IEEE Power & Energy Magazine - March/April 2021 - 78

table 5. An example of additional available capacity with the N−1 intertrip scheme.
Available
Installed
Capacity
Thermal
Without
Capacity
the N−1
Number (100% ×
Operational
Intertrip
Transmission Transmission Voltage of
Number
Capacity
Constraint Scheme
Number
Name
(kV)
Circuits of Circuits) (MW)
Factor
(MW)

Additional
Available
Availability Capacity
of the
with the
N−1
N−1 Intertrip
Intertrip
Scheme
Scheme
(MW)

500

6,580

3,290

Thermal
capacity

2,283

Not
available

500

13,162

6,581

Thermal
capacity

5,737

Not
available

275

1,532

880

Thermal
capacity

568

Available

651

275

612

Thermal
capacity

284

Not
available

275

1,236

648

Thermal
capacity

334

Available

587

Thermal
capacity

Available

102

Thermal
capacity

Available

208

109

Thermal
capacity

Available

generators to connect to power systems without network
facility upgrades, and this offers a great benefit, but there still
is an issue concerning network access by distribution generators as previously described. To realize the full application of
the N−1 intertrip scheme, it is necessary to accurately calculate
the opportunity cost of production losses caused by the N−1
scheme as well as establish a cost settlement system involving many generators based on the degree of their benefit. In
response to this, OCCTO is studying a system that will be
acceptable to both the target generator of the N−1 intertrip and
the cost bearers. OCCTO plans to put it into application within
the 2022 fiscal year.

The Introduction of Nonfirm Access
The shortage of ATC in bulk power systems caused by the
increase in the amount of generation interconnection by the
N−1 intertrip scheme results in an increase in the need for
network upgrades. Under the present cost allocation system
in Japan, upgrades may lead to inefficient power system
development and an increase in electricity costs. Therefore, OCCTO will adopt a system by which the need for a
network upgrade is appropriately determined by using an
evaluation of a cost-benefit analysis as well as comprehensively taking into account the cost-effectiveness and feasibility of mitigation measures. At the same time, OCCTO
is studying nonfirm access as a new generation interconnection mechanism for the power system when network
upgrades are inappropriate.

ieee power & energy magazine

For Further Reading
" Delivering our environmental future: Annual statement, "
National Grid Electricity Transmission, Warwick, 2015.
Accessed Nov. 6, 2020. [Online]. Available: https://www
.nationalgrid.com/uk/electricity-transmission/document/
129751/download
" On the concept of first-step application of N−1 Inter-trip
scheme in the development of power system facility planning
(Network Code, Article 55) (in Japanese), " The Organization
for Cross-Regional Coordination of Transmission Operators,
Tokyo, Japan, 2018. [Online]. Available: https://www.occto
.or.jp/access/oshirase/2018/files/181001_n-1densei.pdf
" Business plan FY 2019 of OCCTO, " The Organization
for Cross-Regional Coordination of Transmission Operators, Tokyo, Japan, 2019. [Online]. Available: https://
www.occto.or.jp/en/about_occto/articles/files/Business_
Plan_FY2019.pdf

Biographies
Noritaka Ohashi is with the Organization for Cross-Regional Coordination of Transmission Operators, Tokyo, 1350061, Japan.
Kazuki Terashima is with the Organization for CrossRegional Coordination of Transmission Operators, Tokyo,
135-0061, Japan.
Makoto Tanaka is with the National Graduate Institute
for Policy Studies, Tokyo, 106-8677, Japan.
p&e

march/april 2021

http://www.nationalgrid.com/uk/electricity-transmission/document/129751/download http://www.nationalgrid.com/uk/electricity-transmission/document/129751/download http://www.nationalgrid.com/uk/electricity-transmission/document/129751/download https://www.occto.or.jp/access/oshirase/2018/files/181001_n-1densei.pdf https://www.occto.or.jp/access/oshirase/2018/files/181001_n-1densei.pdf http://www.occto.or.jp/en/about_occto/articles/files/Business_plan_fy2019.pdf http://www.occto.or.jp/en/about_occto/articles/files/Business_plan_fy2019.pdf http://www.occto.or.jp/en/about_occto/articles/files/Business_plan_fy2019.pdf

IEEE Power & Energy Magazine - March/April 2021

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