Performance test of Residual Current Operated Prot

Performance test of residual current operated protector during operation

installing residual current operated protector is an important safety technical measure, but it is in the protection of long-term operation. Therefore, it is ubiquitous in the fields of electronic appliances, instruments and meters, automobiles, construction industry and so on. Its components will inevitably age or damage, affecting the changes of performance indicators. If it cannot be found and handled in time, it is related to personal safety, The consequences are conceivable. Therefore, the national standard expressly stipulates that the performance index of the protector in operation should be tested every year, which is very necessary

2 one of the misunderstandings in the performance index detection of the protector

is to replace the detection with a test jump. Test jump is the normal work of protector management, but it can only detect the existence of function qualitatively. Use the test jump button to test jump. Because of the different products of protectors, some zero sequence transformers cannot be checked whether they are good or bad; With the grounding test jump, because the protected power normally has the leakage current to the ground, at this time, the test jump grounding current of the protector action is not the real action current, that is to say, it can only preliminarily verify the action function of the protector

the second misunderstanding is the understanding of verifying the numerical error of the action current of the protector. The error of the current value estimated by the grounding test jump resistance is very large, because the resistance error of the general resistance is up to 10%, and there are temperature and other factors. The voltage also affects the size of the grounding current during the test jump. The difference between the maximum value and the minimum value of the voltage has exceeded 10% according to the national standard, so the residual current estimated by the grounding test jump resistance cannot be used as the basis for verifying the technical indicators

the third mistake is that the accuracy of the set current is not considered in the measurement of the action time of the protector. Author: zhushenmin, deputy dean of the school of material science and engineering, Shanghai Jiaotong University. The action time of the protector shall be measured according to the national standard, and the set value of its action current shall be 1, 2 or 5 times the rated action current. As mentioned above, the error of using the test jump resistance to estimate the target current is very large, so the action time measured by this method cannot be compared with the national standard to determine whether the measured action time is qualified

in view of the above reasons, using the above method to detect the performance index of the protector in operation cannot correctly determine whether its performance index is qualified

3 several specific problems in the detection operation

(1) detection and determination of the action current of the protector:

according to the national standard, the actual leakage action current of the tested residual current protector should be greater than the rated residual current non action current, and less than or equal to the rated residual current action current. This actual residual current action current, for the specific residual current protector, There is a numerical range for the values that do not exceed the standard. For example, for the protector with a rated operating current of 30mA, the actual residual current operating current range should be greater than 15mA and less than or equal to 30mA. The larger the rated operating current is, the larger the actual operating current range is. Therefore, in order to ensure the correct detection, one of the methods is to use the detector, which should have the function that the output current can be smoothly adjusted from zero, and its current is expressed to the accuracy of the national standard, so that it can be judged directly according to the check between the detected data and the standard; The second method is that the detector has the function of outputting adjustable current, and the accuracy of its ammeter may be lower than the relevant national standards. Such a detector should be examined and approved for an accuracy level. If the actual action current detected plus the maximum error of the detector does not exceed the national standards, it can be judged as qualified

(2) detection and determination of protector action time:

protector action time is generally related to the residual current connected, so the conditions for detecting leakage action time are: first, the residual current value connected should be accurate; Second, the timing start and the residual current should be connected at the same time; Third, the timer should have a certain accuracy level. Because the action current and time of the protector are related to personal safety and the selectivity of graded protection, the detector of the second method mentioned above cannot be used as the protector time measurement (which can be used as a preliminary judgment) for verification and judgment. Only the instrument with the function of smooth adjustment of the output current from zero and whose current is expressed to the accuracy specified in the national standard can be used

start timing when the preset current with poor anti-interference ability is connected to the protector. In this way, when the protector acts, the recorded time of connecting current is the measured action time. Check this time with relevant standards to determine whether it is qualified or not

(3) protector detection with load condition:

fixed deformation force measurement value. It is proposed that the detection of the action characteristics of the protector itself should generally be carried out offline, otherwise the residual current of the protected electricity will make it impossible for you to judge whether it is qualified by comparing the test data with relevant standards. For the protector with load, since the load neutral line is generally not controlled by the main switch of the protector (except for the four pole switch), the residual electric action current and time test have special requirements for the test instrument and test method. Do not damage the tester due to incorrect use. The actual operating current of each phase tested with load can only reflect the degree of unbalanced leakage of three-phase load, which cannot judge whether the performance index of the protector itself is qualified. As for the action time test of the protector under load, it can not judge whether the performance index of the protector itself is qualified or not, but as an accident investigation, this test may sometimes be required