Source:JASE-W Japanese Smart Energy Products & Technologies

https://www.jase-w.eccj.or.jp/technologies/index.html

E-30

Keywords

Y4system or software

Z4electricity

F33

electricity
TEPCO Power Grid, Inc.

Engineering Service: Network Protection Scheme
Features
Since power outages are inevitable due to lightning and other natural phenomena, it is crucial that thenetwork protection system operates properly in order to isolate the network fault and keep power supply
reliability with reasonable investment.
Depending upon the importance of the area for power supply reliability, following improvement in theprotection system can be applied for further security and reliability.
Duplication of the protection system, including main protection and backup protection with fail safeprotections, with each of them are different operation mechanism
Development of the special protection system which prevents cascading outage and minimizes theoutage area. The improvement of the protection system performance can realize the reliable power
supply, which leads to following benefits.
• Reduction of the time of the forced outage• Minimize the forced outage for the very important area
• Prevent transmission facility damages due to overloads
Basic Concept or Summary
Depending upon the needs of the client, TEPCO Power Grid, Inc. provides the engineering services on
power network protection scheme, for further reliability of the power supply, based upon the wealth ofexperience in operation practices regarding the reviewing of work, relay operation analysis and setting
coordination, etc.
Example 1: Improvement in Protection Relay Performance
If a protection relay fails to properly operate, a cascading failure followed by a large-scale outage is likely
to occur. It is essential that, the actual operation of the existing protection relay be constantly reviewed,including the validity of the relay setting. In addition to this, computational analyses and surveys on theoperation of the protection relay during potential disturbances are to be conducted for the current andfuture system in order to prevent a malfunction.
TEPCO Power Grid, Inc. reviews all aspects of utility’s practices related to the performance of protection
relays. For example, TEPCO Power Grid, Inc. recommends using a combination of voltage and current
elements for a relay operation as shown in the figure below to enhance security against a single failure mode
including either CT or VT failure.

Example 2: Development of Special Protection System (SPS)Power flow, transient stability, voltage stability and system frequency in the future’s bulk power system isstudied with regard to severe faults in order to estimate the needs for a Special Protection System, which can
prevent a disturbance area from expanding. If a cascading fault is expected, the application of SPS is
considered and requirements for the SPS are found out based on offline simulations. Functional
specifications are also determined so as to fulfill the requirements. TEPCO Power Grid, Inc. has developedand operated several types of SPSs.

In addition, TEPCO Power Grid, Inc. helps other utilities to develop their SPS for the overload protection,transient stability, and system islanding. The figure below shows the outline of the system configuration ofthe SPS for transient stability.

Effects or Remarks
These network protection practices and schemes help secure and stable operation of the power system.
Based upon the experiences in Japan, TEPCO Power Grid, Inc. can study the cases as a consultant forthe client, and transfer technology through the study. Typical indices showing TEPCO Power Grid, Inc.’spower supply reliability and efficiency are as follows.
Forced outage frequency per customer per year: 0.09 (2017)
Annual total duration of accidental power outage per user - 6 minutes (2017)
Transmission and distribution loss rate: 3.8% (2017)
Installation in Practice or Schedule
Domestic

Design, construction and operation of power grid protection systems by TEPCO Power Grid,
Inc. (60GW of network capacity)

Overseas◆ Lao People’s Democratic Republic Grid Code Upgrade and Operational Organization
Enhancement (2021)◆ Kingdom of Jordan Reusable Energy System Integration and Stable Supply Promotion(2020)◆ Three Baltic States Promotion of Massive Reusable Energy Implementation, as well as
Supply and Demand Adjustments for Synchronization with European Power Systems(2020)◆ Myanmar Power Transmission and Distribution Technical Capability Improvements (2019)◆ India Supply and Demand Operations, as well as Systematic Stabilization Survey for
Massive Implementation of Reusable Energy (2019)◆ Gujaratis State of India Systematic Stabilization Project (2016)◆ Abu Dhabi Black Start Plan Formulation (2016)

Contact:

Overseas Business Office, Tokyo Electric Power Company Holdings, Inc.
URL: https://www.tepco.co.jp/en/hd/ourbusiness/consulting/index-e.html

E-30