This paper proposes a novel directional pilot protection method based on the transient energy for bipolar HVDC line. Supposing the positive direction of current is from DC bus to the DC line, in the case of an internal line fault, the transient energies detected on both sides of the line are all negative within a short time, which denotes the positive direction fault; while for an external fault, the transient energy on one end is positive, which means a negative direction fault, but the transient energy on the opposite end is negative, which indicates that the fault direction is positive. According to these characteristics, an integration criterion identifying fault direction is constructed. In addition, through setting a fixed energy threshold, the faulted line and lightning disturbance can also be discriminated. Simulation results from UHVDC transmission system show the validity of the proposed protection method.
Objective The aim of this study was to investigate the association of serum carcinoembryonic antigen (CEA), nerve-specific enolase (NSE), cytokeratin 19 fragment (CYFRA21-1), squamous cell carcinoma antigen (SCC-Ag), and pro-gastrin-releasing peptide (ProGRP) with the clinicopathological characteristics and chemotherapeutic outcomes of patients with lung cancer. Methods A total of 189 patients with lung cancer (lung cancer group) diagnosed at the Fourth Affiliated Hospital of Anhui Medical University from January 2020 to December 2021 were included. During the same period, 199 patients with benign lung disorders were included as the benign lung disease group and 75 healthy people were selected as the control group. The serum concentrations of CEA, NSE, CYFRA21-1, SCC-Ag, and ProGRP in all the 3 groups were analyzed and compared in patients with different lung cancer tumor-node-metastasis (TNM) stages and pathological classifications. A total of 11 patients with small cell lung cancer (SCLC) and 18 patients with lung adenocarcinoma (LAC) were further evaluated for the dynamic changes of CEA, NSE, CYFRA21-1, SCC-Ag, and ProGRP before chemotherapy and during the 6 courses of chemotherapy, and the outcome of chemotherapy was evaluated every 2 courses. Results The serum concentrations of CEA, NSE, CYFRA21-1, SCC-Ag, and ProGRP in the lung cancer group were significantly higher than those in the control group (P < .05). We found statistically significant differences in serum CEA, NSE, CYFRA 21-1, SCC-Ag, and ProGRP among patients with different pathological types (LAC, squamous cell carcinoma, or SCLC) and different stages (I–IV). The ProGRP and NSE had the highest expression in SCLC, CEA showed the highest expression in LAC, whereas CYFRA21-1 and SCC-Ag showed the highest expression in lung squamous cell carcinoma (LSCC). The concentrations of all the markers were elevated in the advanced pathological stages. The receiver operating characteristic curve analysis showed that the diagnostic value of the combined detection of CEA, NSE, CYFRA 21-1, SCC-Ag, and ProGRP for lung cancer was significantly higher than using a single biomarker (P < .05). Our dynamic monitoring results show that ProGRP progressively decreased in remission cases of SCLC and CEA progressively decreased in LAC remission cases. Conclusion CEA, NSE, CYFRA 21-1, SCC-Ag, and ProGRP have good clinical value in the early diagnosis, differential diagnosis, and progression monitoring of lung cancer. The ProGRP and CEA concentrations are beneficial for evaluating the outcome of chemotherapy in SCLC and LAC. The combined detection of multiple biomarkers shows improved clinical value in the early diagnosis of lung cancer.
This paper proposes an original busbar protection method, based on the characteristics of the fault components. The method firstly extracts the fault components of the current and voltage after the occurrence of a fault, secondly it uses a novel phase-mode transformation array to obtain the aerial mode components, and lastly, it obtains the sign of the average product of the aerial mode voltage and current. For a fault on the busbar, the average products that are detected on all of the lines that are linked to the faulted busbar are all positive within a specific duration of the post-fault. However, for a fault at any one of these lines, the average product that has been detected on the faulted line is negative, while those on the non-faulted lines are positive. On the basis of the characteristic difference that is mentioned above, the identification criterion of the fault direction is established. Through comparing the fault directions on all of the lines, the busbar protection can quickly discriminate between an internal fault and an external fault. By utilizing the PSCAD/EMTDC software (4.6.0.0, Manitoba HVDC Research Centre, Winnipeg, MB, Canada), a typical 500 kV busbar model, with one and a half circuit breakers configuration, was constructed. The simulation results show that the proposed busbar protection has a good adjustability, high reliability, and rapid operation speed.
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