Achieving a clean energy future – with less reliance on fossil fuels for electricity – is an important goal for Hawaii. HELCO is responsible for providing stable, reliable electricity to all its Big Island customers. Various renewable energy technologies are deployed on our island to provide energy for the utility grid. HELCO has a portfolio of sources, which currently provide electricity for about 35% of our needs. Due to the variable nature of many clean-energy sources,
such as solar and wind energy, these systems must be carefully integrated into the grid for the overall system to meet the standard of stable, reliable service our customers demand and deserve. To meet this standard, HELCO must match power generation with the load demand continuously, while also controlling costs.
The Hawaii Public Utilities Commission (PUC) establishes rules (also known as tariffs) that determine how electricity is to be delivered reliably, safely, and economically to all customers. HELCO provides several options for customers who wish to connect their own generation systems to the HELCO grid at the distribution level (Distributed Generation or DG). Interconnection rules for renewable DG are part of those tariffs and they vary by the type and size of the DG system.
Rule 14 specifies the Standard Interconnection Requirements for systems connected to the HELCO grid. Rule 18 applies to the special case of Net Energy Metering (NEM) systems and sets a maximum size on customer-sited renewable DG units, and limits to the amount of DG on a single circuit. Specific provisions of the Standard Interconnection Requirements vary according to the design maximum power output of the proposed DG facility. These rules can only be changed by approval by the PUC. Reputable renewable energy companies are aware of these rules, and they will advise prospective customers of them. They will also plan to comply with all appropriate interconnection standards in their designs of any DG intended to be connected to the public utility grid. All of HELCO’s tariffs, including the DG interconnection rules and standards, are available online, at www.heco.com.
The island’s utility electrical grid is made of bulk transmission lines and distribution circuits and each circuit has unique characteristics and customer loads. Because electric energy cannot be stored on the utility grid, the total amounts of generation must be balanced with customer demand loads at all times to maintain service at a steady voltage and frequency.
Renewable sources of energy such as solar and wind fluctuate, sometimes quickly. They are called “as available” sources because at any time their output may rise or fall with the availability and intensity of sunlight and wind. Also, the owner/operator may unexpectedly “turn off” the system for maintenance or other reasons. The variable nature of these sources requires that the size of their generating output be balanced to the load on the distribution circuit, and that their interconnection with the circuit be engineered to maintain stable and safe delivery of energy
to all customers.
Therefore, each DG system must be engineered (e.g. size, type, configuration) for the unique characteristics of the circuit to which it is to be connected. In some situations, depending on the feeder and the proposed DG system, a detailed Interconnection Requirement Study (IRS) is required. The IRS looks at both typical and worst-case combinations of electrical supply and demand, and determines whether or not additional control equipment is needed on the distribution circuit to prevent potentially damaging voltage and frequency excursions. Under certain scenarios, it may be necessary to provide for a quick disconnection of the DG facility to
prevent possible damage to customer and utility equipment.
The type of interconnection required therefore depends not only on the size of each individual DG generator on the circuit, but also on the ratio of the total DG output to the distribution circuit load. The current Rule 14 specifies that an IRS is necessary when the ratio of DG output to circuit load exceeds 10%. The Hawaiian Electric companies are proposing a revision to Rule 14; as part of the revision, HELCO hopes to raise the circuit load threshold to 15% before an IRS is needed.
The HELCO Locational Value Map can be used by customers and DG vendors as a starting point to determine the percentage of DG to feeder load at many locations throughout the Big Island. The interactive map shows that DG can be installed more easily in some areas than others. As a general rule, the less complex scenarios are associated with smaller DG systems that are connected in areas with large customer loads, but which do not have an excessive amount of renewable DG already connected to the grid.
Customers can download the latest version of the Locational Value Map. Navigate to the link on the HECO web site:
www.heco.com, select the tab for
Renewable Energy, select the link for
Clean Energy Planning Scenario. Then scroll down the page for the latest version of the maps for each island.
HELCO’s general advisory guidelines for planning DG systems are: 1) Do not over-build; 2) Match generation capacity to load demand; 3) Review the tariff rules carefully for requirements by DG size and circuit penetration, and give yourself some margin so that you do not exceed size limitations for particular rules.
It is strongly advised that the DG developer, or the customer, contact the utility early in the planning process for an initial assessment of the proposed DG project. In this way, HELCO can assist developers and customers to identify any serious engineering concerns, and thereby enable them to plan and implement their project in a timely and cost-effective manner. Please contact Energy Services at HELCO to discuss your plans for a renewable DG system".
___________
* Contact for HELCO West Hawaii: Sue Garrod at (808) 327-0546 or
This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Contact for HELCO East Hawaii: Jim Moulds (808) 969-0161 or
This e-mail address is being protected from spambots. You need JavaScript enabled to view it
How is HELCO presently managing the integration of new Distributed Generation (e.g. from solar and wind) into the existing grid, while maintaining the expected reliable supply of electricity to all its customers? 