IEEE C57.127-2018 pdf free download – IEEE Guide for the Detection, Location and Interpretation of Sources of Acoustic Emissions from Electrical Discharges in Power Transformers and Power Reactors.
3. Detection and measurement of PD- background information Since PD camnot be measured dreely, its energy by-products such as eetrical tanskents, chermical changes, electromagnetie emissions, vibration, sound, lighnt, and heat must be measured. Each of these enengy by- products, when measured, has advantages and disadvantages for idnifying PD. The measurement methods for power transformers and reactors are as ollows:
a) Radio frequency- VHF: The VHP measurement of radio waves is in the frequency range of 30 MHz to 300 MHz. This VHF measurement is usually associated with aeril antenas, but not exclusively. Some window-type reeve devices my also monitor the VHF range. The signal ateuton and noise reduction ane similar but less compared to the UHF frequency. The corona type of PD emits mostly up to a frequency of approximately 300 MHz.
b) Radio frequency- UHF: The UHF measuemeat of radio waves is in the frequency range of 300 MIIz to 3 Gitz. These measurements are oflen prformed using a window style UHF reeier. UHF tests are less afe by external noise. Signals are strongly ateruated when they pass through the bushings or travel longer distances between the source artd the transformer. Cell pbone and TV stations operate in the UHF band and might introduee strong noise unless the antena is shielded. Discharges dreetly in the oil have an uper frequency limit of only a few hundred kilobertr and cannot be detcted by UHF. However, it is likely that gas or bubles will be produed and will make PD measurable by UHF.
c) Radio-frequeney curent transformers (RFCTs) RFCTs are designed to measure up to several tens or hundreis of megabertz. They can be placed on ground Tetumns and/or bushing taps. The RFCT by iselfis generally considered non-intnusive; however, the RFCT may require an outnge to be insalleda,a Installation is simplified with the use of clamp on RFCT. It can be used both for of-line and online measurement states. d Coupling capacitor (CC): The cc sensor iterfaces diretly with the vllage teminal. This is the method described in IEC 60270 [B37], IEEE sSid 5711374 2010 [B40]. This is a common factary test metbod. Results are measured in picoulomnbs. This measurement works well under a contolled nose-tfee envioment but may tot work well in a field envioment. For field measurerments, this method can utilize cither a user-supplied capacitor or the condenser layered bushing seen at the capacitive tap s the CC. When the user supplies an etemal reference capacitor for online measurements, the measunement is considered intrusive. e) Acoustic emission (AE): Consists of one or more ulrasonic rceiving transducers that are sensitive to the AE genented by an etricall soure. IEEE C57.127 pdf download.