Project Subjects
Next-Generation Communication Network System
Background and Objective
Power system ICT (Information and Communication Technology) infrastructures indispensable in thenext-generation grid have been well implemented for power generation and delivery, but have yet to be developed
for customer communications including smart metering and power asset maintenance and diagnosis. In addition, communications for power system protection are still proprietary and legacy (non-IP-based) whereas others
mostly are being IP-based.
This project deals with the network design and the development of fundamental technologies for demandarea communications interconnecting customers, distributed energy resources and distribution grids, wide-areaand high-speed communications promoting reliable and ﬂexible power system protection and control, and sensor
communications enhancing asset management and operations.

Main results
1. Performance evaluation of the communication method for demand area network
We evaluated the performance of IEC 62056 protocol using a test system. The system consists of asimulated utility device and an IEC 62056-implemented embedded board regarded as a customer gateway (Fig.
1) which assists information exchange among utility devices and customer premise devices. The result showsthat major application information can be accommodated in the protocol in the delay time point of view except
for control information transmission of distributed generations requiring several ten milliseconds in delay time
[R090009]. We also developed an estimation method of power line communication (PLC) transmission losses
which is one of principle design parameters of PLC communication network for collective housing [R09022].
2. Evaluations of time synchronism of wide-area and high-speed control network
Fundamental evaluations were conducted for the network architecture that utilizes off-the-shelf andstandardized IP-based technologies, and implements various modular functions and applications in a distributedmanner throughout the network. Employing wide-area Ethernet (L2) and highly precise time synchronization
scheme (IEEE 1588), four prototype devices with four applications implemented were examined to achieve a timesynchronization error of microseconds sufﬁcient for power system protection and cooperative operations among
different functional modules [R09011]. An applicable structure of IEEE 1588-based network suitable to wide
area power system was also proposed [R09012].
3. Evaluation of wireless communication characteristics in the ﬁeld sensor network for power facilities maintenanceFor the wireless sensor network that enables the condition monitoring of power facilities, radio propagation characteristics including reﬂections and shadings by metal structures in substations which inﬂuence communication performance were experimentally estimated. We clariﬁed the characteristics of several radio frequency
bands valid for wireless sensor networks can be represented by the four-wave interference calculation model andproposed a prediction method for stable communication with two frequency channels in a band, by applying theproperties that the receiving power difference by frequency is remarkable at the dip point of the receiving level(Fig. 3) [R09013].
Other reports
70[R09024]

Environmental and Energy Utilization Technology
Metering
Unit

Using
IEC 62056

Distribution
Board

Metering
Data Storage
Customer Device
Management

PVPower
Conditioning
Subsystem

Communication
Interface

Disconnect/Connect
Unit

Battery

Air Conditioner

Communication
Interface

Utility Owned
Communication
network

Customerdata Storage

Customer Gateway

Communication
Interface

Metering, Tariff, Outage
Management

Utility

InternetService
ProviderHeat Pump
Water Heater

PHEV/EV

RouterPC

Processing

Primary
protection(2 terminals)#3#4

Backupprotection

Primaryprotection(3 terminals)

Stability
monitoringand control

Data format conversion (analog, digital)

Communication

Measurement/tt//
Control

Sampling synch.
Instantaneous value
Phasor

L2 network

Effective value

State transition

Analog input(AI)

Input/Output

Time synch. (time stamp)

Trip, control

Digital input
(DI)）

12
Propagation distance

86420Plane

Digital output(DO)

Mean square of power differences
at intervals of 1m [dB](a) Conﬁguration of prototype deviceSynchronization Errors(ns)Plane

Substation

950MHzPlane

Substation

2.4GHz(a) Experimental result (plane area andline switch area of substation)

Power System Equipment

Via 2 repeater switches
Via 6 repeater switches

1,000

Substation

400MHzSignal1,5001≦z≦10 m
10＜z≦20 m
20＜z≦47 m

10(No data)

PQVF
measurement#2(No data)

Functional Modules

Software modules (Applications)
Device #1

Mean square of power differences
at intervals of 1m [dB]Fig. 1 Customer Gateway structure and applied IEC communication standard
IEC 62056 (Electricity metering - Data exchange for meter reading, tariff and load control) was applied for utility-customer
communication and the performance was evaluated.

5000Error span
-500
-1,00012108

Propagation distance1≦z≦10 m
10＜z≦20 m
20＜z≦47 m

64
20
2 wavesmodel

4 wavesmodel

400MHz2 wavesmodel

4 wavesmodel

950MHz2 wavesmodel

4 wavesmodel

2.4GHz-1,500
20

40

60

80

100

Traffic Load on L2 switch Link (%)(b) Time synchronization errors between devices
Fig. 2 Prototype devices and time synchronism
accuracy
The composite of functional and software modules of eachdevice realizes the redundant and distributes conﬁgurationof various applications throughout the network.

(b) Calculation result (2- and 4-wave interferencemodels)Fig. 3 Characteristics of spatial ﬂuctuations ofreceiving power
The ﬂuctuation level of receiving power is estimated bya two-wave interference model (direct wave and reﬂectedwave by ground) in plane area and a four-wave interference model (additionally two reﬂected waves by metalstructures) in substation.

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