1. Ph¹m vi 9 Tµi liÖu tham kh¶o
The minister of posts and telematics
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The minister of posts and telematics
Decides Article 1.- To promulgate together with this Decision 04 technical standards on Telecommunication Terminal Equipment as follows:
Code: TCN 68-207: 2002
Code: TCN 68-208: 2002
Code: TCN 68-209: 2002
Code: TCN 68-210: 2002 Article 2.- These technical standards mentioned in the Article 1 take effect 15 (fifteen) days after signing of this Decision. Article 3.- The Director General of the Ministry’s Office, the Director General of the Department of Science & Technology, the heads of the agencies attached to the Ministry of Posts and Telematics and organizations and individuals engaged shall have to implement this Decision. For the minister of posts and telematicsStanding deputy minister (Signed and sealed) Mai Liem Truc electromagnetic compatibility (EMC) Power frequency magnetic field immunity Testing and measurement techniques (Issued together with the Decision No. 28/2002/QD-BBCVT of December 18, 2002 of the Minister of Posts and Telematics) 1. Scope This technical standard specifies the immunity requirements of equipment, only under operational conditions, to magnetic disturbances at power frequency related to: - Residential and commercial locations; - Industrial installations and power plants; - Medium voltage and high voltage sub-stations. The applicability of this standard to equipment installed in different locations is determined by the presence of the phenomenon, as specified in clause 3. This standard does not consider disturbances due to capacitive or inductive coupling in cables or other parts of the field installation. Other IEC standards dealing with conducted disturbances cover these aspects. The object of this standard is to establish a common and reproducible basis for evaluating the performance of electrical and electronic equipment for household, commercial and industrial applications when subjected to magnetic fields at power frequency (continuous and short duration field). The standard defines: - Recommended test levels; - Test equipment; - Test set-up; - Test procedure. Other kinds of magnetic fields would be object of standardization: - Fields at the power frequencies (16 2/3 - 20 or 30 - 400 Hz); - Fields of harmonic currents (100 Hz to 2000 Hz); - Fields of higher frequencies (up to 150 kHz, e.g. for mains signalling systems); - D.C. fields. Note: This standard could be applied to telecommunication equipments. 2. Normative references
3. General The magnetic fields to which equipment is subjected may influence the reliable operation of equipment and systems. The following tests ate intended to demonstrate the immunity of equipment when subjected to power frequency magnetic fields related to the specific location and installation condition of the equipment (e.g. proximity of equipment to the disturbance source). The power frequency magnetic field is generated by power frequency current in conductors or, more seldom, from other devices (e.g. leakage of transformers) in the proximity of equipment. As for the influence of nearby conductors, one should differentiate between: - The current under normal operating conditions, which produces a steady magnetic field, with a comparatively small magnitude; - The current under fault conditions which can produce comparatively high magnetic fields but of short duration, until the protection devices operate (a few milliseconds with fuses, a few seconds for protection relays). The test with a steady magnetic field may apply to all types of equipment intended for public or industrial low voltage distribution networks or for electrical plants. The test with a short duration magnetic field related to the fault conditions, requires test levels that differ from those for steady state conditions; the highest values apply mainly to equipment to be installed in exposed places of electrical plants. The test field waveform is that of power frequency. In many cases (household areas, sub-stations and power plant under normal conditions), the magnetic field produced by harmonics is negligible. However, in very special cases like heavy industrial areas (large power converters, etc.) they occur, and will be considered in a future revision of this standard. 4. Definitions 4.1. EUT Equipment under test. 4.2. Induction coil Conductor loop of defined shape and dimensions, in which flows a current, generating a magnetic field of defined constancy in its plane and in the enclosed volume. 4.3. Induction coil factor Ratio between the magnetic field strength generated by an induction coil of given dimensions and the corresponding current value; the field is that measured at the centre of the coil plane, without the EUT. 4.4. Immersion method Method of application of the magnetic field to the EUT, which is placed in the centre of an induction coil (figure 1). 4.5. Proximity method Method of application of the magnetic field to the EUT, where a small induction coil is moved along the side of the EUT in order to detect particularly sensitive areas. 4.6. Ground (reference) plane (GRP) A flat conductive surface whose potential is used as a common reference for the magnetic field generator and the auxiliary equipment (the ground plane can be used to close the loop of the induction coil, as in figure 4). (IEV 161-04-36, modified). 4.7. Decoupling network, back filter Electrical circuit intended to avoid reciprocal influence with other equipment not submitted to the magnetic field test. 5. Test levels The preferential range of test levels, respectively for continuous and short duration application of the magnetic field, applicable to distribution networks at 50 Hz and 60 Hz, is given in table 1 and Table 2. The magnetic field strength is expressed in A/m; 1 A/m corresponds to a free space induction of 1.26 T.
Information on the selection of the test levels is given in annex C. Information on actual levels is given in annex D. 6. Test equipment The test magnetic field is obtained by a current flowing in an induction coil; The application of test field to the EUT is by the immersion method. An example of application of the immersion method is given in figure 1. The test equipment includes the current source (test generator), the induction coil and auxiliary test instrumentation.
The generator, with the output waveform corresponding to the test magnetic field, shall be able to deliver the required current in the induction coils specified in 6.2. The generator power capability shall therefore be dimensioned by taking into account the coil impedance; the inductance may range from 2.5 H for the 1m standard coil, to several H (e.g. 6 H) for a rectangular induction coil (1m 2.6 m, see 6.2). The specifications of the generator are: - Current capability, determined by the maximum selected test level and induction coil factor (see 6.2.2 and annex A), ranging from 0.87 m-1 (1 m standard coil for testing table-top or small equipment) to 0.66 m-1 (rectangular induction coil, 1 m 2.6 m, for testing floor standing or large equipment); - Operability in short circuit condition; - Low output terminal connected to the earth terminal (for connection to the safety earth of the laboratory); - Precautions to prevent the emission of large disturbances that may be injected in the power supply network or may influence the test results. The characteristics and performances of the current source or test generator for the different fields considered in this standard are give in 6.1.1.
The current source typically consists of a voltage regulator (connected to the mains distribution network), a current transformer and a circuit for the control of short duration application. The generator shall be able to operate in continuous mode or short duration mode. Specifications
Note: The output current range, for the standard coil is from 1.2 A to 120 A for continuous mode, and from 350 A to 1200 A for short duration mode. The waveform of the output current is a sinusoid. The schematic circuit of the generator is given in figure 2.
In order to compare the results for different test generators, the essential characteristics of the output current parameters shall be verified. The output current shall be verified with the generator connected to the standard induction coil specified in 6.2.1.a; the connection shall be realized by twisted conductors of up to 3m length and suitable cross-section. The emission of disturbances by the generator shall be verified (see 6.1). The characteristics to be verified are: - Output current value; - Total distortion factor. The verifications shall be carried out with a current probe and measurement instrumentation having 2% accuracy. 6.2. Induction coil 6.2.1. Characteristics of the induction coil The induction coil, connected to the test generator previously defined (see 6.1.1), shall generate a field strength corresponding to the selected test level and the defined homogeneity. The induction coil shall be made of copper, aluminum or any conductive non-magnetic material, of such cross-section and mechanical arrangement as to facilitate its stable positioning during the tests. A same coil is suitable for the generation of the magnetic fields considered in this standard; it may be a "single turn" coil and shall have a suitable current capability, as may be necessary for the selected test level. Multi-turn coils may be used in order to have a lower testing current. Induction coil shall be adequately dimensioned to surround the EUT (three orthogonal positions). Depending on the size of the EUT, induction coils of different dimensions may be used. The dimensions recommended below are suitable for the generation of magnetic fields over the whole volume of the EUT's (table-top equipment or floor-standing equipment), with an acceptable variation of 3 dB. The characteristics of induction coils in respect of the magnetic field distribution are given in annex B. a) Induction coil for table-top equipment The induction coil of standard dimensions for testing small equipment (e.g. computer monitors, watt-hour meters, transmitters for process control, etc.) has a square (or circular) form with 1 m side (or diameter), made of a conductor of relatively small cross-section. The test volume of the standard square coil is 0.6 m 0.6 m 0.5 m (height). A double coil of standard size (Helmholtz coil) could be used in order to obtain a field homogeneity better than 3 dB or for testing larger EUT's. The double coil (Helmholtz coil) shall comprise of two or more series of turns, properly spaced (see figure 6, figure B.4, figure B.5). The test volume of a double standard size coil, 0.8 m spaced, for a 3 dB homogeneity is 0.6 m 0.6 m 1 m (height). For example, the Helmholtz coil, for a 0.2 dB inhomogeneity, have dimensions and separation distances as given in figure 6. b) Induction coil for floor-standing equipment Induction coils shall be made according to the dimensions of the EUT and the different field polarizations. The coil shall be able to envelop the EUT; the coil dimensions shall be such as to give a minimum distance of coil conductors to EUT walls equal to 1/3 of the dimension of the EUT considered. The coils shall be made of conductors of relatively small cross-section. Note: Due to the possible large dimensions of EUT's, the coils may be made of "C" or "T" sections in order to have sufficient mechanical rigidity. The test volume is determined by the testing area of the coil (60% 60% of each side) multiplied by a depth corresponding to 50 % of shorter side of the coil. 6.2.2. Calibration of the induction coil, coil factor In order to make it possible to compare the test results from different test equipment, the induction coils shall be calibrated in their operating condition, before conducting the test (without the EUT, in free space condition). An induction coil of the correct dimensions for the EUT dimensions, shall be positioned at 1 m minimum distance from the wall of the laboratory and any magnetic material, by using insulating supports, and shall be connected to the test generator as prescribed in 6.1.2. Appropriate magnetic field sensors shall be used to verify the magnetic field strength generated by the induction coil. The field sensor shall be positioned at the centre of the induction coil (without the EUT) and with suitable orientation to detect the maximum value of the field. The current in the induction coil shall be adjusted to the field strength specified by the test level. The calibration shall be carried out at power frequency. The calibration procedure shall be carried out with the test generator and induction coil. The coil factor is determined (and verified) by the above procedure. The coil factor gives the current value to be injected in the coil to obtain the required test magnetic field (H/I). Information on the measurement of the test magnetic field is given in annex A.
The test instrumentation includes the current measuring system (sensors and instrument) for setting and measuring the current injected in the induction coil. Note: The termination networks, back filters, etc. on power supply, control and signal lines that is part of the test set-up for other tests may be maintained. The current measuring system is a calibrated current, measuring instrument, probe or shunt. The accuracy of the measurement instrumentation shall be 2%. 6.3.2. Auxiliary instrumentation The auxiliary instrumentation comprises a simulator and any other instrument necessary for the operation and verification of the EUT functional specifications. 7. Test set-up The test set-up comprises the following components: - Ground (reference) plane (GRP); - Equipment under test (EUT); - Test generator. Precautions shall be taken if the test magnetic field may interfere with the test instrumentation and other sensitive equipment in the vicinity of the test set-up. Examples of test set-ups are given in the following figures: Figure 3: Example of test set-up for table-top equipment Figure 4: Example of test set-up for floor-standing equipment. 7.1. Ground (reference) plane The ground plane (GPR) shall be placed in the laboratory: the EUT and auxiliary test equipment shall be placed on it and connected to it. The ground plane shall be a non-magnetic metal sheet (copper or aluminum) of 0.25 mm thickness; other metals may be used but in this case they shall have 0.65 mm minimum thickness. The minimum size of the ground plane is 1 m 1 m. The final size depends on the dimensions of the EUT. The ground plane shall be connected to the safety earth system of the laboratory. 7.2. Equipment under test The equipment is configured and connected to satisfy its functional requirements. It shall be placed on the GRP with the interposition of a 0.1 m thickness insulating support (e.g. dry wood). The equipment cabinets shall be connected to the safety earth directly on the GRP via the earth terminal of the EUT. The power supply, input and output circuits shall be connected to the sources of power supply, control and signal. The cables supplied or recommended by the equipment manufacturer shall be used. In absence of any recommendation, unshielded cables shall be adopted, of a type appropriate for signals involved. All cables shall be exposed to the magnetic field for 1m of their length. The back filters, if any, shall be inserted in the circuit at 1 m cable lengths from the EUT and connected to the ground plane. The communication lines (data lines) shall be connected to the EUT by the cables given in the technical specification or standard for this application.
The test generator shall be placed at less than 3 m distance from the induction coil. One terminal of the generator shall be connected to the ground plane as far as used. 7.4. Induction c;oil The induction coil, of the type specified in 6.2.1, shall enclose the EUT placed at its centre. Different induction coils may be selected for testing in the different orthogonal directions, according to the general criteria specified in 6.2.1 a) and b). Induction coils used in the vertical position (horizontal polarization of the field) can be bonded (at the foot of one vertical conductor) directly to the ground plane, which represents the low side of the coil, as a part of it. In this case, 0.1 m minimum distance from EUT to the ground plane is sufficient. The induction coil shall be connected to the test generator in the same way as for the calibration procedure specified in 6.2.2 The induction coil selected for the tests shall be specified in the test plan. 8. Test procedure The test procedure shall include: - Verification of the laboratory reference conditions; - Preliminary verification of the correct operation of the equipment; - Carrying out of the test; - Evaluation of the test results. 8.1. Laboratory reference conditions In order to minimize the effect of the environmental parameters on the test results, the test shall be carried out in climatic and electromagnetic reference conditions as specified in 8.1.1 and 8.1.2. 8.1.1. Climatic conditions The test shall be carried out in standard climatic conditions in accordance with IEC 68-1: - Temperature: 150C to 35oC; - Relative humidity: 25% to 75%; - Atmospheric pressure: 86 kPa to 106 kPa.
The electromagnetic conditions of the laboratory shall be such to guarantee the correct operation of the EUT in order not to influence the test results; otherwise, the tests shall be carried out in a Faraday cage. In particular, the electromagnetic field value of the laboratory shall be at least 20 dB lower than the selected test level.
The test shall be carried out on the basis of a test plan including verification of the performances of the EUT as defined in the technical specification. The power supply, signal and other functional electrical quantities shall be applied within their rated range. If the actual operating signals are not available, they may be simulated. Preliminary verification of equipment performances shall be carried out prior to applying the test magnetic field. The test magnetic field shall be applied by the immersion method to the EUT, previously set-up as specified in 7.2. The test level shall not exceed the product specification.
The test field strength and the duration of the test shall be as determined by the selected test level, according to the different type of field (continuous of short duration field) established in the test plan. a) Table-top equipment The equipment shall be subjected to the test magnetic field by using the induction coil of standard dimensions (1 m 1 m) specified in 6.2.1 a) and show in figure 3. The induction coil shall then be rotated by 900 in order to expose the EUT to the test field with different orientations. b) Floor-standing equipment The equipment shall be subjected to the test magnetic field by using induction coils of suitable dimensions as specified in 6.2.1 b); the test shall be repeated by moving and shifting the induction coils, in order to test the whole volume of the EUT for each orthogonal direction. The test shall be repeated with the coil shifted to different positions along the side of the EUT, in steps corresponding to 50% of the shortest side of the coil. Note: The moving of the induction coil in steps corresponding to 50% of the shortest side of the coil gives overlapping test fields. The induction coil shall then be rotated by 900 in order to expose the EUT to the test field with different orientations and the same procedure. 9. Test results and test report This clause gives a guide for the evaluation of the test results and for the test report, related to this standard. The variety and diversity of equipment and systems to be tested make the task of establishing the effects of this test on equipment and systems difficult. The test results shall be classified on the basic of the operating conditions and the functional specifications of the equipment under test, as in the following, unless different specifications are given by product committees or product specifications: 1) Normal performance within the specifications limits; 2) Temporary degradation or loss of function or performance which is self-recoverable; 3) Temporary degradation or loss of function or performance which requires operator intervention or system reset; 4) Degradation or loss of function which is not recoverable due to damage of equipment (components) or software, or loss of data. Equipment shall not become dangerous or unsafe as a result of the application of the tests defined in this standard. In the case of acceptance tests, the test program and the interpretation of the test results have to be described in the specific product standard. As general rule, the test result is positive if the equipment shows its immunity, for all the period of application of the test, and at the end of the tests the EUT fulfils the functional requirements established in the technical specification. The technical specification may define effects on the EUT, that may be considered insignificant and therefore acceptable. For these conditions it shall be verified that the equipment is able to recover its operative capabilities by itself at the end of the test; the time interval during which the equipment has lost its functional capabilities shall be therefore recorded. These verifications are binding for the definitive evaluation of the test result. The test report shall include the test conditions and the test results. 
Table-top equipment Floor-standing equipment Figure 1: Example of application of the test field by the immersion method
Vr: Voltage regulator C: Control circuit Tc: Current transformer
Figure 3: Example of test set-up for table-top equipment
Figure 4: Example of test set-up for floor-standing equipment References common to figure 3 and figure 4
Figure 5: Example of investigation of susceptibility to magnetic field by the proximity method
Figure 6: Illustration of Helmholtz coils Каталог: Lists -> QuanLyVanBan -> Attachments Attachments -> CỘng hoà Xà HỘi chủ nghĩa việt nam độc lập Tự do -hạnh phúc Attachments -> THỦ TƯỚng chính phủ Số: 118 Attachments -> Tcn 68-187: 1999 MỤc lục lời nóI ĐẦU Attachments -> Lêi nãi ®Çu Tiªu chuÈn Ngµnh tcn 68-176: 2003 "DÞch vô ®iÖn tho¹i trªn m¹ng ®iÖn tho¹i c ng céng Tiªu chuÈn chÊt lîng" Attachments -> Môc lôc Lêi nãi ®Çu 5 QuyÕt ®Þnh ban hµnh cña Tæng côc trëng Tæng côc Bu ®iÖn 7 Ph¹m vi ¸p dông Attachments -> Lêi nãi ®Çu Tiªu chuÈn Ngµnh tcn 68-186: 2003 "DÞch vô ®iÖn tho¹i trªn m¹ng di ®éng mÆt ®Êt c ng céng Tiªu chuÈn chÊt lîng" Attachments -> T¬ng thÝch ®iÖn tõ (emc) miÔn nhiÔm ®èi víi hiÖn tîng phãng tÜnh ®iÖn ph¬ng ph¸p ®o vµ thö Attachments -> 1. Ph¹m vi 9 Tµi liÖu tham chiÕu chuÈn Attachments -> * QuyÕt ®Þnh ban hµnh cña bé trëng bé bu chÝnh viÔn th ng 7 Attachments -> Adsl internet access service tải về 378.46 Kb. Chia sẻ với bạn bè của bạn:
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