CN114167309A - Zero sequence current transformer secondary circuit broken line detection device and method - Google Patents
Zero sequence current transformer secondary circuit broken line detection device and method Download PDFInfo
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- CN114167309A CN114167309A CN202111262289.0A CN202111262289A CN114167309A CN 114167309 A CN114167309 A CN 114167309A CN 202111262289 A CN202111262289 A CN 202111262289A CN 114167309 A CN114167309 A CN 114167309A
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- 238000001514 detection method Methods 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title abstract description 8
- 238000012360 testing method Methods 0.000 claims description 11
- 238000007689 inspection Methods 0.000 claims description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/54—Testing for continuity
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Abstract
The invention discloses a zero sequence current transformer secondary circuit broken line detection device and a method, comprising a direct current generator, a voltage current collector, a central processing unit, a display setting unit and two current lines, wherein the direct current generator is used for generating direct current voltage and direct current; the voltage and current collector converts the direct current voltage and the direct current analog quantity into digital quantity; the central processing unit calculates a corresponding resistance value according to the digital quantity of the direct current voltage and the direct current, and judges whether the CT secondary circuit is disconnected or not according to the direct current and the resistance value; the display setting unit displays the measured magnitude and judgment result of the direct current voltage and the direct current and is used for setting the amplitude and the length of the pulse; and one ends of the two current lines are connected with the direct current generator, and the other ends of the two current lines are inserted into a third current terminal and a fourth current terminal of a secondary circuit of the zero sequence current transformer. The invention can regularly check the zero sequence loop in operation, find the CT disconnection fault in time and avoid the protection failure accident.
Description
Technical Field
The invention relates to a secondary circuit detection device of a current transformer, in particular to a secondary circuit disconnection detection device and method of a zero sequence current transformer.
Background
With the increase of the capacitance current of the power distribution network, the low-voltage side of a transformer substation in coastal areas is transformed into small-resistance grounding from arc suppression coil grounding, a zero-sequence current transformer (zero-sequence CT for short) is additionally arranged on each outgoing line, the zero-sequence current is connected into a protection device, the protection device is also upgraded to have the function of zero-sequence overcurrent tripping, and because the zero-sequence current is basically zero in normal operation, all the protection devices cannot detect whether a zero-sequence loop is broken or not at present. If the secondary side of the zero sequence CT is disconnected, the outgoing line protection is refused to operate when the circuit is in single-phase grounding, and the serious consequence of the override action of the main transformer protection is caused. Therefore, a device capable of detecting whether the zero sequence CT secondary circuit is broken needs to be developed, the zero sequence circuit in operation is periodically checked, CT broken line faults are timely found, and the protection failure accident is avoided.
Disclosure of Invention
The invention aims to provide a zero sequence current transformer secondary circuit line break detection device and method, which can be used for regularly checking a zero sequence circuit in operation, finding CT line break faults in time and avoiding the failure of protection.
The technical scheme for realizing the purpose of the invention is as follows: a zero sequence current transformer secondary circuit line break detection device comprises a zero sequence CT, a first current terminal, a second current terminal, a third current terminal, a fourth current terminal, a first current connecting sheet, a second current connecting sheet and a protection device, wherein the secondary terminal of the zero sequence CT is connected with the first current terminal through a secondary cable, the first current terminal is connected with the second current terminal through the first current connecting sheet, the second current terminal is connected with the protection device, the protection device is connected with the fourth current terminal, the third current terminal is connected with the fourth current terminal through the second current connecting sheet, the third current terminal is connected with the other secondary terminal of the zero sequence CT through a secondary cable, the device includes direct current generator, voltage current collector, central processing unit, demonstration setting element and two electric current lines, wherein:
the direct current generator is used for generating direct current voltage and direct current and outputting the direct current voltage and the direct current to the voltage and current collector;
the voltage and current collector is used for converting the direct current voltage and the direct current analog quantity into digital quantity and outputting the digital quantity to the central processing unit;
the central processing unit calculates a corresponding resistance value according to the digital quantity of the direct current voltage and the direct current, and judges whether the CT secondary circuit is disconnected or not according to the direct current and the resistance value;
the display setting unit is used for displaying the measured direct current voltage and the measured direct current and the judgment result, and is used for setting the amplitude and the length of the pulse;
and one ends of the two current lines are connected with the direct current generator, and the other ends of the two current lines are directly inserted into a third current terminal and a fourth current terminal of a secondary circuit of the zero sequence current transformer.
Further, the step of determining whether the CT secondary circuit is disconnected according to the magnitude of the dc current and the resistance value specifically includes: if the direct current and the resistance value are both in the set range, the secondary circuit is considered to be normal, otherwise, the secondary circuit is disconnected.
Furthermore, the device also comprises an alarm device connected with the central processing unit, and the alarm device gives out an alarm when the secondary circuit is disconnected.
Furthermore, the voltage and current acquisition precision of the voltage and current acquisition device is respectively within +/-2 mV and +/-2 mA.
Further, the direct current generator generates a direct current voltage of 10 mV-30 mV.
Further, the alternating current resistance in the direct current generator is less than 1 ohm, and the alternating current 5A current can be endured.
A detection method based on the zero sequence current transformer secondary circuit disconnection detection device comprises the following steps:
inserting the other ends of two current wires of the zero sequence current transformer secondary circuit disconnection detection device into current terminals at two ends of a first current connecting sheet or a second current connecting sheet of the zero sequence current transformer secondary circuit respectively;
starting the device, wherein the device is qualified by self-inspection, and alternating current flows through the device;
opening the first current connecting sheet or the second current connecting sheet to start testing;
recording the test result displayed on the display setting unit;
after the test is finished, the first current connecting piece or the second current connecting piece is closed, and the two current wires inserted into the current terminals at the two ends of the first current connecting piece or the second current connecting piece are pulled out.
Compared with the prior art, the invention has the following remarkable effects: the invention detects the conduction state of the secondary circuit by adding pulse component to the zero sequence secondary circuit at the current terminal row, the invention can detect under the electrified state without the power failure of primary equipment, and simultaneously does not influence the operation of the zero sequence tripping function of the protection device, can find the disconnection defect of the zero sequence secondary circuit in time according to the detection result, avoids the rejection of the protection when the system has ground fault, and has good application prospect.
Drawings
FIG. 1 is a block diagram of the apparatus of the present invention.
Fig. 2 is a schematic connection diagram of a normal zero sequence CT and a protection device.
Fig. 3 is a schematic diagram of the wiring during the test.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A conventional zero-sequence current transformer (zero-sequence current transformer) and a protection device are connected in a wiring manner as shown in fig. 2, a secondary circuit of the zero-sequence current transformer comprises a zero-sequence CT, a first current terminal a1, a second current terminal a2, a third current terminal B1, a fourth current terminal B2, a first current connecting sheet, a second current connecting sheet and a protection device, wherein the secondary terminal S1 of the zero-sequence CT is connected with the first current terminal a1 through a secondary cable, the first current terminal a1 is connected with the second current terminal a2 through the first current connecting sheet, the second current terminal a2 is connected with the protection device, the protection device is connected with the fourth current terminal B2, the third current terminal B1 is connected with the fourth current terminal B2 through the second current connecting sheet, and the third current terminal B1 is connected to the other secondary terminal S2 of the zero-sequence CT through a secondary cable;
as can be seen from fig. 2, the flow path of the zero-sequence CT secondary current is:
the zero sequence CT secondary S1 terminal-secondary cable-first current connection piece-secondary wiring in the cabinet-protection device-secondary wiring in the cabinet-second current connection piece-secondary cable-zero sequence CT secondary S2 terminal.
For the secondary circuit of the zero sequence current transformer, the secondary current of the zero sequence current transformer is zero when in normal operation, and the existing protection device cannot detect whether the secondary circuit of the zero sequence CT is broken. As shown in fig. 1, a zero sequence current transformer secondary circuit disconnection detection device includes a dc generator, a voltage current collector, a central processing unit, a display setting unit and an external connection, wherein:
the direct current generator is used for avoiding the influence of the direct current quantity on the zero sequence CT, and the direct current quantity is as small as possible. The dc generator needs to generate a dc voltage of 10mV to 30 mV. Considering that a direct current generator is connected in series in a zero sequence secondary circuit, a line is likely to be grounded in a detection process, the alternating current resistance of the direct current generator seen from the outside is less than 1 ohm, and the direct current generator can tolerate the current of alternating current 5A in a short time;
the voltage and current collector can collect the DC voltage generated by the DC generator and the output DC current, and the DC voltage and the output DC current are supplied to the CPU for calculation, and the collection precision is required to be within +/-2 mV and +/-2 mA.
And the central processing unit receives the data of the voltage and current collector, calculates a corresponding resistance value according to the digital quantity of the direct current and the direct current, analyzes the data, and if the direct current and the resistance value are in a set range, the secondary circuit is considered to be normal, otherwise, the secondary circuit is disconnected. If the collected current is zero or very small, the zero sequence CT secondary circuit is judged to be broken, if the measured current is normal and the corresponding resistance value is in a reasonable range, the CT secondary circuit is judged to have no problem.
The display setting unit is a human-computer interaction interface and is used for displaying the measured voltage and current, and the amplitude and the length of the pulse can be set. The detection result can be displayed, whether the zero sequence CT secondary circuit is broken or not can be displayed, and an LCD display screen is adopted.
The external wiring is composed of two current wires, one end of each current wire is connected with a direct current generator, and the other end of each current wire is a standard current connector lug which can be directly inserted into a current terminal of a secondary circuit (on a transformer substation switch cabinet) of the zero sequence current transformer.
The protection device judges whether the line has a ground fault by collecting the magnitude of the zero sequence current, so as to send a tripping command.
A detection method based on the zero sequence current transformer secondary circuit broken line detection device comprises the following steps:
with reference to fig. 3, the two secondary wires of the device of the present invention are inserted into the third current terminal (B1) and the fourth current terminal B2 (or the first current terminal a1 and the second current terminal a2), respectively, to ensure a secure connection.
The device is started, self-checking is qualified, and alternating current can flow through the device.
The second connecting piece between the third current terminal B1 and the fourth current terminal B2 is opened.
And starting the test function of the device to obtain a test result.
And recording the test result displayed on the display setting unit.
Closing a second connecting piece between the third current terminal B1 and the fourth current terminal B2.
The two current lines of the device of the present invention plugged into the third current terminal B1 and the fourth current terminal B2 were removed.
The test is completely finished.
It should be emphasized that the present invention avoids the influence on the operation of the secondary circuit during the detection process, that is, if a single-phase ground fault occurs on the line during the detection process, the detection device does not influence the circulation of the zero-sequence current.
Claims (7)
1. A zero sequence current transformer secondary circuit line break detection device, the zero sequence current transformer secondary circuit includes zero sequence CT, the first current terminal (A1), the second current terminal (A2), the third current terminal (B1), the protection device comprises a fourth current terminal (B2), a first current connecting sheet, a second current connecting sheet and a protection device, wherein a secondary terminal (S1) of the zero sequence CT is connected with the first current terminal (A1) through a secondary cable, the first current terminal (A1) is connected with the second current terminal (A2) through the first current connecting sheet, the second current terminal (A2) is connected with the protection device, the protection device is connected with the fourth current terminal (B2), the third current terminal (B1) is connected with the fourth current terminal (B2) through the second current connecting sheet, and the third current terminal (B1) is connected into the other secondary terminal (S2) of the zero sequence CT through a secondary cable; the device is characterized by comprising a direct current generator, a voltage and current collector, a central processing unit, a display setting unit and two current lines, wherein:
the direct current generator is used for generating direct current voltage and direct current and outputting the direct current voltage and the direct current to the voltage and current collector;
the voltage and current collector is used for converting the direct current voltage and the direct current analog quantity into digital quantity and outputting the digital quantity to the central processing unit;
the central processing unit obtains a corresponding resistance value according to the digital quantity of the direct current voltage and the direct current, and judges whether the secondary circuit is disconnected or not according to the direct current and the resistance value;
the display setting unit is used for displaying the measured direct current voltage and the measured direct current and the judgment result, and is used for setting the amplitude and the length of the pulse;
one ends of the two current lines are connected with the direct current generator, and the other ends of the two current lines are inserted into a third current terminal (B1) and a fourth current terminal (B2) of a secondary circuit of the zero sequence current transformer.
2. The zero sequence current transformer secondary circuit disconnection detecting device according to claim 1, wherein the determining whether the secondary circuit is disconnected according to the magnitude of the direct current and the resistance value specifically comprises: if the direct current and the resistance value are both in the set range, the secondary circuit is considered to be normal, otherwise, the secondary circuit is disconnected.
3. The zero sequence current transformer secondary circuit disconnection detecting device of claim 1, further comprising an alarm device connected with the central processing unit, wherein the alarm device gives an alarm when the secondary circuit is disconnected.
4. The zero sequence current transformer secondary circuit disconnection detecting device of claim 1, wherein the voltage and current collection accuracy of the voltage and current collector is within ± 2mV and ± 2mA, respectively.
5. The zero sequence current transformer secondary circuit disconnection detecting device of claim 1, wherein the dc generator generates a dc voltage of 10mV to 30 mV.
6. The apparatus of claim 5, wherein the AC resistance of the DC generator is less than 1 ohm and can withstand an AC 5A current.
7. A detection method based on the zero sequence current transformer secondary circuit disconnection detection device of any one of claims 1 to 6 is characterized by comprising the following steps:
inserting the other ends of two current wires of the zero sequence current transformer secondary circuit disconnection detection device into current terminals at two ends of a first current connecting sheet or a second current connecting sheet of the zero sequence current transformer secondary circuit respectively;
starting the device, wherein the device is qualified by self-inspection, and alternating current flows through the device;
opening the first current connecting sheet or the second current connecting sheet to start testing;
recording the test result displayed on the display setting unit;
after the test is finished, the first current connecting piece or the second current connecting piece is closed, and the two current wires inserted into the current terminals at the two ends of the first current connecting piece or the second current connecting piece are pulled out.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111262289.0A CN114167309A (en) | 2021-10-28 | 2021-10-28 | Zero sequence current transformer secondary circuit broken line detection device and method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111262289.0A CN114167309A (en) | 2021-10-28 | 2021-10-28 | Zero sequence current transformer secondary circuit broken line detection device and method |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR200383776Y1 (en) * | 2005-02-16 | 2005-05-06 | 삼성계측제어(주) | An apparatus for monitoring open state of the secondary terminals of a current transformer |
| CN103840438A (en) * | 2014-03-25 | 2014-06-04 | 浙江巨力电气有限公司 | Intelligent detecting system for detecting single phase grounding protection function of intelligent switch device based on 10kV neutral non-grounding distribution network system |
| CN110554234A (en) * | 2019-09-03 | 2019-12-10 | 广东电网有限责任公司 | Zero-sequence current loop inspection method for in-service switch cabinet |
| CN112485581A (en) * | 2020-10-19 | 2021-03-12 | 广东电网有限责任公司中山供电局 | Zero sequence current transformer and secondary circuit detection device and method thereof |
-
2021
- 2021-10-28 CN CN202111262289.0A patent/CN114167309A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR200383776Y1 (en) * | 2005-02-16 | 2005-05-06 | 삼성계측제어(주) | An apparatus for monitoring open state of the secondary terminals of a current transformer |
| CN103840438A (en) * | 2014-03-25 | 2014-06-04 | 浙江巨力电气有限公司 | Intelligent detecting system for detecting single phase grounding protection function of intelligent switch device based on 10kV neutral non-grounding distribution network system |
| CN110554234A (en) * | 2019-09-03 | 2019-12-10 | 广东电网有限责任公司 | Zero-sequence current loop inspection method for in-service switch cabinet |
| CN112485581A (en) * | 2020-10-19 | 2021-03-12 | 广东电网有限责任公司中山供电局 | Zero sequence current transformer and secondary circuit detection device and method thereof |
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