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VOL. 11, ISSUE 2 (2026)
Design and evaluation of protection system of 50mva, 138/69/13.8kv power transformer of Bislig Substation of the National Grid Corporation of the Philippines
Authors
Tomas G Virtudez, Daxter William Gulben, Ellen Jane Gulben, Ambrosio B Cultura II
Abstract
Aging power transformers pose increasing risks
to system reliability, safety, and continuity of supply, particularly when
combined with deteriorating auxiliary components and obsolete protection
systems. At the Bislig Substation of the National Grid Corporation of the
Philippines, a 30 MVA power transformer that had been in service for more than
38 years exhibited signs of degradation, including on-load tap changer wear,
oil leakage, and elevated dissolved gas levels. To address these concerns and
support projected load growth in southern Mindanao, the transformer was
replaced with a newly installed 50 MVA, 138/69/13.8 kV unit. This paper
presents a case study on the design and evaluation of the protection system for
the upgraded transformer, incorporating the transition from electromechanical
relays to microprocessor-based protection. Using ETAP-based simulations and
actual system data, the study evaluates short-circuit fault behavior,
overcurrent and differential relay coordination, and arc flash hazard levels in
accordance with applicable IEEE and NGCP standards. Results indicate that
single line-to-ground faults govern protection design at the 69 kV level and
that coordinated relay settings provide selective fault isolation while
reducing arc flash incident energy. The proposed protection scheme satisfies
reliability, selectivity, and personnel safety requirements for transmission
substations.
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Pages:27-34
How to cite this article:
Tomas G Virtudez, Daxter William Gulben, Ellen Jane Gulben, Ambrosio B Cultura II "Design and evaluation of protection system of 50mva, 138/69/13.8kv power transformer of Bislig Substation of the National Grid Corporation of the Philippines". International Journal of Multidisciplinary Education and Research, Vol 11, Issue 2, 2026, Pages 27-34
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