Problems Found During Testing of PDH Devices

8/11/2019 Problems Found During Testing of PDH Devices

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Problems Found During Testing of PDH Devices Used

for Transmitting Data Between Power Systems LineDifferential Protections

Ryszard Kowalik,

Institute of Power Engineering

Warsaw University of Technology,Warsaw, Poland

[email protected];

Marcin Januszewski

Institute of Power Engineering

Warsaw University of Technology,Warsaw, Poland

[email protected]

AbstractThe paper presents the testing methods, laboratory

stand and equipment applied for the tests of exchanging data

from protection devices by the PDH equipment. The paper has

been developed as a result of cooperation between the Power

Engineering Institute of Warsaw University of Technology and

PSE Operator S.A. (PPGC Operator). A number of tests had

been made under this cooperation, including functional tests of

protections and PDH equipment performed with regard to

determining the possibilities, conditions and problems that may

arise or occur during their interoperability

I. THENEEDFORPERFORMINGTESTS

The need for checking and testing the Power EngineeringAutomatics Protection (EAZ) appeared since the beginning ofthe power engineering protections technology existence.Pursuant to the recommendations specific to this technology,the LV power transmission lines should be protected throughthe two, fundamental protections with different operation

principle. It has been adopted that the first protection of theLV line, called the primary protection, should be the sectionrelay (residual current relay or phase comparison relay), whilethe distance relay should act as the second protection. Thesection protections enjoy a number of benefits and are verygood methods of LV line protection, however, they comprisethe equipment installed at the end of the line, which, in orderfor the proper interoperability, must exchange information

among them. This information is sent through thetelecommunications links, which may be of various designsand properties. Currently, in order to eliminate the impact ofinterference, the transmission of information is promotedthrough the optical fiber cables whose properties allow thetransmission with speed 200000 km per second of a number offlows of data with the rate 10Gb/s (e.g. 160 flows for DWDMtechnology). Currently, in order for the proper operation thesection protections require the transmission of the flow of dataat the rate of 64 kilobits per second, which constitutes0.0000064 of one of a number of flows of data with rate

10Gb/s, mentioned above. As can be seen from thecomparison presented, the same fiber, which when used for

power engineering protection purposes, may serve sendingonly data between one complete set of section protections,may also be used for transmission of millions of data flows ofthis type, which may convey a number of types ofinformation, coming from the voice, through the picture to thevarious data of Internet network. No wonder that PDH or SDHsystems, allowing to use light pipe cables in a more efficientway, have been present for a number of years in manycountries, serving the transmission of data for powerengineering section protections.

It should be realized, however, that the section powerengineering protections are not the phone devices, TV sets orcomputers dedicated for browsing through the WWW sites.These are the critical components of the power (grid) system,and the existence of the system interfaces serving transportinglarge rates of electricity from the places of generation to theconsumers is largely dependent on their proper functioning.As is the common knowledge, one superfluous deenergizingof the LV line may lead to the loss of balance of the system

being in the critical operating phase, as a result causingconsequences whose value will considerably multiply theamount that may be obtained through the larger use of opticalfibers.

For the above-mentioned reasons, it is very important todetermine the requirements to be fulfilled by the links andtelecommunication equipment to allow their use for sendinginformation originating from power engineering protections.These requirements determine several key parameters (fromthe protection devices viewpoint), specific totelecommunication systems, including:

time lag introduced by telecommunicationsequipment,

PPGC Operator, Ministry of Science and Higher Education. (sponsors)

978-1-4244-5794-6/10/$26.00 2010 IEEE 1209


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time lag asymmetry introduced bytelecommunications equipment in both directions ofdata transmission,

type of interface allowing entering data to thetelecommunications device,

parameters of the interface allowing introducing datato the telecommunications device (inter alia, of thetype of data frames and transmission rate).

Equally important as the determination of the requirementsis also checking the properties of the telecommunicationdevices used with regard to determining their suitability forsending data from protections.

At the initiative of PPGC Operator in 2006, a number oftests were performed at the tests stand of EXATEL company

found at the seat of the PPGC Operator, to verify theproperties of the PDH telecommunications appliances, ofFMX series and their interoperability with the section

protection devices: P543, REL561, 7SD512, 7SD510, L90 andtele-protections: SWT3000, RFL9745GD/GARD8000 [1], [2],[3], [4], [5], [6], [8].

Under the tests, the following properties were verified:

checking the performance of residual currentprotection devices, type REL561 and P543, in thetelecommunication system employing PDH (FMX)and SDH (Surpass) equipment,

checking the performance of residual current

protection devices type REL561 and P543 in thetelecommunications system employingtelecommunications channels created in the nodes ofthe real (operated) SDH/PDH network ,

checking the performance of protection, phasecomparison devices type 7SD510 and 7SD512 in thetelecommunications system employing PDH (FMX)and SDH (Surpass) equipment,

checking the performance of the protection, phasecomparison devices, type 7SD510 and 7SD512, in thetelecommunications system employingtelecommunications channels created in the nodes of

the operated SDH/PDH network,

checking the performance of the L90 protection,residual current devices in the telecommunicationssystem employing PDH (FMX) and SDH (Surpass)equipment,

checking the performance of the SWT protectionequipment in the telecommunications systememploying PDH (FMX) and SDH (Surpass)equipment,

checking the performance of the RFL9745GDprotection devices in the telecommunications systememploying PDH (FMX) and SDH (Surpass) devices,

checking the performance of the SWT protectiondevices in the telecommunications system employing

telecommunications channels created in the nodes ofthe operated SDH/PDH network,

checking the performance of theRFL9745GD/GARD8000 and protection devices inthe telecommunications system employingtelecommunications channels of the SDH/PDHnetwork,

checking the possibility of obtaining in the PDHtelecommunications network supervision mode thesignalling of the faults to the communications channelused by the protection device (checking the possibilityof entering alarm signals from protection devices tothe supervision system of the PDHtelecommunications network),

checking the possibility of obtaining the signaling bythe telecommunications device of the faults totelecommunication path (checking the possibility ofentering alarm signals from the telecommunicationdevices to protection devices).

Due to the scarcity of space in this paper, limited to severalpages only, merely three issues have been described below:

tests stand of EXATEL, constructed at the seat ofPPGC-Operator and

selected tests regarding the system of two appliancestype REL561, where the data were inter-exchanged atthe rate of 64 kilobits per second through the X.21

standard ports created in the PDH system constructedfrom FMX equipment,

conclusions drawn from all the tests performed.

II. TESTSTANDUSEDPENDINGTESTS

As mentioned, the tests were performed at the test standarranged in the telecommunications accommodations ofEXATEL, found at the seat of PSE Operator S.A. in Warsaw.This stand comprised two parts, notably electrical andtelecommunications, whose architecture, in the block form,has been presented in the Fig. 1.

A. Electrical part of the tests stand

The tests of protection devices were performed with theuse of CMC microprocessor testers in the arrangement asshown in the form of the block diagram presented in theFig. 1. The main components of the measuring systemelectrical part comprised CMC 156 tester and CMS56amplifier, out of which each allowed forcing three currentsand three voltages. The CMC device also allowed monitoringthe state of eight binary inputs and controlling two binarysignals. Both devices were controlled from PC computer,designated in the Fig. 1 as the CMC control computer .

In the case of tests of tele-protection equipment, the CMCtester transmitted the signal +220 V DC to the binary inputs of

both devices checked through the two binary outputs in the

form of contacts. These signals, in the form of data, were sentthrough the telecommunications system to the adjacent tele-

protection device where they caused the change to the status

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TESTER CMCoutputs

cu rr en ts v olt age sbinaryinputs

binaryinputs

currentsvoltages

CMC

control computer

LPT

CMS

Power supply220Vdc

ConverterOPTO/X.21

telecomm.link

OPTO

Converter

OPTO/X.21

OPTO

Telecommunicationlink

twisted pair nx2

Telecommunication

linktwisted pair nx2

Telecommunication system

PDH/SDH

Model B

(PDH) Port X.21

Model SNUS

(PDH) Port X.21

voltagesbinaryoutputs

Protectiondevice (2)

currents

Protectiondevice (1)

binaryinputs

currents vol tagesbinaryoutputs

lublub

binary

outputs

binaryinputs

Electricalpart

Telecommunications

part

X.21 X.21

telecomm.link

telecomm.link

telecomm.link

binary

Komputernadzorujcy

urz. PDH i

SDH

Makieta SNUSPort ? (CPF)

V.24, X.21,G703.1

Makieta BPort ? (CPF)

V.24, X.21,

G703.1

G703.6 Port AMakieta A

G703.6 Port B

G703.6 Port 1CC Makieta

SNUS

G703.6 Port 5

TXa, TXb;Rxa, RXb;

TXa, TXb;Rxa, RXb;

telecomm. link G703.6 (2Mbps)2x2 twisted pair

telecomm. link G703.6 (2Mbps)2x2 twisted pair

RS232

PDH/SDH 2 Mbps Exatel networkchannel with protection of ? nodes

(symmetrical time lag 9.73 ms)

OPTO Port 1, Port 3

SURPASS 1 (L)G703.6 Port 1 (108us)

OPTO Port 1, Port 2

SURPASS 2 (P)G703.6 Port 1 (108us)

telecomm. link OPTO E2000/E2000 ?monomod

protection

deviceP543 (1)

Rxa, RXb TXa, TXb

TESTER CMCbinary

inputsc ur re nt s v ol ta ge s

binary

outputs

CMC controlcomputer

LPT

binary signal

220Vdc

TXa, TXb;

Rxa, RXb;

TXa, TXb;

Rxa, RXb;

TXa, TXb;Rxa, RXb;

TXa, TXb;Rxa, RXb;

Rxa, RXb TXa, TXb

PDH/SDHtelecommunications system

telecommunications linkto protection devices

telecommunications link

to protection devices

of binary output. The binary outputs of the tele-protectionequipment were connected to the binary inputs of the CMCtester. Therefore, the CMC tester was capable of changing the

state of input signals of the tele-protection equipment andchecking the change to the state of binary outputs of thesedevices. In that case, the tests involved forcing changes at theinputs and the observation of outputs response time.

Figure 1. Electrical and telecommunications part of the test system used for

checking the operation of protection devices exchanging data through thePDH/SDH telecommunications system

In the case of tests of residual current and phase comparisonprotective equipment, the CMC tester provided through itsthree current outputs the signals to the current inputs of thefirst of the devices checked, while the CMS amplifier

provided through its three current outputs the signals to thecurrent inputs of the second of the devices checked. Based onthe signals, the protections counted the phase or value ofvectors of currents and transmitted this information throughthe telecommunications system to the neighbouring protectiondevice. On the grounds of the analysis of the informationreceived, the neighbouring protection device receiving thedata decided on the action for disconnection, which involvesthe change to the state of one of binary outputs. The binaryoutputs of the protection devices were connected to the binaryinputs of the CMC tester, owing to each the latter was capableof changing the state of binary outputs of these devices andchanging the input currents of both protection devices. In thatcase, the tests involved forcing the changes to the parameters(amplitude, phase) of the current signals at the inputs of

protection devices and observation of response time of their

outputs or maintaining the constant values of currents(amplitude and phase) of the current signals and observationof the response of outputs in the case of changes made to thetelecommunications system.

B. Telecommunications parts of the tests stand

The tests of devices were performed with the use of thetelecommunications system presented in the form of the blockdiagram in the Fig. 2. The main components of thetelecommunications part of the measuring system involved thePDH equipment, exchanging data by means of the G.703standard links with rate 2 Mbps. The flows of data mentionedwere transmitted by the 2Mbps channel created in thetelecommunications network made with use of SDHequipment.

During tests, the following three configurations of SDHequipment were used :

connections of two SDH nodes (Surpass) introducingthe time lag of some 100s,

connections of about a dozen SDH nodes of theSDH/PDH network operated, introducing the time lagof some 3.3ms ,

connections of several dozen SDH nodes of theFDA/PDH network operated, introducing the time lagof some 150s (basic path) and 8.5ms (protective

path).

Figure 2. Telecommunications system with two directions of transmission

switched to by P543 device

Additionally this system allows commuting eight connectionscreating two complete sets of broadcast signals (TxA, TxB)and reception signals (RxA, RxB) in the G.702 standard withrate 2Mb/s. These sets created two links, through which thePDH equipment (Dummy A and CC Dummy SNUS)exchanged data with SDH equipment . The system describedallowed switching the telecommunications channel from theCMC tester level, which in turn, enabled the dynamic changesto the configuration of telecommunications connection,including the change to the telecommunications connection in

the course of or directly prior to the simulated interference,and introducing the asymmetry in data sending (one directionwas operated by the SDH Surpass equipment, while anotherone through the link made in the SDH/PDH network underoperation) etc.

III. THE SELECTED TESTS OF REL561DEVICE

As mentioned, one of the devices tested involved the set oftwo residual current relays, type REL561 operating as shownin the Fig. 2. During testing, the protection devices exchangeddata between one another with rate 64kb/s through the portswith X.21 standard, interoperating with PDH (FMX)telecommunication equipment ports of the same type. For the

purposes of tests of REL 561 devices, the channels with rate64 kbps were created in FMX devices, two types of X. 21interface cards being used for entering flows of data: cards of

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new type, named CPF2, equipped with CIM X.21 module, andold type cards with the name DSC8-x.21.

The tests were performed with regard to stating anddetermining the impact of time lags appearing with thetransmission of data through the telecommunicationequipment on the performance of these devices duringtransmission of currents with rated value (1 In) and during thesimulation of the internal short circuit with the value ofcurrent amounting to 1 In. The values of settings of residualcurrent function in both relays were the same and respectivelyamounted to: CTfactor=1, Iminsat=100%, Iminop=20%,Idiflvl1=20%Ibias, Idiflvl2=50%Ibias, Ilvl1/2cros=500%,AsymDelay=0ms.

The detailed tests of REL561 devices response to thechanges introduced into the telecommunication systems were

pertinent to the following cases: bidirectional transmission of data through PDH

network, interoperating with SDH equipment(Surpass) under the conditions of symmetric time lagwith the value of 4.7ms,

bidirectional transmission of data through theSDH/PDH network under operation (symmetric timelag with value about 7.3ms or 12.6ms),

unidirectional transmission of data through the SDHSurpass system, and the transmission of data in theother direction through the SDH/PDH network underoperation (asymmetry time lag with value in one

direction 4.3 ms and 7.3 ms in the other direction,

transmission of data switched over at the level of PDHnetwork (through the system of binary relay outputs ofthe P543 protection device),

transmission of data switched over at the level of PDHnetwork on short-circuit occurrence,

transmission of data switched over at the level of SDHnetwork (through forcing by the supervising system toswitch from the primary path to the secondary/reserve

path or vice versa),

changes to the status of CPF2 access cards of PDH

equipment (e.g. restarting, reconfiguring, etc.)

changes to the status of DSC8-x.21access cards ofPDH equipment (e.g. restarting, reconfiguring, etc.)

Usually, several tests were performed for each of the casespresented, whose results were recorded in the text file and asthe screen shots. The screen shot contained the time conductsof binary and analogue signals, shown in the software underthe name Test Universe that controlled the CMC tester.

In the two first cases of tests, characteristic of thesymmetric time lags, no disconnection was obtained duringforcing the load current, i.e. simulating the state of normal lineoperation. In the same cases, while simulating the short-

circuits, the stable disconnection effect was obtained with time25-29 ms (with the time lag in the telecommunicationschannel amounting to 4.7 milliseconds ) and 33-37ms for the

data transmission through the protection channel with time lag12.6ms. It should be mentioned here that the tests mentionedwere performed for the stable configuration of CPF2 cards and

CIM X.21 modules operation (neither cards nor modules wereeither disconnected or configured) and with the additionalcorrection of time asymmetry in one of REL561 relays,through the change to the value of the parameter with thename AsymDelay. The examples of time conducts of thecurrents forced and the observed performance of relays have

been shown in the Fig. 3 and Fig. 4. A table can be seen at thetop of the figures, containing the values of times related to the

places of location of cursors 1 and 2 and the value C2-C1determining the time elapsed between them. The left-handcursor is found at the place determining the moment when thechange to the place of the currents takes place, simulating theoccurrence of the international short circuit, while the right

hand cursor - at the moment of the occurrence of the binarysignal designated as Idiff> showing the response of the first ofprotection devices. Several milliseconds later, the binarysignal designated as Idiff>> appears, proving that the second

protection also responded properly.

During testing, a number of tests were performed withregard to performance of relays in the case of changing to thetransmission paths (e.g. in the course of or at the moment ofthe occurrence of short-circuit). The transmission of datathrough the channel with asymmetric time lags (e.g. throughthe SDH surpass equipment system in one direction, andthrough the SDH/PDH network under operation) caused the

blockage to the performance of the residual current function

for the period of about 12 or 16 seconds, if the short-circuitappeared two seconds as of the moment of asymmetryoccurrence. If the short-circuit occurred within less than twoseconds as of the appearance of the time asymmetry of datatransmission, the relay disconnected with time about 30 ms. Inthe case of the short-circuit occurring at the moment of thereturn of data transmission time symmetry, the operation timemeasured amounted to 140 ms.

Figure 3. Performance of the REL561 protection with the transmission of

data through the symmetric channel - time lag about 4.7ms

For the majority of the tests above described, the type ofthe short-circuit simulated did not influence the time of

equipment response. However, with some other devices, thedifference was noticeable and usually amounted to 5 ms morethan was the case for the one-phase short-circuit.

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Pending testing, a number of tests were performed withregard to performance of relays in the case of the execution ofvarious types of tasks having impact on the status of CPF2

cards with X.21 interface (CIM X.21 module) of PDH (FMX)equipment, concerning:

restarting the card through removing it from the rackand reinserting after some dozen seconds,

restarting the cards through the issuance of thecommand for restarting from the level of thesupervision program,

reconfiguration of the cards through the issuance ofthe command for reconfiguration from the level of thesupervision program,

changes to the placement of CPF2 cards.

Figure 4. Performance of the REL561 protection with the transmission ofdata through the symmetric channel - time lag 12.6ms

It has been established that any manipulations of the abovetype exert considerable influence on the asymmetry of timelag occurring in the telecommunications system, causing theoccurrence of the residual current with various values. Thetable 1 mentions some of the actions executed and theobserved residual current values that appeared following theexecution in the case of forcing the flow of load current withvalue 1A. As can be seen from the table 1, the values of thetime lag asymmetry appearing in the course of variousoperating activities (irrespective of the time lag introduced bythe SDH system) triggered, for the load current as low as 1A,

the occurrence of the residual current bigger than the value setin the residual current relay (Idiff=0.2A), which triggered itsactivation.

TABLE I. THE IMPACT OF OPERATING ACTIVITIES PERFORMED IN THEPDH(FMX)EQUIPMENT ON THE VALUE OF THE RESIDUAL CURRENT OF THE

REL561RELAY IN THE CASE OF DATA TRANSMISSION OVER 64KBPSCHANNEL

The system of telecommunications connections shown in Fig. 3 (the time

lags in the order of 12.7 ms - reserve path of the SDH/PDH network

under operation) 64 kbps channel, CPF2 card, CIM X.21

The description of operating activities executed in the

PDH equipment

The value of

residual current

1. Replacement of CIM X.21 modules of CPF2 cards

(left-hand REL561 relay obtained the CIM X.21 module,

with which the right hand REL561 relay interoperatedbefore and vice versa); in order to compensate the

Idiffwylicz.=0.4

2A (this

corresponds tot=1350s)

asymmetry to Idiff=0.003A in the right hand relay, theparameter AsymDelay=1.35ms was set

2. Replacement of CIM X.21 modules of CPF2 cards

(left-hand REL561 relay obtained the CIM X.21 module,with which the right hand REL561 relay interoperated

before and vice versa); in order to compensate the

asymmetry to Idiff=0.003A in the right hand relay, theparameter AsymDelay=1.05ms was set

Idiffwylicz.=0.3

3A (thiscorresponds to

t=1050s)

3 Replacement of CIM X.21 modules of CPF2 cards

(left-hand REL561 relay obtained the CIM X.21 module,

with which the right hand REL561 relay interoperated

before and vice versa); in order to compensate theasymmetry to Idiff=0.003A in the left hand relay, the

parameter AsymDelay=0.95ms was set

Idiffwylicz.=-

0.3A (this

corresponds to

t=-950s)

System of telecommunications connections as shown in the Fig. 3 (time lags

in the order of 4.3 ms - path through the SDH Surpass equipment - 64 kbps

channel, CPF2 card, CIM X.21

Description of operating activities executed in the

PDH equipment

The value of residual

currentNew lot of measurements, the rate of 64 kbps was

set and:

AsymDelay=0.20ms in the left hand relay,

AsymDelay=0.00ms in the right hand delay

Idiff=0.685A; stable performance

In order to compensate the asymmetry to

Idiff=0.003A in the left-hand relay, the parameter

AsymDelay=2.45ms was set, and in the right hand

relay, AsymDelay=0ms

0.685A (this

corresponds to t=2225s)

Removal and insertion of both CPF2 cards (dummy

B and SNUS)

As a result, Idiff=0.549A was obtained; stable

performance

0.549A (this


Reset of REL561 equipment

As a result, Idiff=0.549A was obtained; stableperformance (i.e. the result the same as prior to

performing the reset of REL 561 equipment)

0.549A (this


Removal and insertion of both CPF2 cards (dummy

B and SNUS)

As a result, Idiff=0.485A was obtained, stable

performance

0.485A (this


Consecutive removal and insertion of both CPF2

cards (dummy B and SNUS)

As a result, Idiff=0.676A was obtained, stable

performance

0.676A (this


New lot of measurements, the rate of 64 kbps was

set, changing from the rate of 256 kbps, and the

following settings were made: AsymDelay=0.0ms

in both relays


0.891A (this


New lot of measurements, the rate of 64 kbps was

set, changing from the rate of 128 kbps

(AsymDelay=0.0ms in both relays)


0.891A (this


In order to check the properties of CPF2 card in the case ofoperation with other transmission rates, the similar type oftests for 256 kbps link were made. In the case of all tests forthis rate, the values of changes to data transmission time lagasymmetry not bigger than 350 s were obtained, i.e. for thetransmission of load current with value 1A they triggered theoccurrence of the residual current with value not larger than0.110A.

In order to compare the performance of various cards ofX.21 interface, the similar type of tests for 64 kbps link weremade where older type cards with symbol DSC8-x.21 were

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used on the side of PDH equipment. In the case of all tests,minor values of changes to asymmetry of transmission datatime lag were obtained, not bigger than 73s, i.e. for the

transmission of the load current with value 1 A, they triggeredthe occurrence of the residual current with value not largerthan 0.073A.

IV. CONCLUSIONSANDCOMMENTS

On the grounds of the tests performed it may be declaredthat:

the PDH telecommunication equipment used duringtesting allows the transmission of data of residualcurrent, phase comparison and tele-protection devices,such as P543, REL561, 7SD510, L90,RFL9745GD/GARD8000, SWT3000, they are

suitable for such applications and in many casesperform properly in the configurations tested,

- the tests of P543 protection devices have confirmedthat the proposed interface of these devices, in theform of the OPTO/G703 external converter, properlyinteroperates with PDH FMX devices, manufactured

by Siemens, through the DSC6-n64C card with therate of data exchange equal to 256kbps. For this typeof connection, the time lag asymmetry in terms ofresidual current occurring with the load current 1A isnot bigger than 64mA,

the tests of REL561 protection devices haveconfirmed that the proposed interface of these devices,

in the form of the internal module of the X.21/V.35port, interoperates with PDH FMX devicesmanufactured by Siemens through the CPF2 card andCIM-X.21 module with the rate of data exchangeequal to 256kbps. For this type of connection, the timelag asymmetry in terms of residual current occurringwith the load current 1A is not bigger than 110mA,

the tests have proved that the exchange of data withthe rate 64kbps and with use of CPF2 cards suffersfrom the large and unstable asymmetry (up to 2.9ms,which corresponds to Idiff=0.879A for Iobc=1A),which may cause and causes the activation of thedifferential/residual function set to 0.2A (the

occurrence of the asymmetry is currently consultedwith the manufacturer),

the tests have proved that the exchange of data withthe rate 64kbps with the use of older type cards,named DSC8-x.21 does not suffer from large andunstable asymmetry (the maximum asymmetryobserved did not exceed 82s), which does not causethe activation of the residual function set to 0.2A.(The residual current occurring in the case oftransmitting the load current with value 1A is notlarger than 0.026A). For this type of cards, theinteroperation of protection and telecommunicationsequipment is proper,

the tests of P543 and REL561 protection devices haveconfirmed that, in the case of SDH system,comprising two SDH Surpass units with identical and

small time lag between the primary path and reservepath, the channels with protection may be used forexchanging data between these protection devices. At

the same time it was found that the protection madeon the actual SDH system, with the differences in timelags amounting to 12ms and 4ms, causes thetransmission of the impulse for disconnection with thetransmission of current with value 1A. Therefore, itseems necessary to verify the time lags pending theinstallation of the protection equipment and checking,

by means of testers, the response of these devices tothe changes to time lags,

the tests of SWT3000 tele-protection devices haveconfirmed their proper performance in thetelecommunication systems checked,

the tests of RFL9745GD/GARD8000 tele-protectiondevices have confirmed their proper performance inthe telecommunication systems checked,

the possibilities have been confirmed of enteringalarm signals from the protection devices to the PDHtelecommunication network supervision system, and

the possibility of blocking the protection by the alarmsignals of the telecommunication equipment has beenconfirmed.

It should be mentioned here that the tests described werepertinent to the protection devices that failed to use the GPS-assisted synchronization, allowing the programmable

compensation of the impact of data transmission timeasymmetry, through which they were very susceptible to theoccurrence of such asymmetry. On the other hand, however,this type of protection equipment constitutes the majority ofsection protections operated in Poland. Therefore, the problemobserved during testing, concerning the impact of operatingactivities of the PDH telecommunication equipment on the

performance of residual protections, should become the areaof interest of particular persons that consider the application ofsuch a system for exchanging data between these protections.

REFERENCES

[1] ABB wiatowodowy system telekomunikacyjny FOX515- Opis

techniczny (FOX515 optical fibre telecommunications system.Technical Description 2003

[2] ABB FOX 512 & FOX 515 Overview 2003

[3] GE Multilin TN1Ue SDH Multiplexer Technical Overview andReference Manual 2004

[4] SIEMENS AG FMX2R3.1 Multiplexer for flexible Voice and DataNetworks FMX2R3.1 2002

[5] ProTel Telecommunication Opis techniczny urzdze SDH firmySIEMENS (Technical description of SDH equipment manufactured bySiemens) 2004

[6] ProTel Telecommunication Opis systemu FMX2/CMX (FMX2/CMXsystem description) - 2004

[7] Protection Using Telecommunications, CIGRE JWG 34/35.11

[8] RFL Communications plc RFL9745GD - 2005

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Problems Found During Testing of PDH Devices