JPS6124899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground fault protection relay system for a resistive grounding system, and more particularly to a current differential relay that is effective in fault selectivity.

Conventional ground fault protection methods for resistance grounding systems include:
Using a direction determination relay based on zero-sequence voltage and zero-sequence current, if there is no terminal in each terminal in the protected area that is considered to be in the external direction, and any terminal is considered to be in the internal direction, it is determined that there is a fault within the area, and a trip is applied to each terminal. It uses a so-called direction comparison relay system that gives commands. In addition, as a measure to improve performance, there is a method in which the detection sensitivity of the directional relay of each terminal is scanned to a low sensitivity as soon as a failure occurs, and as a result, differential characteristics of the zero-sequence effective current are obtained.

However, although the conventional system can obtain the above-mentioned differential characteristics if limited to a two-terminal system, its performance is insufficient for the purpose of protecting multi-terminal power transmission lines with branches of three or more terminals.

An object of the present invention is to comprehensively determine the ground fault active current of each terminal in a protection zone, and to improve failure detection sensitivity even in a multi-terminal system.

As a means for detecting the active component of the zero-sequence current at the time of a fault at each terminal in the protection zone, the present invention distinguishes between the internal direction and the external direction using arbitrary fan-shaped phase characteristics, and detects the passage of the reactive component current and the external fault. It was made possible to obtain ratio differential characteristics for current passage.

An embodiment of the present invention will be described based on a single line diagram of a three-terminal branch system shown in FIG. The symbols and operations shown in the figure will be described below. The power system consists of electric stations A, B, and C, and the contents of each electric station's installations are A,
The locations of B and C shall be shown. E _A , E _B , E _C
is the power supply. Of course, the power supplies E _A , E _B , and E _C are synchronous operation systems in which the short-circuit capacity and voltage phase can be set arbitrarily, and they can also serve as load ends. T _A , T _B , and T _C are each transformers, and their neutral points are shown to be grounded by grounding resistors R _A , R _B , and R _C , but in reality, they are grounded by reactors for compensating ground capacitance. It is possible that CB _A ,
CB _B and CB _C are breakers. PL is the protected transmission line. L _A , L _B , and L _C are inductances for power line carrier blocking filters for transmitting information necessary for the protection relay. C _A , C _B , and C _C are coupling capacitors for power line carrier wave transmission.
CT _A , CT _B , and CT _C are current transformers for taking out the zero-sequence current passing through PL, and their outputs are represented by I _OA , I _OB , and I _OC , respectively. PT _A , PT _B ,
PT _C is a voltage transformer, each with a zero-sequence voltage V
It extracts _OA , V _OB and V _OC . here,
The voltage transformation ratio and polarity are determined so that the output voltages V _OA , V _OB , and V _OC of PT _A , PT _B , and P _C are approximately in phase and at the same voltage.

On the other hand, the polarities of CT _A , CT _B , and CT _C are adjusted so that the current flowing in when the PL fails is in the same phase as V _O . In other words, when the PL internally fails, V _O
and I _O are in phase, and in the event of an external fault, the terminal near the fault point is in the outflow direction, and V _O and I _O are in opposite phase.
The other inflow terminals are connected so that V _O and I _O are in phase. 1 _A , 1 _B , and 1 _C are current/pulse width converters for extracting a pulse width proportional to the effective component current of the zero-sequence current. The contents will be discussed later. 2 _A , 2 _B , and 2 _C are carrier terminal equipment for transmitting and receiving power line carrier waves. 3 _A , 3 _B , and 3 _C are used to obtain the differential characteristics for the effective component current of the zero-sequence current by calculating the pulse widths taken at 1 _A , 1 _B , and 1 _C at each terminal. This is a differential determination section. When it is determined that there is an internal failure in 3 _A , 3 _B , and 3 _C , a power disconnection is activated by each output.
Give a shedding command to CB _A , CB _B , and CB _C. Of course, in order to increase the reliability of the breaker, an OR logic breaker command may be given to all terminals by a separate transfer trip command.

The overall configuration of the present invention has been described above, and the parts that exhibit the effects of the present invention will be specifically explained using examples. Components equivalent to those in FIG. 1 are given the same symbols, and each terminal equivalent will be explained using electric station A as a representative example.

The function of the current pulse width converter of 1 _A in FIG. 1, that is, the zero-sequence effective current, will be described. Here, the following equations (1), (2), and (3) are executed sequentially.

S ₁ = I _OA /2∫ ^x 〓sinθdθ …(1) S ₁ =kI _OA /2∫〓 _p sinθdθ …(2) S=S ₁ +(−S ₂ ) …(3) Here, I _OA is the input zero-sequence current, α
represents an arbitrary delayed phase difference of the zero-sequence current I _OA when the zero-sequence voltage V _OA is the reference phase. Therefore, S ₁ represents the integral value of I _OA when V _OA and I _OA have the same polarity, and S ₂ represents the integral value of I _OA when V _OA and I _OA have opposite polarities. θ is an integral variable regarding the angle, and k in equation (2) is a coefficient for setting the inflow current range of the earth fault protection relay of the present invention. The concept of setting the coefficient k will be explained below.

FIG. 2 is an explanatory diagram of the phase characteristics when extracting the zero-sequence effective current. Figure a shows an example of setting the inflow current region and outflow current region of the zero-sequence current I _O when the zero-sequence voltage V _O is used as a reference. That is, the hatched portion of the phase difference φ (lag and lead absolute phase difference angles) based on V _O is the inflow current region, and the rest is the outflow current region. When you want to obtain the characteristic shown in Figure 2a, as shown in Figure 2b, the waveform of the zero-sequence voltage _VOA is used as a reference, and the area _S1 of the same sign of _IOA is different from the area S1 (formula (1) above). Equation (2) is adjusted according to φ so that the area S ₂ of the code (formula (2) above) becomes equal to each other (S ₁ =S ₂ ) when the phase difference α=φ shown in Figure 2a. It is sufficient to determine the coefficient k of .
That is, k is determined as shown in the following equation.

When this is done, S in equation (3) represents the amount of ground fault active current in the present invention.

According to this method, V _OA and I _OA are in the same phase, that is, when α = 0°, S = I _OA (positive inflow direction), and when α = 180°, S = kI _OA (negative outflow direction), and the effective component is The characteristics are as shown in Figure 3a.

In this way, the current/pulse width converter 1 in FIG.
At _A , pulse width conversion is performed according to the level indicated by S above. In Figure a, S _a means inflow and S _b means outflow. FIG. 3b is a conceptual diagram of pulse width conversion for examples S _a and S _b in FIG. 3 a, where S _a generates a pulse with a width of T _a and S _b generates a pulse with a width of T _b . After outputting a predetermined pulse width, the output is intermittent. In addition, S _a indicates a positive value of the ground fault active current, the pulse level "off" is between T a, and S _b indicates a negative value of the ground fault active current, and the pulse width level "off" is between T _a . ”
This is an example in which T is between T _b .

For each terminal, pulse width conversion of the effective current is performed in the same way, and the pulse widths are converted to
_A transmits them as power line carrier waves via C _A and PL, and the differential determination unit 3 _A calculates the sum of the pulse widths at each terminal. the result When this happens, it is determined that the accident occurred in the PL internal section.

However, S _p is a set value of the detection level.
In addition, in order to calculate equation (4), it is necessary to use input signals at the same time for each terminal of A to C, so
It is necessary to correct the delay time due to transmission, start pulse width conversion, etc. under the same conditions. The operating range of equation (4) under the above conditions is shown using ratio characteristics as an example.
As in the example shown in FIG. 4, the slope is determined by the coefficient k determined according to the phase angle φ.

However, in the same figure, I _p ; Setting value of the equivalent effective current of equation (4) S _p ΣΙ _io ; Sum of effective current inflow direction of each terminal (positive) ΣΙ _put ; Sum of effective current outflow direction of each terminal (negative). The hatched area in the figure is the internal accident determination area.

FIG. 5 shows a detailed embodiment of the configuration of the current/pulse width converter 1 and the differential determination section 3 using a device at electric station A as a representative example. First, at 1A, D is a diode, and an input is given to the integrator 50 only during the period when I _OA and V _OA have the same polarity, and as a result, S ₁ of equation (1) is derived. 51 is also an integrator, but since I _OA is inputted through the polarity inverter 52, integration is performed over a period in which V _OA and I _OA have opposite signs. Moreover, since the multiplier 53 multiplies I _OA by k, the output of the integrator 51 is (2)
S ₁ and S ₂ in Eq. 54 is an adder which calculates the sum S of S ₁ and S ₂ . Note that the addition period 54 is synchronized with the zero point of V _OA and is defined as one cycle period from 0° to 360° of V _OA .

Reference numeral 55 denotes a gate circuit, which uses the signal from the conversion permission signal generator 56 to pass the input S to the comparator 57 in the next stage.
The signal is sent to gate control sign determiners 60 and 61. The conversion permission signal generator 56 may use an operation output signal from a failure detection relay, such as an I _OA overcurrent detection relay or a V _OA overvoltage detection relay. As a result, 56 detects and outputs the occurrence of an accident. Integrator 58 is activated by conversion permit signal generator 56 and provides an output that varies proportionally over time. However, 58a provides an output that changes in the positive direction, and 58b provides an output that changes in the negative direction. The comparator 57 compares its input S with the input from the integrator 58.
The input signals S are compared until the magnitude relationship between the two comparison inputs is reversed. For example, comparator 57a
Then, the level is compared with the output of the integrator 58a, which changes in the positive direction, and the output T _a is output until the output of the integrator 58a becomes greater than the signal S. The output T _a is, for example, a "cut" signal for blocking the power line carrier wave. 58
After the output of a>signal S, T _a becomes an intermittent wave.

Similarly, the comparator 57b compares the level with the output of the integrator 58b, which changes in the negative direction.
The output T _b is output until the output of 58b<signal S. When the output T _b is given, it is regarded as an outflow current and outputs a level "present" so that the power line carrier wave is transmitted. After the output of 58b<signal S, an intermittent wave is output in the same manner as T _a , indicating that the pulse width determination has been completed.

60 and 61 are gate control sign determiners S
>0, gate 62 is opened by 60 and signal T _a is enabled. When S<0, the gate 63 is opened by 61 and the signal T _b is made valid.
That is, a signal that is disabled is set to OFF, for example. 64 is an adder for the signals T _a and T _b , and only the signal deemed valid by the gate circuits 62 and 63 is passed through. The output of adder 64 is passed to _2A shown in FIG.

As is clear from the above explanation, the signal length (period during which continuous output is given) of the signals T _a and T _b sent to the other end depends on the magnitude of the signal S, that is, the magnitude of the ground fault active current. Equivalent to. Also, the presence or absence of a power line carrier corresponds to the polarity of the ground fault active current.

On the other hand, the signal received from 2 _A (including its own terminal)
is time-compensated by a transmission delay compensation timer 65 for equivalently matching received signal transmission times. 66
is an adder that adds the outputs from each terminal, and assumes that the length of the received signal "off" is positive, the received level "present" is negative, and the intermittent wave is "0", and an analog value is calculated according to the signal length. Analog values for all terminals are added up, taking into consideration the polarities obtained, and a level determiner 67 determines the equivalent ground fault active current of the differential relay.

68 is a coincidence gate, which is a circuit for speeding up the judgment result of 67. In other words, with only the output of 67, the final judgment cannot be made until the pulse width conversion signals of all terminals have been calculated to become intermittent waves, but as a differential relay, there is an inflow current exceeding a predetermined value, and the output of the outflow terminal is If there is no signal “present” as a condition, tripping may be allowed.

Reference numeral 68 is a coincidence gate used for this purpose to detect that the outflow end is completely absent.
If even one of the received signals has a reception level "present", a trip permission signal is not output to the next coincidence gate 69. 69 is a coincidence gate, 67 and 68,
Also, as a measure to improve reliability, a trip command is outputted only by the entire trip permission signal outputted from 56 at the appropriate time.

According to the present invention described above, ground fault active component current differential characteristics of a multi-terminal system with high operational reliability can be obtained, and fault detection with high sensitivity can be performed at high speed.

Although the embodiments of the present invention have been described using a three-terminal power transmission line protection model, it is of course possible to apply the same configuration to a multi-terminal system of four or more terminals.

Furthermore, the present invention is applicable not only to power transmission line protection but also to protection relay systems that do not use power line carrier waves for bus bar protection and equipment protection.

In addition, as a means to obtain the phase characteristics shown in Fig. 2a, the level of the input current is shifted as shown in Fig. 6, and the areas of the same sign and the opposite sign are made equal based on the V _OA standard at the characteristic phase difference angle φ. do it.

[Brief explanation of the drawing]

FIG. 1 shows an overall configuration diagram of the present invention. FIG. 2 shows the aim of the characteristics of the invention. FIG. 3 shows an explanatory diagram of the amount of ground fault effective current derived. FIG. 4 shows an example of ratio differential characteristics according to the present invention. FIG. 5 shows an example of the circuit block configuration of the present invention. FIG. 6 shows a modification of the invention. E _A , E _B , E _C ... Power supply, T _A , T _B , T _C ... Transformer, R _A , R _B , T _C ... Earthing resistance, CB _A ,
CB _B , CB _C ...Shiya disconnector, PL...Transmission line, L _A ,
L _B , L _C ... Inductance, C _A , C _B , C _C ...
…Coupling capacitor, CT _A , CT _B , CT _C … Current transformer, I _OA , I _OB , I _OC … Zero-sequence current, P T _A ,
PT _B , PT _C ... Voltage transformer, V _OA , V _OB , V _OC ...
...Zero-sequence voltage, 1 _A , 1 _B , 1 _C ... Current/pulse width converter, 2 _A , 2 _B , 2 _C ... Carrier terminal equipment, 3 _A ,
3 _B , 3 _C ... Differential determination section, A... Electrical station A, B...
...Electric station B, C...Electric station C.

Claims (1)

[Claims] 1. In a ground fault protection relay device that inputs a phase current, a zero-sequence voltage, and the output of a failure detection relay in order to detect a ground fault in a multi-terminal power system, each terminal has a zero-sequence voltage. A first integrator that integrates the zero-sequence current when the zero-sequence current has the same polarity as and a second integrator that integrates the zero-sequence current when the zero-sequence current has the opposite polarity, and an input of one of these integrators. Or, in response to the output of a coefficient unit installed on the output side or a failure detection relay, the first and second
carrier wave control means for controlling the presence or absence of a carrier wave to be sent to other terminals and the length of time for the presence or absence of the carrier wave according to the polarity and magnitude of the difference between the absolute values of the outputs of the integrators; The carrier waves from all terminals are received, and from this the magnitude and polarity of the difference in absolute value between the outputs of the first and second integrators detected at each terminal are derived, and the results are added taking into account the output differences of all terminals. , comprising a determining unit that compares the added value with a predetermined value of a predetermined polarity, and when the added value is larger than the predetermined value, determines that there is an internal accident in the multi-terminal power system and protects the multi-terminal power system;
The coefficient unit is characterized in that the coefficients of the coefficient multiplier are determined so that the absolute value difference between the outputs of the first and second integrators is zero when the input phase difference φ (where φ<90°) Short circuit protection relay device. 2 In a ground fault protection relay device that inputs a phase current, a zero-sequence voltage, and the output of a fault detection relay to detect a ground fault in a multi-terminal power system, each terminal receives a zero-sequence voltage and a biased zero-sequence. A first integrator that integrates the current when it has the same polarity, a second integrator that integrates the zero-sequence current when it has the opposite polarity, and a first and second integrator that integrates the zero-sequence current when the current has the same polarity. carrier wave control means for controlling the presence or absence of a carrier wave to be sent to other terminals and the length of time for the presence or absence of the carrier wave according to the polarity and magnitude of the difference between the absolute values of the outputs of the integrators; The carrier waves from all terminals are received, and from this the magnitude and polarity of the difference in absolute value between the outputs of the first and second integrators detected at each terminal are derived, and the results are added taking into account the output differences of all terminals. , includes a determination unit that compares the added value with a predetermined value of a predetermined polarity, and when the added value is larger than the predetermined value, determines that it is an internal fault in the multi-terminal power system and protects it, and also has a determination unit that performs protection against the internal fault of the multi-terminal power system. However, the bias value applied to the zero-sequence current is determined so that the absolute value difference between the first and second integrator outputs is zero when φ<90°). Short circuit protection relay device.