Meixian Power Plant 125 mw unit has been put into operation since the pump occasionally a closing or tripping problem, without any signal relay card. After excluding the switchgear failure, according to the conventional method of checking the cable , the secondary circuit wiring and the relay and its rating are normal, start again often successful. Suspected to be dcs system soft failure caused, but the change in the control panel operation, there will still be this phenomenon.
2 test find the reason In order to find out the reason for this phenomenon, observe the change of each meter in the process of closing the switch to confirm what caused it to trip. Test voltage meter which monitors the microcomputer trip circuit, mA watch differential relay 1cj, 2cj action, ammeter monitoring thermal protection circuit. Good meter after the start, start to the pump, after a period of testing, and finally once a trip to the pump, while observing the mA ammeter deflection of the watch a bit, the other watch does not respond, the new xjl -0025 / 31-type integrated block signal relay lxj also action card, that is caused by the differential protection action trip. 3 root causes analysis Differential protection action, first of all suspect that there is a fault within the protected equipment. Through routine inspection, the pump motor and its cable are normal, the differential relay is calibrated, and the polarity of the current transformer is connected correctly. After eliminating the causes of equipment failure and wiring errors, differential protection operates during motor start-up, indicating that the differential current of the differential circuit exceeded the differential relay setting during this process. Under normal circumstances, the differential current caused by differential current loop there are two main reasons: First, both sides of the motor current transformer ratio error is different, there is a small difference current, the difference current is less than 5% of the motor rated current id . Second, both ends of the current transformer secondary load difference will cause the difference between the ratio, resulting in a poor current. The difference in current transformer load in the feed pump motor differential protection circuit is only a difference of the secondary cable length of about 50 m, and the power consumption of the differential relay is not more than 3 va at rated current and the secondary load is not weight. Check found to pump motor differential protection with the end of the current transformer models are lmzbj-10, b-level 15 times the rated current, the ratio of 600/5, the capacity of 40 va, fully able to meet the requirements of the secondary load. The above analysis is based on the normal operation of the condition, the motor starts, the situation is different. When the motor starts, the current is very large. The current transformer on both sides of the motor may be saturated. In this case, the secondary differential current may be very large due to the inconsistent magnetization characteristics of the current transformers. According to the relay factory in acheng lcd-12 differential relay setting instructions, the relay operating current setting izd = △ i1 × kk × in / n = 0.06 × 3 × 356/120 = 0.534a (where: △ i1- First, the end of the current transformer maximum error during normal operation, 0.04 ~ 0.06; kk-reliability factor, 2 to 3; in- motor rated current; n- current transformer ratio). Should be set at 1.0a position. The use of b-level transformer case, the differential relay operating current set at 1.5a, the braking factor of 0.4, the differential protection is still occasionally activated when the motor starts, is due to b-level current transformer magnetization saturation point Lower, anti-saturation capacity is low, can not meet the requirements of the differential relay. Usually require differential protection circuit current transformer using d-level, d-level transformer saturation point higher, not so easy to saturation, can reduce the difference between the current flowing through the differential loop when the motor starts. In the replacement of the d-level current transformer, while the differential relay operating current set at 1.0a, the braking factor of 0.4, no longer appeared to switch a switch that trip. | |
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2 test find the reason
In order to find out the reason for this phenomenon, observe the change of each meter in the process of closing the switch to confirm what caused it to trip.
Test voltage meter which monitors the microcomputer trip circuit, mA watch differential relay 1cj, 2cj action, ammeter monitoring thermal protection circuit. Good meter after the start, start to the pump, after a period of testing, and finally once a trip to the pump, while observing the mA ammeter deflection of the watch a bit, the other watch does not respond, the new xjl -0025 / 31-type integrated block signal relay lxj also action card, that is caused by the differential protection action trip.
3 root causes analysis
Differential protection action, first of all suspect that there is a fault within the protected equipment. Through routine inspection, the pump motor and its cable are normal, the differential relay is calibrated, and the polarity of the current transformer is connected correctly. After eliminating the causes of equipment failure and wiring errors, differential protection operates during motor start-up, indicating that the differential current of the differential circuit exceeded the differential relay setting during this process.
Under normal circumstances, the differential current caused by differential current loop there are two main reasons: First, both sides of the motor current transformer ratio error is different, there is a small difference current, the difference current is less than 5% of the motor rated current id . Second, both ends of the current transformer secondary load difference will cause the difference between the ratio, so there is a difference current. The difference in current transformer load in the feed pump motor differential protection circuit is only a difference of the secondary cable length of about 50 m, and the power consumption of the differential relay is not more than 3 va at rated current and the secondary load is not weight. Check found to pump motor differential protection with the end of the current transformer models are lmzbj-10, b-level 15 times the rated current, the ratio of 600/5, the capacity of 40 va, fully able to meet the requirements of the secondary load.
The above analysis is based on the normal operation of the condition, the motor starts, the situation is different. When the motor starts, the current is very large. The current transformer on both sides of the motor may be saturated. In this case, the secondary differential current may be very large due to the inconsistent magnetization characteristics of the current transformers. According to the relay factory in acheng lcd-12 differential relay setting instructions, the relay operating current setting izd = △ i1 × kk × in / n = 0.06 × 3 × 356/120 = 0.534a (where: △ i1- First, the end of the current transformer maximum error during normal operation, 0.04 ~ 0.06; kk-reliability factor, 2 to 3; in- motor rated current; n- current transformer ratio). Should be set at 1.0a position. The use of b-level transformer case, the differential relay operating current set at 1.5a, the braking factor of 0.4, the differential protection is still occasionally activated when the motor starts, is due to b-level current transformer magnetization saturation point Lower, anti-saturation capacity is low, can not meet the requirements of the differential relay. Usually require differential protection circuit current transformer using d-level, d-level transformer saturation point higher, not so easy to saturation, can reduce the difference between the current flowing through the differential loop when the motor starts. In the replacement of the d-level current transformer, while the differential relay operating current set at 1.0a, the braking factor of 0.4, no longer appeared to switch a switch that trip.
ÂXinxiang Lifeierte Filter Co., Ltd is specialized in manufacturing filter elements, filter housing, filter equipment, testing equipment and hydraulic parts.She is located in Xinxiang that is the center of filtration in China.Xinxiang Lifeierte Filter Co., Ltd integrates with oil filtration, water treatment and air purification to provide the society with more professional service and meet customers` demands. What`s more, Lifeierte has top-notch R&D team, professional technical team, effective production network and perfect after-sales service system. The corporate philosophy of Lifeierte is [to purify environment, to serve society, to manage faithfully,and to pursue excellence". The company also established the comprehensive cooperative relations with some famous design & research institutions and colleges. The quality of the product has reached the international advanced level and makes us achieve remarkable economic benefits.
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Mainly including:
National standard filters and filter elements, replacement of abroad filters and filter elements, the hydraulic equipment like oil filter machines and filter series, the filter detective equipment;
Compressed air filters and filter elements, air cleaning filter drums and filter-bag series, various kinds of air cleaning facilities in different patterns;
Kinds of water treating equipment like stainless steel water filters and filter elements, full automatic backwashing filters.
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The endeavor makes us more professional. The performance and the effect of our replace products are comparable with imports; in addition the performance and the quality of domestically-made filters or filter elements are also stable and reliable. All those have been selected and recognized by customers and research institutions.
testing standards are satisfied by the products
ISO2941- filter elements- the testing for the cracking resistance
ISO2942- filter elements-the identifying for the structural integrity
ISO2943- filter elements-the identifying for the compatibility between material and the liquid
ISO3723- filter elements-the testing method for the end load of filter elements
ISO3724- filter elements-the identifying for the fatigue properties of the filter elements
ISO3968- filter elements-the testing for determination of pressure differential/flow characteristics
ISO4572- filter elements-the testing for the multi-pass method for evaluating filtration performance.
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