JPH0750140B2 - Power main circuit checker - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power main circuit checker for confirming the presence or absence of a phase-to-phase short circuit or a ground fault of a main circuit through which power is passed in a power substation or the like.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram of a conventional main circuit for supplying power to a power substation, in which 21 is a disconnecting switch, 22 is a circuit breaker,
23 is a transformer, 24 is a power cable, 25 is an instrument transformer, 26 is a bus bar, 27 is a DC insulation resistance meter (megger) for measuring insulation resistance, U is the first phase of three phases, and V is the second phase. , W indicates the third phase, and X, Y, Z indicate the ground points at the site where the ground for each phase is attached during the power outage work.

FIG. 5 is an explanatory view of the conventional confirmation inspection of the main circuit by applying a low voltage three-phase voltage. 28 is a voltmeter and 29 is a measuring lead wire of the voltmeter 28.

Next, the confirmation inspection method will be described. Figure 4
When performing equipment inspection, new extension, or remodeling work at the substation shown in, some or all of the main circuits (bus bar 26 such as 6600V, 77000V, transformer 23, circuit breaker 22, disconnector) are required as necessary. 21, voltage transformer 2
5, a power circuit composed of the cable 24, etc. is cut off to perform the work.

In that case, first, a field ground is attached to each phase line at points X, Y, and Z. If necessary, the instrument transformer 25 should be disconnected from the circuit to prevent accidents due to reverse voltage.

After the construction work inside the substation is completed, visually check whether the connection of the worked part is correct, or whether there is a short circuit or a ground fault (ground contact) between each phase or the ground, and then remove the field ground. . Next, at the check point of the main circuit, the insulation resistance between the phases and the ground is measured and confirmed by the megger 27. If no abnormality is recognized, a low-voltage three-phase voltage is applied as a reference point with the point where the phase distinction of each U, V, W is known at the portion where the work was finally performed as shown in FIG. The voltage between the points to be checked is measured by connecting the lead wire 29 to the voltmeter 28. If there is no erroneous connection during that time, basically 0 volt is indicated between the same phases, so the confirmation inspection by applying low-voltage three-phase is completed.

After a series of inspections is completed in this way, all of the instrument transformers 25 and the like are connected and restored, and visual confirmation and the like are performed again, and then electricity is supplied.

[0008]

Since the conventional confirmation inspection of the main circuit is carried out as described above, a large-scale place or a substation with a complicated configuration requires a visual check for the main part of the inspection. It takes a lot of time and labor, and when measuring insulation with a megger, if a grounding type voltage transformer is connected, even if the insulation resistance value between the earth and the ground is measured, zero ohms will be indicated for direct current. In addition, there is a problem that it is not possible to confirm, and also regarding the method of applying the low voltage three-phase voltage, whether it is the U phase, V phase, W
It takes 3 measurements to confirm the phase and detect the phase.
There was a problem that the total of 3 phases x 3 times, that is, 9 times of measurements were required.

The present invention has been made in order to solve the above-mentioned problems, and does not rely on the visual inspection of the operator so that a visual confirmation error does not occur, ensuring the safety of the operator and automating the inspection process. The purpose is to obtain a power main circuit checker that can process all of them.

[0010]

SUMMARY OF THE INVENTION A power main circuit checker according to the present invention is a low voltage three-phase voltage generating circuit for generating a low voltage three-phase voltage for a test to be applied to a main circuit through which power is applied, and a low voltage three-phase voltage generating circuit applied to this main circuit. Interphase short-circuit current due to the low-voltage three-phase voltage
A current detection circuit that detects the ground fault current, a comparison circuit that outputs an alarm signal when the detected value exceeds the reference value, an alarm display circuit that displays the above alarm output, and an alarm signal output for the test signal And a storage circuit for storing the alarm output data.

[0011]

The power main circuit checker according to the present invention uses the low-voltage three-phase voltage applied to the main circuit to cause a short circuit between the main circuits.
The presence or absence of a ground fault is detected by the current detection circuit, and when the detected value exceeds the reference value, an alarm signal is output from the comparison circuit. The alarm display circuit displays an alarm according to the output of the alarm signal, the protection circuit cuts off the low-voltage three-phase voltage output, and the output data of the alarm signal is held in the memory holding circuit, so that the interphase short circuit and the ground fault are automatically detected. And phase can be detected.

[0012]

1 is a block diagram of a power main circuit checker according to an embodiment of the present invention, in which 1 is a low voltage 3 for generating a low voltage 3-phase (U, V, W) sine wave having an interphase voltage of 100V. Phase voltage generation circuit, 2 is a current detection circuit that detects a short-circuit ground fault current,
Reference numeral 3 is a comparison circuit that compares the detected value of the current detection circuit 2 with a reference value and outputs an alarm signal, 4 is an alarm display circuit that displays an alarm, and 5 is a protection circuit that shuts off the low-voltage three-phase voltage output.
Is a memory holding circuit for holding alarm data even after the protection circuit 5 cuts off the low voltage 3-phase voltage output, 7U, 7V and 7W are relay contacts for each of the U, V and W phases for cutting off the low voltage 3-phase voltage output, 8U
Is a current detecting current transformer of the U-phase circuit, 8V is a V-phase current detecting current transformer, 8W is a W-phase current detecting current transformer, and 8E is a ground fault current detecting current transformer.

FIG. 2 is a concrete circuit diagram of the power main circuit checker of the present invention constructed as shown in FIG. (Each circuit code in FIG. 2 is given the corresponding constituent circuit name in FIG. 1). 10 from the figure
Are input resistors R ₁ and 11 to which the detection current detected by the detecting current transformer 8U (current detection circuit 2) is input, and an input amplifier (current detection circuit 2) 12 that amplifies the input voltage generated at R _1. A detector (comparison circuit 3) for detecting the output of the amplifier 11 and converting it to a DC voltage, a comparator 13 for comparing and judging the output of the detector 12 and the reference voltage V _S (comparison circuit 3),
Reference numeral 14 is a flip-flop circuit (memory holding circuit 6, comparison circuit 3) for transmitting the output of the comparator 13 as an alarm signal to the next stage and storing and holding it as alarm output data, and 15 is an inverter for alarm output (alarm display circuit 4) , 16U is a U-phase display LED (alarm display circuit 4) that lights up by turning the inverter 15 on and displays an alarm, 17 is an AND circuit (protection circuit 5) for the output of the flip-flop circuit 14, and 18 is an OR circuit (protection circuit). 5) and 19U are U-phase cutoff relays (protection circuit 5) which are activated by the alarm output of the OR circuit 18, and 7U are relay contacts (protection circuit 5) of the relay 19U.

Further, the series of circuits is composed of U, V, W phases and four stages for ground fault current detection. Therefore, 8V, 8W and 8E are the current transformers for detection of each stage, and 16V is V
LED for phase indication, 19V for V phase cutoff relay, 7V for 19
V contact, 16W LED for W-phase display, 19W W-phase cutoff relay, 7W contact for 19W, 16E L for ground fault display
It is ED. Further, in the figure, the range shown by the dotted line is the same circuit as in the case of the U phase, and therefore the correspondence with the names of the constituent circuits in FIG. FIG. 3 is a circuit diagram for phase detection by the power main circuit checker of the present invention.

Next, the operation will be described. The low-voltage three-phase voltage generation circuit 1 shown in FIG. 1 generates a sine wave three-phase voltage having an interphase voltage of 100V and an interphase phase difference of 120 °. After detecting the presence or absence of charge on the main circuit side to be measured and sufficiently checking the safety, connect the U, V and W lines of the main circuit to the U, V and W phase output terminals of the power main circuit checker.

Assuming now that there is an interphase short circuit between the U and V phases on the main circuit side, the current transformers 8U and 8V for detecting short circuit currents.
Detects the short-circuit current and inputs it to the current detection circuit 2.

The following operation will be described in detail with reference to the concrete circuit diagram of FIG. Due to the short-circuit detection current input to the input resistor R ₁ from the current transformer 8U for detection, an input voltage corresponding to the detection current is generated at the R ₁ terminal, amplified by the amplifier 11 and detected by the detector 12 to generate a DC voltage. Is converted to.

The converted DC voltage is compared and judged by the comparator 13 with the reference voltage V _S. When the DC voltage value detected by the short circuit exceeds the reference voltage V _S , the flip-flop circuit 14 operates and outputs a warning signal, whereby the inverter 15 is inverted and the LED 15 lights up to display a warning. At the same time, the alarm output of the flip-flop circuit 14 turns on the AND circuit 17 and the OR circuit 18 to drive the cutoff relay 19U, so that the relay contact 7U opens and cuts off the low-voltage three-phase voltage output of the power main circuit checker.

The above operation simultaneously proceeds in the V-phase circuit, and the V-phase display LED 16V is also turned on. Furthermore AN
The alarm output of the D circuit is ORed to the other phase through the OR circuit 18, the V-phase breaking relay 19V and the W-phase breaking relay 19W are also activated, and the relay contacts 7V and 7W are also opened. If all the outputs are output, the cutoff relays of all phases are activated at the same time, and all the low voltage three-phase voltage outputs of the power main circuit checker are cut off to maintain the state until they are reset.

Since the flip-flop circuit 14 stores and holds the alarm output data even after the low-voltage three-phase voltage output is cut off, the U-phase display LED 16U and the V-phase display LED 1 are provided.
6V keeps the state of being lit, the interphase short circuit between the U phase and the V phase is automatically detected, and the accident handling after the detection can be appropriately performed.

Next, the detection of the ground fault will be described. If a ground fault is now occurring between the W phase and the ground, the current transformers 8W and 8E for detection detect the ground fault current in the same manner as the above circuit operation, and the ground fault display LED 16E and W phase display L
The ED 16W is turned on, and the interruption relays 19U, 19V, 19W are simultaneously activated by the alarm signal of the W-phase stage, and the low-voltage three-phase voltage outputs of the power main circuit checker are all interrupted. Since the ground fault display LED 16E and the W-phase display LED 16W are lit and held even after the interruption, it is possible to automatically detect that the ground fault phase is the W phase.

As a result of the above inspection, when each LED is not lit, it is determined that the main circuit has no interphase short circuit and no ground fault.

Next, phase detection using the power main circuit checker will be described. In the conventional phase detection, it took time and effort to measure the voltage 9 times in total. In the case of the present invention, as shown in FIG. 3, a power main circuit checker is used to apply a low-voltage three-phase voltage from a known reference point for each phase, and at the confirmation point, for example, the W phase is artificially grounded (artificial ground). If a fault occurs), the ground fault display LED 16E and the W-phase display LED 16W of the power main circuit checker are turned on. Therefore, it is possible to easily determine that the phase artificially grounded at the confirmation point is the same W phase as the reference point, that is, The phase can be detected, and the U and V phases are similarly checked and the inspection is completed.

As described above, if the power main circuit checker is used for the confirmation inspection of the main circuit of the substation or the like, it is possible to automatically detect the interphase short circuit, the ground fault, or the phase detection at one test point. You can Further, the power main circuit checker of the present invention has a wide range of applications as a tester for other power circuits and control equipment circuits, in addition to the above-described inspection of the main circuit of the power substation.

[0025]

As described above, according to the present invention, the short-circuit ground fault current is detected by the current detection circuit and an alarm is displayed, and at the same time, the low-voltage three-phase voltage output of the checker is cut off and the alarm data is retained. Since it is configured as described above, the detection and the phase detection of the presence or absence of the short circuit ground fault can be processed by one measuring device, and the automated inspection that does not need to rely on the visual inspection can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a power main circuit checker that is an embodiment of the present invention.

FIG. 2 is a circuit diagram of a power main circuit checker that is an embodiment of the present invention.

FIG. 3 is a phase detection diagram by the power main circuit checker of the present invention.

FIG. 4 is a schematic diagram of a conventional main circuit for supplying electric power.

FIG. 5 is an explanatory diagram of a confirmation inspection of a main circuit by applying a low voltage three-phase voltage in the related art.

[Explanation of symbols]

 1 Low voltage 3-phase voltage generation circuit 2 Current detection circuit 3 Comparison circuit 4 Alarm display circuit 5 Protection circuit 6 Memory retention circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Oki 1 Kibuki-cho, Kasugai-shi, Aichi Chubu Seiki Co., Ltd. (72) Inventor Takahiro Niwa 1 Kibuki-cho, Kasugai-shi, Aichi Chubu Seiki Co., Ltd.

Claims (1)

[Claims] 1. A low-voltage three-phase voltage generating circuit for generating a low-voltage three-phase voltage for a test signal applied to a main circuit for supplying electric power to a substation or the like, and an interphase by the low-voltage three-phase voltage applied to the main circuit. A current detection circuit that detects a short-circuit current and a ground fault current, a comparison circuit that outputs an alarm signal when the detected value exceeds a reference value, an alarm display circuit that displays the alarm signal output, and an alarm signal output described above. A power main circuit checker comprising a protection circuit for interrupting the three-phase voltage output for the test signal and a memory holding circuit for storing the output data of the alarm signal.