CN115224664B - Protection method for CT secondary side open circuit of 10kV pole-mounted circuit breaker - Google Patents
Protection method for CT secondary side open circuit of 10kV pole-mounted circuit breaker Download PDFInfo
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- CN115224664B CN115224664B CN202210763648.9A CN202210763648A CN115224664B CN 115224664 B CN115224664 B CN 115224664B CN 202210763648 A CN202210763648 A CN 202210763648A CN 115224664 B CN115224664 B CN 115224664B
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- 238000000034 method Methods 0.000 title claims abstract description 13
- 239000003990 capacitor Substances 0.000 claims description 10
- 239000003381 stabilizer Substances 0.000 claims description 8
- 230000001105 regulatory effect Effects 0.000 claims description 7
- 230000000087 stabilizing effect Effects 0.000 claims description 6
- 230000002457 bidirectional effect Effects 0.000 claims description 5
- 230000001052 transient effect Effects 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 2
- 238000005070 sampling Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/042—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers for current transformers
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
The invention belongs to the technical field of power grids, and relates to a protection method for secondary side open circuit of a 10kV on-column circuit breaker CT, wherein a protection module is connected in parallel with an incoming line port and an outgoing line port of the on-column circuit breaker CT, and the protection module consists of a voltage clamping unit and an automatic exit unit; when the secondary side of the on-pole circuit breaker CT is opened, the protection module induces voltage, and the voltage value is controlled within a safety range through the voltage clamping unit; during the open circuit of the secondary side of the CT of the on-column circuit breaker, the protection module continuously works, and the voltage of the secondary side is always within a safe range; after the secondary side open circuit fault of the CT of the pole-mounted circuit breaker is relieved, the automatic exit unit starts working, and the protection module is automatically cut off. The invention can ensure that when the secondary side of the CT in the pole-mounted circuit breaker is opened, the voltages at two ends of the CT are clamped, so that equipment is prevented from being burnt out due to thousands of volts of high voltage, and the personal safety is prevented from being damaged; meanwhile, the iron core loss can be restrained, and the burning of the circuit breaker is stopped.
Description
Technical Field
The invention belongs to the technical field of power grids, and particularly relates to a protection method for a secondary side open circuit of a CT (current transformer) of a 10kV pole-mounted circuit breaker.
Background
The CT for the internal assembly of the 10kV pole-mounted circuit breaker converts a large current signal of a bus into a small current signal, so that the collection of the bus current is realized, the current fault identification is realized through the current analysis, and the stable operation of a power system is ensured.
When the CT is used, the main circuit directly passes through the current transformer or winds a plurality of turns, and the secondary side is connected with the measuring instrument or the relay protection circuit. The CT secondary winding is not allowed to open (disconnect) when the line through the current transformer is energized. In the running process of the pole-mounted circuit breaker, once the CT secondary side is opened, high voltage is induced at an output end due to excitation, and the high voltage is extremely easy to cause personal accidents and equipment faults, so that the normal running of a power grid is threatened, and great economic loss is caused.
Currently, in order to prevent loss caused by the open circuit of the secondary side of the CT, some more complex protection devices are mostly configured. For example, patent application number 202011371504.6 discloses a current transformer secondary open circuit protection system comprising: the current sampling unit is used for sampling the current of the secondary circuit of the current transformer; the waveform sampling unit is used for sampling voltage waveforms of the secondary circuit of the current transformer; the control unit is used for judging whether the current signal exists or not, judging the voltage waveform and judging the state of the secondary circuit of the current transformer according to the sampling signals obtained by the current sampling unit and the waveform sampling unit, and sending a driving signal when the secondary circuit is judged to be open circuit; and the power driving unit is used for driving the protection executing unit according to the driving signal and short-circuiting, breaking or connecting the secondary circuit into the analog load. The circuit structure and the judging method of the patent are complex, the operation is complex, and the economic cost is high.
Disclosure of Invention
In order to solve the technical problems, the invention provides a protection method for a CT secondary side open circuit of a 10kV pole-mounted circuit breaker. The technical scheme adopted by the invention is as follows:
a protection method for a CT secondary side open circuit of a 10kV pole-mounted circuit breaker comprises the following steps:
step 1, connecting a protection module in parallel with an incoming line port and an outgoing line port of a column circuit breaker CT, wherein the protection module consists of a voltage clamping unit and an automatic exit unit;
Step 2, when the secondary side of the on-pole circuit breaker CT is opened, the protection module induces voltage, and the voltage value is controlled within a safe range through the voltage clamping unit;
step 3, continuously working a protection module during the open circuit of the CT secondary side of the on-column circuit breaker, wherein the voltage of the secondary side is always within a safe range;
And 4, after the secondary side open circuit fault of the CT of the pole-mounted circuit breaker is relieved, automatically exiting the unit to start the operation, and automatically cutting off the protection module.
The invention has the beneficial effects that:
The invention can ensure that when the secondary side of the CT in the pole-mounted circuit breaker is opened, the voltages at two ends of the CT are clamped, so that equipment is prevented from being burnt out due to thousands of volts of high voltage, and the personal safety is prevented from being damaged; meanwhile, the iron core loss can be restrained, and the burning of the circuit breaker is stopped.
Drawings
In order to more clearly illustrate the embodiments of the present application, or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is apparent that the drawings in the following description are specific embodiments of the application and that other drawings within the scope of the application may be obtained from these drawings by those skilled in the art without inventive effort.
FIG. 1 is a logic flow diagram of an embodiment of the present invention.
Fig. 2 is a schematic circuit diagram of a protection module according to an embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and complete in conjunction with the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the present invention.
As shown in fig. 1, is a logic flow diagram of an embodiment of the present invention. A protection method for a CT secondary side open circuit of a 10kV pole-mounted circuit breaker comprises the following steps:
step 1, connecting a protection module in parallel with an incoming line port and an outgoing line port of a column circuit breaker CT, wherein the protection module consists of a voltage clamping unit and an automatic exit unit;
Step 2, when the secondary side of the on-pole circuit breaker CT is opened, the protection module induces voltage, and the voltage value is controlled within a safe range through the voltage clamping unit;
step 3, continuously working a protection module during the open circuit of the CT secondary side of the on-column circuit breaker, wherein the voltage of the secondary side is always within a safe range;
And 4, after the secondary side open circuit fault of the CT of the pole-mounted circuit breaker is relieved, automatically exiting the unit to start the operation, and automatically cutting off the protection module.
Fig. 2 is a schematic diagram of a circuit structure of a protection module according to an embodiment of the invention. In order to realize the protection method of the CT secondary side open circuit of the 10kV pole-mounted circuit breaker, a circuit structure of the protection module is designed, and the protection module comprises the following components: the MOS transistor comprises a first branch consisting of an end point A and an end point B and a second branch consisting of an end point C and an end point D, wherein the end point A and the end point B are connected with an incoming line port of a CT, the end point C and the end point D are connected with an outgoing line port of the CT, a diode D1 and a diode D3 which are connected in series are connected in parallel on one side of the end point A and one side of the end point C between the first branch and the second branch, and a MOS transistor Q1 and a MOS transistor Q4 which are connected in series are connected in parallel on one side of the end point B and one side of the end point D between the first branch and the second branch. The terminal A is connected with the anode of the diode D1, the cathode of the diode D1 is connected with the cathode of the diode D3, and the anode of the diode D3 is connected with the terminal C. One end of the bidirectional transient diode DZ1 is connected with the cathode of the diode D1, the other end of the bidirectional transient diode DZ1 is connected with the emitter of the triode Q3, the collector of the triode Q3 is connected with the anode of the diode D2, the cathode of the diode D2 is connected with the emitter of the triode Q2, the base of the triode Q2 is connected with the anode of the diode D2, the collector of the triode Q2 is connected with the anode of the precision voltage stabilizing source U1, the cathode of the precision voltage stabilizing source U1 is connected with one end of the resistor R4, the reference end of the precision voltage stabilizing source U1 is connected with one end of the resistor R5, the grid electrode of the MOS tube Q1 is connected with the cathode of the diode D2, the drain electrode of the MOS tube Q1 is connected with the end point B, the source electrode of the MOS tube Q1 is connected with the source electrode of the MOS tube Q4, the grid electrode of the MOS tube Q4 is connected with the emitter of the triode Q2, and the drain electrode of the MOS tube Q4 is connected with the end point D; one end of the resistor R1 is connected with the emitter of the triode Q3, the other end of the resistor R1 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the cathode of the precision voltage stabilizer U1, one end of the resistor R5 is connected with the collector of the triode Q3, the other end of the resistor R5 is connected with the reference end of the precision voltage stabilizer U1, one end of the resistor R6 is connected with the anode of the precision voltage stabilizer U1, the other end of the resistor R6 is connected with one end of the resistor R3, the other end of the resistor R3 is connected with the anode of the capacitor C1, the cathode of the capacitor C1 is connected with one end of the resistor R6, one end of the resistor R2 is connected with the base of the triode Q2, and the other end of the resistor R2 is connected with the source of the MOS tube Q4. The precision voltage stabilizer U1 can be a TL431 parallel voltage-stabilizing integrated circuit.
The protection module is assembled in parallel at the secondary outlet end of the CT used by the pole-mounted breaker, when the external lead is disconnected, the protection module generates voltage, the voltage causes the protection module to work so as to drive the MOS tube to conduct, the rising voltage is short-circuited, the voltage is reduced, the circuit is cycled, and the open circuit voltage is controlled in a safe and reasonable range.
The design principle and the working flow of the protection module are as follows:
(1) After the CT secondary side is opened, voltages are induced at two ends of the D1 and the D3, the D1 and the D3 play a role in rectification, and after the voltage rises to the regulated voltage of the regulated tube DZ1, the regulated tube is conducted to the C1 capacitor, a charging loop is formed through the body diode of the Q4, and the C1 capacitor is charged.
(2) Along with the increase of the voltage at two ends of the C1 capacitor, the voltage divided by the R3 and the R6 is larger than the reference voltage in the U1, so that the internal resistance of the U1 is gradually reduced, the voltage flows through the R1, the R4 and the U1 loops, the voltage difference between the voltage of the terminal electrode of the Q3 and the voltage of the emitter is larger than 0.7V, and the conduction of the Q3 is promoted.
(3) After Q3 is conducted, as the R3 resistor and the R5 resistor are connected in parallel, the voltage at two ends of R6 is further increased, and therefore the internal resistance of U1 is further reduced; and the voltage after the conduction of the Q3 passes through D2, the conduction of the Q1 and the Q4 is driven, and the conduction of the Q1 and the Q4 is performed, so that the voltages at two ends of the CT secondary side are short-circuited, and the voltage is clamped to 0.
(4) In order to accelerate the turn-off of the Q1 and the Q4, the circuit is added with the Q2, when the anode voltage of the D2 is reduced, the gate voltages of the Q1 and the Q4 have no bleeder circuit due to the reverse turn-off of the D2, at the moment, the Q2 is conducted to bleeder the gate voltage because the voltage difference between the emitter and the base is larger than 0.7V, and the R2 plays a role in voltage bias.
(5) During the open circuit of the CT secondary side, the circuit always repeats the above 4 steps; after the secondary side of the CT is recovered to be normal, the step (4) is terminated, and the waveform quality of normal signals at the two ends of the CT is not affected.
If execution proceeds to step (4), CT returns to normal, and may be automatically terminated because no voltage is supplied to the protection module.
After the CT secondary side is opened, the design method promotes the voltage clamping unit to act, can work for a long time, the maximum overload current can reach 50A, the conducting voltage can be adjusted by the circuit, the clamping voltage is within 2V, the leakage current is less than 100uA in normal work, and the conducting time is 10ms; the operation and installation are simple, and after the CT open circuit fault is eliminated, the voltage clamping unit can be automatically cut off, so that the operation, maintenance and overhaul work of the pole-mounted circuit breaker is simplified, and the operation reliability of a power grid is improved. The invention can control the large voltage generated by CT secondary side open circuit in a reasonable and effective range, so that the protected CT, secondary circuit, column circuit breaker and related equipment and operation operators are safer. The maximum current 50A is determined according to the parameters of the MOS tube; the clamping voltage is the average voltage, actually measured; the leakage current less than 100uA is determined according to the leakage current of the MOS tube and the leakage current of the bidirectional transient diode DZ1, and is obtained according to a manual, and the conduction time oscilloscope is actually tested.
Finally, it should be noted that: the above examples are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention. Those skilled in the art will appreciate that: any person skilled in the art may modify or easily conceive of changes to the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention.
Claims (2)
- The protection method for the CT secondary side open circuit of the 10kV pole-mounted circuit breaker is characterized by comprising the following steps:step 1, connecting a protection module in parallel with an incoming line port and an outgoing line port of a column circuit breaker CT, wherein the protection module consists of a voltage clamping unit and an automatic exit unit;Step 2, when the secondary side of the on-pole circuit breaker CT is opened, the protection module induces voltage, and the voltage value is controlled within a safe range through the voltage clamping unit;Step 3, continuously working a protection module during the open circuit of the CT secondary side of the on-column circuit breaker, wherein the voltage of the secondary side is always within a safe range;Step 4, after the secondary side open circuit fault of the CT of the on-column circuit breaker is relieved, automatically exiting the unit to start working, and automatically cutting off the protection module;The circuit structure of the protection module comprises: the MOS transistor comprises a first branch consisting of an end point A and an end point B and a second branch consisting of an end point C and an end point D, wherein the end point A and the end point B are connected with an incoming line port of a CT, the end point C and the end point D are connected with an outgoing line port of the CT, a diode D1 and a diode D3 which are connected in series are connected in parallel at one side of the end point A and one side of the end point C between the first branch and the second branch, and a MOS transistor Q1 and a MOS transistor Q4 which are connected in series are connected in parallel at one side of the end point B and one side of the end point D between the first branch and the second branch; the end point A is connected with the anode of the diode D1, the cathode of the diode D1 is connected with the cathode of the diode D3, and the anode of the diode D3 is connected with the end point C; one end of the bidirectional transient diode DZ1 is connected with the cathode of the diode D1, the other end of the bidirectional transient diode DZ1 is connected with the emitter of the triode Q3, the collector of the triode Q3 is connected with the anode of the diode D2, the cathode of the diode D2 is connected with the emitter of the triode Q2, the base of the triode Q2 is connected with the anode of the diode D2, the collector of the triode Q2 is connected with the anode of the precision voltage stabilizing source U1, the cathode of the precision voltage stabilizing source U1 is connected with one end of the resistor R4, the reference end of the precision voltage stabilizing source U1 is connected with one end of the resistor R5, the grid electrode of the MOS tube Q1 is connected with the cathode of the diode D2, the drain electrode of the MOS tube Q1 is connected with the end point B, the source electrode of the MOS tube Q1 is connected with the source electrode of the MOS tube Q4, the grid electrode of the MOS tube Q4 is connected with the emitter of the triode Q2, and the drain electrode of the MOS tube Q4 is connected with the end point D; one end of the resistor R1 is connected with the emitter of the triode Q3, the other end of the resistor R1 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the cathode of the precision voltage stabilizer U1, one end of the resistor R5 is connected with the collector of the triode Q3, the other end of the resistor R5 is connected with the reference end of the precision voltage stabilizer U1, one end of the resistor R6 is connected with the anode of the precision voltage stabilizer U1, the other end of the resistor R6 is connected with one end of the resistor R3, the other end of the resistor R3 is connected with the anode of the capacitor C1, the cathode of the capacitor C1 is connected with one end of the resistor R6, one end of the resistor R2 is connected with the base of the triode Q2, and the other end of the resistor R2 is connected with the source of the MOS tube Q4;the workflow of the protection module is as follows:(1) After the CT secondary side is opened, voltages are induced at two ends of D1 and D3, the D1 and the D3 play a role in rectification, and after the voltage rises to the regulated voltage of the regulated tube DZ1, the regulated tube is conducted to supply the regulated voltage to the C1 capacitor, and a charging loop is formed through a body diode of Q4 to charge the C1 capacitor;(2) Along with the increase of the voltage at two ends of the C1 capacitor, the voltage divided by R3 and R6 is larger than the reference voltage in U1, so that the internal resistance of U1 is gradually reduced, the voltage flows through R1, R4 and U1 loops, the voltage difference between the voltage of the terminal electrode of Q3 and the voltage of the emitter is larger than 0.7V, and the conduction of Q3 is promoted;(3) After Q3 is conducted, as the R3 resistor and the R5 resistor are connected in parallel, the voltage at two ends of R6 is further increased, and therefore the internal resistance of U1 is further reduced; the voltage after the conduction of the Q3 passes through D2, the conduction of the Q1 and the Q4 is driven, the conduction of the Q1 and the Q4 is realized, the voltage at two ends of the CT secondary side is short-circuited, and the voltage is clamped to 0;(4) When the anode voltage of the D2 is reduced, the gate voltages of the Q1 and the Q4 have no bleeder circuit due to the reverse cut-off of the D2, and at the moment, the Q2 is conducted to bleeder the gate voltage because the voltage difference between the emitter and the base is more than 0.7V, and the R2 plays a role in voltage bias;(5) After the secondary side of the CT is recovered to be normal, the step (4) is terminated, and the waveform quality of normal signals at the two ends of the CT is not affected.
- 2. The method for protecting the secondary side open circuit of the 10kV pole-mounted circuit breaker CT according to claim 1, wherein the precision voltage stabilizer U1 is a TL431 parallel voltage-stabilizing integrated circuit.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210763648.9A CN115224664B (en) | 2022-06-30 | 2022-06-30 | Protection method for CT secondary side open circuit of 10kV pole-mounted circuit breaker |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210763648.9A CN115224664B (en) | 2022-06-30 | 2022-06-30 | Protection method for CT secondary side open circuit of 10kV pole-mounted circuit breaker |
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| CN115224664B true CN115224664B (en) | 2024-05-14 |
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|---|---|
| CN115224664A (en) | 2022-10-21 |
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