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Subject: search.filters.subject.Distribution Transformer

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    The Experiment of Dielectric Frequency Response of Serviced Aged Distribution Transformer
    (2024-01-01)
    Posrimahapoch, Purichaya
    ;
    Maneerat, Noppadol
    ;
    Daengdee, Danaiwat
    ;
    Jeenmuang, Siwakorn
    ;
    Pannil, Pittaya
    Outdoor Distribution Transformers typically encounter random environments and affect moisture in any ingress ways, e.g., defective breathing, oil leakage, or human error during internal inspection, etc. Such moisture is a very important enemy of the insulation integrity of the transformer. It may cause the failure of the transformer eventually. Therefore, the condition of the transformer insulation needs to be monitored. Dielectric Frequency Response (DFR), also known as Frequency Domain Spectroscopy (FDS), and Polarization and Depolarization Current (PDC) are nondestructive tests providing efficient diagnostic for transformer insulation. The test results can be used to estimate moisture content and oil conductivity. In this paper, the dielectric investigation of a 315 kVA, 22 kV serviced aged distribution transformers, which have been retired for 6 months after being utilized for more than 20 years, was conducted. The experiment results of the DFR and the PDC tests including the investigated mineral oil characteristics (i.e., oil breakdown voltage, moisture content, and tan delta) are reported and analyzed. They should be useful to understand the condition of the transformers.
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    Partial Discharge Investigation of 22kV Distribution Transformer
    (2024-01-01)
    Dechothamsathit, Vorawut
    ;
    Pannil, Pittaya
    ;
    Yamsiri, Thummanoon
    ;
    Chumpiboon, Komin
    ;
    Jeenmuang, Siwakorn
    This paper presents an off-line partial discharge (PD) experiment conducted on a 22 kV/400 V distribution transformer, which was decommissioned after 20 years of service. The study investigates the impact of reduced oil levels within the transformer on PD characteristics that are expected to facilitate PD activity within the transformer. The experiments were performed with reduced oil levels below the top clamp and using both single-phase and three-phase voltage excitations, with PD measurements recorded for each case. The PD signals were measured using High-Frequency Current Transformers (HFCTs) and capturing current pulses of PD in the frequency range of 100 kHz to 20 MHz. Additionally, transformer oil tests were performed, including moisture content, oil breakdown voltage, and oil conductivity. The results of the PD measurements and oil tests are introduced and discussed in this paper.
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    An analysis and selection of distribution transformer for losses reduction
    (2000-01-01)
    Suechoey, B.
    ;
    Ekburanaway, J.
    ;
    Kraisnachinda, N.
    ;
    Banjongjit, S.
    ;
    Chompoo-Inwai, C.
    Thailand's medium-sized industries, with demands ranging from 30-1999 kW., currently need to select transformers that provide the highest efficiency regarding transformer losses. This is partly because the energy authorities that provide the electricity have fixed the loss ratio values for transformers. In this paper, an analysis of how to select the suitable size of transformer is presented. The considered factors include efficiency, losses, rating, capital cost throughout the transformer commission time, the cost of the energy, and % interest rate. The analysis includes an example of calculation and selection.