A study of oil-paper insulation voltage dependency during frequency response analysis

People often believe that power factor/dissipation factor testing at power frequency (50/60 Hz) usually exhibits a flat response as a function of test voltage if the insulation is in good condition. Dielectric Frequency Response, DFR is the extension of power factor testing except that the measurement is performed from 1 kHz down to typically 1 mHz. It is a very useful tool for evaluating the moisture content in solid insulation of HV and EHV components such as power transformers, bushings, instrument transformers and PILC cables. The voltage dependent phenomenon also called “the Garton effect”, caused by paper absorbing electric charges in oil is investigated. The application of DFR in HV and EHV substations required a conceptual analysis of the phenomenon to better interpret the condition of the insulation system while increasing the signal to noise ratio to minimize the effect of surrounding interference. As a result of this work, authors provide practical recommendations regarding test voltages and frequency ranges to be used under high interference environments. The wide application of the method is supported with experimental field data.Instituto de Investigaciones Tecnológicas para Redes y Equipos Eléctrico

TGFBR1 variants TGFBR1*6A and Int7G24A are not associated with an increased familial colorectal cancer risk

Variants of the transforming growth factor-beta receptor type 1 (TGFBR1) gene, TGFBR1*6A and Int7G24A, have been suggested to act as low-penetrance tumour susceptibility alleles with TGFBR1*6A being causally responsible for some cases of familial colorectal cancer (CRC). We performed a case–control study of 262 unrelated familial CRC cases; 83 hereditary non-polyposis colorectal cancer (HNPCC) and 179 non-HNPCC. Patients were genotyped for TGFBR1*6A and Int7G24A and compared with 856 controls. Further, we screened the coding region of TGFBR1 in affected members of a large family with CRC linked to 9q22.32-31.1. TGFBR1*6A allelic frequency was not significantly different in all of the familial cases compared with controls (0.107 and 0.106, respectively; P=0.915). In a subgroup analysis allele frequencies were, however, different between HNPCC and non-HNPCC familial cases (0.157 and 0.084, respectively; P=0.013). TGFBR1*6A genotype did not influence age of onset. Int7G24A allele frequencies were similar in cases and controls. No germ-line mutation was identified in the family with CRC linked to this chromosomal region. Our study provides no substantial support for the hypothesis that the polymorphic variants TGFBR1*6A or Int7G24A contribute to familial CRC risk. We cannot, however, exclude the possibility that TGFBR1 variants have a modifying effect on inherited risk per se