CN111413562B - Monitoring and control method for high-overload transformer system - Google Patents
Monitoring and control method for high-overload transformer system Download PDFInfo
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- CN111413562B CN111413562B CN202010241885.XA CN202010241885A CN111413562B CN 111413562 B CN111413562 B CN 111413562B CN 202010241885 A CN202010241885 A CN 202010241885A CN 111413562 B CN111413562 B CN 111413562B
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Abstract
The invention provides a monitoring and control method for a high overload transformer system, which comprises an upper-level linkage protection method and a lower-level linkage protection method; the upper and lower linkage protection method comprises the following steps: acquiring the oil top temperature of the transformer, the temperature of an oil tank cover, the bottom temperature of a radiating fin, the current value of each low-voltage outgoing line loop of the transformer and the current value of a bus; and judging the oil top temperature of the transformer, the temperature of the oil tank cover, the bottom temperature of the radiating fin, the current value of each low-voltage outlet loop and the current value of the bus, judging the upper-level fault, the lower-level single-path fault and the lower-level bus fault, and executing protection according to conditions. The invention has the function of upper and lower linkage protection, can judge whether the fault of the high overload transformer occurs in a high-voltage part or a low-voltage part, and carries out different treatments on different fault types after judging the fault condition, thereby not only effectively protecting the high overload transformer, but also fully connecting the high overload transformer into a power grid for use, and leading the high overload transformer to safely, efficiently and reasonably operate.
Description
Technical Field
The invention relates to the technical field of transformer monitoring, in particular to a monitoring and control method for a high-overload transformer system.
Background
The short-time electric load rapid increase condition exists in rural power grid power distribution in China, namely the load is in a light load state in most of the whole year, but the load rapidly increases in ten days or half a month, and exceeds the rated load by 1.5 times or even 2 times, and the load is concentrated in the load condition within 2 to 3 hours; such as spring load, busy farming load, etc. in a farming net.
The high overload distribution transformer is a distribution transformer developed for solving the problem of short-term and rapid increase of electrical load; on the premise of ensuring the basic power consumption capacity, the requirement of small-load long-term power consumption is met, and the requirement of overload short-term power consumption is also considered; the energy-saving, high-efficiency and environment-friendly energy-saving transformer has the characteristics of energy conservation, high efficiency, environmental protection, small no-load current, low reactive loss, strong sudden short circuit resistance and the like. However, high overload distribution transformers are costly, have high overload capabilities, require more sophisticated and elaborate monitoring and control of the transformer, or else the burning out of the transformer results in greater losses and greater impact.
At present, the fault on-line detection of a high overload transformer can not distinguish whether the fault occurs in a high-voltage part or a low-voltage part; generally, when a fault occurs, the whole high overload transformer is directly tripped and protected by an open circuit; therefore, the power failure is performed in a part of unnecessary power failure areas, which is not beneficial to fully and reasonably utilizing the high overload transformer.
In addition, at present, there is no delay control method specially designed for a high overload transformer, and a long delay protection mode of a common transformer is usually applied to the high overload transformer, and only by increasing the long delay protection current, the high overload long delay protection function is realized, and various protection and thermal memory protection functions for the transformer are not provided. This approach clearly does not better embody the advantages of and fully exploit the performance of high overload transformers.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a monitoring and control method for a high overload transformer system, which has an upper-level and lower-level linkage protection function, can judge whether the fault of the high overload transformer occurs in a high-voltage part or a low-voltage part, and carries out different processing on different fault types after the fault condition is judged, so that the high overload transformer can be effectively protected, and can be fully connected into a power grid for use, and the high overload transformer can be safely, efficiently and reasonably operated.
In order to achieve the purpose, the invention is realized by the following technical scheme: a monitoring and control method for a high overload transformer system is characterized in that: the method comprises an upper-level linkage protection method and a lower-level linkage protection method; the upper-level and lower-level linkage protection method comprises the following steps:
acquiring the oil top temperature of the transformer, the temperature of an oil tank cover, the bottom temperature of a radiating fin and the current value of each low-voltage outgoing line loop of the transformer; adding current values of all low-voltage outgoing line loops of the transformer to obtain a bus current value;
judging the sizes of the oil top temperature of the transformer, the temperature of the oil tank cover, the bottom temperature of the radiating fin, the current value of each low-voltage outgoing line loop and the current value of a bus:
when the bus current value is less than a set safety value, and any one of the transformer oil top temperature, the oil tank cover temperature and the cooling fin bottom temperature is greater than a set protection value, or when the cooling fin bottom temperature is greater than the transformer oil top temperature set protection value, judging that a superior fault occurs; executing high-voltage tripping and open-circuit protection;
when the current value of any low-voltage outlet loop of the transformer is larger than the protection current value of the corresponding loop, judging that a lower-level single-path fault occurs, and judging the low-voltage outlet loop as a fault loop; executing fault loop tripping and open circuit protection;
when the bus current value is larger than the transformer protection current value, judging that a lower-level bus fault occurs; sequentially carrying out tripping and open circuit protection on the low-voltage outgoing line loops one by one according to a preset priority; and after any low-voltage outlet loop executes tripping and breaking protection, detecting whether the bus current value is larger than the transformer protection current value, if so, continuing to execute tripping and breaking protection of the next priority low-voltage outlet loop until the bus current value is smaller than or equal to the transformer protection current value.
According to the invention, the upper-lower linkage protection method can judge the front-end fault or the rear-end outgoing line fault of the high-overload transformer according to the current and the temperature, overcomes the difficulty that the high-voltage part of the high-overload transformer is difficult to directly detect, judges the running condition of the high-voltage part according to the size of the sum of the circuit values of the low-voltage outgoing line loop and the temperature condition of the high-overload transformer, and effectively judges the upper-level fault, namely the high-voltage part fault; in addition, the upper and lower linkage protection method can judge whether the fault of the high overload transformer occurs in a high-voltage part or a low-voltage part, and different fault types are processed after the fault condition is judged, so that the high overload transformer can be effectively protected, and can be fully connected into a power grid for use, and the high overload transformer can be safely, efficiently and reasonably operated.
Preferably, in the upper and lower level linkage protection methods, when the high voltage tripping and circuit breaking protection is executed, if the high voltage tripping and circuit breaking protection is failed to be executed, the tripping and circuit breaking protection is sequentially performed on the low voltage outgoing line loop according to a preset priority, so that the damage of the high overload transformer can be reduced;
when the tripping and open-circuit protection of the fault loop is executed, if the tripping and open-circuit protection of the fault loop fails to be executed, the high-voltage tripping and open-circuit protection is executed, so that the safety of lower-end power distribution facilities can be protected;
when tripping and open-circuit protection are carried out on the low-voltage outgoing line loops in sequence according to a preset priority, if the tripping and open-circuit protection execution of the low-voltage outgoing line loop of the current priority fails, tripping to execute the tripping and open-circuit protection of the low-voltage outgoing line loop of the next priority; and if the bus current value is still larger than the transformer protection current value after the low-voltage outlet loop tripping open-circuit protection of the last priority level is executed, executing high-voltage tripping open-circuit protection.
The invention detects whether the execution of the protection is successful or not when the protection is executed, if not, other protection measures are executed, thereby avoiding the damage of the high overload transformer or the lower end power distribution facility caused by communication fault or line fault and incapability of executing the protection, and further improving the safety performance.
Preferably, when the superior fault is determined to occur, an alarm prompt is also executed.
Preferably, a transient protection method is also included; the instantaneous protection method comprises the steps of detecting current data of three-phase current at the low-voltage side of a high overload transformer to obtain the maximum current value in the current data; and when the maximum current value is larger than or equal to the set instantaneous current protection value, tripping and open-circuit protection are executed.
Preferably, a short-delay protection method is also included; the short-delay protection method is characterized by detecting current data of three-phase current at the low-voltage side of the high-overload transformer and acquiring the maximum current value in the current data; when the maximum current value is larger than or equal to the short-delay protection current and is smaller than the set time limit switching value, executing inverse time limit delay timing; when the maximum current value is larger than or equal to the set time limit switching value, executing timing time limit delay timing; and when the timing reaches the set time, executing tripping and open circuit protection.
Preferably, the method also comprises an undervoltage protection method; the under-voltage protection method comprises the following steps: detecting voltage data of three-phase voltage at the low-voltage side of the high overload transformer to obtain the minimum voltage value in the voltage data; and when the minimum voltage value is less than the set undervoltage protection value, executing undervoltage alarm or tripping open-circuit protection.
Preferably, an overvoltage protection method is also included; the overvoltage protection method comprises the following steps: detecting voltage data of three-phase voltage at the low-voltage side of the high-overload transformer to obtain the maximum voltage value in the voltage data; and when the maximum voltage value is larger than the set overvoltage protection value, executing overvoltage alarm or tripping open-circuit protection.
Preferably, the method also comprises a multi-segment long delay protection method; the multi-segment long delay protection method comprises the following steps:
s1, setting the segment number N of the high overload transformer delay protection and setting each segment of long delay current LixValue of (3) and each section of long-time-delay thermal memory switch LhSWxThe on-off state of (a); wherein x is 1,2 … N; n is more than or equal to 2;
calculating the protection energy value Qa of each sectionxAnd unit cooling energy Qcx(ii) a Integrating the energy values Qv of each segmentxInitialization is zero;
s2, sampling current data of a sampling period for the three-phase current of the low-voltage side of the high overload transformer;
s3, acquiring a current effective value, a current period time Ci and a current maximum value Imax from current data of one sampling period;
s4, respectively connecting the maximum value Imax of the current with each segment of long delay current LixAnd (3) comparison:
for a current maximum value Imax ≦ long-delay current LixThe step A is executed:
step A, judging the long time-delay thermal memory switch LhSWxWhether to start: if the section is long, the thermal memory switch LhSW is delayedxOn, the period cooling energy value is subtracted to update the energy accumulation value QvxAnd jumping to step S2 to sample current data of the next sampling period; if the section is long, the thermal memory switch LhSW is delayedxClosing, then integrating the energy value QvxClearing and jumping to S2 step to sample current data of next sampling period;
for a maximum current value Imax > long delay current LixB1 and B2 steps are executed:
b1, calculating a period energy value Qe; will be usedAccumulating the period energy value Qe to the original energy accumulation value QvxAs the new energy accumulation value Qv of the segmentx；
B2, judging the new energy accumulation value Qv of the segmentxWith the protective energy value Qa of the segmentxThe size of (A) to (B):
if the new energy accumulation value Qv of the segmentxLess than or equal to the protection energy value Qa of the sectionxJumping to step S2 to sample current data of the next sampling period;
if the new energy accumulation value Qv of the segmentxGreater than the protective energy value QaxThen, whether protection has occurred is determined: if yes, directly jumping to the step S2 to sample current data of the next sampling period; otherwise, protection is performed, and then the step S2 is skipped to sample the current data of the next sampling period.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the invention has the function of upper and lower linkage protection, can judge whether the fault of the high overload transformer appears in the high-voltage part or the low-voltage part, and can carry out different treatments on different fault types after judging the fault condition, thereby not only effectively protecting the high overload transformer, but also fully connecting the high overload transformer into a power grid for use, and leading the high overload transformer to safely, efficiently and reasonably operate; when the protection is executed, whether the execution of the protection is successful is detected, if not, other protection measures are executed, the damage of a high overload transformer or a lower-end power distribution facility caused by communication fault or line fault and incapability of executing the protection is avoided, and the safety performance is further improved;
2. the invention has the function of multi-section long-delay protection, has the functions of section protection and thermal memory for the overload protection of the high overload transformer, can fully exert the high overload performance of the high overload transformer and can realize safe long-delay protection for the high overload transformer; the output is accurate; the protection curves can be set according to the performance pertinence of the high overload transformer, and are set in a compatible way and protected independently; the long-delay protection method can be flexibly applied to different units and different scenes;
3. the invention has the functions of instantaneous protection, short delay protection, undervoltage protection and overvoltage protection, and can improve the safety and reliability of the high overload transformer.
Drawings
FIG. 1 is a flow chart of a superior-inferior linkage protection method according to the present invention;
FIG. 2 is a flow chart of a multi-segment long delay protection method according to the present invention;
FIG. 3 is a flow chart of a preferred embodiment of the multi-segment long-delay protection method of the present invention;
FIG. 4 is a flow chart of the sampling step of the preferred embodiment of the multi-segment long delay protection method of the present invention;
FIG. 5 is a three-segment protection curve diagram of the multi-segment long delay protection method of the present invention;
fig. 6 is a protection curve diagram of the multi-segment long delay protection method in the invention when single-segment protection is adopted.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Example one
The embodiment provides a monitoring and control method for a high overload transformer system, which comprises an upper-level linkage protection method and a lower-level linkage protection method; the upper and lower linkage protection method comprises the following steps:
acquiring the oil top temperature of the transformer, the temperature of an oil tank cover, the bottom temperature of a radiating fin and the current value of each low-voltage outgoing line loop of the transformer; adding current values of all low-voltage outgoing line loops of the transformer to obtain a bus current value;
judging the sizes of the oil top temperature of the transformer, the temperature of the oil tank cover, the bottom temperature of the radiating fin, the current value of each low-voltage outgoing line loop and the current value of a bus:
when the bus current value is less than a set safety value, and any one of the transformer oil top temperature, the oil tank cover temperature and the cooling fin bottom temperature is greater than a corresponding set protection value, or when the cooling fin bottom temperature is greater than the transformer oil top temperature set protection value, determining that a superior fault occurs; executing high-voltage tripping and open-circuit protection;
when the current value of any low-voltage outlet loop of the transformer is larger than the protection current value of the corresponding loop, judging that a lower-level single-path fault occurs, and judging the low-voltage outlet loop as a fault loop; executing fault loop tripping and open circuit protection;
because the rated currents of the low-voltage outgoing line loops are not consistent, the current value of each low-voltage outgoing line loop is compared with the protection current value of the corresponding loop for judgment.
When the bus current value is larger than the transformer protection current value, judging that a lower-level bus fault occurs; sequentially carrying out tripping and open circuit protection on the low-voltage outgoing line loops one by one according to a preset priority; and after any low-voltage outlet loop executes tripping and breaking protection, detecting whether the bus current value is larger than the transformer protection current value, if so, continuing to execute tripping and breaking protection of the next priority low-voltage outlet loop until the bus current value is smaller than or equal to the transformer protection current value. The priority is set by a user and can be set according to the importance level of the low-voltage outgoing line loop.
The set safety value, the set protection value of the oil top temperature of the transformer, the protection current value of the corresponding loop and the protection current value of the transformer are set by a user according to the parameters of the high overload transformer.
The temperature of the oil top of the transformer, the temperature of the oil tank cover and the temperature of the bottom of the cooling fin can be obtained by installing the existing temperature sensor at the corresponding position of the transformer. The current value of each low-voltage outgoing line loop of the transformer can be obtained through a current sensor, and the prior art can be adopted. The high-voltage tripping and circuit breaking protection and the low-voltage outlet circuit tripping and circuit breaking protection can be realized by the prior art, such as a circuit breaker.
According to the invention, the upper and lower-stage linkage protection method can judge the front-end fault or the rear-end outgoing fault of the high overload transformer according to the current and the temperature, and overcomes the difficulty that the high-voltage part of the high overload transformer is difficult to directly detect; for example, by monitoring the load of the low-voltage part, when the load of the low-voltage part is within the rated load of the transformer but the oil temperature of the transformer is abnormal, it is determined that the high-voltage part is abnormal, i.e. a superior fault; in addition, the upper and lower linkage protection method can judge whether the fault of the high overload transformer occurs in a high-voltage part or a low-voltage part, and different fault types are processed after the fault condition is judged, so that the high overload transformer can be effectively protected, and can be fully connected into a power grid for use, and the high overload transformer can be safely, efficiently and reasonably operated.
The preferred scheme is as follows: and when the superior fault is judged to occur, alarm prompt is also executed. When the high-voltage tripping and circuit breaking protection is executed, if the high-voltage tripping and circuit breaking protection is failed to execute, tripping and circuit breaking protection is sequentially carried out on a low-voltage outgoing line loop according to a preset priority, and damage to a high-overload transformer can be reduced;
when the tripping and open-circuit protection of the fault loop is executed, if the tripping and open-circuit protection of the fault loop fails to be executed, the high-voltage tripping and open-circuit protection is executed, so that the safety of lower-end power distribution facilities can be protected;
when tripping and open-circuit protection are carried out on the low-voltage outgoing line loops in sequence according to a preset priority, if the tripping and open-circuit protection execution of the low-voltage outgoing line loop of the current priority fails, tripping to execute the tripping and open-circuit protection of the low-voltage outgoing line loop of the next priority; and if the bus current value is still larger than the transformer protection current value after the low-voltage outlet loop tripping open-circuit protection of the last priority level is executed, executing high-voltage tripping open-circuit protection.
The invention detects whether the execution of the protection is successful or not when the protection is executed, if not, other protection measures are executed, thereby avoiding the damage of the high overload transformer or the lower end power distribution facility caused by communication fault or line fault and incapability of executing the protection, and further improving the safety performance.
Example two
The embodiment is a monitoring and control method for a high overload transformer system, and the difference from the first embodiment is that: the embodiment further includes a multi-segment long delay protection method, as shown in fig. 2; the multi-segment long delay protection method comprises the following steps:
s1, setting the segment number N of the high overload transformer delay protection and setting each segment of long delay current LixValue of (3) and each section of long-time-delay thermal memory switch LhSWxAnd each segment of the long delay time LtxAnd each section of long delay cooling time LthxThe value of (d); wherein x is 1,2 … N;
calculating the protection energy value Qa of each sectionxAnd unit cooling energy Qcx；
Qax＝Lix×Lix×Ltx
Qcx＝Qax/Lthx
Integrating the energy values Qv of each segmentxInitialization is zero;
s2, sampling current data of a sampling period for the three-phase current of the low-voltage side of the high overload transformer;
step S3, calculating a current effective value, a current period time Ci and a current maximum value Imax from the current data of one sampling period; the maximum current value Imax refers to the maximum value of three-phase current on the low-voltage side of the high overload transformer;
s4, respectively connecting the maximum value Imax of the current with each segment of long delay current LixAnd (3) comparison:
for a current maximum value Imax ≦ long-delay current LixThe step A is executed:
step A, judging the long time-delay thermal memory switch LhSWxWhether to start:
if the section of long-delay thermal memory switch LhSWxOn, the period cooling energy value is subtracted to update the energy accumulation value QvxAnd jumping to step S2 to sample current data of the next sampling period; if the section of long-delay thermal memory switch LhSWxClosing, then integrating the energy value QvxClearing and jumping to S2 step to sample current data of next sampling period;
specifically, the segment energy accumulation value Qv is updated by subtracting the period cooling energy valuexThe method comprises the following steps: comparing the energy accumulation value QvxAnd a periodic cooling energy value; wherein the periodic cooling energy value is unit cooling energy QcxX current cycle time Ci: if the energy accumulation value Qv of the segmentxIf the period cooling energy value is less than the period cooling energy value, the accumulated value Qv of the energy of the period is calculatedxClearing and jumping to S2 step to sample current data of next sampling period; otherwise, accumulating the energy of the sectionEvaluating QvxSubtracting the single-period cooling energy value as a new energy accumulation value Qv of the periodxThen jumping to step S2 to sample current data of next sampling period;
for a maximum current value Imax > long delay current LixB1 and B2 steps are executed:
b1, calculating a period energy value Qe;
Qe＝Imax×Imax×Ci；
accumulating the period energy value Qe to the original energy accumulated value QvxAs the new energy accumulation value Qv of the segmentx；
B2, judging the new energy accumulation value Qv of the segmentxWith the protective energy value Qa of the segmentxThe size of (A) to (B):
if the new energy accumulation value Qv of the segmentxLess than or equal to the protective energy value Qa of the sectionxJumping to step S2 to sample current data of the next sampling period;
if the new energy accumulation value Qv of the segmentxProtection energy value Qa of this segmentxThen, whether protection has occurred is determined: if yes, directly jumping to the step S2 to sample current data of the next sampling period; otherwise, protection is performed, and then the step S2 is skipped to sample the current data of the next sampling period.
The current data sampling of the three-phase current at the low-voltage side of the high overload transformer can be realized by a current sensor, and the prior art can be adopted; the protection can be implemented by adopting the prior art, and generally refers to the protection of a high-overload transformer by tripping and breaking a circuit breaker.
The multi-section long-delay protection method has the functions of opening or closing the thermal memory and can be selected by a user; the overload protection of the high overload transformer is generally judged according to the accumulated heat generated after the overload of the high overload transformer, and when the energy accumulated value Qvx(calorific value) to or above the protective energy value Qax(safe heat accumulation amount), tripping protection occurs; if the overload condition of the transformer with high overload occurs, the transformer recovers to the condition of being less than the rated current after being overloaded for a period of time, and then the overload condition occurs until the heating value is more than the safe heat accumulated quantity, and the transformer is trippedProtection; at this time, if the thermal memory function is started, the accumulated thermal energy generated when overload occurs can not be neglected, and the heat reduction in the time period smaller than the rated current can not be neglected, so that the accurate protection of the high overload transformer is realized.
The related parameters of the thermal memory function can be set by the user, and the cooling time LthxDifferent cooling coefficients can be correspondingly set according to different heat dissipation media, use environments and the located segmented protection intervals, and accurate protection control is performed on the high overload transformer.
The multi-section long-delay protection method aims at the overload protection of the high overload transformer, has the functions of section protection and thermal memory, can give full play to the high overload performance of the high overload transformer, and can also realize safe long-delay protection on the high overload transformer; the output is accurate; the transformer overload protection circuit has multi-section long delay protection, can be set according to the performance pertinence of a high overload transformer, and is characterized in that protection curves of all sections are set in a compatible manner and are protected independently; the long-delay protection method can be flexibly applied to different units and different scenes.
Preferably, as shown in fig. 3, in step B2, the new energy accumulation value Qv is obtainedxLess than or equal to the protection energy value Qa of the sectionxBefore the step S2, the method further includes the steps of: judging the protection energy value Qa of the sectionxEnergy accumulation value Qv new to the segmentxWhether the difference between is greater than or equal to the period energy value Qe: if yes, directly jumping to the step S2 to sample current data of the next sampling period; otherwise, the pre-trip protection mark is opened, and the long delay current Li of the section is usedxSetting the value as a protection value; calculating distance protection time Tb and pre-tripping times Tnum; then the next sampling period current data is sampled by jumping to step S2.
The calculation method of the distance protection time Tb and the pre-trip times Tnum is as follows:
Tb＝(Qax-Qvx)/Qcx×Ci
Tnum＝(Qax-Qvx)/Qcx×ADCnum；
ADCnum is the number of sampling points in a sampling period.
Correspondingly, in the step S2, in the sampling process, when the pre-trip protection flag is turned on, the sampled current values are compared with the protection values one by one, and the number of the sampled current values greater than the protection value in the sampling period is accumulated; and when the accumulated number exceeds the pre-trip times Tnum, executing protection.
Specifically, the step S2 includes the following sub-steps, as shown in fig. 3:
s21, initializing the accumulated value to zero;
s22, sampling the current value of the high overload transformer;
and step S23, judging whether the pre-trip protection mark is opened:
if the pre-tripping protection mark is closed, judging whether the sampling period is finished: if the sampling is finished, jumping to the step S3, otherwise, jumping to the step S22 to continue sampling;
if the pre-trip protection flag is on, executing step S24;
and step S24, comparing the sampled current value with the protection value:
if the sampling current value is less than the protection value, judging whether the sampling period is finished: if the sampling is finished, jumping to the step S3, otherwise, jumping to the step S22 to continue sampling;
if the sampling current value is larger than or equal to the protection value, adding one to the accumulated value times; comparing the accumulated value times with the pre-trip times Tnum:
if the accumulated value times is less than or equal to the pre-tripping times Tnum, judging whether the sampling period is finished: if the sampling is finished, jumping to the step S3, otherwise, jumping to the step S22 to continue sampling; and if the accumulated value times is larger than the pre-tripping times Tnum, executing protection.
In this embodiment, a 630KVA high overload transformer is taken as an example for explanation, a rated current is set to be 900A, the high overload transformer supports overload protection in a segmented manner, one segment supports 1.5 times of overload for 10 hours, the second segment supports 1.75 times of overload for 4 hours, and the third segment supports 2 times of overload for 1 hour, under the above overload conditions, the service life of the high overload transformer is not affected, and for the high overload transformer, the method is used on a high overload controller to perform three-segment long-delay protection on the high overload transformer.
The embodiment further provides a specific example, setting:
one section of parameters: one-segment long delay current Li1900A, a long delay time Lt 1600 minutes and a long delay cooling time Lth1A long-time-delay thermal memory switch LhSW of 600 minutes1Is closed;
two-stage parameters: two-stage long delay current Li21350A, two-stage long delay time Lt2240 minutes and a two-stage long delay cooling time Lth2A two-stage long-time-delay thermal memory switch LhSW of which the time is 500 minutes2Is closed;
three parameters are as follows: three-segment long delay current Li31575A, three-stage long delay time Lt360 minutes and three sections of long delay cooling time Lth3Is a three-section long-time-delay thermal memory switch LhSW with the time of 200 minutes3Is off.
Setting the number N of the sections of the high overload transformer delay protection to be 3; the obtained three-stage protection curve is shown in fig. 5, and as can be seen from fig. 5, the method of the embodiment can fully exert the high overload performance of the high overload transformer and can also realize safe long-delay protection on the high overload transformer.
If the number N of the segments of the high overload transformer delay protection is set to 1, and any one of the first-segment parameter, the second-segment parameter and the third-segment parameter is sampled for protection, the protection curve is as shown in fig. 6.
For example, if the setting is performed according to a certain parameter, when the overload current exceeds 900A, the delay time is too long, which easily causes the transformer to burn out; according to the two-stage parameter setting, when the current is less than 900A and is overloaded, the delay time is too short, premature protection tripping is easily caused, the performance of the high overload transformer is also wasted, and when the current exceeds 1350A and is overloaded, the delay time is too long, the high overload transformer is easily burnt; according to the three-stage parameter setting, when the current is less than 900A, the overload, the delay time is too short, premature protection tripping is easily caused, and the performance of the high overload transformer is very wasted. Therefore, the number N of segments for the time delay protection of the high overload transformer is set to 1, which is undesirable. Thus, N needs to be ≧ 2, e.g., N is 2, 3, 4, 5, 6, or even more.
EXAMPLE III
The present embodiment is a monitoring and control method for a high overload transformer system, and the difference from the first embodiment or the second embodiment is that: the embodiment also comprises an instantaneous protection method, a short-delay protection method, an undervoltage protection method and an overvoltage protection method.
The instantaneous protection method comprises the following steps: detecting current data of three-phase current at the low-voltage side of the high overload transformer to obtain the maximum current value in the current data; and when the maximum current value is larger than or equal to the set instantaneous current protection value, tripping and open-circuit protection are executed.
The short delay protection method comprises the following steps: detecting current data of three-phase current at the low-voltage side of the high overload transformer to obtain the maximum current value in the current data; when the maximum current value is larger than or equal to the short-delay protection current and is smaller than the set time limit switching value, executing inverse time limit delay timing; when the maximum current value is larger than or equal to the set time limit switching value, executing timing time limit delay timing; and when the timing reaches the set time, executing tripping and open circuit protection.
The under-voltage protection method comprises the following steps: detecting voltage data of three-phase voltage at the low-voltage side of the high-overload transformer to obtain the minimum voltage value in the voltage data; and when the minimum voltage value is smaller than the set undervoltage protection value, undervoltage alarm or tripping and open-circuit protection is executed.
The overvoltage protection method comprises the following steps: detecting voltage data of three-phase voltage at the low-voltage side of the high-overload transformer to obtain the maximum voltage value in the voltage data; and when the maximum voltage value is larger than the set overvoltage protection value, executing overvoltage alarm or tripping open-circuit protection.
The invention has the functions of instantaneous protection, short delay protection, undervoltage protection and overvoltage protection, and can improve the safety and reliability of the high overload transformer.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such modifications are intended to be included in the scope of the present invention.
Claims (8)
1. A monitoring and control method for a high overload transformer system is characterized in that: comprises an upper-level linkage protection method and a lower-level linkage protection method; the upper-level and lower-level linkage protection method comprises the following steps:
acquiring the oil top temperature of the transformer, the temperature of an oil tank cover, the bottom temperature of a radiating fin and the current value of each low-voltage outgoing line loop of the transformer; adding current values of all low-voltage outgoing line loops of the transformer to obtain a bus current value;
judging the sizes of the oil top temperature of the transformer, the temperature of the oil tank cover, the bottom temperature of the radiating fin, the current value of each low-voltage outgoing line loop and the current value of a bus:
when the bus current value is less than a set safety value, and any one of the transformer oil top temperature, the oil tank cover temperature and the cooling fin bottom temperature is greater than a corresponding set protection value; or when the bottom temperature of the radiating fin is larger than the set protection value of the oil top temperature of the transformer, judging that the upper-level fault occurs; executing high-voltage tripping and open-circuit protection;
when the current value of any low-voltage outlet loop of the transformer is larger than the protection current value of the corresponding loop, judging that a lower-level single-path fault occurs, and judging the low-voltage outlet loop as a fault loop; executing fault loop tripping and open circuit protection;
when the bus current value is larger than the transformer protection current value, judging that a lower-level bus fault occurs; sequentially carrying out tripping and open circuit protection on the low-voltage outgoing line loops one by one according to a preset priority; and after any low-voltage outlet loop executes tripping and breaking protection, detecting whether the bus current value is larger than the transformer protection current value, if so, continuing to execute tripping and breaking protection of the next priority low-voltage outlet loop until the bus current value is smaller than or equal to the transformer protection current value.
2. The monitoring and control method for a high overload transformer system according to claim 1, wherein: in the upper and lower level linkage protection method, when high-voltage tripping and open-circuit protection is executed, if the high-voltage tripping and open-circuit protection is failed to be executed, tripping and open-circuit protection is sequentially carried out on a low-voltage outgoing line loop according to a preset priority;
when the tripping and open-circuit protection of the fault loop is executed, if the tripping and open-circuit protection of the fault loop fails to be executed, the high-voltage tripping and open-circuit protection is executed;
when tripping and open-circuit protection are carried out on the low-voltage outgoing line loops in sequence according to a preset priority, if the tripping and open-circuit protection execution of the low-voltage outgoing line loop of the current priority fails, tripping to execute the tripping and open-circuit protection of the low-voltage outgoing line loop of the next priority; and if the bus current value is still larger than the transformer protection current value after the low-voltage outlet loop tripping open-circuit protection of the last priority level is executed, executing high-voltage tripping open-circuit protection.
3. The monitoring and control method for a high overload transformer system according to claim 1, wherein: and when the superior fault is judged to occur, alarm prompt is also executed.
4. The monitoring and control method for a high overload transformer system according to claim 1, wherein: also includes a transient protection method; the instantaneous protection method comprises the steps of detecting current data of three-phase current at the low-voltage side of a high overload transformer to obtain the maximum current value in the current data; and when the maximum current value is larger than or equal to the set instantaneous current protection value, tripping and open-circuit protection are executed.
5. The monitoring and control method for a high overload transformer system according to claim 1, wherein: also includes short delay protection method; the short-delay protection method is characterized by detecting current data of three-phase current at the low-voltage side of the high-overload transformer and acquiring the maximum current value in the current data; when the maximum current value is larger than or equal to the short-delay protection current and is smaller than the set time limit switching value, executing inverse time limit delay timing; when the maximum current value is larger than or equal to the set time limit switching value, executing timing time limit delay timing; and when the timing reaches the set time, executing tripping and open circuit protection.
6. The monitoring and control method for a high overload transformer system according to claim 1, wherein: the method also comprises an undervoltage protection method; the under-voltage protection method comprises the following steps: detecting voltage data of three-phase voltage at the low-voltage side of the high overload transformer to obtain the minimum voltage value in the voltage data; and when the minimum voltage value is less than the set undervoltage protection value, executing undervoltage alarm or tripping open-circuit protection.
7. The monitoring and control method for a high overload transformer system according to claim 1, wherein: the method also comprises an overvoltage protection method; the overvoltage protection method comprises the following steps: detecting voltage data of three-phase voltage at the low-voltage side of the high-overload transformer to obtain the maximum voltage value in the voltage data; and when the maximum voltage value is larger than the set overvoltage protection value, executing overvoltage alarm or tripping open-circuit protection.
8. The monitoring and control method for a high overload transformer system according to claim 1, wherein: the method also comprises a multi-segment long delay protection method; the multi-segment long delay protection method comprises the following steps:
s1, setting the segment number N of the high overload transformer delay protection and setting each segment of long delay current LixValue of (3) and each section of long-time-delay thermal memory switch LhSWxThe on-off state of (c); wherein x is 1,2 … N; n is more than or equal to 2;
calculating the protection energy value Qa of each sectionxAnd unit cooling energy Qcx(ii) a Integrating the energy values Qv of each segmentxInitialization is zero;
s2, sampling current data of a sampling period for the three-phase current of the low-voltage side of the high overload transformer;
s3, acquiring a current effective value, a current period time Ci and a current maximum value Imax from current data of one sampling period;
s4, respectively connecting the maximum value Imax of the current with each segment of long delay current LixAnd (3) comparison:
for a current maximum value Imax ≦ long-delay current LixThe step A is executed:
step A, judging the length of the sectionTime-delay thermal memory switch LhSWxWhether to start: if the section is long, the thermal memory switch LhSW is delayedxOn, the period cooling energy value is subtracted to update the energy accumulation value QvxJumping to S2 step to sample current data in next sampling period; if the section of long-delay thermal memory switch LhSWxClosing, then integrating the energy value QvxClearing and jumping to S2 step to sample current data of next sampling period;
for a maximum current value Imax > long delay current LixB1 and B2 steps are executed:
b1, calculating a period energy value Qe; accumulating the period energy value Qe to the original energy accumulation value Qv of the sectionxAs the new energy accumulation value Qv of the segmentx；
B2, judging the new energy accumulation value Qv of the segmentxWith the protective energy value Qa of the segmentxThe size of (A) to (B):
if the new energy accumulation value Qv of the segmentxLess than or equal to the protective energy value Qa of the sectionxJumping to step S2 to sample current data of the next sampling period;
if the new energy accumulation value Qv of the segmentxGreater than the protective energy value QaxThen, judge whether protection has taken place: if yes, directly jumping to the step S2 to sample current data of the next sampling period; otherwise, protection is performed, and then the step S2 is skipped to sample the current data of the next sampling period.
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