BENATO IT Session 4 – Block 3 – Question 6 Barcelona 12-15 May 2003 THE ISLANDING PROBLEM PASSIVE PROTECTIONS AS DEMONSTRATE THE POSSIBILITY OF FAILING

BENATO IT Session 4 – Block 3 – Question 6

Barcelona 12-15 May 2003

THE ISLANDING PROBLEMTHE ISLANDING PROBLEM

PASSIVE PROTECTIONS AS PASSIVE PROTECTIONS AS Max/min voltage relaying Over/under frequency relaying Rate of change of frequency relays Phase displacement monitoring DEMONSTRATE THE DEMONSTRATE THE POSSIBILITY OF FAILING THE POSSIBILITY OF FAILING THE ISLAND DETECTION ISLAND DETECTION

HV Busbar

MV Busbar

After system switching operation, After system switching operation, a section of the utility network a section of the utility network remains connected to the DG !remains connected to the DG !

HV Busbar

MV Busbar



MV Lines

Capacitor Bank

Overhead Line

Cable Line

HV/MV

MV/LV

HV network

Transmitter Location

Receiver Location MV/LV

LV loads

MV/LV

MV/LV

DG Line Breaker

DG

Rx Tx

Tx Rx

Rx

DLC-BASED PROTECTION SCHEMEDLC-BASED PROTECTION SCHEME

Under normal conditions, Under normal conditions, guard frequencyguard frequency detected by RXdetected by RX

Guard frequencyGuard frequency injected at MV injected at MV

busbarbusbar



MV Lines

Capacitor Bank

Overhead Line

Cable Line

HV/MV

MV/LV

HV network



LV loads

MV/LV

MV/LV

DG Line Breaker

DG

Rx Tx

Tx Rx

Rx

When the breaker is openedWhen the breaker is opened

there is a loss of guard frequency for the DG receiverthere is a loss of guard frequency for the DG receiver

MV Lines

Capacitor Bank

Overhead Line

Cable Line

HV/MV

MV/LV

HV network



LV loads

MV/LV

MV/LV

DG Line Breaker OPENS

DG

Rx Tx

Tx Rx

Rx



FEASIBILITY OF DLC PROTECTIONFEASIBILITY OF DLC PROTECTIONTHE CARRIER SIGNAL PROPAGATION IN MV NETWORKS THE CARRIER SIGNAL PROPAGATION IN MV NETWORKS

CAN FIND DIFFICULTIES DUE TO:CAN FIND DIFFICULTIES DUE TO:

overhead and cable line attenuation;overhead and cable line attenuation;

the presence of capacitor banks;the presence of capacitor banks;

different line segments;different line segments;

branching;branching;

mismatching and standing wave patterns.mismatching and standing wave patterns.



DEVELOPMENT OF A TOOL FOR THE DEVELOPMENT OF A TOOL FOR THE CARRIER SIGNAL TRANSMISSION CARRIER SIGNAL TRANSMISSION

ANALYSISANALYSIS

0 0.5 1 1.5 2 2.5 3 0

10

20

30

40

50 ZM=3000 ZM=100

Atte

nuat

ion

[db]

Receiver Location x [km]

f= 72 kHz

0 100 200 300 400 500 600 700 800 900 1000 4

6

8

10

12

14

16

18

20

22

24

Z MR1 [ ]

Atte

nuat

ion

[dB

]

15 dB

O M Z

R1

R2

ZMR2 =460

STANDING WAVE CONDITIONSSTANDING WAVE CONDITIONS OPTIMAL MISMATCHING ZONEOPTIMAL MISMATCHING ZONE

Cable Lines ZCable Lines ZM M = 460 = 460 Overhead Lines Overhead Lines Z ZM M = 3000 = 3000 Combination of Combination of OHL and CL ZOHL and CL ZM M = 1500 = 1500



OVERHEAD AND CABLE OVERHEAD AND CABLE LINE ATTENUATIONLINE ATTENUATION

0 100 460 500 1000 1500 2000 2500 3000 0 1 2 3 4 5 6

8

10

12

14 Line lenght 2 [km]

OHL ACSR S=150 mm2 CL EPR - insulated S=185 mm2

CL paper - insulated S=185 mm2

Atte

nuat

ion

[dB

]

Impedance Matching ZM

Cable Lines

OverHead Line

Attenuation as a function of receiver impedance ZAttenuation as a function of receiver impedance ZMM

10.25 m

1.250.70

MV overerhead line

ACSR =15.85 mmCC =10.70 mm

Conductors

less than 0.5 [dB/km]less than 0.5 [dB/km]

r tan

3

4

Trefoil Configuration MV Cable

EPR

Impregnated paper 0.01

0.02

Insulation

PVC 8 0.1

1 m All S=185mm2

r1=8.05 mm; r2=13.55;r3=16.55;r4=18.9

about 1.5about 1.54 4 [dB/km][dB/km]



EXAMPLE OF A CAPACITIVE EXAMPLE OF A CAPACITIVE COUPLING DEVICECOUPLING DEVICE

phase R

phase S

XCouplingSide 20 kV

Transmitter/Receiving

Side

C L Tr1 Tr2PG CR

C : Coupling Capacitance;L : Tuning Inductance;Tr1: Insulating Transformer;PG: Protective Gaps;X: Compensation Reactance;Tr2: Impedance Trasformer;S: Protection Screen.

S

Electric circuitElectric circuit

The Coupling Capacitance :The Coupling Capacitance : pF67004610722

1010Zf2

BWC 23

3

M2c



HV/MV 2528 m EPR-insulated cable S=185 mm2

Paper-insulated cable S=240 mm2

310 m

6 lines

3.6 Mvar 95 m

MV/LV

Tx CD Rx CD

URBAN FEEDER

MEASUREMENT CAMPAIGN I MEASUREMENT CAMPAIGN I

15

17

19

21

23

25

27

70 71 72 73 74 75 Frequency [kHz]

Atte

nuat

ion

[dB

]

29

31

33 r = 3.2 4 Measured values

13

11

9

7

Comparison between Comparison between computed and measured computed and measured

valuesvalues

ATTENUATION at 72 kHz = 20 dbATTENUATION at 72 kHz = 20 db

GOOD AGREEMENT !GOOD AGREEMENT !



3.6 Mvar

# Line Total LenghtKm

OHL lenghtKm

CL lenghtKm

#1 47.7 45 2.7#2 5.8 1.7 4.1#3 48.6 44.7 3.9#4 26.4 23.8 2.6#5 4.8 0.4 4.4

50 m

#1

4 lines#2

#5#4

#3 7542 m

450 m

5667 mHV/MV

MV/LVTx CDRxCD

RURAL RADIAL FEEDER

MEASUREMENT CAMPAIGN II MEASUREMENT CAMPAIGN II

This measurement campaign seems to be representative of the DLC This measurement campaign seems to be representative of the DLC transmission length limit without the use of repeater devices. transmission length limit without the use of repeater devices.

-80

-70

-60

-50

-40

-30

-20

-10

0

70 71 72 73 74 75 76 77 78Frequency [kHz]2 khZ/Div

Cursor -49.37 dB / 72.000 kHz

IMP 150 BWTH: 25 Hz START: 70.000 kHz STOP : 78.000 kHz

Sign

al S

treng

th [d

B]

TX: 20 db on 75 RX: -49.37 db ATTENUATION: 70 db



CONCLUSIONCONCLUSION A novel protection method to prevent DG islanding; A novel protection method to prevent DG islanding;

A suitable analysis procedure has been developed;A suitable analysis procedure has been developed;

Good agreement of test results with the theoretical calculations Good agreement of test results with the theoretical calculations (accuracy of the multiconductor matrix procedure);(accuracy of the multiconductor matrix procedure);

Distance limit between TX and RX about Distance limit between TX and RX about 10 10 15 15 km for a typical km for a typical Italian radial branched MV feeder;Italian radial branched MV feeder;

(If longer distances are needed, the use of repeaters must be taken into (If longer distances are needed, the use of repeaters must be taken into consideration).consideration).

Documents

BENATO IT Session 4 – Block 3 – Question 6 Barcelona 12-15 May 2003 THE ISLANDING PROBLEM PASSIVE PROTECTIONS AS DEMONSTRATE THE POSSIBILITY OF FAILING