JPH0221549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention adds a simple phase angle measuring circuit etc. to the conventional one, and the absolute value of the vector difference in the output voltage due to the zero-sequence current immediately before and after the disconnection fault |V〓−V 〓′｜That is, using the actual change value or its approximate value,
This invention relates to an improvement of a disconnection detection method for power distribution lines that increases the accuracy of detection sensitivity.

In the conventional disconnection detection method for power supply side detection, a zero-phase current transformer for disconnection detection is installed at the outlet of each distribution line.
An analog/digital conversion circuit is connected to the secondary side, and only the output voltage induced by the zero-sequence current of each distribution line is converted from analog to digital, and the sampling time (e.g. 0.5 seconds) is controlled by a microcomputer. The latest output of each distribution line stored in the memory is stored at each sampling time, and this is repeated and continued every scanning period (example 15 seconds). The maximum absolute value (hereinafter referred to as data change value) of the difference between the voltage and the output voltage before the scanning period (e.g. 15 seconds) is successively selected, and the disconnection failure of any distribution line is detected. If the maximum change value of this data is larger than the set value and continues for more than the set time, it is determined that the distribution line with the maximum change value of this data has a disconnection fault, and the disconnection fault display for the distribution line is displayed. and a disconnection feeder detection method that selectively shuts off the wire.
After disconnecting the distribution line with the disconnection fault, the circuit breaker is reclosed and the power is sent to each distribution section in sequence, and the output voltage of the zero-phase current transformer for disconnection detection is stored in memory, and when the distribution line is healthy, it is sent to each distribution section. Calculate and set the absolute value of the difference in the output voltage of the zero-phase current transformer for detecting disconnection at the time of disconnection failure and during construction for each section based on the output voltage stored in other memories when moving sequentially through the sections. The present invention has developed a disconnection section detection method that determines that the distribution line is in a disconnection fault section if it is larger than the value and continues for a set time, and the distribution line is shut off again.

The conventional method described above uses only the absolute value of the arithmetic difference between the output voltages of the zero-phase current transformers for detecting disconnection in each distribution line immediately before and after a disconnection fault, and only when the zero-sequence current is extremely small. is extremely smaller than the actual change value of the output voltage due to the zero-sequence current immediately before and after the disconnection fault, that is, the absolute value of the vector difference between these two output voltages, and there is a drawback that it is not possible to obtain a disconnection detection method with high detection sensitivity accuracy. Ta.

Figure 1 shows that the zero-sequence current at the outlet of a distribution line is always present in a considerable amount just before a disconnection failure occurs in a normal distribution line.
It shows the output voltage of the zero-phase current transformer for wire breakage detection immediately after and its vector difference, that is, the actual change value. In the figure, V and θ are the output voltage induced by the zero-sequence current of the zero-sequence current transformer for detecting wire breakage immediately before the wire breakage fault, and its phase, and V′θ′ is the output voltage induced by the zero-sequence current immediately after the wire breakage fault. These are the output voltage and its phase. The absolute value of the change value of the output voltage immediately and after the disconnection fault is V〓,
V〓′ is the absolute value of the vector difference and is as follows from Figure 1.

As is clear from the vector diagram in Fig. 1 and the calculation formula above, in the conventional detection method, only the first term of the calculation formula, |V〓′−V|, is used to calculate the phase angle θ ₀ =θ′−θ The second term related to is omitted, which is the actual change value |
There is a drawback that the accuracy of detection sensitivity is extremely low for disconnection faults that are much smaller than V〓′−V〓|, that is, for disconnection faults in the same extension of the distribution line.

The invention, having eliminated the drawbacks mentioned above, will now be described in detail with reference to the drawings. In other words, a digital wire breakage detection device based on the following principle installed only at substations and an automatic sectional switch for existing progressive distribution lines can be used as is, and the system can detect wire breaks in one or two wires or slight ground faults. It automatically detects electric wires without power outages, detects faulty sections after two power outages, and allows disconnection.

If there is a disconnection fault in one or two wires in any distribution line, the zero-sequence current at the outlet of each distribution line will change due to the change in ground capacitance, and the absolute value of the increase or decrease will depend on the length of each distribution line. As a result of various test studies on simulated distribution lines, the inventor of the present application discovered and verified that, regardless of the size, the distribution line with disconnection failure is the largest, and the difference between it and the one in good condition is extremely large.

The present invention utilizes this principle.

FIG. 2 is an explanatory diagram of a distribution line according to an embodiment of the present invention, where O is a high voltage bus of a substation, _T1 is a main supply transformer, _T2 is a grounding transformer, r is a grounding current limiting resistor,
C is a neutral point grounding capacitor, CB is a circuit breaker,
SS is automatic sectional switch, 1, 2, 3, 4 are distribution lines,
_{. _ _ _}・ZCT is a zero-phase current transformer for disconnection detection installed at the outlet of each distribution line.

FIG. 3 is an explanatory diagram showing an embodiment of the disconnection detection circuit device of the present invention, in which 5 is a filter, 6 is an amplification circuit,
7 is an analog-to-digital converter circuit, 8 is a phase measuring circuit, and _T1 in FIG. 2, which is connected to these circuits, is a reference voltage transformer. The filter 5 may be omitted depending on the load on the distribution line. P〓 is the digital output voltage of the zero-phase current transformer D/ZCT for disconnection detection of each distribution line and the digital value of its phase (hereinafter simply V ₁ , θ ₁ ,
11, 12, 13, and 14 are terminals for each power distribution line. PO is an output port for detecting a disconnection fault in a distribution line and outputting a disconnection indication signal to the outside, and 21, 22, 23, and 24 are output terminals for each distribution line. CPU is the central processing unit that calculates and controls the operation of the disconnection detection device, M is the memory, and the digital voltage of each distribution line input from the input port PI,
The digital value V, θ of that phase, the number of the distribution line with the disconnection fault, the constant of each distribution section [digital voltage V when sequentially sent to each distribution section when healthy, the digital value θ of that phase], and the number of the disconnection detection device. This is a memory circuit in which operating programs, etc. are written. For X, input the digital output voltage V of the D/ZCT for disconnection detection of each distribution line and the digital value θ of its phase at the data desk.
The central processing unit is a signal line that outputs disconnection display signals, etc.
CPU, memory M, input port PI, output port
Shared by PO. Y is an address bus and is a signal line that outputs the number when the central processing unit CPU selects memory M, input port PI, and output port PO, and only the selected circuit can use data bus X. SCR is thyristor, 1P, 2P, 3
P, 4P are electromagnetic relays, and each distribution line 1, 2, 3,
4 is a structural part of an embodiment of a circuit device for disconnection failure indication and disconnection in No. 4. 1p ₁ , 1p ₂ , 2p ₁ , 2p ₂ . . . are make contacts of each electromagnetic relay, and S is a return contact of each electromagnetic relay.

The digital output voltages V ₁ , V ₂ , ... of the D/ZCT for detecting disconnection of each distribution line, the digital value of the phase θ ₁ ,
θ ₂ ... are terminals 11, 12, 13, 1 of input port PI
4 and is stored in each memory M under the control of the central processing unit CPU.

Figure 4 is for explaining the operation of the order in which the digital output voltage of the D/ZCT for detecting disconnection of each distribution line and the digital value of its phase (hereinafter referred to as data V, θ for each distribution line) are stored in the memory M. , V ₁ θ ₁ , V ₂ θ ₂ ,
V ₃ θ ₃ and V ₄ θ ₄ are data of distribution lines 1, 2, 3, and 4. The memory consists of 31 sets of 1, 2, 3...30 and O, and the data of each distribution line V ₁ θ ₁ , V ₂ θ ₂ , V ₃ θ ₃ , V ₄ θ ₄ is stored under the control of the central processing unit CPU. is stored once in each memory group O for the digital output voltage V and the digital value θ of the phase at each sampling time (e.g. 0.5 seconds), and then stored in each memory 1, 2, and 3.
...30 in sequence and memorize it. Memory O
The latest data of each distribution line stored in the group V ₁ θ ₁ ,
V ₂ θ ₂ ... and the data of each distribution line _{15 seconds} before the scanning _period stored in 30 sets of memory _. Absolute value of vector difference in output voltage of D・ZCT |V〓 ₁ −V〓′ ₁ |, |V〓 ₂
―V〓′ ₂ ｜,｜V〓 ₃ ―V〓′ ₃ ｜,｜V〓 ₄ ―V〓′ ₄ ｜ by the above calculation formula. For example, |V〓 ₁ −V〓′ ₁ |≒|V ₁ −V′ ₁ +V ₁ |K(θ ₁ −θ′ ₁
)｜
Calculate by However, K is a constant. The first data stored in 30 sets of memories.
V′ ₁ θ′ ₁ , V′ ₂ θ′ ₂ , V′ ₃ θ′ ₃ , V′ ₄ θ′ ₄ and the latest data stored in memory group O at the 31st time V ₁ θ ₁ , V ₂ θ ₂ , V ₃ θ ₃ ,
From V ₄ θ ₄ , the second data V′ ₁ θ′ ₁ , V′ ₂ θ′ ₂
，
From V′ ₃ θ′ ₃ , V′ ₄ θ′ ₄ and the latest data stored in memory O group at the 32nd time V ₁ θ ₁ , V ₂ θ ₂ , V ₃ θ ₃ , V ₄ θ _4, as above The absolute value or an approximate value of the vector difference in the output voltage of the D/ZCT for detecting disconnection of each distribution line before and after the scanning period is compared and calculated. This operation is repeated and continued in sequence. After the calculation, the data in memory O set is transferred to 1 set of memory, and 1
The items in one set of memories are sequentially transferred to two sets of memories. Also, the data in 30 sets of memory will be automatically deleted.

(1) Detection of disconnection feeder (distribution line) Data of each distribution line input to input port PI
V ₁ θ ₁ , V ₂ θ ₂ ... are the latest data V ₁ θ ₁ , V ₂ θ ₂ ,
V ₃ θ ₃ , V ₄ θ ₄ and 30 sets of data stored in the memory at a scanning period of 15 seconds earlier V′ ₁ θ′ ₁ , V′ ₂ θ′ ₂ ,
From V' ₃ θ' ₃ , V' ₄ θ' ₄ , the absolute value of the vector difference in the output voltage of the D/ZCT for detecting disconnection of each distribution line before and after the scanning cycle |V〓 ₁ -V〓' ₁ |, |V〓 ₂ ―V〓′ ₂ |, |V
〓 ₃ -
V〓′ ₃ | Alternatively, the maximum value of this approximate value (hereinafter referred to as data change value) is selected for each sampling time, and this maximum value is the feeder detection sensitivity (e.g.
40mV) and continues for a set time (eg 4 seconds), it is determined that there is a disconnection fault in the distribution line with the largest change value of this data.

As described above, if a disconnection faulty distribution line is determined, the number of the distribution line is stored in the disconnection feeder storage memory under the control of the central processing unit CPU. The contents of this memory M will not be changed until the next disconnection fault occurs and the disconnection feeder is detected.
It also outputs the address of the output port PO to the address bus, and outputs the number of the distribution line with the disconnection failure to the data bus. The output port PO operates when the content of the address bus is the address of the output port PO, and inputs the number of the disconnection faulty distribution line on the data bus.For example, when distribution line 1 is disconnected, the corresponding output port PO is activated. A voltage is output to the output side terminal 21 of the thyristor SCR, the electromagnetic relay 1P is operated, and the make contacts 1P ₁ and 1P ₂ are closed to pressurize the disconnection indicating circuit and indicate a disconnection failure. Also, pressurize the cutoff circuit of the circuit breaker CB of the broken distribution line,
Block this. The electromagnetic relay 1P is designed so that the circuit breaker CB automatically resets, for example, 4 seconds after the circuit breaker is disconnected. Also, the disconnection failure display can be reset manually.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 shows a zero-phase current transformer for detecting disconnection immediately before and after a disconnection failure in a normal distribution line where there is always a considerable amount of zero-sequence current at the outlet of the distribution line. Fig. 2 is an explanatory diagram of a distribution line according to an embodiment of the method of the present invention, and Fig. 3 is an embodiment of the disconnection detection device of the method of the present invention. FIG. 4 is an explanatory diagram of the order and operation of storing the digital output voltage for detecting disconnection of each distribution line and the digital value of its phase in the memory. In the figure, O is the high-voltage bus of the substation, _T1 is the main supply transformer, _T2 is the grounding transformer, r is the grounding current limiting resistor, C is the neutral point grounding capacitor,
CB is circuit breaker, SS is automatic sectional switch, 1, 2,
3 and 4 are distribution lines, ,,, are distribution sections,
C〓, CC〓, C〓, C〓 are also C ₁₀ , C ₂₀ ,
C ₃₀ and C ₄₀ are the ground capacitance D of the entire section of each distribution line.
ZCT is a zero-phase current transformer for disconnection detection provided at the outlet of each distribution line, 5 is a filter, 6 is an amplification circuit, 7 is an analog-to-digital conversion circuit, 8 is a phase measurement circuit,
T ₃ is the reference voltage transformer, PI is the input port, PO is the output port, CPU is the central processing unit, M is the memory, X is the data bus, Y is the address bus, SCR
is a thyristor, 1P, 2P, 3P, 4P are electromagnetic relays for cutting off each distribution line and indicating disconnection, 1P ₁ ,
1P ₂ , 2P ₁ , 2P ₂ . . . are make contacts of each electromagnetic relay, and S is a return contact of each electromagnetic relay.

Claims (1)

[Claims] 1. A zero-phase current transformer for disconnection detection is installed at the outlet of each distribution line connected to the same bus in the substation, and a filter, amplifier circuit, and analog-to-digital conversion circuit are connected in series on the secondary side. In addition to connecting this to the input port, an amplification circuit, a phase measurement circuit, and an analog-to-digital conversion circuit are connected in series to the above filter and connected to the input port, and the reference voltage transformer on the bus bar is connected to each of the above phases. Connect to the measurement circuit, connect the central processing unit and memory to the above input port, connect this central processing unit to the output port, and connect the circuit devices for disconnection fault indication and cutoff of each distribution line to the output port. Then, the output voltage and its phase induced by the zero-sequence current of each distribution line are stored in multiple sets of memories at each sampling time, and this is repeated and continued at each scanning period, and the above-mentioned output voltage is stored at each sampling time. The latest output voltage and its phase of each distribution line stored in the memory, and the values before and after the scanning cycle of the zero-phase current transformer for disconnection detection of each distribution line calculated from the latest output voltage and its phase for each distribution line before the scanning cycle. The absolute value of the vector difference of the output voltage or the maximum value of its approximate value is successively selected, and the absolute value of this vector difference or the maximum value of its approximate value is If the vector difference is larger than the set value and continues for longer than the set time, it is determined that the distribution line with the largest absolute value of this vector difference has a disconnection or slight ground fault, and a disconnection failure display is displayed for the distribution line. An improvement to the disconnection detection method is characterized in that the disconnection detection method is selectively cut off.