Hawaiian Electric, in a Feb. 1 application filed with the Hawai’i Public Utilities Commission, requested commission approval to commit funds in excess of $2.5m – currently estimated at about $5.9m – for the proposed Iwilei Substation Downtown Network Transformer and Switchgear N2 Replacement project.
The company said that its “Downtown Network” is a specialized distribution system that serves the Downtown Honolulu area from the company’s 138-kV Iwilei substation with an underground network system. For the Iwilei substation, that network consists of three separate transformer and switchgear units named N1, N2, and N3, respectively, the company said.
As noted in the filing, network systems are characterized by distribution transformers, served from different primary circuits, whose secondary circuits are interconnected forming a grid.
Power delivery to the network is only possible through the three substation network transformers at the Iwilei substation. Due to the design of the downtown network, tapping into the conventional Hawaiian Electric grid as an alternate source is not feasible as the radial system is not capable of serving the downtown network, the company added.
The company noted that since the Downtown Network is completely isolated from the remainder of the Hawaiian Electric distribution grid, the unique double-contingency transformer configuration of the network provides redundancy so that the failure or removal from service of any one primary circuit, primary breaker, or network distribution transformer, will not disrupt service to customers.
Deterioration of the Iwilei substation transformers and switchgears is putting the reliability of the Downtown Network at risk, the company said, adding, “Most urgently, Transformer and Switchgear N2, which were purchased and installed in 1972, are incapable of operating as designed.”
Therefore, it is critical that Transformer and Switchgear N2 be replaced in order to maintain the reliability of electric service to Downtown Honolulu, the company said.
The proposed project, which also supports a larger, long-term program to rehabilitate the power source – Iwilei substation – of the Downtown Network system, includes the replacement of the Iwilei Network 138-kV-12-kV, 50 Mega Volt Amp Transformer N2 (Transformer N2), and 12-kV Switchgear N2. Replacing the existing equipment will restore the original intended capacity and reliability of the system, but with such improved technology as microprocessor relays and supervisory control and data acquisition (SCADA), the company said. The improved technology will benefit customers of the Downtown Network by reducing the frequency and duration of possible service interruptions, the company said.
Hawaiian Electric said that it plans to order the long lead-time materials for the replacement by January 2019, in order to begin construction in January 2020, and complete the project by June 2020.
The project cost is currently estimated at about $5.9m, excluding customer contributions, the company said.