COVER FEATURE CABLE TEST AND DIAGNOSIS THE NEXT GENERATION ALL-IN-ONE SYSTEM FROM SEBA Network operators can now get faster and significantly more reliable information about the quality and the condition of their cables. This is made possible thanks to the brand-new 50 Hz Slope Technology from Megger’s SebaKMT division. N ever before has it been possible to immediately locate faults in underground cables during actual partial discharge (PD) measurement. This is set to change with the 50 Hz Slope Technology where a withstand test with VLF cosine-rectangular voltage (VLF CR) and PD diagnosis with damped alternating voltage (DAC) is combined. This combination allows an efficient and integrated solution for precise inventory of the network infrastructure. The important fact here is that the PD measurement data, gained with the VLF CR or with the DAC test voltage, can be compared directly with the 50/60 Hz network voltage. This facilitates reliable decision making using one unit. TDS NT consists of a multifunctional, compact voltage source and a PD detector. It can be used to test cables according to the international standards, such as IEC 60502-2 and IEEE 400.2 with VLF-CR. In addition, a PD diagnosis using the new 50 Hz Slope Technology, can be performed simultaneously with the help of the PD detector. Alternatively, the TDS NT can also be used for PD diagnosis with the proven damped AC voltage (DAC). In practice, the PD diagnosis has been established nationally and internationally as an effective method of 16 resonance phase the TDS and the cable form a resonant circuit whose natural resonance frequency is determined by the fixed inductance and the support capacitor of the power source, and the capacitance of the test object. The support capacitor has been designed in such a way that the resonance frequency will always fall in a specific frequency window comparable to that of the network frequency – thus a 50 Hz Slope is attained for every test object. TDS NT system measurement. It is especially useful for commissioning testing, as it is the only way to reliably check the quality of workmanship of the accessories. THE PRINCIPLE For both voltage waveforms, these two fundamental conditions are present: the charging phase and the resonance phase. During the charging phase the test object is charged to the desired voltage, or the voltage losses of the cable during measurement are recharged. During the THE UNIQUE “ALL- IN-ONE” SOLUTION The new TDS NT series offers the highest degree of flexibility in the area of cable testing and diagnosis, consisting of a multifunctional, compact voltage source and a modern PD detector. The TDS test voltage source can be used for both simple VLF tests or for meaningful commissioning tests with accompanying PD diagnosis in connection with the PD detector. In addition to the proven VLF and DAC test voltage the TDS can also be used for DC tests and sheath tests in compliance with IEC 60229. Furthermore, in combination with the step voltage sensor ESG NT, it can also be used for precise pinpointing of sheath faults. LONG-LASTING EXPERIENCE IN PD DIAGNOSIS The new PD detector PDS 60 combines many years of field experience, customer ESI AFRICA ISSUE 4 2014