High-voltage equipment fault judgment method based on voltage abnormity

Abstract

The invention discloses a high-voltage equipment fault judgment method based on voltage abnormity, and relates to the technical field of high-voltage equipment fault property judgment, and the method comprises the steps: determining whether an undervoltage or overvoltage condition occurs or not through monitoring the voltage level of each phase voltage of a voltage transformer; if the undervoltage or overvoltage condition occurs, determining voltage abnormity indication information corresponding to different conditions; and determining high-voltage equipment fault information according to the voltage abnormity indication information. The fault property can be quickly judged according to the voltage abnormal information in combination with other fault phenomena, so that the fault searching efficiency is improved, and the situation that fault downtime is prolonged due to misjudgment, even the fault range is expanded, and greater loss is caused to a user is prevented. And safe and stable operation of equipment power supply can be ensured.

Description

Technical Field

[0001] The present application relates to the technical field of high-voltage equipment fault determination, and in particular to a method for determining high-voltage equipment fault based on voltage anomaly. Background Art

[0002] There are many equipment failures in the power supply and distribution system, such as system grounding, blown fuses on the high and low voltage sides of the voltage transformer, resonance, overhead line disconnection, etc., which will affect the safe and stable operation of the system equipment. When these failures occur, they will cause abnormal voltage indication.

[0003] Traditional methods for locating power supply and distribution system equipment faults rely primarily on empirical judgment, visual inspection, and step-by-step troubleshooting. These methods include visual inspection, which involves checking the equipment's exterior for abnormalities such as burns, deformation, or cracks, and checking whether indicator lights and instrument displays are normal. A step-by-step troubleshooting method divides the power supply and distribution system into multiple parts (such as power supplies, lines, and loads), checks each one individually, and narrows the scope of the fault by disconnecting or connecting some circuits. A logical reasoning method analyzes possible causes based on the fault symptoms (such as tripping, heating, and odor) combined with the system schematic. An empirical summary method draws a fault tree based on the fault symptoms and troubleshoots possible causes layer by layer. However, traditional fault detection and processing methods can lead to inaccurate fault identification and long processing times, impacting users' stable and reliable power supply. Therefore, after a fault occurs, how to quickly determine the fault nature based on voltage anomaly information, and then take targeted measures to quickly restore power supply, is a technical problem that needs to be solved in this field. Summary of the Invention

[0004] In order to solve the above technical problems, this application proposes the following technical solutions: In a first aspect, an embodiment of the present application provides a method for determining a high-voltage equipment fault based on voltage anomaly, comprising: Determine whether undervoltage or overvoltage occurs by monitoring the voltage level of each phase voltage of the voltage transformer; If undervoltage or overvoltage occurs, determine the voltage abnormality indication information corresponding to the different situations; High-voltage equipment fault information is determined based on the voltage anomaly indication information.

[0005] In one possible implementation, the determining whether an undervoltage or overvoltage condition occurs by monitoring the voltage level of each phase voltage of the voltage transformer includes: Determine and monitor the monitoring equipment of the voltage transformer, the monitoring equipment includes: a voltmeter on the voltage transformer cabinet, a background monitoring microcomputer, and a microcomputer protection and measurement control device on each feeder cabinet and the main transformer protection and measurement control screen; The voltage information of each phase of the voltage transformer is obtained through the monitoring information of the monitoring device.

[0006] In a possible implementation, if an undervoltage or overvoltage situation occurs, determining voltage abnormality indication information corresponding to different situations includes: The phase voltage of one phase of the voltage transformer is zero, and the voltages of the other two phases are line voltages. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is the first voltage. At the same time, the insulation monitoring of the busbar on the high-voltage or low-voltage side of the main transformer is activated and an alarm is sounded. All voltage transformers of the busbar system supplied by the same main transformer will have the above-mentioned abnormal voltage indication; or, The phase voltage of one phase of the voltage transformer decreases but is not zero, while the phase voltages of the other two phases increase but are less than the line voltage. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is less than the first voltage but higher than the voltage start setting value of the ground fault protection alarm. At the same time, the insulation monitoring of the busbar on the high-voltage or low-voltage side of the main transformer will activate the alarm, and all voltage transformers of the busbar system supplied by the same main transformer will have the above abnormal voltage indication; or, The voltage of one phase of the voltage transformer is lower than the phase voltage, but not zero. The phase voltages of the other two phases are normal. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is close to the second voltage and higher than the voltage start setting value of the ground protection alarm. A ground signal is issued. At the same time, the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located all report a voltage transformer disconnection alarm. or, The voltage of one phase of the voltage transformer is the phase voltage, and the phase voltages of the other two phases are close to 0V. The zero-sequence voltage generated at both ends of the open delta voltage transformer is close to the second voltage, which is higher than the voltage start setting value of the ground protection alarm and sends a ground signal; or, The voltage of one phase of the voltage transformer is lower than the phase voltage, but not zero. The phase voltages of the other two phases are normal. The zero-sequence voltage at both ends of the open delta of the voltage transformer is zero. At the same time, the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located all report a voltage transformer disconnection alarm. or, The three-phase voltage fluctuates frequently and instantaneously, and the voltage amplitude of one phase is large. In the middle, the three-phase voltage of the bus increases simultaneously, but the phase-to-phase voltage remains at the rated voltage. There is a large voltage at both ends of the open delta of the voltage transformer, and the main transformer bus insulation inspection device sometimes sends a grounding signal. or, The phase voltage of one phase increases but does not exceed the first preset multiple of the rated phase voltage, and the phase voltages of the other two phases decrease and approach but do not fall below the second preset multiple of the rated phase voltage, accompanied by a ground fault alarm phenomenon.

[0007] In a possible implementation, determining high-voltage equipment fault information according to the voltage anomaly indication information includes: If the phase voltage of one phase of the voltage transformer is zero, the voltages of the other two phases are line voltages, the zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is the first voltage, and at the same time, the insulation monitoring of the busbar on the high-voltage or low-voltage side of the main transformer is alarmed, and all voltage transformers of the busbar system supplied by the same main transformer have the above-mentioned abnormal voltage indication, then it is determined that the high-voltage equipment fault information is a metallic ground fault of one phase of the system; or, If the phase voltage of one phase of the voltage transformer decreases but is not zero, and the phase voltages of the other two phases increase but are lower than the line voltage, the zero-sequence voltage across the open delta winding of the voltage transformer is lower than the first voltage but higher than the voltage start setting value of the ground protection alarm, and at the same time, the busbar insulation monitoring on the high-voltage or low-voltage side of the main transformer activates an alarm, and all voltage transformers in the busbar system supplied by the same main transformer have the above abnormal voltage indications, then the high-voltage equipment fault information is determined to be a non-metallic ground fault on one phase of the system; or, If the voltage of one phase of the voltage transformer is lower than the phase voltage but not zero, and the phase voltages of the other two phases are normal, the zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is close to the second voltage, and is higher than the voltage start setting value of the ground protection alarm, a ground signal is issued, and at the same time, the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located report a voltage transformer disconnection alarm, then the high-voltage equipment fault information is determined to be a blown fuse of one phase on the high-voltage side of the voltage transformer; or, If the voltage of one phase of the voltage transformer is the phase voltage, and the phase voltages of the other two phases are close to 0V, the zero-sequence voltage generated at both ends of the open delta voltage transformer is close to the second voltage, which is higher than the voltage start setting value of the ground protection alarm, and a ground signal is issued, then the high-voltage equipment fault information is determined to be a blown fuse failure of two phases on the high-voltage side of the voltage transformer; or, If the voltage of one phase of the voltage transformer is lower than the phase voltage but not zero, the phase voltages of the other two phases are normal, the zero-sequence voltage at both ends of the open delta of the voltage transformer is zero, and at the same time, the microcomputer protection and measurement and control devices of each switchgear on the bus where the voltage transformer is located report a voltage transformer disconnection alarm, then the high-voltage equipment fault information is determined to be a blown fuse on the low-voltage side of the voltage transformer. or, If the three-phase voltage fluctuates frequently and instantaneously, and the voltage amplitude of one phase is large, and the three-phase bus voltage increases simultaneously, but the phase-to-phase voltage remains at the rated voltage, there is a large voltage at both ends of the open delta voltage transformer, and the main transformer bus insulation inspection device occasionally sends a grounding signal, then the high-voltage equipment fault information is determined to be a system resonance fault; or, If the phase voltage of one phase increases but does not exceed the first preset multiple of the rated phase voltage, and the phase voltages of the other two phases decrease and approach but do not fall below the second preset multiple of the rated phase voltage, and there is a grounding alarm, then the high-voltage equipment fault information is determined to be a bus system voltage increase phase break but no grounding fault.

[0008] In one possible implementation, if the high-voltage equipment fault information is a single-phase metallic ground fault and a single-phase non-metallic ground fault, the three-phase voltage and zero-sequence voltage indications are checked on the voltage transformer cabinet or the microcomputer protection and measurement and control device, and the busbar insulation monitoring action is checked on the high backup or low backup protection and measurement and control device of the main transformer microcomputer protection and measurement and control panel to see if there is any alarm information.

[0009] In a possible implementation, the voltage triggering setting value of the ground fault protection alarm is 15V or 30V.

[0010] In a possible implementation, the high-voltage equipment fault information is a system resonance fault, including fundamental frequency resonance, frequency division resonance, and high-frequency resonance, wherein: If one phase voltage decreases but is not zero, and the two phase voltages increase and exceed the line voltage; or if the two phase voltages decrease but are not zero, and the one phase voltage increases, and the open delta voltage of the voltage transformer is less than the first voltage, then the resonance is the fundamental frequency resonance; The three-phase voltages increase in turn and exceed the line voltage, and swing at a low frequency within the range of 1.2 to 1.4 times the phase voltage. The open delta voltage of the voltage transformer is less than the first voltage, and the resonance is a frequency division resonance. The three-phase voltages increase at the same time, far exceeding the line voltage, and the open triangle voltage of the voltage transformer is less than the first voltage, then the resonance is a high-frequency resonance.

[0011] In a possible implementation, for high-voltage equipment fault information of a busbar system voltage increase phase disconnection but no grounding fault, the busbar system is divided into a busbar system with only one feeder line and a busbar system with multiple feeder lines.

[0012] In one possible implementation, when there is only one outgoing line on the busbar and it is broken at the line outlet, the phase voltage due to the broken line fault increases, with the maximum value no greater than 1.5 times the phase voltage, while the voltages relative to the other two phases to ground decrease by the same amount, and their minimum value is greater than 0.866 times the phase voltage.

[0013] In one possible implementation, when there are multiple feeder lines on a busbar, the voltage anomaly information is as follows: the voltage of the broken phase increases, the voltage of the non-broken phase decreases slightly, and the power supply voltage of users below the fault point will be obviously abnormal. The user-side distribution transformer generally has two commonly used connection groups, Yyn0 and Dyn11. Different transformer connection levels will display different voltage values.

[0014] In the embodiments of the present application, the nature of the fault can be quickly determined based on the voltage anomaly information combined with other fault phenomena, thereby improving search efficiency and preventing misjudgments that extend fault downtime and even expand the fault range, causing greater losses to users. This ensures the safe and stable operation of the equipment power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flowchart of a method for determining a high-voltage equipment fault based on voltage anomaly provided in an embodiment of the present application; Figure 2 A schematic diagram of high-voltage equipment fault information corresponding to different voltage anomaly indication information provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] The present solution will be described below with reference to the accompanying drawings and specific implementation methods.

[0017] See also Figure 1 The method for determining a high-voltage equipment fault based on voltage anomaly provided in this embodiment includes: S101 , determining whether an undervoltage or overvoltage condition occurs by monitoring the voltage level of each phase voltage of a voltage transformer.

[0018] Voltage transformer (PT) is an electrical device that converts high voltage into low voltage in proportion. Usually, its secondary side rated voltage is 100V (line voltage) or 100 / V (phase voltage). By monitoring the voltage of each phase on the secondary side of the voltage transformer and comparing it with the set normal voltage range, it is possible to determine whether undervoltage or overvoltage conditions exist.

[0019] The normal voltage range is typically determined by the rated voltage and operating requirements of the power system. For example, in a 10kV power system, if the voltage transformer ratio is 10000 / 100, the normal secondary-side line voltage should be around 100V (a certain fluctuation range is permitted, such as ±5% to ±10%, with specific requirements varying depending on the system voltage level). When the secondary-side phase voltage falls below the lower limit of the normal range, it is considered undervoltage; when it exceeds the upper limit of the normal range, it is considered overvoltage.

[0020] In this embodiment, the monitoring equipment for determining and monitoring the voltage transformer includes: a voltmeter on the voltage transformer cabinet, a background monitoring microcomputer, and microcomputer protection and measurement control devices on each feeder cabinet and the main transformer protection and measurement control panel. The voltage information for each phase of the voltage transformer is obtained from the monitoring information of the monitoring equipment.

[0021] S102: If undervoltage or overvoltage occurs, determine voltage abnormality indication information corresponding to different situations.

[0022] In this embodiment, the voltage abnormality indication information corresponding to different undervoltage or overvoltage conditions of the three-phase voltage of the voltage transformer is described one by one, as follows: Abnormal voltage indication situation 1: The phase voltage of one phase of the voltage transformer is zero, and the voltages of the other two phases are line voltages. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is 100V. At the same time, the insulation monitoring of the busbar on the high-voltage or low-voltage side of the main transformer activates the alarm, and all voltage transformers in the busbar system powered by the same main transformer will have the above abnormal voltage indication.

[0023] Abnormal voltage indication situation 2: The phase voltage of one phase of the voltage transformer decreases but is not zero, and the phase voltages of the other two phases increase but are less than the line voltage. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is less than 100V, but higher than the voltage start setting value of the ground protection alarm. At the same time, the busbar insulation monitoring on the high-voltage or low-voltage side of the main transformer will activate the alarm, and all voltage transformers of the busbar system powered by the same main transformer will have the above-mentioned abnormal voltage indication.

[0024] Abnormal voltage indication condition three: The voltage on one phase of the voltage transformer is less than the phase voltage, but not zero. The phase voltages of the other two phases are normal. The zero-sequence voltage across the delta winding of the voltage transformer is approximately 33V, exceeding the voltage trigger setting for the ground fault protection alarm, generating a ground fault signal. Simultaneously, the microcomputer protection and measurement and control devices in each switchgear cabinet on the busbar where the voltage transformer is located all report a "voltage transformer disconnection" alarm.

[0025] Abnormal voltage indication situation four: The phase voltage of one phase of the voltage transformer is the phase voltage, and the phase voltages of the other two phases are close to 0V. The zero-sequence voltage generated at both ends of the voltage transformer delta is about 33V, which is higher than the voltage start setting value of the ground protection alarm and sends a ground signal.

[0026] Abnormal voltage indication five: The voltage of one phase of the voltage transformer is less than the phase voltage, but not zero, while the phase voltages of the other two phases are normal. The zero-sequence voltage across the open delta voltage transformer is zero, and the microcomputer protection and measurement and control devices of each switchgear on the busbar where the voltage transformer is located all report a "voltage transformer disconnection" alarm.

[0027] Abnormal voltage indication 6: Frequent, transient alternating fluctuations in the three-phase voltages, with one phase exhibiting a large amplitude. Sometimes, the three-phase busbar voltages increase simultaneously, while the phase-to-phase voltage remains at rated voltage. A high voltage is present across the open delta voltage transformer. The main transformer busbar insulation inspection device may sometimes emit a "ground" signal.

[0028] Abnormal voltage indication situation seven: The phase voltage of one phase increases but does not exceed 1.5 times the rated phase voltage, and the phase voltages of the other two phases decrease slightly but not less than 0.866 times the rated phase voltage, accompanied by a grounding alarm phenomenon.

[0029] S103: Determine high-voltage equipment fault information according to the voltage anomaly indication information.

[0030] For the above seven voltage abnormality indications in S102, see Figure 2 Different voltage abnormality indications correspond to different high-voltage equipment fault information.

[0031] Abnormal voltage indication: A metallic ground fault on one phase of the system is identified. Specifically, check the three-phase voltage and zero-sequence voltage indications on the voltage transformer cabinet or the microcomputer protection and measurement control device. Check the busbar insulation monitoring action alarm on the high-backup or low-backup protection and measurement control device on the main transformer microcomputer protection and measurement control panel. The low-current grounding line selection device can be used to determine which line has experienced the ground fault.

[0032] Abnormal voltage indication 2: A non-metallic ground fault on one phase of the system is determined. Check the three-phase voltage and zero-sequence voltage indications on the voltage transformer cabinet or the microcomputer protection and measurement and control device. Check the busbar insulation monitoring for alarms on the high-backup or low-backup protection and measurement and control devices on the main transformer microcomputer protection and measurement and control panel. Check the low-current ground fault selection device to determine which line has experienced the ground fault. Specifically, the voltage trigger setting for the ground fault protection alarm can be 15V or 30V.

[0033] The third abnormal voltage indication is that the fuse of one phase on the high voltage side of the voltage transformer has blown.

[0034] The voltage start setting value of the ground protection alarm can be 15V or 30V.

[0035] Specifically, the above-mentioned abnormality will only occur in the voltage on the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located.

[0036] The fourth abnormal voltage indication is that the two-phase fuses on the high-voltage side of the voltage transformer have blown.

[0037] Specifically, the above-mentioned abnormality will only occur in the voltage on the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located.

[0038] The fifth abnormal voltage indication is that the fuse of one phase on the low-voltage side of the voltage transformer has blown.

[0039] Specifically, when the fuse of one phase on the low-voltage side of the voltage transformer blows, the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located will report a "voltage transformer disconnection" alarm, but the bus system will not issue a grounding signal alarm.

[0040] Abnormal voltage indicates situation six, which is determined to be a system resonance fault.

[0041] Specifically, the voltage of one phase decreases but is not zero, while the voltage of the two phases increases, exceeding the line voltage (generally not exceeding 3 times the phase voltage); or the voltage of the two phases decreases but is not zero, while the voltage of one phase increases, and the open delta voltage of the voltage transformer is less than 100 V. This resonance is called fundamental frequency resonance.

[0042] Specifically, the three-phase voltages rise in turn, exceeding the line voltage (generally no more than twice the phase voltage), and then swing at a low frequency within a range of 1.2 to 1.4 times the phase voltage. The open-delta voltage of the voltage transformer is generally less than 100V. This type of resonance is called frequency-division resonance.

[0043] Specifically, the three-phase voltages rise simultaneously, far exceeding the line voltage, and the open delta voltage of the voltage transformer is less than 100 V. This resonance is a high-frequency resonance.

[0044] In a grid system with an ungrounded neutral point, under normal circumstances, the three phases of the grid are basically balanced and the displacement voltage at the grid neutral point is very small. When a disturbance occurs in the grid system, the saturation degree of the three-phase inductance of the voltage transformer will be different, which will cause a higher displacement voltage to be generated at the grid neutral point and may excite a resonant overvoltage.

[0045] The resonance that occurs in a system with an ungrounded neutral point is called parallel resonance. Parallel resonance refers to a resonant circuit formed by the system's capacitance to ground and the inductance of the grounded primary neutral point of the voltage transformer. In this system, the nonlinear inductance of the voltage transformer often forms a ferromagnetic resonance with the system's capacitance to ground, causing the system's neutral point to shift, generating a zero-sequence voltage and a grounding signal. This phantom grounding can easily be mistaken for a single-phase grounding.

[0046] The moment a power source closes and energizes an empty busbar equipped only with a voltage transformer, a transient single-phase grounding or arc grounding of the line, and the three-phase out-of-phase switching of the circuit breaker during closing can cause the voltage transformer's inductive reactance to ground to match the grid's capacitive reactance to ground, leading to sudden voltage changes and saturation of the voltage transformer's core. This leads to asymmetric three-phase-to-ground distributed capacitance and the excitation of ferromagnetic resonance. This resonance typically causes resonant overvoltage, posing a serious threat to the safe operation of the power system. Based on the resonance mechanism of power systems, resonance can be categorized into three types: fundamental frequency resonance (50 Hz), fractional frequency resonance (25 Hz), and high-frequency resonance (100-150 Hz). Resonance phenomena vary with frequency.

[0047] If the system is judged to be resonant based on abnormal voltage phenomena, the on-duty controller must adjust the operating mode in a timely manner. This can be done by putting a certain line into operation to change the system operating parameters to achieve the purpose of destroying the resonant conditions and thus eliminating the resonance.

[0048] Abnormal voltage indication situation seven: the busbar system voltage is increased and the phase is broken but there is no grounding fault.

[0049] Specifically, the above-mentioned busbar system refers to a busbar with only one outgoing line, and when the line is broken at the line outlet, the phase voltage of the broken fault increases, and the maximum value will not exceed 1.5 times the phase voltage, and the voltages of the other two phases to the ground will decrease, and the decrease values ​​are equal, and the minimum value will not be less than 0.866 times the phase voltage.

[0050] Specifically, if the busbar system described above has multiple outgoing lines, the voltage anomaly information will be: the voltage of the disconnected phase increases, the voltage of the undisconnected phase decreases slightly, and the power supply voltage of users below the fault point will be significantly abnormal. User-side distribution transformers generally have two common connection groups: Yyn0 and Dyn11. Different transformer connection levels will display different voltage values.

[0051] In a power grid with an ungrounded neutral point and a single-phase line disconnected, the system's ground capacitance decreases relative to the disconnected line. If the reduction in ground capacitance current is minimal, the neutral point displacement voltage on the power supply side is small, and the fault characteristics are not obvious. The voltage across the open-delta voltage transformer will not reach the tripping value of the relay protection, and no "ground fault" signal will be issued. However, there may still be some difference in the three-phase voltage to ground, with the voltage of the disconnected phase increasing and the voltage of the undisconnected phase decreasing slightly. This will cause noticeable abnormalities in the power supply voltage to users below the fault point (user-side distribution transformers generally have two common connection groups, Yyn0 and Dyn11, and the displayed voltage values ​​vary depending on the transformer connection level). In the extreme case, if there is only one outgoing line on the busbar and a line disconnection occurs at the line outlet, the maximum voltage increase in the phase due to the disconnection fault will not exceed 1.5 times the phase voltage. The voltages of the other two phases to ground will decrease by an equal amount, and their minimum value will not be less than 0.866 times the phase voltage.

[0052] In the event of a busbar disconnection and ungrounded fault, the busbar voltage is significantly impacted by system capacity, the number of busbar feeder lines, line length, and capacitive current. If a busbar feeder line is numerous, the cables are long, and the capacitive current is high, a disconnection and ungrounded fault on a line will directly impact normal power consumption for users below the fault point, while having little impact on the busbar voltage. In situations where the busbar has only a single or few feeder lines, the voltage relative to ground increases due to a disconnection. This causes asymmetry in the three-phase current and voltage, putting the system into a non-full-phase operation state. This causes a change in the capacitance relative to ground in the system, leading to a shift in the transformer neutral point. The capacitance and voltage changes vary with the distance of the fault point from the power source.

[0053] It should be noted that line breakage is often accompanied by grounding, and this must be distinguished and judged when analyzing the fault phenomenon.

[0054] The power supply system of the high-voltage equipment is a neutral point ungrounded power grid system, including power systems with voltage levels such as 35kV, 10kV, and 6kV.

[0055] The following is an application example of the method for determining high-voltage equipment failure based on voltage anomaly provided by the above embodiment.

[0056] (1) Single-phase grounding fault Example 1: The 35kV Nanling Substation's back-end monitoring computer indicated the three-phase voltages on the 6kV II busbar were UA = 6.39 (kV), UB = 0.2 (kV), and UC = 6.1 (kV). Simultaneously, the insulation monitoring system for the No. 2 main transformer's low-voltage busbar activated. Analysis determined the fault to be a metallic ground fault on phase B of the 6kV II busbar. A check of the low-current grounding line selection device revealed no grounding alarm for some reason. On-site inspection of the zero-sequence current values ​​on the microcomputer-based protection and measurement and control devices in each feeder cabinet of the 6kV busbar section II revealed a zero-sequence current of 3I0 = 55.84 mA and a zero-sequence voltage of 3U0 = 104.1 V on the 6kV Jinding IV line. The protection settings were I0 = 23 mA, 3U0 = 15 V, and a 4-second delay. Therefore, the ground fault was identified as the 6kV Jinding IV line.

[0057] After the power outage and safety measures were arranged, the line inspection found that the grounding fault point of the 6kV Jinding IV line was the breakdown and grounding of the B phase of the lightning arrester on the user side of pole No. 13.

[0058] (2) Voltage transformer fuse blown failure Example 1: Fuse failure on the high-voltage side of a voltage transformer At the 35kV Taidong Station, power was being supplied to the 35kV Section I busbar (the voltage transformer was already in hot standby mode). The voltmeter on the voltage transformer cabinet displayed: UA = 21.4 kV, UB = 21.3 kV, and Uc = 3.7 kV. The backend monitoring computer and the Section I busbar protection and control device reported a "voltage transformer disconnection alarm." Simultaneously, the insulation monitoring alarm for the No. 1 main transformer's high-voltage busbar was activated. A multimeter was used to test the voltage transformer's three-phase secondary fuses, but the voltages before and after the fuses were blown remained unchanged. Further analysis confirmed that the fault was a blown fuse on the high-voltage side of Phase C of the 35kV Section I busbar voltage transformer.

[0059] Pull out the voltage transformer isolation switch, take safety measures, replace the C phase high voltage side fuse, and power supply is normal.

[0060] When a single-phase fuse on the high-voltage side of a voltage transformer blows, the voltage on the faulty phase is lower than the normal phase voltage, but not zero (some synthetic magnetic flux will flow through the iron core leg of the blown phase). The voltage on the non-faulty phase is at the normal phase voltage. A zero-sequence voltage of approximately 33V is generated across the open delta, triggering the alarm voltage relay and issuing a grounding signal. Simultaneously, the microcomputer-based protection and control device issues a "voltage transformer disconnection" alarm. This indicates that the high-voltage side fuse has blown.

[0061] Example 2: Fuse failure on the low-voltage side of a voltage transformer When a single-phase low-voltage side fuse blows, the three-phase voltages on the primary side remain balanced, and the three-phase voltages on the secondary side behave similarly to when a single-phase high-voltage side fuse blows. However, since the fuse blows on the low-voltage side, it only affects the voltage of a single winding. Zero-sequence voltage does not appear at the open-delta terminal, and the open-delta voltage is zero. Therefore, a blown low-voltage fuse in a voltage transformer does not generate a ground fault signal.

[0062] (3) Resonance failure Example 1 After the replacement and renovation of the new switchgear for the 10kV I busbar at a 110kV oxygen plant was completed, and power was being supplied to the new switchgear busbar from the No. 1 main transformer, the No. 1 main transformer's microcomputer protection screen displayed unbalanced and fluctuating three-phase voltages (Ua, Ub, and Uc). The following readings were recorded on several occasions: Ua = 80 (V), Ub = 57 (V), Uc = 49 (V); Ua = 45.3 (V), Ub = 66.1 (V), Uc = 77.9 (V); and Ua = 63.4 (V), Ub = 47.1 (V), Uc = 76.2 (V). At the same time, the insulation check device occasionally issued a "ground fault" signal, similar to a single-phase ground fault. This confused the operator and made them hesitant to proceed. This was a fundamental frequency resonance.

[0063] Inspection of the busbar and connected equipment revealed no abnormalities, suggesting the voltage anomaly could be attributed to resonance. This phenomenon can be eliminated by energizing one of the substation's feeder lines or removing the transformer from service, thereby changing the busbar's no-load operation mode. Once normal, the three-phase voltages are Ua = 62.2 (V), Ub = 61.8 (V), and Uc = 61.3 (V).

[0064] Example 2 The three-phase voltages of the 6kV I busbar system in the 110kV three-step-down substation were abnormal: UA = 5.0 (kV), UB = 5.2 (kV), and Uc = 5.3 (kV). The three-phase voltages fluctuated abnormally, and the voltage transformers were making unusual operating sounds. Analysis indicated a possible resonance fault, possibly a frequency-division resonance or a high-frequency resonance.

[0065] Disconnect the 6kVⅠ section capacitor 6314 circuit breaker in the station, break the resonance point between the inductive reactance and the capacitive reactance, and the voltage returns to normal.

[0066] In the embodiments of the present application, "at least one" refers to one or more, and "multiple" refers to two or two or more. The "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Wherein A, B can be singular or plural. The character " / " generally represents that the associated objects before and after are in an "or" relationship. "At least one of the following" and the like means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b and c can represent: a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, c can be single or multiple.

[0067] The above is only a specific embodiment of the present application, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. The protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for determining high-voltage equipment failure based on voltage anomaly, characterized in that: include: Determine whether undervoltage or overvoltage occurs by monitoring the voltage level of each phase voltage of the voltage transformer; If undervoltage or overvoltage occurs, determine the voltage abnormality indication information corresponding to the different situations; High-voltage equipment fault information is determined based on the voltage anomaly indication information.

2. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 1, characterized in that: The method of determining whether an undervoltage or overvoltage condition occurs by monitoring the voltage level of each phase voltage of the voltage transformer includes: Determine and monitor the monitoring equipment of the voltage transformer, the monitoring equipment includes: a voltmeter on the voltage transformer cabinet, a background monitoring microcomputer, and a microcomputer protection and measurement control device on each feeder cabinet and the main transformer protection and measurement control screen; The voltage information of each phase of the voltage transformer is obtained through the monitoring information of the monitoring device.

3. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 1, characterized in that: If undervoltage or overvoltage occurs, determining voltage abnormality indication information corresponding to different situations includes: The phase voltage of one phase of the voltage transformer is zero, and the voltages of the other two phases are line voltages. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is the first voltage. At the same time, the insulation monitoring of the busbar on the high-voltage or low-voltage side of the main transformer is activated and an alarm is sounded. All voltage transformers of the busbar system supplied by the same main transformer will have the above-mentioned abnormal voltage indication; or, The phase voltage of one phase of the voltage transformer decreases but is not zero, while the phase voltages of the other two phases increase but are less than the line voltage. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is less than the first voltage but higher than the voltage start setting value of the ground protection alarm. At the same time, the insulation monitoring of the busbar on the high-voltage or low-voltage side of the main transformer will activate the alarm, and all voltage transformers of the busbar system supplied by the same main transformer will have the above abnormal voltage indication; or, The voltage of one phase of the voltage transformer is lower than the phase voltage, but not zero. The phase voltages of the other two phases are normal. The zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is close to the second voltage and higher than the voltage start setting value of the ground protection alarm. A ground signal is issued. At the same time, the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located all report a voltage transformer disconnection alarm. or, The voltage of one phase of the voltage transformer is the phase voltage, and the phase voltages of the other two phases are close to 0V. The zero-sequence voltage generated at both ends of the open delta voltage transformer is close to the second voltage, which is higher than the voltage start setting value of the ground protection alarm and sends a ground signal; or, The voltage of one phase of the voltage transformer is lower than the phase voltage, but not zero. The phase voltages of the other two phases are normal. The zero-sequence voltage at both ends of the open delta of the voltage transformer is zero. At the same time, the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located all report a voltage transformer disconnection alarm. or, The three-phase voltage fluctuates frequently and instantaneously, and the voltage amplitude of one phase is large. In the middle, the three-phase voltage of the bus increases simultaneously, but the phase-to-phase voltage remains at the rated voltage. There is a large voltage at both ends of the open delta of the voltage transformer, and the main transformer bus insulation inspection device sometimes sends a grounding signal. or, The phase voltage of one phase increases but does not exceed the first preset multiple of the rated phase voltage, and the phase voltages of the other two phases decrease and approach but do not fall below the second preset multiple of the rated phase voltage, accompanied by a ground fault alarm phenomenon.

4. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 3, characterized in that: The determining of high-voltage equipment fault information according to the voltage anomaly indication information includes: If the phase voltage of one phase of the voltage transformer is zero, the voltages of the other two phases are line voltages, the zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is the first voltage, and at the same time, the insulation monitoring of the busbar on the high-voltage or low-voltage side of the main transformer is alarmed, and all voltage transformers of the busbar system supplied by the same main transformer have the above-mentioned abnormal voltage indication, then it is determined that the high-voltage equipment fault information is a metallic ground fault of one phase of the system; or, If the phase voltage of one phase of the voltage transformer decreases but is not zero, and the phase voltages of the other two phases increase but are lower than the line voltage, the zero-sequence voltage across the open delta winding of the voltage transformer is lower than the first voltage but higher than the voltage start setting value of the ground protection alarm, and at the same time, the busbar insulation monitoring on the high-voltage or low-voltage side of the main transformer activates an alarm, and all voltage transformers in the busbar system supplied by the same main transformer have the above abnormal voltage indications, then the high-voltage equipment fault information is determined to be a non-metallic ground fault on one phase of the system; or, If the voltage of one phase of the voltage transformer is lower than the phase voltage but not zero, and the phase voltages of the other two phases are normal, the zero-sequence voltage generated at both ends of the open delta winding of the voltage transformer is close to the second voltage, and is higher than the voltage start setting value of the ground protection alarm, a ground signal is issued, and at the same time, the microcomputer protection and measurement and control devices of each switch cabinet on the bus where the voltage transformer is located report a voltage transformer disconnection alarm, then the high-voltage equipment fault information is determined to be a blown fuse of one phase on the high-voltage side of the voltage transformer; or, If the voltage of one phase of the voltage transformer is the phase voltage, and the phase voltages of the other two phases are close to 0V, the zero-sequence voltage generated at both ends of the open delta voltage transformer is close to the second voltage, which is higher than the voltage start setting value of the ground protection alarm, and a ground signal is issued, then the high-voltage equipment fault information is determined to be a blown fuse failure of two phases on the high-voltage side of the voltage transformer; or, If the voltage of one phase of the voltage transformer is lower than the phase voltage but not zero, the phase voltages of the other two phases are normal, the zero-sequence voltage at both ends of the open delta of the voltage transformer is zero, and at the same time, the microcomputer protection and measurement and control devices of each switchgear on the bus where the voltage transformer is located report a voltage transformer disconnection alarm, then the high-voltage equipment fault information is determined to be a blown fuse on the low-voltage side of the voltage transformer. or, If the three-phase voltage fluctuates frequently and instantaneously, and the voltage amplitude of one phase is large, and the three-phase bus voltage increases simultaneously, but the phase-to-phase voltage remains at the rated voltage, there is a large voltage at both ends of the open delta voltage transformer, and the main transformer bus insulation inspection device occasionally sends a grounding signal, then the high-voltage equipment fault information is determined to be a system resonance fault; or, If the phase voltage of one phase increases but does not exceed the first preset multiple of the rated phase voltage, and the phase voltages of the other two phases decrease and approach but do not fall below the second preset multiple of the rated phase voltage, and there is a grounding alarm, then the high-voltage equipment fault information is determined to be a bus system voltage increase phase break but no grounding fault.

5. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 4, characterized in that: For high-voltage equipment fault information of one-phase metallic grounding fault and one-phase non-metallic grounding fault, check the three-phase voltage and zero-sequence voltage indications on the voltage transformer cabinet or the microcomputer protection and measurement and control device, and check whether there is any alarm information on the busbar insulation monitoring action on the high backup or low backup protection and measurement and control device of the main transformer microcomputer protection and measurement and control panel.

6. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 5, characterized in that: The voltage start setting value of the ground protection alarm is 15V or 30V.

7. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 4, characterized in that: The fault information of high-voltage equipment is system resonance fault, including fundamental frequency resonance, frequency division resonance and high frequency resonance, among which: If one phase voltage decreases but is not zero, and the two phase voltages increase and exceed the line voltage; or if the two phase voltages decrease but are not zero, and the one phase voltage increases, and the open delta voltage of the voltage transformer is less than the first voltage, then the resonance is the fundamental frequency resonance; The three-phase voltages increase in turn and exceed the line voltage, and swing at a low frequency within the range of 1.2 to 1.4 times the phase voltage. The open delta voltage of the voltage transformer is less than the first voltage, and the resonance is a frequency division resonance. The three-phase voltages increase at the same time, far exceeding the line voltage, and the open triangle voltage of the voltage transformer is less than the first voltage, then the resonance is a high-frequency resonance.

8. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 4, characterized in that: For high-voltage equipment fault information of busbar system voltage increase and phase disconnection but no grounding fault, the busbar system is divided into two types: one with only one feeder line and one with multiple feeder lines.

9. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 8, characterized in that: When there is only one outgoing line on the busbar and it is broken at the line outlet, the phase voltage due to the broken line fault will increase, with the maximum value not exceeding 1.5 times the phase voltage. The voltages of the other two phases to ground will decrease, with the same decrease value, and the minimum value will be higher than 0.866 times the phase voltage.

10. The method for determining high-voltage equipment failure based on voltage anomaly according to claim 8, characterized in that: When there are multiple feeder lines on a busbar, the voltage anomaly information is as follows: the voltage of the disconnected phase increases, the voltage of the non-disconnected phase slightly decreases, and the power supply voltage of users below the fault point will be obviously abnormal. The user-side distribution transformer generally has two commonly used connection groups, Yyn0 and Dyn11. Different transformer connection levels will display different voltage values.

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