EUROLAB, with its state-of-the-art accredited laboratories and expert team, provides precise and fast testing services within the scope of IEC EN 60885-3 testing. IEC EN 60885-3 specifies test methods for partial discharge (PD) measurements on extruded power cable lengths, but does not include measurements on installed cable systems. Reference is made to IEC 60270 which gives techniques and considerations applicable to partial discharge measurements in general.
The purpose of the test is to determine the discharge magnitude at a certain voltage and with the minimum declared accuracy, or to check that the discharge magnitude does not exceed a certain value.
Short cable lengths behave the same as a single capacitor because the magnitude of discharge can be measured directly by considering the cable as a single capacitor. However, longer cables behave like a transmission line, and PD pulses travel away from their source in the form of a wave in both directions along the cable. When the far end is reached from the measuring equipment, the pulse will be reflected with the same polarity if the lead is open circuit. The reflected pulse will then travel back along the cable and reach the detector at a time directly after the received pulse. If the time between the arrival of the two pulses is short (time difference depending on the length of the cable), then the sensing device may give an incorrect response by showing a larger or smaller discharge size than what it actually is. The methods detailed in this standard allow for accurate measurement of partial discharges under these conditions.
The test circuit includes the high-voltage power supply, the test object, the coupling capacitor, and the HV and PD measuring equipment. The measuring circuit consists of the measuring impedance (the input impedance of the measuring device and the input unit selected in accordance with the wire impedance), the connecting cable and the measuring device. The meter or detector includes an amplifying device, an oscilloscope, or other instrument suitable for indicating the presence of partial discharges and measuring the apparent charge.
This is an electronic switch designed to block the input of the meter from reflected impulses from the open end of the cable. This is achieved by blocking the input for a fixed time after the first pulse is received.
EUROLAB assists manufacturers with IEC EN 60885-3 test compliance. Our test experts, with their professional working mission and principles, provide you, our manufacturers and suppliers, the best service and controlled testing process in our laboratories. Thanks to these services, businesses receive more effective, high-performance and quality testing services and provide safe, fast and uninterrupted service to their customers.
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