Impact of DC Current Interruption on Transient Voltage Test Requirements of HVDC Cable Systems for Multiterminal Grids
T.R. Karmokar (TenneT TSO GmbH)
R.D. Zhang (TenneT TSO GmbH)
M. Ghaffarian Niasar (TU Delft - High Voltage Technology Group)
M. Popov (TU Delft - Intelligent Electrical Power Grids)
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Abstract
Multiterminal (MT) HVDC grids require dependable DC circuit breaker (DCCB) operation. Electromagnetic-transient (EMT) simulations show that DCCB interruption produces relatively slow-front transient overvoltage (TrOV) whose crest- and duration-stresses on HVDC cable systems are not fully exercised by today’s standard lightning (ULI,std) and switching (USI,std) impulse voltage tests. This paper quantifies these stresses and proposes a parameterized hybrid impulse (Uhyb) superimposed on DC that envelopes SI-class wavefronts and LTrOV-class durations using SI-referenced exceedance metrics (S1, Sn) and t90/t70/t50 checks. A unified type test sequence is outlined, preserving IEC measurement tolerances and existing qualifications, and enabling robust insulation coordination for MT-HVDC grids.