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12 articles
How are harmonic-current limits allocated among multiple users? Why can't Table 2 be applied directly?
The harmonic-current allowable values in Table 2 of GB/T 14549 are the limits that all users at a point of common coupling must meet collectively, not the limit for one user. To apply them to an individual user, first convert the value using the actual minimum short-circuit capacity, then allocate it according to contracted capacity; the allocation exponent changes with harmonic order. This article explains the two-step mechanism and identifies four common errors caused by copying the table directly.
How Should a PE Conductor Be Sized? Table 54.2 Is Only the Minimum—Circuit Length Is Critical
Use an illustrative TN-S circuit to verify both the thermal withstand and protection sensitivity of a PE conductor. A tabulated cross-section alone does not resolve the effect of circuit length.
How Is Reactive-Power Compensation Calculated, and Why Shouldn't a 400 V Capacitor Be Selected Directly?
Calculate reactive-power compensation from the target power factor, then examine how a series reactor raises capacitor-terminal voltage and changes both the required rated voltage and actual reactive output.
Solid-State Transformers Have Technical Specifications—Why Are Acceptance Tests Still Performed at Power Frequency?
Product specifications for solid-state transformers are emerging, but insulation tests matched to high-frequency operation remain incomplete. This article compares power-frequency and high-frequency waveforms and relevant industry experience.
How Should Transformer Capacity Be Selected, and Why Is the Demand Factor Sometimes Applied Twice?
Distinguish the roles of demand factor, coincidence factor, and load factor, then use an illustrative calculation to see how duplicate adjustments change transformer capacity selection.