protective relay device of the present invention.

FIG. 6 is a circuit diagram showing a conventional busbar protection relay device.

FIG. 7 is a characteristic diagram showing a relationship between a differential current and a suppression current of a conventional busbar protection relay device.

[Description of Reference Signs] 21 Differential Derivation Means 22 Suppression Derivation Means 23 Ratio Calculation Means 24 Overcurrent Detection Means 25, 30 ANDing Means (Lock Means) 26 Effective Component Differential Derivation Means 27 Effective Component Suppression Means 28 Ratio Calculation Means 29 Overcurrent detection means

Claims (2)

[Claims] 1. A differential derivation means for taking a vector sum of each terminal zero-phase current, a suppression derivation means for taking a maximum value or a scalar sum of each terminal current, and a differential current and a suppression derivation from the differential derivation means. A ratio calculation means for performing a ratio calculation based on the suppression current from the means, an overcurrent detection means for outputting a signal when the suppression current is equal to or greater than a predetermined value proportional to the zero-phase voltage, and the overcurrent detection means outputs a signal. A busbar protection relay device, comprising: a lock unit that locks the output of the ratio calculation unit when it is output. 2. A differential derivation means for taking a vector sum of zero-phase currents at respective terminals, an effective differential derivation means for deriving an effective differential current from the differential current from the differential derivation means, and each terminal. An effective component suppression derivation means for deriving an effective component suppression amount from a zero-phase current and a zero-phase voltage; an effective component differential current from the effective component differential derivation means and an effective component suppression amount from the effective component suppression derivation means. The ratio calculation means for calculating the ratio by means of the above, the overcurrent detection means for outputting a signal when the output of the effective component suppression derivation means is equal to or greater than a predetermined value proportional to the zero phase voltage, and the overcurrent detection means for outputting the signal. A bus protection relay device, which is sometimes provided with a lock means for locking the output of the ratio calculation means.