MPD-600-ANP-10032-ENU

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Application Note

Calibrator check

Author Dr.-Ing. Kay Rethmeier | [email protected]

Date Sep, 2008

Related OMICRON Product MPD 600

Application Area Calibration

Version v2.0

Document ID ANP_10032_ENU

' OMICRON 2013 Page 2 of 7

Content

1 Short Cut ......................................... .......................................................................................................3

2 PD measuring results do have consequences ......... ..........................................................................3

3 Checking your equipment is an IEC recommendation .. ....................................................................3

4 Check calibrator with FFT-function ................ .....................................................................................3

5 Start the calibrator check ........................ .............................................................................................4

6 Calibrator OK? .................................... ...................................................................................................6

Please use this note only in combination with the related product manual which contains several important safety instructions. The user is responsible for every application that makes use of an OMICRON product. OMICRON electronics GmbH including all international branch offices is henceforth referred to as OMICRON. ' OMICRON 2010. All rights reserved. This applicati on note is a publication of OMICRON.

All rights including translation reserved. Reproduction of any kind, for example, photocopying, microfilming, optical character recognition and/or storage in electronic data processing systems, requires the explicit consent of OMICRON. Reprinting, wholly or in part, is not permitted.

The product information, specifications, and technical data embodied in this application note represent the technical status at the time of writing and are subject to change without prior notice.

We have done our best to ensure that the information given in this application note is useful, accurate and entirely reliable. However, OMICRON does not assume responsibility for any inaccuracies which may be present. OMICRON translates this application note from the source language English into a number of other languages. Any translation of this document is done for local requirements, and in the event of a dispute between the English and a non-English version, the English version of this note shall govern.


1 Short Cut 1. Connect calibrator directly to the PD input of the MPD by short coax-cable 2. Set the charge division factor to 1 3. Check injected charge level 4. Check pulse in time-domain 5. Check horizontal FFT curve 6. Check dependence of the measuring center

2 PD measuring results do have consequences Measuring Partial Discharges (PD) will provide important information about the condition of the device under test (DUT). As a consequence the results of a PD measurement can lead to serious decisions like switching off a power transformer immediately or declare its condition as safe for ongoing operation. It is obvious that errors will have immense consequences, as outages, black-outs and financial penalty fees.

3 Checking your equipment is an IEC recommendation To rely on the results of a PD measurement the PD measuring instrument and the Charge Calibrator has to work probably. For new calibrators this is guaranteed by the ISO 9001 ff certificated OMICRON Quality Assurance System including detailed calibration documents. However, due to unpredictable impacts like mechanical damages or poor battery power level the calibrator could be affected. Therefore it is necessary to check the functionality of your calibrator from time to time, regarding to IEC 602700:2000 (Chapter 7).

4 Check calibrator with FFT-function OMICRON integrated a FFT-Analyzer into the PD-Measuring software to check the frequency spectrums a fast and simple way. Over the whole analogue frequency input range of 20 MHz a pulse can by analyzed regarding to its spectral components.


5 Start the calibrator check Just connect the output port of the calibrator to the PD input port of the MPD 600 acquisition unit by a short coax-cable, as to be seen in figure 1.

Figure 1: Connect Calibrator and MPD

As a next step select the Q-Card and set the Division Factor in the charge calibration menu manually to 1 (fig. 2).

Figure 2: Set Charge Devision Factor to 1

Set the Measuring Center Frequency to 1 MHz and the Bandwidth to 300 kHz after selecting the Q-Card.


Select the V-Card and set the voltage trigger to Line. Six PD events for 50 Hz (see black Arrows in fig. 3) will be visible in the main measuring window; the QIEC reading should fit to the selected output charge of the calibrator (see red mark in fig. 3).

Figure 3: Check PD Events, Charge reading and Time-Domain

Use the Time-Window to visualize the pulse (blue mark in fig. 3). The pulse-width and the amplitude will depend on the selected charge level, polarity and on the type of calibrator (CAL542 A-B-C-D). The oscilloscope settings can be changed in the PD-Card. The frequency spectrum of the calibration pulse should be flat and linear up to a certain cut-off frequency. Choose the FFT-Window and compare it with the curve exemplarily shown in figure 4.

Figure 4: Check Flat and Horizontal FFT Curve up to Cutt-Off

Please remember that any calibrator will only inject the displayed charge level if the FFT curve is horizontal from nearly 0 MHz up to the selected measuring center frequency. Regarding to IEC 60270:2000 (Chapter 6.1 figure 5) the upper cut-off frequency of your calibrator has to be higher than the selected bandwidth of the PD measuring system .


Figure 5 shows the FFT-curve of a calibrator NOT DESIGNED TO BE USED over the whole frequency range

Figure 5: Non-flat FFT Characteristic

Due to "Einbrche" notches in the frequency spectru m at 7 MHz the calibrator cannot inject the displayed charge level at these frequencies. THE CALIBRATION WILL BE UNVALID in this case; the PD measurements will led to FALSE RESULTS . This calibrator can only be used in a frequency range of 0 MHz up to 2 MHz, which may be sufficient for many cases.

6 Calibrator OK? As a High Quality Supplier of High-End PD Measuring Technique OMICRON expects that Your CAL 542 will pass this system check at any time. In the unlikely event of greater derivations, or if you are even uncertain about some results do not hesitate to contact OMICRON Technical Support. We will be pleased to help you. Even if this Self-Test procedure does NOT substitute the IEC recommended performance checks it provides you quick and easy information about the status of your calibrator. To gain reliable PD measuring results we recommend to invest these few minutes to check your calibrator before every PD measurement.

OMICRON is an international company serving the electrical power industry with innovative testing and diagnostic solutions. The application of OMICRON products provides users with the highest level of confidence in the condition assessment of primary and secondary equipment on their systems. Services offered in the area of consulting, commissioning, testing, diagnosis, and training make the product range complete.

Customers in more than 130 countries rely on the companys ability to supply leading edge technology of excellent quality. Broad application knowledge and extraordinary customer support provided by offices in North America, Europe, South and East Asia, and the Middle East, together with a worldwide network of distributors and representatives, make the company a market leader in its sector.

Europe, Middle East, Africa OMICRON electronics GmbH Oberes Ried 1 6833 Klaus, Austria Phone: +43 5523 507-0 Fax: +43 5523 507-999 [email protected]

Asia -Pacific OMICRON electronics Asia Limited Suite 2006, 20/F, Tower 2 The Gateway, Harbour City Kowloon, Hong Kong S.A.R. Phone: +852 2634 0377 Fax: +852 2634 0390 [email protected]

Americas OMICRON electronics Corp. USA 12 Greenway Plaza, Suite 1510 Houston, TX 77046, USA Phone: +1 713 830-4660 +1 800-OMICRON Fax: +1 713 830-4661 [email protected]

For addresses of OMICRON offices with customer service centers, regional sales offices or offices for training, consulting and commissioning please visit our web site. www.omicron.at www.omicronusa.com

MPD-600-ANP-10032-ENU

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