Power

Hitachi has won a contract to use Advanced Gas Path^* (AGP) to improve output and efficiency at Ohgishima Power Station (natural gas, 1220 MW), which is jointly owned by Tokyo Gas Co., Ltd. and Showa Shell Sekiyu K.K.

The work involves the incorporation of high-performance, high-temperature components into three gas turbines to improve their thermal efficiency. This also has the potential to reduce nitrogen oxide (NOx) emissions through the use of a low-NOx combustor and to expand the combustion range.

Improving the thermal efficiency of a power station increases its output and efficiency, reducing its fuel use and improving its economics. Another benefit from the incorporation of high-temperature components is that it can significantly lengthen the time between inspections.

The work on the project was conducted during inspections, with on-site staff, including those engaged in design and commissioning, working together to complete the work on Unit 2 in June 2018, on schedule and without any accidents or damage. (The other units are Units 1 and 3, with work on the next unit planned for 2019.)

Hitachi is currently planning the work on the next unit to ensure that it, too, is undertaken without any accidents or damage.

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Advanced Gas Path is a service supplied by General Electric Company (GE) that utilizes the latest technology for gas turbines.

Paiton Power Station is a coal-fired power plant located in East Java in Indonesia. Unit 3 at the plant plays an important role in the electricity grid on the island of Java, having the largest capacity of any generator in Indonesia. Accordingly, the requirements for the new transformer included not only high quality, but also that its installation be moved forward drastically so that generation would be able to commence at as early a date as possible. Hitachi's large transformers typically require 12 months for design, parts procurement, manufacturing, and delivery, with a further month or more being needed for installation. In this case, however, to satisfy the customer's requirements, the delivery time for this contract was unprecedentedly short, with delivery in five and a half months and only 28 days for installation.

To accommodate this short delivery time, Hitachi drew on the comprehensive capabilities of “One Hitachi” to fulfill its promise to the customer, shortening the delivery and installation times by one week and six days respectively. Along with establishing a project management team that encompassed sales, operations, and manufacturing, Hitachi put a strong emphasis on managing the project in a way that would ensure smooth communications with the customer and achieve the best overall result. This effort also included working with suppliers to prioritize quick delivery; taking steps at the manufacturing facility to work double shifts, allow for holidays, and reassign staff across different departments; and engaging in collaborative creation with Hitachi's Indonesia subsidiary, PT. Hitachi Asia Indonesia, to shorten the installation schedule.

Hitachi intends to continue supplying reliable products with high quality by drawing on the experience gained from this work in future projects.

Gas circuit breakers play an important role in protecting power transmission networks from short circuit currents such as those resulting from lightning strikes. To shut off the current on detection of an abnormal condition, a high-speed mechanism inside the circuit breaker mechanically separates the contacts, and arc-extinguishing gas is blasted to cool the arc plasma that is generated between the contacts as they disconnect. This means that understanding the behavior of the gas inside the circuit breaker, including the arc plasma, is important for improving circuit breaking performance and equipment reliability.

In response, Hitachi has developed a technique for thermal gas flow analysis with enhanced models of various phenomena, including the emission of heat and light by the arc plasma generated between the contacts, ablation of the insulation nozzle, and the behavior of compressible thermal fluids. The technique provides more accurate assessments of the interactions between these different phenomena and of the spatial distributions and temporal variations in the temperatures and pressures of the high-temperature gas heated by the arc plasma. Hitachi intends to utilize the technique to develop smaller and more reliable gas circuit breakers with lower switching energy, and through the resulting products to contribute to the reliable supply of electric power.

Hitachi manufactured and delivered a highly efficient 20-MW-class frequency converter using a zero-sequence canceling modular multi-level converter (ZC-MMC) as part of the replacement of a frequency converter type line commutated converter (LCC) used to transfer electric power between the 50-Hz and 60-Hz power systems at a customer site^*.

The converter is a world-first product, using a ZC-MMC and with the main circuit having 21 chopper cells in series (including one redundant cell). The control system performs individual control of each cell and has a standby backup system for high reliability. The upgrade was intended to deliver the following operational benefits.

1. A wider operating range that allows unconstrained and uninterrupted operation, even when reversing power flow direction.
2. Reduced harmonics [due to the multi-level converter type voltage source converter (VSC)] means there is no need for a harmonic filter.
3. Reduced voltage fluctuations (through use of the converter type VSC to control reactive power) enables control of voltage fluctuations in the on-site distribution system and power factor with respect to the grid connection.

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This converter commenced operation in December 2016.

There is rising demand for solutions that can make the electric power infrastructure more flexible and robust, including by facilitating the adoption of renewable energy, coping with frequently occurring natural disasters, and introducing market mechanisms to reduce the cost to society. Also in demand are enhancements to multi-faceted management systems for administering, operating, and maintaining electric power infrastructure in response to the shrinking workforce, a consequence of the aging population.

As a first step toward satisfying these diverse requirements, Hitachi has analyzed the utility of core technologies for online optimization. In particular, Hitachi is involved in a feasibility study as part of a project (P11013) by Japan's New Energy and Technology Development Organization (NEDO) in which Hitachi joint venture subsidiary THE Power Grid Solution Ltd. is playing a central role. The study is looking at ways of using systems to obtain benefits such as lower transmission losses by achieving an optimal voltage profile.

Hitachi also aims to supply even more effective solutions by taking on the associated issues from a variety of different perspectives, including trialing battery management systems and enhancing the functions of electric power distribution systems to that optimization and other sophisticated computing techniques can be used as part of the system.