An ungrounded bipolar photovoltaic (PV) DC link has no stable voltage reference: the bus swings 500–1500 V under normal maximum power point tracking (MPPT), irradiance and temperature changes, so a fixed threshold false-starts or misses low-voltage faults. We combine two physically different observables in a layered, non-redundant trigger: a millisecond voltage-imbalance arm and a persistent insulation-resistance confirmation before latching, with a resistance-only backup and a slow-aging branch, each judged against the episode’s own baseline, not an ohmic cutoff. Sampling (400 Hz anti-alias, 10 kHz, 1 kHz) is Nyquist-consistent; the nominal 4.7 MΩ spans 2.1–5.6 MΩ across baselines. On 18,000 Monte Carlo cases the detector reaches an overall Pd=0.9223, detects 233/234 faults at the empirical 2 MΩ 95% limit with 0/6000 false records (bound 5.0 × 10−4), a 329 ms median confirmation latency and a 263 ms median arm lead. With the voltage channel unusable the resistance backup retains coverage (McNemar p=1); independent C and Python detectors agree sample by sample. Stress tests give Pd=1.00 under simultaneous bipolar breakdown, zero false records under 80 V ringing or strong common mode, and only a bounded delay during an estimator gap.
Electric drive units are a key component of the powertrain in today’s electric vehicles. As innovations and advancements in the field of electrified powertrains have progressed, the product topologies of the motor and the associated manufacturing techniques have evolved. China has established itself as the leading global market and a pioneer in electric mobility, and is therefore one of the innovation leaders in the field of electric drive units. To identify key manufacturing and product development trends in this globally influential and dynamic Chinese market environment, this paper primarily analyses electric motors from electric vehicles on the Chinese market and compares them with European and U.S. electric motors. To this end, 115 electric traction motors installed in 80 electric vehicles from 2019 through 2025 are subjected to a systematic analysis. The investigation is conducted using a top-down analysis that begins with a macroscopic examination of the electric motor and concludes with a microscopic analysis of individual components at the power electronics, transmission, stator, and rotor levels. The collected and analysed data is then compared with existing data on electric motors from European and U.S. vehicle manufacturers to identify similarities and differences in product design and related manufacturing processes. The main contribution of this study is thus an extended and updated dataset that builds on an existing benchmarking framework and available data.
This study conducts an in-depth analysis of the disparities in upstream oil and gas asset scale and cost–benefit performance between PetroChina and major international oil companies. By comparing core indicators, including oil and gas asset distribution, reserves, production scale and structural changes, cost management capacity, profitability, and return on investment over the past five years among PetroChina and seven mainstream international oil corporations, namely ExxonMobil, Shell, BP, Chevron, TotalEnergies, Equinor, and Eni, this paper identifies the competitive strengths and weaknesses of PetroChina in the global energy market. The research question is: what is PetroChina’s competitive position relative to IOCs across three dimensions—asset scale, cost–benefit performance, and strategic management—and what is the nature and magnitude of the gaps, and what are the actionable pathways for improvement? PetroChina and the seven benchmark companies are all SEC-reporting firms and cover both U.S. and European IOC models, ensuring comparability of reserve and financial data. The results show that PetroChina holds a clear advantage in overall asset scale, while a notable gap remains in cost control and capital investment returns compared with peer international enterprises. This gap is particularly pronounced in exploration expenditure, but is partly attributable to geological endowment and investment timing rather than operational efficiency alone. Accordingly, targeted strategies are proposed to optimize its asset portfolio, promote technological innovation, improve capital allocation efficiency, and accelerate the low-carbon energy transition, so as to enhance its global competitive edge. This research can provide reliable references for the internationalization layout and strategic decision-making of Chinese petroleum enterprises.
To address the coupling and timescale differences between network reconfiguration and Source-storage dispatch in active distribution networks, this paper proposes a hierarchical source-network-storage coordinated scheduling method for low-carbon and economic operation. A three-layer framework is developed to coordinate hourly network reconfiguration with 15-min source-storage dispatch, where carbon flow theory is incorporated to formulate a comprehensive low-carbon economic objective. A Trajectory-Centered Advantage-Driven Proximal Policy Optimization algorithm is proposed for high-dimensional topology decision-making, while a carbon-flow-driven three-path differential reward mechanism and curriculum learning are integrated into Multi-Agent Proximal Policy Optimization for source-storage dispatch. The coordination layer further adjusts network topology according to source-storage operating states. Simulations on a modified IEEE 33-bus system demonstrate that, across renewable penetration levels of 20–100%, the proposed method reduces daily carbon emissions by 934.64–1091.66 kg and operating costs by 212.90–246.26 CNY, while reducing active power losses and improving voltage performance. The method also demonstrates good generalization capability under unseen renewable penetration levels and achieves scheduling performance comparable to mathematical optimization, while reducing online computation time by 98.14%.
Grounding is one of the key elements ensuring the reliable operation of overhead lines. The purpose of this paper is to provide a comprehensive assessment of grounding using a 400 kV overhead line as an example. The paper presents the results of diagnostic grounding measurements of various types of 400 kV overhead line poles, performed according to technical documentation and taking into account local terrain characteristics. The paper examines a large number of overhead line poles in both uniform and varied terrains, taking into account soil conditions based on geotechnical documentation. Furthermore, the paper presents a simulation analysis of lightning current dissipation through the grounding of a selected pole, taking into account geotechnical soil investigations with respect to soil stratification. The final section of the paper includes guidelines on grounding and assessment of the technical condition of grounding systems, which may be useful to transmission and distribution network operators.
