<![CDATA[Contract Change Orders (CCOs) remain a major issue in power infrastructure projects because they can affect both contract schedule and contract value. However, empirical studies examining CCOs specifically in high-voltage transmission line and substation projects remain limited. This study analyzes the impact, causes, and mitigation of CCOs in 150 kV transmission line and substation projects using a mixed-method approach. We conducted a quantitative analysis of historical data from 62 projects implemented in South, East, and North Kalimantan between 2017 and 2025, including Extension Substation, New Substation, and Transmission Line projects. We used descriptive statistics, Shapiro–Wilk tests, Kruskal–Wallis tests, and Dunn’s post-hoc tests to compare variations in schedule and contract value across project categories. We obtained qualitative data through semi-structured interviews with owners, engineering consultants, contractors, supervision consultants, and operation units. The results indicate that Transmission Line projects have significantly more variation in schedule and contract value than substation projects, particularly Extension Substation projects. Design and consultant issues, uncertainties about site conditions, gaps in stakeholder coordination, owner-initiated changes, regulatory and governance issues, land acquisition and right-of-way issues, and external factors are the main causes of CCOs. The results also show that land acquisition and right-of-way issues are a dominant project-specific driver for Transmission Line projects and often result in route adjustments, design revisions, quantity changes, and schedule extensions. This research contributes to change order management by providing sector-specific evidence for power infrastructure projects. It highlights the importance of early design maturity, site verification, stakeholder coordination, and land and ROW readiness in mitigating avoidable CCOs.]]>
