CN113629671B - 110kV line disconnection protection method for measuring low-voltage lateral line voltage of transformer - Google Patents
110kV line disconnection protection method for measuring low-voltage lateral line voltage of transformer Download PDFInfo
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- CN113629671B CN113629671B CN202110880490.9A CN202110880490A CN113629671B CN 113629671 B CN113629671 B CN 113629671B CN 202110880490 A CN202110880490 A CN 202110880490A CN 113629671 B CN113629671 B CN 113629671B
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- 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
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/267—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for parallel lines and wires
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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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
Abstract
The invention discloses a 110kV line disconnection protection method for measuring the voltage of a low-voltage side line of a transformer, which is characterized in that a negative sequence voltage and a line voltage of the low-voltage side of the transformer are measured at a 110kV transformer substation, whether the negative sequence voltage is a short-circuit fault or not is judged, then disconnection protection is started according to the negative sequence voltage, finally, a disconnection phase and a fault type are identified by using the line voltage, and disconnection warning and fault removal are carried out. The invention can not only identify the broken line phase, but also judge the fault type, and is more convenient for maintenance personnel to maintain the line. Meanwhile, the invention designs the short-circuit identification criterion by depending on the current magnitude, designs the starting criterion and the fault phase selection criterion by depending on the voltage magnitude, and the short-circuit current and the voltage magnitude are irrelevant to the load magnitude, so the reliability of the disconnection identification is not influenced when the load is light or no-load.
Description
Technical Field
The invention relates to a 110kV line disconnection protection method for measuring low-voltage lateral line voltage of a transformer, and belongs to the technical field of relay protection of power systems.
Background
With the continuous development of socioeconomic of China, the requirements on the power supply quantity and the supply stability are continuously improved, the scale of a 110kV power line in a power grid of China is continuously and rapidly enlarged, and the situations that the 110kV power line passes through complex terrains and severe weather conditions are increased. In an electric power system, the safety and stability of power utilization are crucial factors, and a disconnection fault can cause the electric power system to be in a non-full-phase operation state, so that the voltage on a low-voltage side is seriously unbalanced, the normal power utilization of a user is influenced, and even equipment is damaged. However, due to the small probability of occurrence of disconnection failure and the light failure characteristics, the research in the related direction is insufficient at present. Meanwhile, some current disconnection fault protection schemes rely on the variable quantity of current, so that disconnection faults cannot be accurately identified when a line is in light load and no load. In addition, the current research on the disconnection fault lacks the judgment of the condition that the disconnection fault is accompanied by load side grounding, and different types of disconnection faults cannot be distinguished. Therefore, more intensive research on a method, a solution and a protection device for judging the disconnection fault of the power transmission line is urgently needed so as to be beneficial to safe and stable operation of a power grid.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a 110kV line disconnection protection method for measuring the low-voltage side line voltage of a transformer, so that the fault type and the fault phase can be judged and protected quickly and accurately when a 110kV power transmission line has a disconnection fault.
The purpose of the invention is realized by the following technical scheme:
a110 kV line disconnection protection method for measuring the voltage of a low-voltage side line of a transformer comprises the following steps:
step 1: judging whether the short-circuit fault occurs or not, and if the short-circuit fault occurs in the line, not executing the subsequent steps 2-4; if the circuit is judged not to have short-circuit fault, the subsequent step 2 is continuously executed;
step 2: judging whether the starting condition of the disconnection protection is met
Calculating secondary a-phase negative sequence voltage U of 110kV main transformer low-voltage side voltage transformer TV a2 B phase negative sequence voltage U b2 C phase negative sequence voltage U c2 Judging whether the following conditions are met:
(1) secondary a-phase negative sequence voltage U a2 Greater than or equal to a setting value: u shape a2 ≥K rel.u (U 2min +U unb )
(2) Negative sequence of secondary b phaseVoltage U b2 More than or equal to a setting value: u shape b2 ≥K rel.u (U 2min +U unb )
(3) Secondary c-phase negative sequence voltage U c2 More than or equal to a setting value: u shape c2 ≥K rel.u (U 2min +U unb )
In the formula, K rel.u For the reliability factor, U 2min According to 1/3E a Setting, E a Measuring a secondary value of power electromotive force for a voltage transformer at the low-voltage side of a 110kV main transformer; u shape unb When the system normally operates, the 110kV bus of the load-end substation presents unbalanced voltage with negative sequence characteristics;
if any condition is met, the disconnection protection starting condition is considered to be met, and the subsequent step 3 is continuously executed; when the three conditions are not met, judging that the line is not broken, and not executing the subsequent step 3-4;
and step 3: identifying phase and type of fault in broken line
The neutral point of a main transformer on the load side of the 110KV circuit runs without the ground, the types of the line breaking faults are divided into a line breaking condition 1 and a line breaking condition 2, the line breaking condition 1 is that the line breaking fault is not accompanied by line grounding, the line breaking condition 2 is that the line breaking fault is accompanied by the line grounding on the load side, and the secondary line voltage U of a voltage transformer TV on the low voltage side of the 110KV main transformer is acquired ab 、U bc 、U ca And judging whether the following fault criteria are met:
1) the method for judging the phase and the type of the broken line fault in the broken line condition 1 comprises the following steps: :
(1) the phase A broken line identification method comprises the following steps:
low voltage side TV secondary line voltage U ab At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV bc At the setting value U 1 、U 2 The following steps: u shape 1 ≤U bc ≤U 2
③ Low-Voltage side TV Secondary line Voltage U ca Less than or equal to setting value U 3 ：U ca ≤U 3
When all the criteria are met, judging that the line of the phase A circuit is broken;
(2) b phase disconnection identification method:
low voltage side TV secondary line voltage U ab Less than or equal to setting value U 3 ：U ab ≤U 3
② secondary line voltage U of low-voltage side TV bc At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U bc ≤U 2
③ Low-Voltage side TV Secondary line Voltage U ca At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ca ≤U 2
When the criteria are all met, judging that the phase B line has a disconnection fault;
(3) c-phase disconnection identification method:
low voltage side TV secondary line voltage U ab At the setting value U 1 、U 2 The following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV bc Less than or equal to setting value U 3 ：U bc ≤U 3
③ Low-Voltage side TV Secondary line Voltage U ca At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ca ≤U 2
When the criteria are all met, judging that the line of the phase C line is broken;
2) the method for judging the phase and the type of the broken line fault in the broken line condition 2 comprises the following steps:
(1) a phase disconnection identification method comprises the following steps:
first, the low voltage side TV secondary line voltage U ab At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV bc At the setting value U 4 、U 5 The following steps: u shape 4 ≤U bc ≤U 5
Third, the low-voltage side TV secondary line voltage U ca At the setting value U 6 、U 7 The following steps: u shape 6 ≤U ca ≤U 7
When the criteria are all met, judging that the line disconnection fault of the phase A line is accompanied by a load side line grounding fault;
(2) b phase disconnection identification method:
first, the low voltage side TV secondary line voltage U ab At a setting value of U 6 、U 7 The following steps: u shape 6 ≤U ab ≤U 7
② secondary line voltage U of low-voltage side TV bc At a setting value of U 4 、U 5 The method comprises the following steps: u shape 4 ≤U bc ≤U 5
③ Low-Voltage side TV Secondary line Voltage U ca At a setting value of U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When the criteria are all met, judging that the phase B line has a disconnection fault and is accompanied with a load side line grounding fault;
(3) c phase disconnection identification method:
low voltage side TV secondary line voltage U ab At a setting value of U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV bc At the setting value U 6 、U 7 The method comprises the following steps: u shape 6 ≤U bc ≤U 7
③ Low-Voltage side TV Secondary line Voltage U ca At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When the criteria are all met, judging that the line disconnection fault of the line C is accompanied by a load side line grounding fault;
E ab the secondary rated line voltage value of a voltage transformer TV on the low-voltage side of a 110kV main transformer is set in the above discriminant 1 According to
0.95 times of the total value of the 2 According to
1.05 times of the total weight; setting value U 3 According to E ab Is set to 0.1 times; setting value U 4 According to electricity
0.95 times of the total value of the 5 According to the following
1.05 times of the total weight; setting value U 6 According to E ab 0.95 times of/3 to set value U 7 According to E ab Setting 1.05 times of/3;
when the disconnection fault of the disconnection condition 1 or the disconnection condition 2 of a certain phase is identified, continuing to execute the subsequent step 4; when the three-phase line is not judged to have the line break fault of the line break condition 1 and the line break condition 2, the subsequent step 4 is not executed;
and 4, step 4: disconnection warning and fault removal
According to the results of the phase and type of the broken line fault in the step 3, the time is delayed by t 1 Then sends out the broken line alarm signal of the fault phase and delays t 2 And the corresponding circuit breaker of the back trip cuts off a fault line and is connected into a standby power supply to recover power supply.
In the method for protecting the 110kV line from being broken by measuring the voltage of the low-voltage side line of the transformer, the method for judging whether the line has a short-circuit fault in the step 1 comprises the following steps: collecting secondary side a-phase current I of 110kV line current transformer TA a Secondary side b-phase current I b Secondary side c-phase current I c Judging whether the following conditions are met:
(1) secondary side a phase current I a More than or equal to a setting value: i is a ≥K rel.i I l.max
(2) Secondary side b-phase current I b More than or equal to a setting value: I.C. A b ≥K rel.i I l.max
(3) Secondary side c-phase current I c More than or equal to a setting value: i is c ≥K rel.i I l.max
In the formula, K rel.i Is a current reliability factor; i is l.max The maximum load current is the maximum load current of the normal operation of the system and is measured by an actual line; and if any condition is met, judging that the short-circuit fault occurs in the line, identifying and removing the fault through the short-circuit protection of the line, and if the three conditions are not met, judging that the short-circuit fault does not occur in the line.
The 110kV line disconnection protection method for measuring the low-voltage lateral line voltage of the transformer has the current reliability coefficient K rel.i The value is 1.3-1.5.
The method for protecting the 110kV line from being broken by measuring the low-voltage side line voltage of the transformer comprises the step 2 of measuring the reliability coefficient K rel.u The value is 1.1-1.2.
The 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer comprises the step 2 of measuring the U value 2min Take 19.25V, U unb Taking 4-6V.
The 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer and the setting value U 1 Taking 82.27V and setting value U 2 Taking 90.93V and setting value U 3 Taking 10.00V and setting value U 4 Taking 83.78V and setting value U 5 Taking 92.60V and setting value U 6 Taking 31.67V and setting value U 7 35.00V was taken.
The 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer t 1 The time is set to 0.1-0.3 s, t 2 And setting the time to be 0.2-0.5 s when the time avoids the three-phase asynchronous time when the switch is switched on.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention fully considers the fault characteristics of different types of disconnection faults of the 110kV line, can better distinguish the disconnection fault without the load side grounding from the disconnection fault with the load side grounding, and is more convenient for maintenance personnel to maintain the line.
2. The invention fully utilizes the characteristic that the current is sharply increased after the short-circuit fault occurs and the current is not obviously increased after the disconnection, and separates the short circuit from the disconnection. Considering that the faults of the power transmission line mainly comprise short circuit and broken line, and the probability of the occurrence of the short circuit is far higher than that of the broken line, if the short circuit fault can be eliminated, the reliability of broken line identification can be effectively improved.
3. The invention designs the short circuit identification criterion by depending on the current magnitude as the auxiliary criterion, designs the starting criterion and the fault phase selection criterion by depending on the voltage magnitude as the main criterion, and the short circuit current and the voltage magnitude are irrelevant to the load magnitude, so the reliability and the accuracy of the wire break identification are not influenced when the load is light load or no load, and the problem that the wire break fault is difficult to identify under the condition of light load or no load is solved.
4. In consideration of the fact that a main transformer of a 110kV transformer substation usually has no voltage transformer at a high-voltage side and cannot carry out measurement, the invention identifies the disconnection fault of the high-voltage side through the voltage characteristics of the low-voltage side after disconnection, does not need to carry out large-scale transformation on the existing commonly-used 110kV line, and is more convenient to put into practical use.
Drawings
FIG. 1 is a system configuration diagram of a 110kV line disconnection condition 1;
FIG. 2 is a vector diagram of main transformer low-voltage side line voltage when a 110kV line is disconnected 1;
FIG. 3 is a system configuration diagram of a 110kV line disconnection condition 2;
FIG. 4 is a vector diagram of main transformer low-voltage side line voltage when a 110kV line is disconnected, wherein 2 is shown;
FIG. 5 is a primary main wiring diagram of a single bus segment of a 110kV substation;
FIG. 6 is a schematic diagram of a 110kV line break protection method for measuring the low-voltage side line voltage of a transformer;
FIG. 7 is a flow chart of a 110kV line break protection method for measuring the low-voltage side line voltage of a transformer;
fig. 8 is a schematic wiring diagram of the disconnection protection device.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
1.110 kV disconnection fault analysis:
1.1 case of wire breakage 1
Fig. 1 shows a schematic diagram of a disconnection fault when a disconnection condition 1 occurs at 110kV, the disconnection fault is not accompanied by line grounding, and a load-side main transformer neutral point is in ungrounded operation. Setting the phase A as a broken line fault phase, and specifically analyzing the change law of high-voltage side current, low-voltage side negative sequence voltage and low-voltage side line voltage after the broken line:
(1) high side current
Setting the 110kV side power supply potential of the upper-level transformer substation as E A 、E B 、E C . When a 110kV line is broken at a certain position, taking A-phase broken line as an example, I is caused by the fact that a neutral point of a transformer is not grounded and zero-sequence current does not flow A0 0, calculated by the symmetric component method:
wherein Z is 1 Is the positive sequence equivalent reactance of the system.
From the vector relationship between the A, B, C phase sequence components, the amplitude of each phase current on the high-voltage side is obtained as follows:
wherein, I Load(s) The magnitude of the load current is equal to E when the system normally operates A /Z 1 。
After a disconnection fault of the disconnection case 1, the current of the faulty phase will drop to 0, while the current of the non-faulty phase drops to the load current
And (4) doubling.
(2) Negative sequence voltage on low voltage side
The positive and negative sequence voltages of the phase A at the high-voltage side are respectively as follows:
for a transformer wired with Yd11, assume a transformer transformation ratio of 1: 1, considering the change of each phasor angle; IIIThe positive sequence voltage on the angular side always leads the positive sequence voltage on the Y side by 30 °, the negative sequence voltage on the triangular side always lags the negative sequence voltage on the star side by 30 °, and the zero sequence voltage on the star side cannot be transmitted to the triangular side. Let the power supply potential delivered to the triangle side be E a 、E b 、E c And then, the amplitude of the negative sequence voltage of each phase at the low-voltage side is as follows:
U a2 ＝U b2 ＝U c2 ＝E a /2 (4)
after the line break fault of line break case 1, the system full phase presents a negative sequence voltage component, whose magnitude is 1/2 of the power supply potential.
(3) Low side line voltage
The amplitude of each line voltage at the low-voltage side is as follows:
when the line breaking fault of the line breaking condition 1 occurs, two groups of line voltage amplitude values are to be the line voltage amplitude values before the fault
The remaining set of line voltages drops to 0, and the triangular side line voltage vector diagram is shown in FIG. 2.
1.2 case of wire breakage 2
Fig. 3 shows a schematic diagram of a disconnection fault in the case of a disconnection 2 of 110kV, where the disconnection fault is accompanied by grounding of a load-side line, and a neutral point of a load-side main transformer is in ungrounded operation. And (3) setting the phase A as a broken line fault phase, and specifically analyzing the change rules of high-voltage side current, low-voltage side negative sequence voltage and low-voltage side line voltage after the broken line:
(1) high side current
Setting the 110kV side power supply potential of the upper-level transformer substation as E A 、E B 、E C . When a certain part of the 110kV line is broken and the broken line of the load side is grounded, taking A-phase broken line as an example, the neutral point of the transformer is not grounded, and no zero-sequence current flows, so I A0 0, calculated by the symmetric component method:
wherein Z is 1 Is the positive sequence equivalent reactance of the system.
From the vector relationship between the A, B, C phase sequence components, the amplitude of each phase current on the high-voltage side is obtained as follows:
upon the occurrence of the disconnection fault of disconnection case 2, the current of the failed phase will drop to 1/3 of the load current, while the current of the non-failed phase will drop to the load current
And (4) doubling.
(2) Negative sequence voltage on low voltage side
The positive sequence voltage and the negative sequence voltage of the phase A at the high-voltage side are respectively as follows:
for a transformer wired with Yd11, assume a transformer transformation ratio of 1: 1 (ideal transformer), considering the change of each phasor angle; the positive sequence voltage on the triangle side always leads the positive sequence voltage on the star side by 30 °, the negative sequence voltage on the triangle side always lags the negative sequence voltage on the star side by 30 °, and the zero sequence voltage on the star side cannot be transmitted to the triangle side. Let the power supply potential delivered to the triangle side be E a 、E b 、E c And then, the amplitude of the negative sequence voltage of each phase at the low-voltage side is as follows:
U a2 ＝U b2 ＝U c2 ＝E a /3 (9)
after the line break fault of line break case 2, the system full phase presents a negative sequence voltage component, whose magnitude is 1/3 of the power supply potential.
(3) Low side line voltage
The amplitude of each line voltage at the low-voltage side is as follows:
when the line break fault of the line break condition 2 occurs, two groups of line voltage amplitude values are to be the line voltage amplitude values before the fault
The remaining set of line voltages drops to 1/3 times before failure, and the triangular side line voltage vector diagram is shown in fig. 4.
Summarizing the data obtained by the fault analysis, the principle of the 110kV line disconnection protection method for measuring the voltage of the low-voltage side line of the transformer is made and shown in FIG. 6. According to the protection principle, the process flow of the 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer is shown in FIG. 7.
2. Embodiment of 110kV line disconnection protection method for measuring voltage of low-voltage side line of transformer
FIG. 5 is a 110kV single-bus segmented electrical main wiring diagram, wherein an incoming line 1# and an incoming line 2# are respectively connected with a 110kV bus 1# and a 110kV bus 2 #; a segmented circuit breaker 3QF is arranged between the 110kV bus 1# and the 110kV bus 2 #; the incoming line 1# interval equipment is a circuit breaker 1QF, and a current transformer TA1 is connected in series with a 110kV bus 1 #; the incoming line 2# interval equipment is a circuit breaker 2QF, and a current transformer TA2 is connected in series with a 110kV bus 1 #; the 110kV bus 1# is also connected with a bus voltage transformer TV 1; the 110kV bus 2# is also connected with a bus voltage transformer TV 2; a circuit breaker 4QF is arranged on the load side of the incoming line 1# line, a circuit breaker 5QF is arranged on the load side of the incoming line 2# line, and a 110kV spare power automatic switching device is arranged on the 110kV side of a 110kV transformer substation at the load end. The following specifically describes the 110kV line disconnection protection process for measuring the low-voltage side line voltage of the transformer by taking a 110kV single-bus sectionalized electric main connection as an example:
step 1: judging whether the fault is a short-circuit fault
(1) Method for judging short-circuit fault of incoming line 1# of 110kV line
Collecting secondary side a-phase current I of 110kV line current transformer TA1 a Secondary side b-phase current I b And secondary side cPhase current I c Judging whether the following conditions are met:
(1) secondary side a phase current I a More than or equal to a setting value: I.C. A a ≥K rel.i I l.max
(2) Secondary side b-phase current I b More than or equal to a setting value: i is b ≥K rel.i I l.max
(3) Secondary side c-phase current I c More than or equal to a setting value: i is c ≥K rel.i I l.max
In the formula, K rel.i Is a current reliability factor; i is l.max The maximum load current is the maximum load current of the normal operation of the system and is measured by an actual line;
if any condition is met, judging that the line has a short-circuit fault, identifying and removing the fault by the short-circuit protection of the line, and not executing the subsequent steps 2-4; meanwhile, when the three conditions are not met, judging that the short circuit fault does not occur on the line, and continuing to execute the subsequent step 2;
(2) method for judging 2# short-circuit fault of incoming line of 110kV line
Collecting secondary side a-phase current I of 110kV line current transformer TA2 a Secondary side b-phase current I b Secondary side c-phase current I c Judging whether the following conditions are met:
(1) secondary side a phase current I a More than or equal to a setting value: i is a ≥K rel.i I l.max
(2) Secondary side b-phase current I b More than or equal to a setting value: i is b ≥K rel.i I l.max
(3) Secondary side c-phase current I c More than or equal to a setting value: I.C. A c ≥K rel.i I l.max
In the formula, K rel.i The value is 1.3-1.5 for the short circuit of the current reliability coefficient; i is l.max The maximum load current is the maximum load current of the normal operation of the system and is measured by an actual line;
if any condition is met, judging that the line has a short-circuit fault, identifying and removing the fault by the short-circuit protection of the line, and not executing the subsequent steps 2-4; meanwhile, when the three conditions are not met, judging that the short circuit fault does not occur on the line, and continuing to execute the subsequent step 2;
step 2: judging whether the starting condition of the disconnection protection is met
(1) Incoming line 1# starting judgment method for 110kV line
Calculating secondary a-phase negative sequence voltage U of a voltage transformer TV1 on the low-voltage side of a 110kV main transformer a2 B phase negative sequence voltage U b2 C phase negative sequence voltage U c2 And judging whether the following conditions are met:
1) negative sequence voltage of phase a U a2 More than or equal to a setting value: u shape a2 ≥K rel.u (U 2min +U unb )
2) Negative sequence voltage U of phase b b2 Greater than or equal to a setting value: u shape b2 ≥K rel.u (U 2min +U unb )
3) c-phase negative sequence voltage U c2 More than or equal to a setting value: u shape c2 ≥K rel.u (U 2min +U unb )
In the formula, K rel.u The negative sequence voltage starting reliability coefficient is 1.1-1.2; minimum value U of negative sequence voltage 2min Setting the minimum value of the secondary negative sequence voltage of the low-voltage side voltage transformer TV in two disconnection types of the disconnection condition 1 and the disconnection condition 2, wherein the secondary negative sequence voltage of the low-voltage side voltage transformer TV in the disconnection condition 1 is 1/2E a And the secondary negative sequence voltage of the low-voltage side voltage transformer TV in the disconnection condition 1 is 1/3E a ，U 2min Namely 1/3E a ；E a Measuring a secondary value of power electromotive force for a voltage transformer at the low-voltage side of a 110kV main transformer; u shape unb In order to ensure that the 110kV bus of the load-end substation presents unbalanced voltage with negative sequence characteristics when the system normally operates, 4-6V is selected;
if any condition is met, the disconnection protection starting condition is considered to be met, and the subsequent step 3 is continuously executed; when the three conditions are not met, judging that the line is not broken, and not executing the subsequent step 3-4;
(2) incoming 2# starting judgment method for 110kV line
Calculating the low voltage side of a 110kV main transformerSecondary a-phase negative sequence voltage U of voltage transformer TV2 a2 B phase negative sequence voltage U b2 C phase negative sequence voltage U c2 And judging whether the following conditions are met:
1) negative sequence voltage of phase a U a2 More than or equal to a setting value: u shape a2 ≥K rel.u (U 2min +U unb )
2) Negative sequence voltage U of phase b b2 More than or equal to a setting value: u shape b2 ≥K rel.u (U 2min +U unb )
3) c-phase negative sequence voltage U c2 More than or equal to a setting value: u shape c2 ≥K rel.u (U 2min +U unb )
In the formula, K rel.u The negative sequence voltage starting reliability coefficient is 1.1-1.2; u shape 2min According to the two disconnection types of the disconnection condition 1 and the disconnection condition 2, the minimum value of the secondary negative sequence voltage of the low-voltage side voltage transformer TV is set, namely 1/3E a ；U unb In order to ensure that the 110kV bus of the load-end substation presents unbalanced voltage with negative sequence characteristics when the system normally operates, 4-6V is selected;
if any condition is met, the disconnection protection starting condition is considered to be met, and the subsequent step 3 is continuously executed; when the three conditions are not met, judging that the line is not broken, and not executing the subsequent step 3-4;
and step 3: identifying phase and type of fault in broken line
(1) Method for identifying fault phase and fault type of 110kV line incoming 1#
Secondary line voltage U of voltage transformer TV1 at low-voltage side of 110kV main transformer is collected ab 、U bc 、U ca And judging whether the following fault criteria are met:
wire breakage condition 1:
1) the phase A broken line identification method comprises the following steps:
(ii) Low Voltage side TV1 Secondary line Voltage U ab At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV1 bc At a setting value of U 1 、U 2 The method comprises the following steps: u shape 1 ≤U bc ≤U 2
③ Low-Voltage side TV1 Secondary line Voltage U ca Less than or equal to setting value U 3 ：U ca ≤U 3
When the criteria are all met, judging that the A-phase line has a disconnection fault;
2) b phase disconnection identification method:
(ii) Low Voltage side TV1 Secondary line Voltage U ab Less than or equal to setting value U 3 ：U ab ≤U 3
② secondary line voltage U of low-voltage side TV1 bc At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U bc ≤U 2
③ Low-Voltage side TV1 Secondary line Voltage U ca At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ca ≤U 2
When all the criteria are met, judging that the B-phase line has a line break fault;
3) c phase disconnection identification method:
(ii) Low Voltage side TV1 Secondary line Voltage U ab At a setting value of U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV1 bc Less than or equal to setting value U 3 ：U bc ≤U 3
③ Low-Voltage side TV1 Secondary line Voltage U ca At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ca ≤U 2
When the criteria are all met, judging that the line of the phase C line is broken;
wire breakage condition 2:
1) the phase A broken line identification method comprises the following steps:
(ii) Low Voltage side TV1 Secondary line Voltage U ab At a setting value of U 4 、U 5 The following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV1 bc At the setting value U 4 、U 5 The following steps: u shape 4 ≤U bc ≤U 5
③ Low-Voltage side TV1 Secondary line Voltage U ca At the setting value U 6 、U 7 The following steps: u shape 6 ≤U ca ≤U 7
When the criteria are all met, judging that the line disconnection fault of the phase A line is accompanied by a load side line grounding fault;
2) b phase disconnection identification method:
(r) Low Voltage side TV1 Secondary line Voltage U ab At the setting value U 6 、U 7 The method comprises the following steps: u shape 6 ≤U ab ≤U 7
② secondary line voltage U of low-voltage side TV1 bc At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U bc ≤U 5
③ Low-Voltage side TV1 Secondary line Voltage U ca At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When the criteria are all met, judging that the phase B line has a disconnection fault and is accompanied by a load side line grounding fault;
3) c-phase disconnection identification method:
(r) Low Voltage side TV1 Secondary line Voltage U ab At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV1 bc At the setting value U 6 、U 7 The method comprises the following steps: u shape 6 ≤U bc ≤U 7
Low voltage side TV1 secondary line voltage U ca At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When all the criteria are met, judging that the line disconnection fault of the line C is accompanied by a load side line grounding fault;
when the disconnection fault of the disconnection condition 1 or the disconnection condition 2 of a certain phase is identified, continuing to execute the subsequent step 4; when the three-phase line is not judged to have the line break fault of the line break condition 1 and the line break condition 2, the subsequent step 4 is not executed;
(2) method for identifying 2# fault phase and fault type of incoming line of 110kV line
Collecting secondary line voltage U of 110kV main transformer low-voltage side voltage transformer TV2 ab 、U bc 、U ca And judging whether the following fault criteria are met:
wire breakage condition 1:
1) the phase A broken line identification method comprises the following steps:
(ii) Low Voltage side TV2 Secondary line Voltage U ab At a setting value of U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV2 bc At a setting value of U 1 、U 2 The method comprises the following steps: u shape 1 ≤U bc ≤U 2
③ Low-Voltage side TV2 Secondary line Voltage U ca Less than or equal to setting value U 3 ：U ca ≤U 3
When all the criteria are met, judging that the line of the phase A circuit is broken;
2) b phase disconnection identification method:
(ii) Low Voltage side TV2 Secondary line Voltage U ab Less than or equal to setting value U 3 ：U ab ≤U 3
② secondary line voltage U of low-voltage side TV2 bc At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U bc ≤U 2
Low voltage side TV2 secondary line voltage U ca At the setting value U 1 、U 2 The following steps: u shape 1 ≤U ca ≤U 2
When all the criteria are met, judging that the B-phase line has a line break fault;
3) c-phase disconnection identification method:
(ii) Low Voltage side TV2 Secondary line Voltage U ab At a setting value of U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV2 bc Less than or equal to setting value U 3 ：U bc ≤U 3
Low voltage side TV2 secondary line voltage U ca At a setting value of U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ca ≤U 2
When the criteria are all met, judging that the line of the phase C line is broken;
wire breakage case 2:
1) the phase A broken line identification method comprises the following steps:
(r) Low Voltage side TV2 Secondary line Voltage U ab At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV2 bc At a setting value of U 4 、U 5 The following steps: u shape 4 ≤U bc ≤U 5
③ Low-Voltage side TV2 Secondary line Voltage U ca At the setting value U 6 、U 7 The method comprises the following steps: u shape 6 ≤U ca ≤U 7
When the criteria are all met, judging that the line disconnection fault of the phase A line is accompanied by a load side line grounding fault;
2) b phase disconnection identification method:
(ii) Low Voltage side TV2 Secondary line Voltage U ab At the setting value U 6 、U 7 The method comprises the following steps: u shape 6 ≤U ab ≤U 7
② secondary line voltage U of low-voltage side TV2 bc At a setting value of U 4 、U 5 The method comprises the following steps: u shape 4 ≤U bc ≤U 5
③ Low-Voltage side TV2 Secondary line Voltage U ca At a setting value of U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When the criteria are all met, judging that the phase B line has a disconnection fault and is accompanied by a load side line grounding fault;
3) c-phase disconnection identification method:
(ii) Low Voltage side TV2 Secondary line Voltage U ab At the setting value U 4 、U 5 The following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV2 bc At the setting value U 6 、U 7 The method comprises the following steps: u shape 6 ≤U bc ≤U 7
③ Low-Voltage side TV2 Secondary line Voltage U ca At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When the criteria are all met, judging that the line disconnection fault of the line C is accompanied by a load side line grounding fault;
in the above discriminant, the voltage setting value U 1 According to
Is adjusted by 0.95 times of U 2 According to
1.05 times of the total weight; voltage setting value U 3 According to E ab Setting by 0.1 times; voltage setting value U 4 According to electricity
Is adjusted by 0.95 times of U 5 According to
1.05 times of the total weight; voltage setting value U 6 According to E ab 0.95 times of/3 to set U 7 According to E ab 1.05 times of/3; in the power line generally applicable to the embodiment, the secondary value E of the rated line voltage measured by the voltage transformer TV at the low-voltage side of the 110kV main transformer ab When the voltage is 100V, U is calculated 1 ＝82.27V，U 2 ＝90.93V，U 3 ＝10.00V，U 4 ＝83.78V，U 5 ＝92.60V，U 6 ＝31.67V，U 7 ＝35.00V。
When the disconnection fault of the disconnection condition 1 or the disconnection condition 2 of a certain phase is identified, continuing to execute the subsequent step 4; when the three-phase line is not judged to have the line break fault of the line break condition 1 and the line break condition 2, the subsequent step 4 is not executed;
and 4, step 4: disconnection warning and fault removal
(1) Incoming line 1# line breakage warning and fault removing mode
According to the results of the phase and type of the broken line fault in the step 3, the time is delayed by t 1 Then sends out the broken line alarm signal of the fault phase and delays t 2 And the corresponding circuit breaker of the back trip cuts off a fault line and is connected into a standby power supply to recover power supply.
(2) Incoming line 2# line breakage warning and fault removal mode
According to the results of the phase and type of the broken line fault in the step 3, the time is delayed by t 1 Then sends out the broken line alarm signal of the fault phase and delays t 2 And the corresponding circuit breaker of the back trip cuts off a fault line and is connected into a standby power supply to recover power supply.
Time t 1 Setting the time to be 0.1-0.3 s and t 2 Setting three-phase asynchronous time of 0.2-0.5 s when the switch is closed.
In power system relay protection, the protection operation must be accurate and rapid, and must also prevent the refusal or misoperation. In the self-adaptive identification and protection method for the disconnection fault of the 110kV line, the reason that the step 2 is set to judge the disconnection fault protection starting condition, if the condition is met, the relay protection device is pre-started, and then the step 3 is further carried out is that a negative sequence voltage component appears after the disconnection fault occurs in the line, the step 2 detects the corresponding negative sequence voltage component, the line disconnection relay protection device is pre-started, preparation can be made for the next step of rapidly carrying out protection action once the disconnection fault is confirmed, but the line disconnection fault does not exist enough after the disconnection starting condition in the step 2 is met, and the disconnection fault phase identification in the step 3 is still required to be carried out to further determine whether the disconnection fault occurs and which phase is the fault phase because the disconnection fault can exist in other types of faults. The criteria of step 2 and step 3 are complementary to each other, so that preparation can be made for quick action, and misoperation of protection caused by identifying fault phases by directly executing step 3 when slight disturbance (such as voltage fluctuation or other abnormal conditions) occurs to the 110kV power transmission line can be avoided.
3. Relay protection circuit for implementing the method of the invention
Taking phase a open line of fault case 2 as an example, as shown in fig. 8:
the current transformer TA, the current relay KA1, the current relay KA2 and the current relay KA3 realize the function of judging the short-circuit fault in the step 1, once any phase current flowing into the current relay is larger than a setting value, the corresponding normally closed contact is immediately disconnected, and the subsequent action is not executed any more;
the voltage transformer TV and the negative sequence voltage filter KVN1 realize the function of judging the start of the negative sequence voltage in the step 2, and if and only if the corresponding normally open contact of the voltage measured by the negative sequence voltage relay is more than or equal to the setting value, the normally start is protected;
the function of identifying the fault phase in the step 3 is realized by the voltage transformer TV, the voltage relay KV1, the voltage relay KV2, the voltage relay KV3, the voltage relay KV4, the voltage relay KV5 and the voltage relay KV6, taking the A-phase broken line as an example, the setting value set by the voltage relay KV1 at the moment is U 4 Setting value set by the voltage relay KV2 is U 5 The setting value set by the voltage relay KV3 is U 6 Setting value set by the voltage relay KV4 is U 7 Setting value set by the voltage relay KV5 is U 4 Setting value set by the voltage relay KV6 is U 5 Only when the secondary value of the corresponding phase voltage at the low-voltage side falls into a specified range, all normally open contacts are closed, the disconnection fault of the A is judged, and the protection device starts to act;
the time relay KT1 and the signal relay KS realize the disconnection warning function in the step 4, and when the protection action condition is met, the disconnection warning function is realized through t 1 Sending a disconnection warning signal in a delayed manner, wherein the signal relay KS does not reset automatically, and the warning can be stopped by a manual operator after the warning signal is sent;
the time relay KT2 and the outlet tripping relay KCO realize the fault removal function in the step 4, and when the protection action condition is met, the fault is removed by t 2 And (5) jumping the corresponding circuit breaker in a delayed manner and starting the backup power automatic switch to recover power supply.
4. Load recovery mode
In combination with the above method for protecting the disconnection of the 110kV line for measuring the voltage of the low-voltage lateral line of the transformer, taking the electrical main connection of the 110kV single-bus sectional connection shown in fig. 5 as an example, a load recovery mode after the disconnection fault occurs is given:
(1) bus tie spare power automatic switching operation mode
When the 110kV bus 1# and the 110kV bus 2# operate independently, the circuit breakers QF1 and QF2 are both in a switching-on position, and the circuit breaker QF3 is in a switching-off position. At the moment, once the action condition of the disconnection protection is met and an alarm signal is sent, the time is delayed by t 2 Then, the fault line circuit breaker QF1 or QF2 is prepared to be jumped firstly, and then QF3 is closed, and the bus which does not run is taken as a spare bus to recover the power supply of the power-losing bus in time.
(2) Incoming line 1# spare power automatic switching operation mode
When the 110kV bus 1# runs and the 110kV bus 2# is in hot standby, the circuit breakers QF1 and QF3 are both in a switch-on position, and the circuit breaker QF2 is in a switch-off position. At the moment, once the action condition of the disconnection protection is met and an alarm signal is sent, the time is delayed by t 2 Then preparing to jump a fault line breaker QF1 firstly, closing QF3 and QF2, taking the 110kV bus 2# as a spare, and recovering the power supply of the power-losing bus in time.
(3) Incoming line 2# spare power automatic switching operation mode
When the 110kV bus 2# runs and the 110kV bus 1# is in hot standby, the circuit breakers QF2 and QF3 are both in a switch-on position, and the circuit breaker QF1 is in a switch-off position. At the moment, once the condition of the line break protection action is met and an alarm signal is sent, the time is delayed by t 2 And then preparing to jump a fault line breaker QF2, closing QF3 and QF1, taking the 110kV bus 1# as a spare, and recovering the power supply of the power-losing bus in time.
5. Application scenarios
The inventive solution can be used in the following cases: (1) the operation mode of the neutral point of the load end 110kV transformer substation transformer is as follows: the operation is carried out without the ground; (2) the 110kV side of the 110kV transformer substation is provided with a spare power automatic switching device, or the middle and low voltage sides are provided with spare power automatic switching devices. The primary main wiring such as 110kV single-bus subsection primary main wiring of a 110kV transformer substation can be met. The scheme of the invention can be implemented by adopting a microcomputer relay protection device.
In addition to the above embodiments, the present invention may have other embodiments, and any technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of the claims of the present invention.
Claims (7)
1. A110 kV line disconnection protection method for measuring the voltage of a low-voltage side line of a transformer is characterized by comprising the following steps:
step 1: judging whether the short-circuit fault occurs or not, and if the short-circuit fault occurs in the line, not executing the subsequent steps 2-4; if the circuit is judged not to have short-circuit fault, the subsequent step 2 is continuously executed;
step 2: judging whether the starting condition of the disconnection protection is met
Calculating secondary a-phase negative sequence voltage U of 110kV main transformer low-voltage side voltage transformer TV a2 B phase negative sequence voltage U b2 C phase negative sequence voltage U c2 And judging whether the following conditions are met:
(1) secondary a phase negative sequence voltage U a2 More than or equal to a setting value: u shape a2 ≥K rel.u (U 2min +U unb )
(2) Secondary b-phase negative sequence voltage U b2 Greater than or equal to a setting value: u shape b2 ≥K rel.u (U 2min +U unb )
(3) Secondary c-phase negative sequence voltage U c2 More than or equal to a setting value: u shape c2 ≥K rel.u (U 2min +U unb )
In the formula, K rel.u For the reliability factor, U 2min According to 1/3E a Setting, E a Measuring a secondary value of power electromotive force for a voltage transformer at the low-voltage side of a 110kV main transformer; u shape unb When the system normally operates, the 110kV bus of the load-end substation presents unbalanced voltage with negative sequence characteristics;
if any condition is met, the disconnection protection starting condition is considered to be met, and the subsequent step 3 is continuously executed; when the three conditions are not met, judging that the line is not broken, and not executing the subsequent step 3-4;
and step 3: identifying phase and type of broken line fault
The neutral point of a main transformer on the load side of the 110kV main transformer runs without the ground, the types of disconnection faults are divided into disconnection conditions 1 and disconnection conditions 2, the disconnection condition 1 is that the disconnection fault position is not grounded along with the circuit, the disconnection condition 2 is that the disconnection fault position is grounded along with the load side circuit, and the secondary line voltage U of a voltage transformer TV on the low voltage side of the 110kV main transformer is acquired ab 、U bc 、U ca Judging whether the following fault criteria are met:
1) the method for judging the phase and the type of the broken line fault in the broken line condition 1 comprises the following steps:
(1) the phase A broken line identification method comprises the following steps:
low voltage side TV secondary line voltage U ab At the setting value U 1 、U 2 The following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV bc At the setting value U 1 、U 2 The following steps: u shape 1 ≤U bc ≤U 2
③ Low-Voltage side TV Secondary line Voltage U ca Less than or equal to setting value U 3 ：U ca ≤U 3
When the criteria are all met, judging that the A-phase line has a disconnection fault;
(2) b phase disconnection identification method:
low voltage side TV secondary line voltage U ab Less than or equal to setting value U 3 ：U ab ≤U 3
② secondary line voltage U of low-voltage side TV bc At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U bc ≤U 2
Third, the low-voltage side TV secondary line voltage U ca At a setting value of U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ca ≤U 2
When the criteria are all met, judging that the phase B line has a disconnection fault;
(3) c-phase disconnection identification method:
low voltage side TV secondary line voltage U ab At the setting value U 1 、U 2 The method comprises the following steps: u shape 1 ≤U ab ≤U 2
② secondary line voltage U of low-voltage side TV bc Less than or equal to setting value U 3 ：U bc ≤U 3
③ Low-Voltage side TV Secondary line Voltage U ca At the setting value U 1 、U 2 The following steps: u shape 1 ≤U ca ≤U 2
When the criteria are all met, judging that the line of the phase C line is broken;
2) the method for judging the phase and the type of the broken line fault in the broken line condition 2 comprises the following steps:
(1) the phase A broken line identification method comprises the following steps:
low voltage side TV secondary line voltage U ab At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV bc At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U bc ≤U 5
③ Low-Voltage side TV Secondary line Voltage U ca At a setting value of U 6 、U 7 The method comprises the following steps: u shape 6 ≤U ca ≤U 7
When the criteria are all met, judging that the line disconnection fault of the phase A line is accompanied by a load side line grounding fault;
(2) b phase disconnection identification method:
low voltage side TV secondary line voltage U ab At the setting value U 6 、U 7 The method comprises the following steps: u shape 6 ≤U ab ≤U 7
② secondary line voltage U of low-voltage side TV bc At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U bc ≤U 5
③ Low-Voltage side TV Secondary line Voltage U ca At a setting value of U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When the criteria are all met, judging that the phase B line has a disconnection fault and is accompanied by a load side line grounding fault;
(3) c-phase disconnection identification method:
first, the low voltage side TV2Secondary line voltage U ab At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ab ≤U 5
② secondary line voltage U of low-voltage side TV bc At the setting value U 6 、U 7 The following steps: u shape 6 ≤U bc ≤U 7
③ Low-Voltage side TV Secondary line Voltage U ca At the setting value U 4 、U 5 The method comprises the following steps: u shape 4 ≤U ca ≤U 5
When the criteria are all met, judging that the line disconnection fault of the line C is accompanied by a load side line grounding fault;
E ab the secondary rated line voltage value of a voltage transformer TV on the low-voltage side of a 110kV main transformer is set in the above discriminant 1 According to the following
0.95 times of the total value of the 2 According to
1.05 times of the total weight; setting value U 3 According to E ab Setting by 0.1 times; setting value U 4 According to electricity
0.95 times of the total value of the 5 According to
1.05 times of the total weight; setting value U 6 According to E ab 0.95 times of/3 to set value U 7 According to E ab 1.05 times of/3;
when the disconnection fault of the disconnection condition 1 or the disconnection condition 2 of a certain phase is identified, continuing to execute the subsequent step 4; when the three-phase line is not judged to have the line break fault of the line break condition 1 and the line break condition 2, the subsequent step 4 is not executed;
and 4, step 4: disconnection warning and fault removal
According to the results of the phase and type judgment of the broken line fault in the step 3, simultaneously delaying t 1 Then sends out the broken line alarm signal of the fault phase and delays t 2 And the corresponding circuit breaker of the back trip cuts off a fault line and is connected into a standby power supply to recover power supply.
2. The 110kV line disconnection protection method for measuring the voltage of the low-voltage side line of the transformer as claimed in claim 1, wherein the method for judging whether the line has a short-circuit fault in the step 1 comprises the following steps: collecting secondary side a-phase current I of 110kV line current transformer TA a Secondary side b-phase current I b Secondary side c-phase current I c Judging whether the following conditions are met:
(1) secondary side a phase current I a More than or equal to a setting value: i is a ≥K rel.i I l.max
(2) Secondary side b-phase current I b More than or equal to a setting value: I.C. A b ≥K rel.i I l.max
(3) Secondary side c-phase current I c More than or equal to a setting value: i is c ≥K rel.i I l.max
In the formula, K rel.i Is a current reliability factor; i is l.max The maximum load current is the maximum load current of the normal operation of the system and is measured by an actual line; and if any one of the conditions is met, determining that the short-circuit fault occurs in the line, identifying and removing the fault through the short-circuit protection of the line, and if the three conditions are not met, determining that the short-circuit fault does not occur in the line.
3. The 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer as claimed in claim 2, wherein the current reliability coefficient K is rel.i The value is 1.3-1.5.
4. The 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer as claimed in claim 1, wherein the reliability coefficient K in step 2 rel.u The value is 1.1-1.2.
5. The 110kV line disconnection protection method for measuring the voltage of the low-voltage side line of the transformer as claimed in claim 1, wherein in the step 2, U is adopted 2min Take 19.25V, U unb Taking 4-6V.
6. The 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer as claimed in claim 1, wherein the setting value U is 1 Taking 82.27V and setting value U 2 Taking 90.93V and setting value U 3 Taking 10.00V and setting value U 4 Taking 83.78V and setting value U 5 Taking 92.60V and setting value U 6 Taking 31.67V and setting value U 7 35.00V was taken.
7. The 110kV line disconnection protection method for measuring the low-voltage side line voltage of the transformer as claimed in claim 1, wherein t is 1 The time is set to 0.1-0.3 s, t 2 And setting the time to be 0.2-0.5 s when the time avoids the three-phase asynchronous time when the switch is switched on.
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| CN110794340B (en) * | 2019-11-13 | 2022-06-14 | 深圳供电局有限公司 | Disconnection protection method and circuit for high-voltage overhead line |
| CN110729709B (en) * | 2019-11-28 | 2020-12-15 | 国网江苏省电力有限公司镇江供电分公司 | 110kV line disconnection relay protection method for measuring neutral point voltage of transformer |
| CN110676823B (en) * | 2019-11-28 | 2021-03-02 | 国网江苏省电力有限公司镇江供电分公司 | 110kV line disconnection relay protection method |
| CN110829390B (en) * | 2019-11-28 | 2020-11-10 | 国网江苏省电力有限公司镇江供电分公司 | 110kV wire break protection method for measuring load side voltage and matching with spare power automatic switching |
| CN111313379B (en) * | 2019-12-09 | 2021-03-30 | 国网江苏省电力有限公司镇江供电分公司 | Disconnection protection method for comparing line voltage on two sides of line and spare power automatic switching |
| CN111337855B (en) * | 2020-03-18 | 2022-06-21 | 贵州电网有限责任公司 | Active power distribution network disconnection fault protection method based on negative sequence current ratio |
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