HVDC Leyte–Luzon

Also known as: 8LI1NAG-ORMOC — the grid line identifier · 8LI1NAG-ORMOC HVDC — the identifier with the system suffix · Ormoc–Naga HVDC transmission line — the converter-station pairing name · Leyte–Luzon HVDC interconnection — the descriptive system name

Places

Definition

HVDC Leyte–Luzon is the high-voltage direct-current transmission link of the Philippine grid that connects the island of Leyte to Luzon, placed in commercial service on August 10, 1998. Built for the National Power Corporation by ABB in cooperation with Marubeni, the link runs from the Ormoc converter station on Leyte to the Naga converter station in Camarines Sur on Luzon — 451 kilometres in all, of which 430 kilometres is overhead line and 21 kilometres is submarine cable laid across the San Bernardino Strait between Cabacungan (Allen, Samar) and Santa Magdalena (Sorsogon). It is rated at 440 MW at 350 kV DC, and its purposes are the delivery of bulk geothermal power from Leyte’s fields to Luzon, the interconnection of the two island grids, and the stabilization of the alternating-current network of the Manila region. (Wikipedia — HVDC Leyte–Luzon, Rudervall et al. — HVDC Transmission Systems)

The transmission line’s identifier in the grid’s numbering is 8LI1NAG-ORMOC, and it is also called the Ormoc–Naga HVDC transmission line. (Wikipedia — HVDC Leyte–Luzon, Wikidata — Q4129360) Although described in the technical literature as a bipolar HVDC line with triple-bundle conductors, it was implemented as a monopolar 350 kV link returning through grounding electrodes at Albuera, Leyte and near Calabanga, Camarines Sur, connected to the converter stations by 25 and 15 kilometres of 69 kV DC electrode line. On the Leyte–Samar section the line crosses the San Juanico Strait as an overhead crossing carried by a tower set on an island in the strait — recorded as the first HVDC tower erected in the Philippines. The link is owned by the National Transmission Corporation (TransCo) since March 1, 2003 and has been operated by the National Grid Corporation of the Philippines (NGCP) since January 15, 2009. (Wikipedia — HVDC Leyte–Luzon, Dolor — Ownership, Financing and Licensing of Geothermal Projects)

Identities

Source Type	Identity
Wikipedia	HVDC Leyte–Luzon
Wikidata	HVDC Leyte–Luzon (Q4129360)
DBpedia	N/A
ProductOntology	N/A
Wiktionary	N/A
Library of Congress Subject Headings (LCSH)	N/A
MeSH	N/A
NCBI Taxonomy	N/A
AGROVOC	N/A
Google Scholar	HVDC Leyte-Luzon Ormoc Naga converter station 440 MW 350 kV monopolar submarine cable San Bernardino Strait San Juanico overhead crossing geothermal Tongonan NAPOCOR TransCo NGCP ABB Marubeni
ConceptNet	N/A
OpenCyc	N/A

Also Known As

8LI1NAG-ORMOC — the grid line identifier
8LI1NAG-ORMOC HVDC — the identifier with the system suffix
Ormoc–Naga HVDC transmission line — the converter-station pairing name
Leyte–Luzon HVDC interconnection — the descriptive system name

Examples and Analogies

A bridge for electrons between islands: alternating current loses its advantage across long submarine crossings, so the Leyte–Luzon link works like a ferry terminal pair at each end — rectifying the islands’ AC into DC for the 21-kilometre cable under San Bernardino Strait and the long overhead runs, and inverting it back at Ormoc and Naga, which is precisely why the project’s sponsors chose HVDC “to enable supply of bulk geothermal power across an island interconnection, and to improve stability to the Manila AC network.” (Rudervall et al. — HVDC Transmission Systems)
The earth as the return wire: the monopolar design uses the ground itself as the return conductor — electrode stations at Albuera and Calabanga complete the circuit through the earth, saving a second pole’s worth of conductor at the cost of careful electrode engineering. (Wikipedia — HVDC Leyte–Luzon)
Verified technical data:
Commissioning: in service August 10, 1998; owner National Power Corporation from that date to March 1, 2003 (Wikipedia — HVDC Leyte–Luzon)
Rating: 440 MW at 350 kV DC; described as a triple-bundle bipolar line in the technical literature, implemented as monopolar (Wikipedia — HVDC Leyte–Luzon, Rudervall et al. — HVDC Transmission Systems)
Converter stations: Ormoc (Leyte) and Naga, Camarines Sur (Luzon) (Wikipedia — HVDC Leyte–Luzon)
Route: Leyte–Samar overhead line; 21 km of submarine cable across San Bernardino Strait between Cabacungan (Allen, Samar) and Santa Magdalena (Sorsogon); Luzon overhead line; total length 451 km, of which 430 km overhead (Wikipedia — HVDC Leyte–Luzon)
San Juanico crossing: overhead crossing with a tower on an island in the strait; the first tower, (8LI1NAG-ORMOC HVDC)0001, was the first HVDC tower erected in the Philippines (Wikipedia — HVDC Leyte–Luzon)
Electrodes: grounding electrodes at Albuera (Leyte) and near Calabanga (Camarines Sur), connected by 25 km and 15 km of 69 kV DC electrode line (Wikipedia — HVDC Leyte–Luzon)
Contractor: ABB in cooperation with Marubeni (Wikipedia — HVDC Leyte–Luzon)
Ownership and operation: owned by TransCo since March 1, 2003; operated by the National Power Corporation, then TransCo, then by the privately owned NGCP since January 15, 2009 (Wikipedia — HVDC Leyte–Luzon)

Usage Scenarios

1. Delivering Leyte Geothermal Power to Luzon

The link exists to move the output of Leyte’s geothermal plants — the Tongonan field’s generating complex above all — into the Luzon grid: the National Power Corporation “constructed a 440 MW, 350 kV monopolar HVDC link to transfer power from the geothermal power plant on the island of Leyte, to the southern part of the main island of Luzon to feed the existing AC grid in the Manila region.” (Rudervall et al. — HVDC Transmission Systems, Dolor — Ownership, Financing and Licensing of Geothermal Projects)

2. Stabilizing the Manila Grid

Because HVDC converters control power flow electronically, the interconnection doubles as a stability device for the capital’s AC network — the second purpose the project’s sponsors recorded — allowing power injections from Visayas geothermal capacity to be modulated against Luzon’s load. (Rudervall et al. — HVDC Transmission Systems)

3. Crossing the Straits

The route’s two strait crossings make it a reference case in Philippine transmission engineering: the submarine cable at San Bernardino Strait and the overhead crossing of San Juanico Strait on an island tower — the geography that ties the link to both straits in the public mind, though only the San Juanico crossing is by tower and only San Bernardino carries the cable. (Wikipedia — HVDC Leyte–Luzon)

4. Operating Under NGCP

Since January 15, 2009 the link has been operated by the National Grid Corporation of the Philippines within the concession that privatized the country’s transmission business, while ownership remained with TransCo — the division of custody that governs the line’s maintenance regime, outage planning, and grid-security reporting today. (Wikipedia — HVDC Leyte–Luzon)

5. Studying Geothermal Development Finance

Researchers of Philippine energy finance read the link alongside the geothermal build-out it serves: the World Bank’s energy-sector lending to the Tongonan area and the build-operate-transfer plants of the “Leyte-Luzon/Optimization” program — 386 MW contracted to CalEnergy and Ormat with PNOC EDC as steam supplier — the supply chain that fills the interconnector. (Dolor — Ownership, Financing and Licensing of Geothermal Projects)

Strategies

DC for the long island hop: the sponsors chose HVDC because the distances and the submarine crossing defeat AC transmission economically — bulk power over long distance and under water at minimum loss, with converter control thrown in as a stability dividend. (Rudervall et al. — HVDC Transmission Systems)
Monopolar economy: implementing the line monopolar at 350 kV with earth return — rather than as a full bipole — halved the conductor requirement for the initial rating, leaving the bipolar description as the design’s grown-up form. (Wikipedia — HVDC Leyte–Luzon)
Staging the Visayas interconnection: the feasibility lineage — a 1981 JICA study for the Leyte power transmission project, World Bank approval in June 1994, co-financing by the Japan Export-Import Bank — shows the link built as the trunk line of a staged Visayas–Luzon interconnection, with extensions toward Cebu marked as planned in the project’s own documentation. (Wikipedia — HVDC Leyte–Luzon, Dolor — Ownership, Financing and Licensing of Geothermal Projects)
Geothermal and transmission built together: the Leyte program paired steam-field development with the line to carry it away — the World Bank’s energy-sector projects shifting drilling to the Upper Mahiao and Malitbog sectors of the Tongonan area, 28 of 38 wells of one program in Leyte, so that generation and transmission matured on the same schedule. (Dolor — Ownership, Financing and Licensing of Geothermal Projects)

Security and Safety Measures

Grid security through controllability: the converters’ fast electronic control of power flow is itself a protective feature — the stabilizing effect on the Manila AC network that the project documentation lists among its purposes, damping disturbances that would otherwise propagate between islands. (Rudervall et al. — HVDC Transmission Systems)
Electrode and grounding discipline: the earth-return design concentrates return current at the Albuera and Calabanga electrodes, which are connected by dedicated 69 kV DC electrode lines — installations whose siting and maintenance are the standing safety obligation of a monopolar scheme. (Wikipedia — HVDC Leyte–Luzon)
Strait crossings engineered by type: the submarine cable is reserved for the wide San Bernardino crossing while the narrow San Juanico Strait is spanned overhead from an island tower — route choices that respond to navigation, depth, and typhoon exposure across the Eastern Visayas. (Wikipedia — HVDC Leyte–Luzon)
Custody divided for accountability: ownership (TransCo) and operation (NGCP) have been institutionally separated since the 2009 concession, so the asset’s capital stewardship and its operational security reporting answer to different bodies — the framework within which outage and maintenance data are now published. (Wikipedia — HVDC Leyte–Luzon)
For researchers: keep the two straits straight — the submarine cable crosses San Bernardino, the overhead line crosses San Juanico — and keep the dates distinct: commissioning August 10, 1998, transfer to TransCo March 1, 2003, NGCP operation January 15, 2009. (Wikipedia — HVDC Leyte–Luzon)

Historical Context

The link descends from the Philippine geothermal program of the 1970s. Temperature-gradient wells drilled at Tongonan in Leyte (and Palinpinon in Negros) proved the fields; in 1976 the Philippine National Oil Company created the Energy Development Corporation to take over exploration and development while the National Power Corporation kept generation; and by the 1980s the World Bank was financing the sector — a US$36 million geothermal exploration loan in 1982, and an energy-sector project whose drilling program was shifted toward the Upper Mahiao and Malitbog sectors of the Tongonan area, 28 of its 38 wells in Leyte. A 1981 feasibility study by the Japan International Cooperation Agency defined the transmission project that would carry this power northward; the World Bank approved financing in June 1994, co-financed by the Japan Export-Import Bank; and ABB, with Marubeni, delivered the converter stations and cable. (Dolor — Ownership, Financing and Licensing of Geothermal Projects, Wikipedia — HVDC Leyte–Luzon)

The link entered service on August 10, 1998 under National Power Corporation ownership, feeding Luzon with Leyte geothermal power and propping up the Manila network’s stability. The build-out around it continued — the “Leyte-Luzon/Optimization” build-operate-transfer plants of CalEnergy and Ormat totalling 386 MW, and the separate Leyte–Cebu interconnection — while the link itself changed hands with the industry’s restructuring: to TransCo on March 1, 2003, and into NGCP’s operating concession on January 15, 2009, under which it runs today as the country’s operating HVDC backbone. (Wikipedia — HVDC Leyte–Luzon, Dolor — Ownership, Financing and Licensing of Geothermal Projects)

Challenges and Controversies

Monopolar or Bipolar?

The project’s own documentation is not of one voice: the line is described as a bipolar triple-bundle HVDC design in the engineering literature while the implemented scheme is monopolar at 350 kV with earth return, and the standard reference lists a single pole — a discrepancy researchers should report rather than smooth over, since it encodes the design’s unfinished second stage. (Wikipedia — HVDC Leyte–Luzon, Rudervall et al. — HVDC Transmission Systems)

The Two Straits and a Recurring Confusion

Popular accounts often call the whole link a submarine crossing of the San Juanico Strait; the verified route is otherwise — the cable lies at San Bernardino, and San Juanico carries only the overhead span on its island tower — a confusion that matters to navigation, fisheries, and disaster planning around both straits. (Wikipedia — HVDC Leyte–Luzon)

Concentration on Leyte’s Geothermal Fleet

Because the interconnector’s payload is Leyte geothermal power, the Luzon grid’s incremental supply rides on the island’s fields and steam contracts — the Tongonan complex, PNOC EDC’s steam supply, and the BOT plants — a concentration that ties Luzon’s margin to Visayas resource performance and to the continuation of the BOT arrangements. (Dolor — Ownership, Financing and Licensing of Geothermal Projects, Rudervall et al. — HVDC Transmission Systems)

Privatization’s Custody Split

The link’s passage from NAPOCOR to TransCo ownership and NGCP operation tracks the electric power industry reform debate itself — critics of privatization and defenders of the concession argue over maintenance adequacy and grid investment under the split custody that has governed the asset since 2003–2009, questions that belong to the industry’s larger politics rather than to the engineering record. (Wikipedia — HVDC Leyte–Luzon)