JPH02195275A - Ground fault phase detecting device - Google Patents

Abstract

PURPOSE:To remove the effect of the situation of a ground fault accident on a time for detection and to enable definite setting of limits of detection by detecting the ground fault accident on the basis of a zero-phase voltage and a reference voltage. CONSTITUTION:The products of a zero-phase voltage V0 and reference voltages Ua to Uc from a phase shifter 9, and of a differential voltage DELTAV0 of the voltage V0 and reference voltages U'a to U'c intersecting the reference voltages Ua to Uc at right angles, are determined by multipliers 11a to 11c and 14a to 14c. An alternating-current component is offset by adders 15a to 15c from the results of these products and only a direct-current component is integrated selectively by integrators 16a to 16c. Subsequently, it is determined by comparators 17a to 17c whether or not the result of integration exceeds a prescribed value and has a prescribed polarity, and thereby a ground fault accident is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ground fault phase detection device for detecting a ground fault phase in a high resistance grounded system or an ungrounded system.

[Conventional technology]

FIG. 12 is a circuit diagram showing an example of a conventional ground fault phase detection device. In FIG. 12, la, lb.

1c is a power supply forming a three-phase balanced power supply consisting of a, b, and C phases, and 2a, 2b, and 2c are power supplies 1a and lb.

The distribution lines of each phase are connected to 1c, and 3a, 3b, and 3C are distribution lines 2a shown isometrically by capacitors.

The ground capacitance of 2b and 2c, 4 indicates a fault point of a ground fault, which will be exemplified for the explanation of the operation below, and the distribution line 2a is grounded by a resistor Rg. 5a, 5b, and 5C are voltage dividers 6a which are composed of capacitors and divide the ground voltages of the distribution lines 2a, 2b, and 2C at an appropriate ratio;

6b and 8c are operational amplifiers, and a voltage divider 5a.

Voltages VB and Vl+ output from 5b and 5c; Vb.

VC; VC* Add Va to get voltage Was Vxe
The adder 7 that outputs Vs is a resistor having a resistance value RN that grounds the neutral points of the power supplies 1a, lb, and lc.

FIG. 13 is a vector diagram illustrating the operation of the apparatus shown in FIG. 12. Here, if the distribution line 2a has a ground fault at the fault point 4, the neutral point 0 shifts to O', and the voltage dividers 5a, 5
b, 5c output the voltage Va*Vb*v(.The ground capacitance 3 of the distribution lines 2a, 2b, 2c changes depending on the ground fault situation.
At the values of a, 3b, 3c and the ground fault resistance Rg, the point O falls somewhere on the circle diagram 8. The voltages V, , v□tV3 of the adders 6a, 6b, and 6c are expressed by the following equations, and are input to a ground fault phase determination circuit (not shown).

As shown in FIG. 13, in this case, the voltage v1 of the a phase, which is the fault phase, becomes the minimum value, lv, l<1eaf<l
The relationship V, l or 1v, 1 holds true. A similar relationship holds true in the case of ground faults in other phases.

When the determination circuit determines that the voltage V is at the minimum value, it outputs a signal indicating that a ground fault has occurred in the distribution line 2a.

[Problem to be solved by the invention]

Since the conventional ground fault phase detection device is configured as described above, if both the ground capacitance and the ground fault resistance of the distribution line are large at the time of a ground fault, the difference in the judgment voltage between the normal state and the fault state will occur. becomes extremely small, making it impossible to distinguish between the two. Therefore, for example, by increasing the gain of the amplifier,
It is possible to improve the detection function, but this requires a high degree of balance between the phases, and unless the signal-to-noise ratio is improved, the device is prone to malfunction. Further, the conventional ground fault detection device has a problem in that the response speed to a ground fault near the detection limit is slow.

This invention was made to solve the above-mentioned problems, and provides a ground fault phase detection device in which the detection time is not affected by the ground fault situation and the detection limit can be clearly set. The purpose is to

[Means to solve the problem]

The ground fault phase detection device according to the first claim includes a detector for detecting a zero-sequence voltage generated due to the occurrence of a ground fault, and a differentiator for differentiating the zero-sequence voltage to obtain a differential voltage for each phase. A first reference voltage is obtained by shifting the voltage of each phase of the distribution lines forming the power system by a predetermined phase, and a second reference voltage is obtained by shifting the phase to a phase orthogonal to this first reference voltage. with a phase shifter.

A first multiplier that multiplies the zero-phase voltage and the first reference voltage, and a second multiplier that multiplies the differential voltage and the second reference voltage are provided for each phase.

An adder is provided for adding the alternating current components included in the outputs of the first and second multipliers for each phase so as to cancel each other for each phase,
A comparator is provided for each phase, which integrates the output of the adder and detects that the absolute value of the integrated output exceeds a predetermined threshold and that the integrated output has a predetermined polarity.

In the ground fault phase detection device according to the second aspect, the first and second multipliers each include a converter that converts the first and second reference voltages into rectangular waves.

In the ground fault phase detection device according to the third aspect, the first and second multipliers include a converter that converts a zero-phase voltage and its differential voltage into a rectangular wave.

[Effect]

The ground fault phase detection device in claim 1 detects a zero-sequence voltage from a distribution line to be protected, and detects the zero-sequence voltage, a first reference voltage detected from the distribution line, a differential voltage of the zero-sequence voltage, and a first reference voltage detected from the distribution line. and a second reference voltage that is orthogonal to the reference voltage of By detecting a ground fault by determining whether or not the ground fault occurs, the detection time is not affected by the ground fault situation, and the detection limit can be clearly set.

The ground fault phase detection device according to the second aspect converts the first and second reference voltages into rectangular waves and then performs multiplication processing, thereby making the device stable against noise and preventing malfunctions of the device.

The ground fault phase detection device according to the third aspect can clearly set the detection limit by converting the zero-phase voltage and its differential voltage into a rectangular wave and then performing multiplication processing.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1 showing a first embodiment according to the present invention, 9 is a winding 9a connected to distribution lines 2a, 2b, 2c, and a voltage delayed by an angle α from the voltage ea eh + eC of the distribution lines 2a, 2b, 2c. Reference voltage ua.

Winding 9b generating ul, uc and reference voltage u1u
A transformer having a winding 9c that generates a reference voltage ua # uk * uc # that is orthogonal to b + uc, that is, 90 @ phase advanced from these, and also has the function of a phase shifter.

10 is connected to the distribution lines 2a, 2b, 2c, and has a zero-phase voltage V
, a capacitive transformer that detects 5 voltage dividers and zero-sequence voltage v
It functions as a 0 detector. lla.

1 l b, 11 c are the zero-sequence voltage V, and the reference voltage uat
A multiplier 12 that performs multiplication between ulltuc and ulltuc differentiates the zero-sequence voltage v0 to obtain a differential voltage V. , (=on l dJ) ω dt , a differentiator, 14a, 14b, 14a are differential voltages v,
Multipliers 15a, 15b, and 15c are multipliers 11a and 11a for multiplying / by the reference voltages u@, u, and uc'.
b, lie voltage W @1 g W @1 @ W (
1 and the voltages of the multipliers 14a, 14b, 14o Vast W
Adder for adding ba+w(, 16a, 16b, 1
6C is addition @ 16 a , 15 b , 15 c
The voltage W a tW b * W c is integrated, and the voltage W
&* Wbe W(integral [%, 17a, 17b,
17c is a voltage WasW.

A comparator that compares Wc and a threshold value -wth, 18 a selector that selects the minimum value from the voltages wa, wb, and Wc of the adders 15a, 15b, and 15c, that is, the phase in which the accident occurred; 19 a selector Voltage Wlkl' output from 18
Comparator for comparing jlb or Wc with threshold value -vth, 2
0a, 20b, and 20c are comparators 17a.

An AND gate that ANDs the outputs of 17b and 17c and the output of comparator 19, and generates signals F, , F indicating the detection of a ground fault.
and outputs FC.

Next, the operation will be explained. Power supply 1a, lb.

The voltage e & s efi, ac of 1c is expressed by the following equation.

Reference voltage of transformer 9 uat ul+e ue, ua
tubu cI is calculated from equation (1) as follows.

Reference voltage ua+ ube ucs ua e ub
+ uc is related to the line voltage, so there is no change in a ground fault like fault point 4. However, due to such a ground fault, the potential at the neutral point O changes, and the zero-sequence voltage V,
occurs. The zero-sequence voltage v0 is the ground capacitance 3 a +
3 b * 3 c capacity C0, ground fault resistance Rg, resistance 7
The relationship between the resistance value R, and the following equation is v, = -v, s
in (ωt-θ)...(4) However, N g u@' wEcos ((II t -a) In Figure 2, the voltage eas f3b* 'ec, the reference voltage ua+ub
e ucs ua + ub v uc' and the zero-sequence voltage v0. The crab is coming. Multiplication 1111a
, llb, llc voltage W at t W h1* W
cl is expressed as follows.

W　l+11　W　C@ is expressed by the following formula.

Since the second term on the right side of equation (9) has the opposite sign to the second term on the right side of equation (7), the adders 15a, 15b, and 15c.

By adding both, the alternating current component is eliminated. That is, the first term in equation (7) is a DC component and is proportional to ■ and E, and the second term is an AC component of 2ω.

When the zero-sequence voltage v0 is differentiated by the differentiator 12, (4)
From the equation, differential voltages v and I are generated as shown in the following equation.

Va'=-V, C08 ((1) -〇') Fist---・-・
(8) Therefore, the voltage w of multipliers 14a, 14b, 14c
□.

The voltage Was Why W (is the integrator 16a, 16b, 1
6c, it is integrated as shown in the following equation.

The voltages wa, w, and wc shown in equation (11) are related to the zero-phase voltage va, so if there is no ground fault and the voltages f3 & t eb * ac of each phase are balanced, they are zero. Become. However, when a zero-sequence voltage v0 occurs due to a ground fault, the voltages Wa, W, .

Figure 3 shows the voltage Wa when a ground fault occurs at time tg.
, Wb-Wc waveforms are shown. In this way, the fault phase voltage W
Only voltage a increases in the negative direction, and the other voltages Wb and Wc increase in the positive direction. Since the voltage Wa crosses the threshold value -wth at time td, this is detected by the comparator 17a, and its output becomes 1. The voltage wa is input to the comparator 19 via the selector 18 and compared with the threshold value -vth, and immediately crosses the threshold value -vth at one time tg as shown in FIG. Therefore, the comparator 19 sets the output to 1, the AND gate 20a opens, and the signal F indicating the a-phase, that is, the ground fault in the distribution line 2a, is output. In the case of a ground fault in the distribution line 2b or 2c, the explanation is similar to that in the case of the a-phase.

Although the case where the integrators 16a, 16b, 16c perform complete time integration has been described, the multipliers 14a, 14b, 1
If the output of 4c contains even a small amount of DC component due to its calculation accuracy, the integrator 16 a * 16 b *
16 c, a DC component is accumulated and increases the error. Therefore, a transfer function is used in the integrators 16a, 16b, and 16c. 77 primary feed elements may be provided, and the time constant T may be set to be longer than the phenomenon of a ground fault.

Furthermore, the voltage wat Why Wc may have a DC component of a certain value before a ground fault occurs due to the unbalance associated with the distribution lines 2a, 2b, 2c.
As shown in the figure, the voltages W a e W b * W c may be outputted through capacitors C, respectively. The capacitors C form a differentiating circuit together with the resistor R, and the time constant CR is determined by the expected ground fault. It may be set to be longer than the phenomenon of an accident or the disturbance that constantly occurs in the system.

Further, in the first embodiment, the reference voltage u as u 11
uC.

Although ua e ul # uc' is a sine wave,
As shown in Fig. 6, for example, the multiplier may be equipped with a converter to convert these sine waves into rectangular waves of constant amplitude, and then the multiplication process may be performed. 1 reference voltage ua, (b) is the second reference voltage ua (c) is the zero-sequence voltage v@, (d) is the differential voltage vs' (8
) is the voltage Wai, (f) is the voltage W6m, (g) is the voltage w
In this case, when a ground fault occurs at time tg, the waveforms of voltages wa# w, , Wo change as shown in FIG. Voltage wa# Wb-Wc shown in FIG.
The waveform differs from that shown in FIG. 3 and has a vibration component, but the basic points are the same: the voltage Wa crosses the threshold value -wth at time td, and a ground fault fault is determined.

In addition, in the first embodiment, the zero-phase voltage and its differential voltage were used as sine waves for calculation processing, but for example, a converter is provided in the multiplier to convert them into rectangular waves and then perform multiplication processing. This embodiment also produces the same effects as the first embodiment.

Furthermore, in the first embodiment, a case was explained in which the zero-sequence voltage and its differential voltage are multiplied by the reference voltage using a multiplier, but as is clear from the waveform diagram shown in FIG. 8, the multiplication is performed using a gate circuit. Even if the same functions are executed, the same effects as in the first embodiment can be obtained.

In FIG. 8, (a) is the zero-sequence voltage vll and its differential voltage v,' (b) is the reference voltage ua and ua (c)
shows the voltages fax and wa2, and (d) shows the waveform of the voltage Wfi. In this case, when a ground fault occurs at time tg, the voltages w, , W, and eWc change as shown in FIG. 9, and from the above explanation, it is understood that a ground fault can be determined.

Further, in the first embodiment, the reference voltage ua* ub+uc
The case where +ua*u and *uC' are obtained from the transformer 9 has been described, but as shown in FIGS. 10 and 11, the voltage divider 5a is composed of a capacitor.

It may also be obtained from 5b and 5c. In FIG. 10, adders 21a, 21b, 21c are voltage dividers 5a, 5b.
, 5c are input and added for each two phases to obtain a reference voltage uat ub + uc, and the differentiators 22a and 22b
, 22c differentiate these to obtain the reference voltage u%, u gloss',
Obtain u(' In Fig. 11, differentiators 23a, 2
3b and 23c input and add two phases each from the reference voltage ull*ub+uc, and add the reference voltage ua s ub
'Get euc.

〔Effect of the invention〕

As described above, according to the first claim, the zero-sequence voltage is detected from the distribution line to be protected, and the product of this zero-sequence voltage and the reference voltage detected from the distribution line and their orthogonal signals is calculated. , ground faults are detected by selectively integrating only the DC component from the results of these products and determining whether the result exceeds a predetermined value and has a predetermined polarity. , the detection time is not affected by the ground fault situation, is stable against noise, and is not affected by the detection speed, and has the effect of clearly setting the detection limit.

According to the second claim, by adding a function of converting the first and second reference voltages into rectangular waves to the first and second multipliers of the ground fault phase detection device, it is stabilized against noise; The effect is that malfunctions do not occur.

The third claim provides the effect of clearly setting the detection limit by adding a function of converting the zero-sequence voltage and its differential voltage to a rectangular wave to the first and second multipliers of the ground fault phase detection device. It will be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a ground fault phase detection device according to a first embodiment of the present invention, FIG. 2 is a vector diagram of voltages at various parts of the device shown in FIG. 1, and FIGS. FIG. 5 is a block diagram of the ground fault phase detection device according to the second embodiment of the present invention, and FIGS. 6 and 7 are waveform diagrams of the operation of the device shown in FIG. FIGS. 8 and 9 are waveform diagrams of the operation according to the fourth embodiment of the present invention, and FIGS.
The figure is a block diagram according to a fifth embodiment of the present invention. FIG. 11 is a block diagram according to a sixth embodiment of the present invention;
Figure 12 is a plot diagram of a conventional ground fault phase detection device, Figure 13
The figure is a vector diagram of voltages at various parts of the device shown in FIG. 12. 2a, 2b, 2c--・Distribution line, 5a,
5b, 5o. i o... Voltage divider, 9... Transformer, lla, ll
b, 11 o, 14 a, 14 b, l
4 e-・-multiplier, 12°22 a, 22 b
, 22 c-differentiator, 15a, 15b, 15c, 21
a, 21b, 21c, 23a. 23b, 23cm adder, 16a, 16b, 16e'
...Integrator, 17 a, 17 b, l 7
c, 19-comparator, 18...selector, 20 a
, 20 b I20 c ・"And gate. Note that the same reference numerals in Figure 1 indicate the same parts. Agent Masuo Oiwa Wj2 Figure e Figure Figure Figure Figure Figure Figure Figure Figure Figure Va' 1-- −−− −−−−+++ −−wj Figure 10 Figure Figure Figure

Claims (3)

[Claims] (1) A detector that detects a zero-sequence voltage from each voltage of distribution lines of each phase forming an electric power system, and a differentiator that generates a differential voltage obtained by differentiating the zero-sequence voltage, and each of the voltages a phase shifter that generates a first reference voltage by shifting the phase by a predetermined phase and generates a second reference voltage by shifting the phase of each of the voltages to a phase orthogonal to the predetermined phase; and the first reference voltage; a second multiplier that multiplies the differential voltage and the second reference voltage; and the first and second multipliers. an adder that adds the output of the adder so as to cancel the alternating current component included in the output; an integrator that integrates the output of the adder; A ground fault phase detection method, in which each phase is equipped with a comparator that detects that the output of the device has a predetermined polarity, and the detection output of the comparator is used as a signal indicating the occurrence of a ground fault accident in the corresponding distribution line. Device. (2) The ground fault phase detection device according to claim 1, wherein the first and second multipliers each include a converter that converts the first and second reference voltages into rectangular waves. (3) The ground fault phase detection device according to claim 1, wherein the first and second multipliers each include a converter that converts the zero-phase voltage and its differential voltage into a rectangular wave.