Regulatory authority use EMC PARTNER's HAR1000 to enforce Harmonic and Flicker CE requirements in Germany

Transcription

1 Emission Measurements Regulatory authority use EMC PARTNER's HAR1000 to enforce Harmonic and Flicker CE requirements in Germany Martin Lutz, Reto Casanova, Nicholas Wright Contents 1. Introduction Important points when selecting a Harmonics and Flicker measurement system Measurement of HAR1000-1P at RegTP in Berlin... 6

2 1. Introduction The Regulatory Authority for Telecommunication and Post (RegTP), is a high level federal authority within the Federal Ministry of Economics and Labour, with headquarters in Bonn Germany. The Authority was established on 1st January 1998 with the aim of enforcing European regulations relating to CE marking. HAR1000s have been purchased to support the RegTP in fulfilling this aim. RegTP has effective procedures and instruments with which to enforce the regulatory aims, these include information and investigative rights as well as sanctions against transgressors. In September 2003, the German RegTP ordered 12 HAR1000-1P Harmonic & Flicker systems with an option on a further 13 units which they took up in June Making a total of 25 systems. The request was based on a public tender dated 2nd September 2003 for Harmonics and Flicker measurement systems. The Technical specification of the tender stated that the equipment should comply with the following published standards IEC Harmonic Measurements IEC Flicker Measurements IEC Definition of Harmonic measurement systems When the RegTP awarded the tender to EMC PARTNER, the failed bidders attempted to discredit the HAR1000 and EMC PARTNER. Neither attempt succeeded. The RegTP did however decide to test two units before accepting delivery of the remaining 10. Exhaustive tests on the HAR1000s carried out by RegTP personnel did show some discrepancies that had to be rectified before they could accept delivery of these units. EMC PARTNER classified these discrepanices into 2 areas, minor software anomalies and, minor hardware issues. EMC PARTNER resolved the minor software glitches immediately and the hardware issues were defined as the following: 1. Conducted emissions in the frequency range 150 khz to 30 MHz were too high. 2. Flicker measured above 1.8 kw was not correct because the HAR1000 amplifier could not compensate for disturbances and the voltage drop of the EUT. 3. The tender specified an A/D converter type not used in HAR1000. These issues were consequently investigated and resolved by the following actions: 1. Emission measurements showed that the Pentium computer used in the HAR1000 was the source of this disturbance. The original 288 MHz computer used in HAR1000 was verified by an accredited Swiss test house and the emission levels were within specification. The problem was solved by additional filters in Pentium equipped HAR1000s. 2. Software in the HAR1000 was updated to guarantee the amplifier can compensate all disturbances on the power supply up to a power rating of 2 kw. 3. The A/D converter type was replaced by the type specified. Comparisons show there is no difference in test results obtained using the original HAR1000 and the new A/D converter types. 4. Additionally the software was updated to comply with the latest IEC requirements (200 ms measuring windows and the inclusion of interharmonics). 2 In a second test round with the 2 modified HAR1000 units, a detailed verification

3 program was carried out by RegTP and EMC PARTNER personnel. The HAR1000 was accepted as fully meeting the tender specification and all remaining units were delivered. 2. Important points when selecting a Harmonics and Flicker measurement system When selecting a solution for Harnomic and Flicker testing a number of issues need to be considered. Over the past ten years many issues have been introduced which are based more on the limitations of available measurement systems or to "justify" the cost of over-priced system's non-relevant features. This section attempts to clarify some of the more important selection considerations and why these are applicable. 2.1 Amplifiers To measure Harmonics or Flicker correctly, a linear amplifier must be used, to prevent distortion on the public power supply from influencing measurement results. It has been claimed that the HAR1000 uses an active filter instead of an amplifier and therefore the measurement results will be influenced by disturbances and impedance of the public power supply. EMC PARTNER's Comments HAR1000 uses an amplifier with limited working range. Within its working range the amplifier is equivalent to a full range amplifier. During Flicker measurements the amplifier reduces power supply impedance to nearly zero Ohm and during Harmonics measurement the power supply harmonic distortion is maintained below the limit of IEC The voltage distortion is continuously checked and included in the test report. Measurements made by RegTP, back-up the EMC PARTNER statement. HAR1000-1P including harmonics and flicker analysis, amplifier and LIN 2.2 Standard compliance Changes to the standards, particularly for Harmonics & Flicker, have been frequent. Sometimes changes have been introduced before test equipment to the old version has been established on the market. This is frustrating for users and test equipment manufacturers alike but reflects the complexity of the subject. Major issues with the first Harmonics standard published 1995 were the class D evaluation and non repeatable measurement results for fluctuating Harmonics. These two points, along with other housekeeping issues have been taken care of in Amendment 14 or IEC Ed.2.1 published Class D is now limited to only a few product types which are listed in the standard and the measurement and calculation of Harmonics has been change to an averaging method. Finally IEC published 2002 has resolved problems of harmonic measurement on 50 and 60 Hz power supplies and the increased interharmonics caused be counter measure such as Power Factor Correction (PFC). EMC PARTNER's Comments EMC Partner has always updated the HARCS software to meet latest published standards within a short time period. Updates for existing HAR1000 customers are avaialble as free downloads from our website (www-emc-partner.com). HARCS software versions >4.01 include all measurement techniques called out in the above standards. 3

4 Flicker emission measurement with the HARCS Software Harmonic emission measurement with the HARCS Software 2.3 Use of Windows software Windows software cannot be used for real time processes such as the Fourier analysis used in Harmonic measurements. EMC PARTNER's Comments HAR1000 only uses Window software to provide the user interface and for data presentation. This has many advantages for users, who are able to evaluate measurement results in a clear visual format. Inside HAR1000 is a separate PC which runs firmware in real time to perform the Fourier analysis. 2.4 Using Windows 2000 or Windows XP Windows 2000 and Windows XP have particular requirements over previous versions. EMC PARTNER's Comment Earlier versions of HARCS software did have problems communicating under Windows 2000 or XP. The problem has been overcome by using HAR1000 on a USB port through a USB to Serial converter. 2.5 Harmonic Current Measurement Accuracy IEC defines the measurement accuracy to be within 5 % of the limits or 0.2 % of the nominal current. EMC PARTNER's Comment HAR1000 guarantees this accuracy for currents between 30% and 100% of the nominal (EUT current). Should the current drop below 30% of the selected measurement range, the range will automatically be switched, or if manual mode is selected, a message is displayed suggesting the operator change ranges. 2.6 The 2.5 minute test time myth There is a myth that a test time of 2.5 minutes for harmonic testing is a requirement. 4

5 EMC PARTNER's Comment IEC does not specify a test time of 2.5 minutes. The 2.5 minutes mentioned is an observation period. Test time for each product is different and will be greater than the 2.5 minute observation period. 2.7 IEC specifies a voltage range of 400 V IEC specifies a measurement system for single AND three phase systems up to 400 V. EMC PARTNER's Comment HAR1000-1P is a single phase measurement system suitable for L to N voltages up to 280 V. The three phase HAR1000-3P is designed for voltages up to 415 V between phases. The HAR1000 system provides its users a choice and investment protection that fulfils the IEC requirement for both one and three phase product testing. 2.8 The test system should deliver 16 A to an EUT There is a mis-conception that part of the EUT input current is used for the power amplifier in HAR1000, thus reducing EUT power availability and the operating range of HAR1000. EMC PARTNER's Comment The innovative solution of EMC PARTNER enables 16 A EUTs to be tested to full rating. Power for the amplifier is separate to the EUT power. HAR1000 can be used on public power supplies rated to 16 A because of the separate connection solution. Total power consumption consists of the EUT power (maximum 16 A) plus the amplifier and controller power rated separately at 5 A. 2.9 Power supply impedance must be reduced to nearly zero Ohm The public power supply has an impedance which is not constant at every location. In order to accurately determine Flicker levels, voltage fluctuations can only be measured over a defined impedance. The impedance value for Flicker measurements is specified in the IEC for single phase to be j 0.25 and for three phase to be j 0.15 (Line) and j 0.10 (Neutral). It is therefore essential to eliminate the undefined public power supply impedance. EMC PARTNER's Comment HAR1000 uses an amplifier to compensate the public power supply to zero Ohm impedance. Measurements by the RegTP verified this important point. Every HAR1000 owner can easily verify this (see measurement 3.3). 3.0 Verification of hardware impedance network It is desirable, during instrument calibration, to verify the LIN hardware. These components, used for Flicker measurement provide a defined network impedance of j EMC PARTNER's Comment HAR1000 has both a hard and software Line Impedance Network (LIN). Verification is made easier by plugs on the HAR1000 rear panel. These give direct access to the hardware LIN components. 5

6 3. Measurement of HAR1000-1P at RegTP in Berlin 3.1 Measurements with Harmonics analyser RegTP had prepared some special loads to be used for verification of the Harmonic analyser. The loads have well defined emissions verified indepedantly by previous measurements. Results obtained using the HAR1000 were always well within the accuracy requirements of the IEC standard. HAR1000 results compared very favourably with measurement taken on other test systems. As a consequence, more emphasis was placed on verifying the source (HAR1000 amplifier) and the Flicker analyser. 3.2 Testing effectiveness of the HAR1000 amplifier RegTp had recorded waveforms of the public power supply in several of their laboratories which indicated both flat-top and over-swing distortions were present. These waveforms were recreated using a programmable voltage power supply and used as the EUT supply input to the HAR1000. Both with and without loads up to 2 kw, HAR1000 amplifier was able to compensate the distortion and deliver a clean sinusoidal waveform to the EUT. 3.3 Testing the Flicker analyser For Flicker measurement it is important that the amplifier can compensate the impedance of the public power supply to zero Ohms Verifying LIN influence and correct operation of the amplifier for Flicker measurements clean source low impedance U1 230 V ampli LIN reference load EMC PARTNER Monitor Measurement and Analysis of the HARMONICS-1000 reference analysators Block diagram of the HAR1000 Important Note: Each block illustrated above is a discreet hardware part of the HAR1000. Each block can be switched in or out of circuit by the HARCS software Verification procedure 1. A load of 2000 W is switched ON and OFF with a repetition of 1 second. 2. The amplifier is turned OFF and the LIN is switched ON. 3. A high impedance public power supply is simulated by 50 m of power cable wound on a cable drum. 6

7 Flicker measurement results of the verification set-up (without amplifier) 4. The amplifier is turned ON and the LIN is turned OFF 5. The measurement is repeated. Short time Flicker is below 0.09 much better than the standard specification (0.4) Flicker generated by the high impedance power supply and additional 50 m cable is completely compensated by the HAR1000 amplifier. 6. Switch ON the LIN Correct measurement of Flicker The value Pst is only generated by the impedance of the LIN. The influence of the public power supply impedance is compensated by the HAR1000 amplifier. 7

8 3.3.3 Verification of the hardware LIN. LIN Resistance Neutral LIN Resistance Phase LIN Inductance Phase and Neutral Location of hardware LIN components The hardware LIN is made of a resistance in series with an inductor. Both components can be independantly verified using the procedures detailed. R = 0.4 ohm j = 0.25 ohm Line Impedance Network (LIN) Impedance Verification (j) Measure voltage at the HAR1000 rear panel connectors and load current as indicated in the diagram below: V Amplifier on MC-Plugs Brown LIN = on/off L in L out 0.24+j V Line Flickermeter Load about 2kW LIN = on/off N in N out 0.16+j0.10 MC-Plugs White Location of MC-Plug measurement points V Apply a 2 kw load to the HAR1000. This generates approximately V. System conditions : Amplifier = on ; Line Voltage = 230 V ; Load = 8.5 A Complete the table below using measured values of V & A. 8

9 LIN Voltage drop At current Impedance dv / A [V] [A] [ohm] Phase [L]??? Neutral [N]??? Nominal value calculation : Xz = (0.4)2 + (0.25)2 = Ohm Allowable tolerance ± 5% = to Important Note: To reduce transition resistance of the LIN bypass relays, switch off the LIN with EUT-Power Input and load on Power Output connected Resistance Verification (R) Measure Resistance at the HAR1000 EUT output connectors and connect a short circuit to EUT power input as indicated in the diagram below: Amplifier = off LIN = on/off L in L out 0.24+j0.15 Short circuit Flickermeter Precision Ohmmeter LIN = on/off N in 0.16+j0.10 N out Connection of a short circuit to a EUR power input System conditions : Amplifier = off ; Line Voltage = 0 V Complete the table below using measured values of R from the precision ohmmeter. LIN Resistance DifferenceR(on) - R(off) [ohm] [ohm] OFF ON Lout to Nout Lout to Nout Contact Nominal value : Ohm +/- 5% = to ohm 9

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12 For further information please do not hesitate to contact EMC PARTNER s representative in your region. You will find a complete list of our representatives and a lot of other useful information on our website: The Headquarters in Switzerland EMC PARTNER AG Baselstrasse 160 CH Laufen Switzerland Phone: Fax: sales@emc-partner.ch Web-Site: Your local representative 12 Version July Subject to change without notice. Copyright by EMC PARTNER AG, Switzerland.