communication on high voltage systems

7/29/2019 Communication on High Voltage Systems

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CIGRE SC D2 Meeting and Colloquium 2009

Tokio, Japan

EMERGENCY COMMUNICATION SYSTEMFOROPERATIONOF HIGH VOLTAGE DIRECT

CURRENT LINES

SUBJECT: Information and Telecommunication Systems Available in Emergencies at

Electric Utilities.

CARLOS DI PALMA

ARGENTINA

GUILLERMO GALARZA

ABB S.A.

ARGENTINA

SYNOPSIS

Within the High Voltage Transmission System planning in Argentina, the installation of

High Voltage Direct Current (HVDC) Lines is under consideration.

In this kind of power networks, the need of transmission of full information goes far

beyond the possibilities of power line carrier technology for the main communicationsystem.

In order to transmit digital protection links, packet switched control networks, video

surveillance, corporate Ethernet networks, generation shedding automatisms, etc., it is

mandatory to adopt solutions based on fibre optic transmission technologies, as the only

way to provide enough bandwidth.

However, fibre optic systems will boosters, preamplifier, Raman gain amplifiers, etc.,

due to the long distances involved in HVDC Lines, and all of them will add a high prob-

ability of faults. Besides, they will also include repeaters and remote amplifiers, which

are located outside of the substations, becoming real weak points in case of any natural

disaster (flood, earthquakes, rainstorms, etc.) or attack. As direct consequence, both re-liability and maintenance costs will be strongly affected.

In order to have a reasonable back-up communication system, and consequently to in-

crease Reliability and Availability figures of the HVDC Lines, it is desirable to use Di-

gital Power Line Carrier System (DPLC) with 512 kbps capacity, in order to obtain the

maximum channel efficiency (Cd/BWd), with the minimum cost/link length ratio.

By means of this solution, it will be possible to carry the minimal required information

for an acceptable and safe operation of the HVDC Lines in case of an emergency.

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This work describes the main criteria necessary to be taken into account for the design

of power line carrier links for long haul lines, as well as to describe the technologiesnormally applied for this purpose in Power Utility.

The paper will develop two main aspects in order to obtain a good emergency commu-

nication system:

* design and planning considerations

* main equipment features to be taken into account

The independence between the choice of the RF operating frequencies for new HVDC

Lines and the existing RF spectrum on HVAC systems, due to the isolation between AC

and DC high voltage systems, will allow the usage of extremely low frequencies (20-24kHz) and consequently obtain a high quality of services.

The main design considerations to reach the highest possible link Availability (Ai), will

be described. Among them, coupling modes, transmission capacity, maximum BER,

maximum efficiency, etc, will be discussed.

The absence of corona noise in the signal-to-noise ratio (S/N) of the HVDC Lines will

be taken into account, as well as the presence of residual noise originated after the con-

version process (see note *).

The behavior of the DPLC link capacity in function of a given (S/N)min will be studied.

The criteria for the maximum availability will be analyzed, as well as the complete

design based on the worst case, in order to assure the permanent link operation under

adverse S/N conditions.

The limit for the information capacity established by the Shannon Theorem, will be dis-

cussed. The required BW in order to transmit the amount of data assigned to the emer-

gency communication system, will be contrasted with the DPLC`s equipment features.

From the equipment point of view, the main desirable characteristics to have in the

DPLC device will be described. Subjects like capability of dynamic resource allocation,allocation of a hierarchy of the different functions to be transmitted in an emergency op-

eration, will be also developed in the paper.

Analysis of different alternatives of reduction of transmission speed as well as reduction

of quantity of services transmitted will be analyzed. The convenience of the use of the

fall-back/ fall-forward function to adjust the transmission capacity under adverse condi-

tions, and subsequent recovery process, will be evaluated.

Additionally, the paper will analyze the advantage of the usage of equipment that can be

configured as both, DPLC as well as APLC, so as to obtain an additional alternative for

the security in the transmission of the information.

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Finally, a summary will show the comparative analysis of the information to be trans-

mitted by each communication system (Main and Backup), under normal operation and

emergency respectively, in order to clarify how the goal is obtained with the proposed

integrated solution.

(*) The paper will not analyze the noise generated for the Converter Station, based on

the assumption that high frequency filters must be taken into account in the electric

design procedures.

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communication on high voltage systems

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