CN206962435U - Small resistance grounding system wireline inspection equipment and system - Google Patents
Small resistance grounding system wireline inspection equipment and system Download PDFInfo
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Abstract
A kind of small resistance grounding system wireline inspection equipment and system are the utility model is related to, small resistance grounding system wireline inspection equipment includes：Processing unit and of ac harvester, the processing unit include first comparator and the second comparator；The first comparator is connected with the of ac harvester and the second comparator respectively, and second comparator is connected with tripping operation outlet device.Above-mentioned small resistance grounding system wireline inspection equipment and system, by setting first comparator and the second comparator in processing unit, and the cooperation of of ac harvester and processing unit, faulty line during small resistance grounding system high resistance ground can be detected, and special zero sequence CT polarity need not be verified, there are good Detection results.
Description
Technical Field
The utility model relates to a power equipment's protection and control technical field especially relate to a small resistance ground connection system circuit check out test set and system.
Background
When a ground fault occurs, the neutral point can quickly identify and cut off a fault line through low-resistance grounding equipment, so that the method is increasingly applied to newly-built urban power grids.
The neutral point can remove the small-resistance grounding fault through small-resistance grounding equipment, and at present, the neutral point can only remove the grounding fault below 100 ohms of a transition resistor through zero-sequence current protection of 10kV equipment with the small resistance. When the low-resistance grounding equipment has a high-resistance grounding fault, the fault characteristics are not obvious and often cannot be removed for a long time, so that the personal safety of passers-by is threatened, and even the reliability of power supply is seriously influenced. At present, the fault detection of the high-resistance grounding mainly takes a steady-state quantity criterion as a main basis in consideration of the strong damping action of the high-resistance grounding. When the steady-state quantity criterion is taken as a main basis, the fault quantity is small, the requirement on the precision is high, and a special zero-sequence CT (current transformer) is required to be adopted for zero-sequence overcurrent protection, but the polarity of the special zero-sequence CT is difficult to check, so that the detection effect is poor.
SUMMERY OF THE UTILITY MODEL
Therefore, it is necessary to provide a small-resistance grounding system line detection device and system for the problem that the polarity of the special zero-sequence CT is difficult to check, resulting in poor detection effect.
A small resistance grounding system line detection apparatus comprising:
the device comprises a processing device and an alternating current quantity acquisition device, wherein the processing device comprises a first comparator and a second comparator;
the first comparator is respectively connected with the alternating current quantity acquisition device and the second comparator, and the second comparator is connected with the tripping outlet device;
the alternating current quantity acquisition device acquires the bus voltage and the open triangle zero sequence voltage as zero sequence currents when the low-resistance grounding system is grounded in a high resistance mode, and respectively outputs the bus voltage, the open triangle zero sequence voltage and the zero sequence currents of all lines to the first comparator;
the first comparator receives the bus voltage and the open triangle zero sequence voltage as a zero sequence current, calculates a threshold value of a zero sequence active power absolute value and a zero sequence active power absolute value, compares the threshold value of the zero sequence active power absolute value and the zero sequence active power absolute value to obtain a first comparison signal, and sends the first comparison signal to the second comparator;
and after receiving the first comparison signal, the second comparator compares the zero sequence active power absolute values of all lines of the small-resistance grounding system and sends a tripping command to a tripping outlet device.
A line detection system of a low-resistance grounding system comprises high-resistance grounding fault line detection equipment and a tripping outlet device connected with a second comparator of the high-resistance grounding fault line detection equipment;
and the tripping outlet device receives the tripping command sent by the second comparator and drives the breaker of the corresponding line to trip.
According to the small-resistance grounding system line detection equipment and system, the first comparator and the second comparator are arranged in the processing device, and the alternating current quantity acquisition device is matched with the processing device, so that a fault line when the small-resistance grounding system is grounded in a high-resistance mode can be detected, the polarity of the special zero-sequence CT does not need to be verified, and a good detection effect is achieved.
Drawings
Fig. 1 is a schematic structural diagram of a circuit detection device of a low-resistance grounding system according to a first embodiment of the present invention;
fig. 2 is a schematic diagram of a main connection of a neutral point through a small resistance system according to an embodiment of the present invention;
fig. 3 is a phasor diagram of a high-resistance ground fault of a low-resistance grounding system when the polarity of the zero-sequence CT is positive according to an embodiment of the present invention;
fig. 4 is a phasor diagram of the high-resistance ground fault of the small-resistance grounding system when the polarity of the zero-sequence CT is reversed in an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a circuit detection device for a low-resistance grounding system according to a second embodiment of the present invention;
fig. 6 is a schematic structural diagram of a circuit detection device for a low-resistance grounding system according to a third embodiment of the present invention;
fig. 7 is a schematic diagram of the outline structure of the circuit testing apparatus for implementing the small-resistance grounding system of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
An embodiment of a high resistance ground fault line detection device is set forth below in connection with fig. 1.
Fig. 1 is the utility model discloses a high resistance ground fault line detection equipment schematic diagram of an embodiment includes:
a processing device 102 and an alternating current collecting device 101, wherein the processing device 102 comprises a first comparator 1021 and a second comparator 1022;
the first comparator 1021 is respectively connected with the alternating current quantity acquisition device 101 and the second comparator 1022, and the second comparator 1022 is connected with the trip outlet device 103;
the alternating current quantity acquisition device 101 acquires a bus voltage and an open triangle zero sequence voltage as zero sequence currents when the low resistance grounding system is grounded in a high resistance mode, and respectively outputs the bus voltage, the open triangle zero sequence voltage and the zero sequence currents of all lines to the first comparator 1021;
the first comparator 1021 receives the bus voltage and the open triangle zero-sequence voltage as a zero-sequence current, calculates a threshold value of a zero-sequence active power absolute value and a zero-sequence active power absolute value, compares the threshold value of the zero-sequence active power absolute value and the zero-sequence active power absolute value to obtain a first comparison signal, and sends the first comparison signal to the second comparator 1022;
the second comparator 1022 compares the zero sequence active power absolute values of each line of the small resistance grounding system after receiving the first comparison signal, and sends a trip command to the trip exit device 103.
In the above embodiments, the Processing device 102 may be a Central Processing Unit (CPU) device. The ac collecting device 101 may be configured to collect the bus voltage, the zero-sequence voltage of the open triangle, and the zero-sequence current of each line when the low resistance grounding system is grounded in the high resistance state, convert the collected signals into corresponding low-voltage analog signals, and transmit the signalsthe voltage U △ led out from the open triangle is the zero sequence voltage of the open triangle, the first comparator 1021 receives the low voltage analog quantity signal sent by the alternating current quantity acquisition device 101, and is used for carrying out the threshold value | P of the absolute value of the zero sequence active power0|Door sillAnd the absolute value of the active power | P of the zero sequence0Calculating | and comparing the magnitudes of the two, when any line meets the absolute value | P of zero sequence active power0Threshold value | P of | greater than zero sequence active power absolute value0|Door sillThen, the zero sequence active power absolute value condition can be considered to be satisfied: i P0|＞|P0|Door sillThe low resistance grounding system has a high resistance grounding fault characteristic. After determining that the high-resistance ground fault characteristic exists, the second comparator 1022 may be used to compare the absolute value | P of the zero-sequence active power of each line0Selecting the absolute value | P of the zero sequence active power0And if the line with the maximum I is judged as the high-resistance grounding fault line.
The above example describes in detail the judgment basis for judging whether the line has a high-resistance ground fault, and by arranging the first comparator and the second comparator in the processing device and matching the alternating current quantity acquisition device with the processing device, the situation of polarity reversal of the special zero-sequence CT can be adapted, the polarity of the special zero-sequence CT does not need to be checked, and the influence of the non-fault line capacitance current can be reliably prevented. The method for comparing all lines is adopted, the characteristic that the fault characteristic quantity is small and accurate measurement is needed when the high-resistance grounding is adopted can be adapted, and the maximum capability of detecting the transition resistance can reach 990 ohms.
As shown in fig. 5, in an embodiment of the present invention, the processing device 102 further includes an operator 1023; the operator 1023 is connected with the switching value input device 104 of the circuit; the operator 1023 receives the reset signal sent by the switching value input device 104 and performs signal reset operation; and/or the operator 1023 receives the remote control signal sent by the switching value input device 104 and performs remote control operation on the switch of the power distribution room of each line; and/or the operator 1023 receives the device maintenance signal sent by the switching value input device 104, and shields the operation of sending up the signal when performing the device maintenance.
In addition, a switching value input device 104 connected to the operator 1023 is further included; the switching value input device 104 acquires a signal reset signal, a remote control signal, and/or a device maintenance signal, and transmits the signal reset signal, the remote control signal, and/or the device maintenance signal to the operator 1023.
In a particular embodiment, the switching value input device 104 can convert the relevant signals reflecting the production process into digital signals that can be received by the CPU device. The signal resetting signal is to refresh the signal to return to the original state, for example, after the line detects a fault, the signal to drive the hard contact outlet of the relay to be closed is received, and after the line returns to normal, the received signal is restored to the signal to trip the hard contact outlet of the relay, so that the trip protection action can be executed when the line fails again next time. The remote control signal can ensure that the switch of the power distribution room of each line is remotely controlled and operated, and when the line of the power distribution room far away breaks down, the switch of the power distribution room can be timely controlled to execute protection tripping and isolation faults. The device maintenance signal can ensure that the device does not receive other signals when in maintenance, namely, the operation of sending the signal is shielded, and the device returns to normal after maintenance to receive the sent signal again.
In the above embodiment, a series of operations can be performed by matching the switching value input device 104 with the operator 1023, so that the protection trip isolation fault can be timely executed when the line fails, the reliability of power supply of other normal lines is ensured, and the high-resistance ground fault discrimination method does not need to check the polarity of the special zero-sequence CT, so as to ensure the detection effect of the line fault.
In a specific embodiment, the low resistance grounding system line detection apparatus further includes a power supply device connected to the first comparator 1021, the second comparator 1022 and the ac collecting device 101 respectively; the power supply device is used for supplying power to the first comparator 1021, the second comparator 1022 and the alternating current quantity acquisition device 101, so as to ensure the normal operation of each component.
As shown in fig. 6, which is a schematic structural diagram of a line detection system of a low-resistance grounding system according to an embodiment of the present invention, the line detection system includes the high-resistance grounding fault line detection device, and a trip outlet device 103 connected to a second comparator 1022 of the high-resistance grounding fault line detection device; the trip outlet device 103 is connected with a relay of a line; the trip exit device 103 receives the trip command sent by the second comparator 1022 and sends a first driving signal to the relay, which drives the relay hard contact exit to close, causing the circuit breaker of the corresponding line to trip. Specifically, fig. 7 is a schematic diagram of an outline structure of a small-resistance grounding system circuit detection device.
In the embodiment of the present invention, the relay hard contact refers to the contact of the relay, and the contact of the relay is in the normally open or normally closed state, i.e. the contact that is simply understood as the switch normally open or normally closed to make the signal connect or disconnect is called the contact of the relay. The contacts of the relay in the embodiment are in a normally open state, and the relay is closed when receiving a driving signal, so that the circuit breaker of the corresponding line is tripped, and relays with different types of contacts can be selected according to requirements.
According to the embodiment, after the high-resistance grounding fault is judged to occur, the tripping outlet command is formed and sent to the tripping outlet plug-in for actual execution, the fault line can be controlled to trip in time, the reliability of power supply of other normal lines is ensured, the high-resistance grounding fault judging method does not need to check the polarity of a special zero sequence CT, and the influence of non-fault line capacitance current can be reliably prevented.
In addition, the utility model also provides a little resistance ground system circuit detection system, include little resistance ground system circuit check out test set of stated and with the tripping operation time-recorder that the second comparator 1022 of the stated high resistance ground fault circuit check out test set of stated links; the trip timer receives the second driving signal sent by the second comparator 1022, and feeds back a trip command to the second comparator 1022.
In the embodiment, after the high-resistance grounding fault line is judged, the tripping timer is started, and when the tripping timer reaches the preset tripping timing threshold value, tripping can be started to isolate the fault line. And if the zero sequence active power absolute value condition is not met or the zero sequence active power absolute value of the line is not the maximum of all lines before the tripping timing threshold is reached, returning the high-resistance grounding protection, and resetting the tripping timer. The embodiment of the utility model provides an in the tripping operation time-recorder can be a timer, begins the timing when the high resistance earth fault appears in the circuit, when the timer reaches tripping operation timing threshold value, think that this circuit has high resistance earth fault characteristic, can carry out protection tripping operation isolation fault, when carrying out protection tripping operation, also can start alarm system, can in time discover specific fault location through alarm system maintainer to in time overhaul, in time resume normal power supply.
Through above-mentioned embodiment, can accurate detection high resistance earth fault, the phenomenon of avoiding erroneous judgement appears, when distribution lines takes place high resistance earth fault, can in time be amputated, can not only avoid the pedestrian of crossing the way to be endangered the pedestrian of crossing because of step voltage or the contact voltage that distribution lines dropped ground production, can also guarantee that last one-level grounding transformer is unlikely to receive the influence of trouble, has improved the reliability of power supply.
In a specific embodiment, the line detection system of the low-resistance grounding system further comprises a relay connected with the trip exit device 103; the relay receives a first driving signal sent by the trip outlet device 103, and drives the hard contact outlet of the relay to be closed.
In the above embodiments, the hard contacts of the relay refer to the contacts of the relay, and the contacts of the relay are in a normally open state or a normally closed state, that is, the contacts where the switch is normally open or normally closed to make the signal on or off are simply understood as the contacts of the relay. The contacts of the relay in the embodiment are in a normally open state, and the relay is closed when receiving a driving signal, so that the circuit breaker of the corresponding line is tripped, and relays with different types of contacts can be selected according to requirements.
Through above-mentioned embodiment, can accurate detection high resistance earth fault, the phenomenon of avoiding erroneous judgement appears, when distribution lines takes place high resistance earth fault, can in time be amputated, can not only avoid the pedestrian of crossing the way to be endangered the pedestrian of crossing because of step voltage or the contact voltage that distribution lines dropped ground production, can also guarantee that last one-level grounding transformer is unlikely to receive the influence of trouble, has improved the reliability of power supply.
Specifically, in a specific embodiment, the line detection system of the low-resistance grounding system further comprises a circuit breaker connected with the relay, and the closing of the hard contact outlet of the relay drives the circuit breaker to trip.
Further, in a specific embodiment, the number of the relays in the line detection system of the low-resistance grounding system is multiple, and each relay is respectively arranged on one line of the low-resistance grounding system.
Furthermore, in a specific embodiment, the number of the circuit breakers in the line detection system of the low-resistance grounding system is multiple, and each circuit breaker is connected with one relay and arranged on one line.
In the above embodiments, the circuit breaker is an automatic switch with large on and off capacity, and plays a role in protection and control in the power system, the circuit breaker is divided into a high-voltage circuit breaker and a low-voltage circuit breaker according to the application range, the high-voltage and low-voltage boundary line is divided more clearly, and the circuit breaker is generally called as a high-voltage circuit breaker with more than 3 kV. The embodiment of the utility model provides an in the circuit breaker can be high-voltage short circuiter.
According to the embodiment, the relay and the circuit breaker are matched to protect the circuit, the circuit can be automatically cut off when faults such as serious overload, short circuit, undervoltage and the like occur, the circuit is protected, tripping protection and fault isolation can be timely executed when the circuit fails, the reliability of power supply of other normal circuits is guaranteed, the polarity of a special zero sequence CT does not need to be verified by the high-resistance grounding fault judging method, and the detection effect of the circuit fault can be guaranteed.
The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.
The following describes, with reference to specific examples, the conditions according to the absolute value of the active power of the zero sequence and the absolute value of the active power of the zero sequence | P of each line0And the magnitude is used as a theoretical basis for judging whether the line has a high-resistance ground fault. It is emphasized that the invention does not reside in the improvement of the procedure but in the improvement of the structure of each device in the apparatus.
The connection diagram of the neutral point through the small-resistance grounding system line is shown in fig. 2, and the neutral point can be a 10kV grounding system, and comprises four lines: line 1, line 2, line 3 and line 4, in which the grounding transformer is a grounding transformer, wherein line 4 has a grounding fault via transition resistance, A, B and C are three-phase different circuits, RrIs a neutral point ground resistance, RgFor ground fault transition resistance, neutral grounding resistance RrCan be 6-20 ohm and the ground fault transition resistance RgCan be in the range of 100-1000 ohms.
The zero sequence voltage of the neutral point of the grounding transformer is set to beNeglecting the grounding variable impedance, the three-phase voltage of the 10kV bus is deviated due to the neutral point voltage, respectivelyAccording to kirchhoff's current law, there is formula (1):
wherein,andand the rated values of the three-phase voltages of a, b and c are respectively.Is the sum of the three-phase currents of the power supply,is the sum of three-phase currents of the lines, RrThe grounding resistance is changed into a neutral point grounding resistance.
When the three-phase parameters are symmetrical and the loads are symmetrical, the sum of the three-phase currents of the power supply branch and each non-fault line is calculated to beI.e. a three-phase capacitance-to-ground current ofWherein j is an imaginary unit, j2And omega is the angular velocity corresponding to the power frequency, for 50Hz, the power frequency is omega 2 pi multiplied by 50, and C is the single-phase ground capacitance of the circuit, and the following is the same. For faulty lines, except three-phase capacitive current to earthThere is also a transition resistance R due to ground faultgThe generated ground current is assumed to have a ground fault at a distance of l from the bus, and the unit length of the ground currentWhen the reactance of (A) is x, the phase A is grounded, RgThe generated current to ground is: byBringing the above result into formula (1), the result is converted into formula (2):
according to the above analysis, for the nth non-faulty line, the zero sequence currentIs composed ofCapacitance current to ground produced by action:
in equation (3), n is the number of the non-faulty line, corresponding to fig. 2, where n is 1, 2, 3, CnIs the nth line capacitance.
For faulty lines, zero sequence currentFor three-phase capacitive current to earthAnd ground fault transition resistance RgSum of the generated currents to ground:
in the formula (4), sigma C is the sum of the system capacitance to ground, C4Is the capacitance of the fault line to ground.
Zero sequence current and zero sequence voltage of non-faulty and faulty lines according to equations 3 and 4The phasor relationship of (a) is shown in fig. 3, wherein the magnitude of the zero-sequence current is 3I0. If the polarity of the special zero sequence CT is reversed, the phasor diagram is shown in FIG. 4.
According to fig. 3 and 4, the active power P is analyzed0＝U0×3I0And multiplying Cos theta, wherein theta is an included angle between the zero-sequence current and the zero-sequence voltage, and I _0 and U _0 are the amplitude of the zero-sequence current and the amplitude of the zero-sequence voltage respectively. For a non-fault line, the zero sequence active power is 0 no matter the polarity of the special zero sequence CT is positive or negative, and for a fault line, the absolute value of the positive connection and the negative connection of the polarity of the special zero sequence CT is equal, and the absolute value of the zero sequence active power is equal if the positive and negative polarities are opposite. For a system with a neutral point grounded through a small resistor, the zero sequence active absolute value is used as a basis for distinguishing a fault line from a non-fault line, and obvious distinguishing degree is provided. Therefore, the zero sequence active power absolute value is adopted to detect the earth fault, and the influence of the polarity of the special zero sequence CT can be prevented.
According to the formula (4), when the zero sequence active power is calculated for the fault line, only the zero sequence active power is calculatedPartial participation in the calculation, j3 omega (Sigma C-C)4) And the zero sequence active power generated in part is 0. Therefore, the absolute value of the active power is obtained as follows:
in the formula (2), in the case of high-resistance grounding, R is consideredgIn the range of 100-1000 ohms, lx is far less than RgAnd can be ignored. Considering the case of the overhead line, the unit of the overhead line is about 6pF/km for the ground, the admittance is about 5.7 mu S/km in conversion, and the system scale is equivalent to 100km of framesThe admittance to the ground is 0.570mS when the air wire is empty, the grounding resistance of the grounding to neutral point is generally 6-20 ohms, the admittance is more than 20mS in conversion, and the admittance is far greater than the system admittance to the ground, so the system admittance to the ground is realized, and the system admittance to the ground is improvedAlso, neglect, we get the following approximate calculation formula for the grounded-to-neutral voltage:
Eais composed ofThe amplitude of (c). In the formula (5), an approximate calculation formula of the absolute value of the zero sequence active power is obtained:
for the condition that the cable lines are abundant or the power grid scale is large, the capacitance and current of the system to the ground are large, and the capacitance and current cannot be directly ignoredThen, the following can be obtained:
according to equation (4), j3 ω (∑ C-C) when it cannot be ignored4) A zero sequence reactive power part can be formed, and the following can be obtained:
Q0zero sequence reactive power. For the same small-resistance grounding system, the neutral grounding resistor RrIs constant, | P according to formula 8 and formula 90L along with the ground resistance RgDecreases with increasing system size, | Q0L will increase with increasing system size.
The above analysis is based on the transition resistance R when the high resistance is groundedgOn the premise of obviously being greater than line reactance lx from a fault point to a bus, the grounding device is suitable for the grounding condition of the transition resistor of 100 ohms or more. In addition, considering the influence of distributed resistance, error and other factors, the zero sequence active power of the non-fault line is not completely 0, but the zero sequence reactive power is far larger than the zero sequence active power, while the fault line has obvious zero sequence active power, and the zero sequence power is different in distribution.
In addition, the system in fig. 2 was subjected to electromagnetic transient simulation using electromagnetic transient simulation software (PSCAD, Power Systems Computer Aided Design) software, with a voltage level of 10.5kV and a neutral ground resistance of 10 ohms. The transition resistance is selected in the range of 100-1000 ohms, the zero sequence voltage at the 10kV bus and the zero sequence current flowing through each distribution line are calculated, and the absolute value of the zero sequence active power of each line is calculated.
| P of each line corresponding to different transition resistances0|、|Q0As shown in tables 1 and 2, with secondary values, units W, Var:
TABLE 1 | P of lines at different transition resistances0|
| Rg(Ω) | Line 1 | Line2 | Line 3 | Line 4 |
| 100 | 1.33e-3 | 4.21e-4 | 2.24e-3 | 4.81 |
| 200 | 3.74e-4 | 1.18e-4 | 6.27e-4 | 1.35 |
| 400 | 9.91e-5 | 3.13e-5 | 1.66e-4 | 0.358 |
| 600 | 4.49e-5 | 1.42e-5 | 7.54e-5 | 0.162 |
| 800 | 2.55e-5 | 8.05e-6 | 4.28e-5 | 0.0921 |
| 1000 | 1.64e-5 | 5.18e-6 | 2.76e-5 | 0.0592 |
TABLE 2 | Q of each line at different transition resistances0|
In table 1, the zero sequence active power absolute value of the line 4 is consistent with the calculation result of equation (7). The system scale is enlarged, the total amount of the system capacitance to ground is increased, and the simulation results of different transition resistances are shown in the following table:
TABLE 3 | P of lines at different transition resistances0|
| Rg(Ω) | Line 1 | Line 2 | Line 3 | Line 4 |
| 100 | 0.0248 | 0.0115 | 0.0608 | 3.31 |
| 200 | 7.11e-3 | 3.29e-3 | 0.0175 | 0.951 |
| 400 | 1.91e-3 | 8.84e-4 | 4.69e-3 | 0.255 |
| 600 | 8.70e-4 | 4.03e-4 | 2.13e-3 | 0.116 |
| 800 | 4.95e-4 | 2.29e-4 | 1.22e-3 | 0.0662 |
| 1000 | 3.19e-4 | 1.48e-4 | 7.83e-4 | 0.0427 |
TABLE 4 | Q of lines at different transition resistances0|
| Rg(Ω) | Line 1 | Line 2 | Line 3 | Line 4 |
| 100 | 0.458 | 0.353 | 0.618 | 2.12 |
| 200 | 0.131 | 0.101 | 0.177 | 0.609 |
| 400 | 0.0353 | 0.0273 | 0.0477 | 0.164 |
| 600 | 0.0161 | 0.0124 | 0.0217 | 0.0745 |
| 800 | 9.15e-3 | 7.06e-3 | 0.0124 | 0.0424 |
| 1000 | 5.90e-3 | 4.55e-3 | 7.96e-3 | 0.0273 |
The above simulation results are consistent with theoretical formula derivation. In the above embodiment, due to the characteristic of a small fault amount of the high-resistance ground fault, the requirement on the precision is high, and the special zero-sequence CT can be adopted as much as possible, but the polarity of the special zero-sequence CT is difficult to check. The zero sequence current of the embodiment is accessed by adopting the special zero sequence CT, and the polarity of the zero sequence CT can be self-adapted, so that the requirement of high-resistance grounding fault judgment on the precision is ensured.
Specifically, in an embodiment of the present invention, the zero sequence active power threshold | P0|Door sillNeutral grounding resistor R according to low-resistance grounding systemrAnd an anti-transresistance level RgAnd calculating according to the following formula:
in the formula, EaFor the rated value of phase voltage, the protection adopts secondary value calculation, and 57.74V is taken;considering that the secondary rating of the switched-in open-delta voltage is 100V, and the phase voltage hasA time relation; krThe reliability coefficient is adopted, 0.5-0.8 is adopted to ensure the sensitivity of high-resistance grounding protection, and the typical value is 0.6; rrIs a neutral point ground resistance, RgFor resisting transition resistance level, the embodiment of the utility model provides ana、Kr、Rr、RgThe meaning of all is the same. For each line zero sequence active power absolute value | P0Threshold value | P of absolute value of | and zero sequence active power0|Door sillAnd comparing, namely judging that the small-resistance grounding system has high-resistance grounding fault characteristics when any line meets the following formula, and starting high-resistance grounding protection:
the utility model discloses an in all embodiments, high resistance ground protection starts to indicate that high resistance ground protection device starts. The above embodiment can obtain the threshold value | P of the absolute value of the zero sequence active power0|Door sillAbsolute value of zero sequence active power | P in distribution line0The value | is larger than the threshold value | P of the absolute value of the zero sequence active power0|Door sillThe judgment condition is that the distribution line has high-resistance grounding fault. Can be obtained by comparing the absolute value | P of the zero sequence active power0Threshold value | P of absolute value of | and zero sequence active power0|Door sillTo determine whether a high impedance ground fault has occurred.
Claims (9)
1. A small resistance grounding system line detection device, comprising:
the device comprises a processing device and an alternating current quantity acquisition device, wherein the processing device comprises a first comparator and a second comparator;
the first comparator is respectively connected with the alternating current quantity acquisition device and the second comparator, and the second comparator is connected with the tripping outlet device;
the alternating current quantity acquisition device acquires bus voltage, zero sequence voltage of an opening triangle and zero sequence current of each line when the low-resistance grounding system is grounded in a high resistance mode, and outputs the bus voltage, the zero sequence voltage and the zero sequence current to the first comparator respectively;
the first comparator receives the bus voltage and the zero sequence voltage as a zero sequence current, calculates a threshold value of a zero sequence active power absolute value and a zero sequence active power absolute value, compares the threshold value of the zero sequence active power absolute value and the zero sequence active power absolute value to obtain a first comparison signal, and sends the first comparison signal to the second comparator;
and after receiving the first comparison signal, the second comparator compares the zero sequence active power absolute values of all lines of the small-resistance grounding system and sends a tripping command to a tripping outlet device.
2. The small resistance grounding system line detection apparatus as claimed in claim 1, wherein the processing means further comprises an operator;
the operator is connected with a switching value input device of a circuit;
the operator receives the reset signal sent by the switching value input device and performs signal reset operation;
and/or
The operator receives the remote control signal sent by the switching value input device and carries out remote control operation on the switch of the power distribution room of each line;
and/or
The operator receives the device maintenance signal sent by the switching value input device and shields the operation of sending the signal when the device is maintained.
3. The small-resistance grounding system line detection device as claimed in claim 1 or 2, further comprising a power supply device connected to the first comparator, the second comparator and the alternating current amount acquisition device, respectively;
the power supply device is used for supplying power to the first comparator, the second comparator and the alternating current quantity acquisition device.
4. The low resistance grounding system line inspection apparatus of claim 2, wherein the switching value input device obtains a signal reset signal, a remote control signal and/or a device repair signal and sends the signal reset signal, the remote control signal and/or the device repair signal to the operator.
5. A low resistance earth fault line detection system comprising a high resistance earth fault line detection device according to any one of claims 1 to 4, and a trip exit means connected to the second comparator of the high resistance earth fault line detection device;
and the tripping outlet device receives the tripping command sent by the second comparator and drives the breaker of the corresponding line to trip.
6. The low resistance grounding system line detection system of claim 5, further comprising a relay connected to said trip exit device;
and the relay receives the first driving signal sent by the tripping outlet device and drives the hard contact outlet of the relay to be closed so as to trip the circuit breaker of the corresponding line.
7. The line detection system of claim 6, wherein the number of the relays is multiple, and each relay is respectively arranged on one line of the low-resistance grounding system.
8. The line detection system of claim 7, wherein the number of the circuit breakers is multiple, and each circuit breaker is disposed on one line and connected to the relay of the corresponding line.
9. The low resistance grounding system line detection system of claim 5, further comprising a trip timer connected to the second comparator of the high resistance ground fault line detection device;
and the trip timer receives a second driving signal sent by the second comparator and feeds a trip command back to the second comparator.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110907750A (en) * | 2019-11-21 | 2020-03-24 | 国电南瑞南京控制***有限公司 | Power distribution main station single-phase earth fault positioning method and system based on medium resistance method |
| CN113746069A (en) * | 2020-05-28 | 2021-12-03 | 中国南方电网有限责任公司 | Protection method for grounding fault of grounding transformer |
-
2017
- 2017-08-23 CN CN201721065502.8U patent/CN206962435U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110907750A (en) * | 2019-11-21 | 2020-03-24 | 国电南瑞南京控制***有限公司 | Power distribution main station single-phase earth fault positioning method and system based on medium resistance method |
| CN113746069A (en) * | 2020-05-28 | 2021-12-03 | 中国南方电网有限责任公司 | Protection method for grounding fault of grounding transformer |
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Effective date of registration: 20210412 Address after: No.2, Tianhe south 2nd Road, Tianhe District, Guangzhou City, Guangdong Province Patentee after: Guangzhou Power Supply Bureau of Guangdong Power Grid Co.,Ltd. Patentee after: NR ELECTRIC Co.,Ltd. Address before: 510620, No. two, No. 2, Tianhe South Road, Guangzhou, Guangdong, Tianhe District Patentee before: GUANGZHOU POWER SUPPLY Co.,Ltd. Patentee before: NR ELECTRIC Co.,Ltd. |