111-187_prot of mv and lv systems_quazvin

8/13/2019 111-187_Prot of MV and LV Systems_Quazvin

http://slidepdf.com/reader/full/111-187prot-of-mv-and-lv-systemsquazvin 1/77

2007-08

PTD SE PTI Author

Protection of Medium and Low

Voltage DistributionSystems

2007-08

PTD SE PTI Author

Table of Content

• Network Structures

• Typical Calculation procedures

• Protection Principles and Co-ordination:

- Overcurrent Protection (relay, MCB, fuses)

- Distance Protection

2007-08

PTD SE PTI Author

Urban network structure

Building A

Building C

Building D

Building B

2007-08

PTD SE PTI Author

Industrial network structures

Ring network Central substation

2007-08

PTD SE PTI Author

Urban low voltage network

400 V three phases

Meshed systems – radial systems

open point

2007-08

PTD SE PTI Author

Typical Calculation Procedures

2007-08

PTD SE PTI Author

Short-circuit current calculations

U0 = Un /√3

2007-08

PTD SE PTI Author

Simple Short - Circuit Calculation

2007-08

PTD SE PTI Author

Protection Principles and Co-ordination:

Overcurrent Protection (Relays, MCBs, fuses)

2007-08

PTD SE PTI Author

Typical fuse and LC circuit breaker

tripping characteristics

2007-08

PTD SE PTI Author

Selectivity of Low Voltage Fuses

2007-08

PTD SE PTI Author

Selective tripping of fuses in meshed networks

•Cable of same cross-section

•Same LV fuses

Siemens LV-Fuses:

Selectivity (only

Fuse F3 blows) is

guranteed at high

currents up to a

ratio of :

1K ≤+

2007-08

PTD SE PTI Author

Selectivity: Circuit Breaker → Downstream Fuse

I current dependent delayed overload trip

s short time delayed overcurrent trip

t A safety marginId pick-up current of the s-release

ts melting time of the fuse

td delay time of the s-release

2007-08

PTD SE PTI Author

Selectivity: Fuse→ Downstream Circuit Breaker

Selectivity check

in the short-circuit range by

I2t - comparison> 70ms

Overload

2007-08

PTD SE PTI Author

Selectivity: Three similar infeeding transformators

Necessary CB protection functions:

1. Inverse time Overload element a

2. Short time delayed I>>-element z

2007-08

PTD SE PTI Author

Tripping Characteristic in Medium- and High-Voltage Network

2007-08

PTD SE PTI Author

CT-connections dependent on neutral-earthing

2- phase connection for

isolated networks3- phase connection for

earthed networks

2- phase + earth connection

for an increased earth fault sensitivity

Obsolete!

Only in old

substations,

no more

recommended!

Obsolete!

Practised only with

electromechanical

protection. !

Now generally applied,

independent of neutral-earthing

2007-08

PTD SE PTI Author

L3 L1L2L3

I R = I L1 + I L2 + I L3

Digital relayc.t.s

Calculated: I R = I 1 + I 2 + I 3

Measurement (analog) and digital calculation of earth current

„Holmgreen“ connection

2007-08

PTD SE PTI Author

High sensitive earth fault relaying using a window-type CT

3 · I 0 = I L1 + I L2 + I L3

I earth

I shield I Fault

2007-08

PTD SE PTI Author

Coordination of overcurrent relays: time grading

0,1 1,3 1,3 0,1

0,9 0,9 0,1

0,1 0,10,10,1

0,5 0,5

Starting from the

furthest

downstream

located relay, theoperating time is

step by step

increased in

direction of the

infeed.

2007-08

PTD SE PTI Author

Current grading

fault location

Example: >> for faults at HV-side

in 1 K = 110 kV

3 2,4= 26,5 kA

⋅ Ω

K =110 kV

3 62,9= 2,4 kA

⋅ Ω

U N = 100 kVS K = 5 GVAZ N = 2,4S N = 20 MVAu K = 10%Z Tr = 60,5

MVAS'kVU =Z

line impedanceneglected!

Coordination of overcurrent relays: Current grading

2007-08

PTD SE PTI Author

Selectivity by current grading

>>, t 1

0,15 s

>, t 2 0,3 s

>, t 3 0,1 s

2007-08

PTD SE PTI Author

Definite and inverse overcurrent relay characteristics

t = 700 ms

t = 400 ms

t = 100 ms

I > I > I >

2007-08

PTD SE PTI Author

Inverse time characteristics acc. To IEC 60255

10 1001

DT (4 s)

Normal inverse:

−⎟⎟ ⎠ ⎞⎜⎜

⎝ ⎛

Very inverse:

−⎟⎟ ⎠ ⎞⎜⎜

⎝ ⎛

Extremely inverse:

I80t 2

−⎟⎟ ⎠

⎞⎜⎜⎝

[ ]s t

2007-08

PTD SE PTI Author

Application of different O/C characteristics

Definite time (DT)Easy to coordinate

Constant tripping time independent of infeed variation and fault location

Normal inverse (NI)Relativey small change in time per unit of change of current.

Most frequenly used in utility and industrial circuits.

Especially applicable where the fault magnitude is nmainly dependent on

the system generating capacity at the time of fault.

Very inverse (VI)Suitable if there is a substantial reduction of fault current as the fault

distance from the power source increases.

Extemely inverse (EI)Suitable for protection of distribution feeders with peak currents on

switching in (refrigerators, pumps, water heaters and so on).

Particular suitable for grading with fuses.

2007-08

PTD SE PTI Author

Fault current dependent on the fault location

11kV250MVA

0,4Ω 0,1 Ω/km

0.4 Ω/km

Infeed250MVA,11 kV

Equivalent circuit

faultcurrent

fault location

Current grading

depends on the SIR ratio!0.4 Ω/km (OH-Line)

0.1 Ω/km (cable)

2007-08

PTD SE PTI Author

Time grading: definite and inverse time characteristics

A B C D

fault location

51 51 51

2007-08

PTD SE PTI Author

⎥⎥

⎢⎢

⎡−

⎟⎟ ⎠

⎜⎜⎝

⎛ ⋅

−+=⇒

−⎟⎟ ⎠

⎞⎜⎜⎝

⋅+−=

−⎟⎟ ⎠

⎞⎜⎜⎝

⋅⇒

ms400200TT

T14.0ms400200

T14.002.0

1n, pn, p02.0

Time grading of normal inverse time characteristics

ms400200tt23g12g −==

Grading requirement:

Conventional grading principle: Isc = maximum SC-current in the network

tg12 tg23

2007-08

PTD SE PTI Author

Disk emulation: Simulatin of the induction disc

0 0,2 0,4 0,6 0,8 1

Without

Disc emulation

2 Ip 0,4 Ip

position

2007-08

PTD SE PTI Author

The back-up tripping time can be reduced by

Combining inverse and definite time characteristics

gain oftripping

Combined use of inverse and definit time characteristics

2007-08

PTD SE PTI Author

Overcurrent protection co-ordination

2007-08

PTD SE PTI Author

Two definite overcurrent relays in series

2007-08

PTD SE PTI Author

Protection scheme acceleration

2007-08

PTD SE PTI Author

Definite overcurrent protection in cable ring

2007-08

PTD SE PTI Author

Protection in closed cable ring

2007-08

PTD SE PTI Author

Cable ring with advanced protection

Co-ordination of distance protection at infeeding cables

2007-08

PTD SE PTI Author

Co-ordination of distance protection at infeeding cables

and overcurrent protection at downstream feeder cables

Advanced overcurrent protection

2007-08

PTD SE PTI Author

feeder protection blockins thethe fast 50ms-stage at the

infeeding relay via blocking

bus and is only tripping its own CB

Infeeding relay trips within 50ms,as blocking bus is not activated

t0 = 50ms

t= xx ms

Pick-up Pick-up. Pick-up.+ ++

blocking bus

Directionof power flow

Advanced overcurrent protectionReverse interlocking principle

51 5151

Di ti l i i t l ki

2007-08

PTD SE PTI Author

A B C D

R 1.1 R 1.2 R 2.1 R 2.2 R 3.1 R 3.2

Fault between station B – C

R1.1 forward, blocked by R1.2

R1.2 reverse, is blocking R1.1R2.1 forward, is blocking BB-protection and trips

R2.2 forward, trips

R3.1 reverse, is blocking R3.2

R4 no actionR5 no actionR6 no action

Directional comparison + reverse interlocking

Undelayed tripping for

busbar faults (t3 ca. 50ms)

and cable faults using only

one relay per feeder!!

2007-08

PTD SE PTI Author

A B C D

R 1.1 R 1.2 R 2.1 R 2.2 R 3.1 R 3.2

Fault at outgoing feeder

R3.1 reverse, is blocking R3.2R3.2 forward, blocked by R3.1

R4 no actionR5 no action

R6 is blocking BB-protection and trips

Di ti l i i t l ki

2007-08

PTD SE PTI Author

A B C D

R 1.1 R 1.2 R 2.1 R 2.2 R 3.1R 3.2

Fault at busbar B

R1.2 reverse, is blocking R1.1 and trips BB-protectionR2.1 reverse, is blocking R2.2 and trips BB-protection

R2.2 forward, is blocked by R2.1

R4 no actionR5 no actionR6 no action

2007-08

PTD SE PTI Author

Protection Principles and Co-ordination:

- Distance Protection

B i i i l f di t t ti

2007-08

PTD SE PTI Author

Undelayed trip in first zone

Trip in second (back-up) zone

delayed with second zone time

e.g. in case of breaker failure

Graphical

representations:

Tripping zones in the impedance plane grading chart

Basic principle of distance protection

breaker failure

Zone 1 Setting guidelines

2007-08

PTD SE PTI Author

Zone 1 - Setting guidelines

Line characteristic

If the measured impedance is within the set characteristicand the set time has expired, a TRIP command is issued

Recommendation for Zone 1 settings:

X1 ≈ 80...90% of line reactance

R1 ≈ 100% of arc resistance

R1E≈ 100% of arc resistance

t1 = 0 ms

Di t t ti Z characteristics

2007-08

PTD SE PTI Author

• Distance zones

– Inclined with line angle ϕ

– Angle α prevents overreach of

Z1 on faults with fault

resistance that are fed from

both line ends

• Fault detection (7SA6)

– no fault detection polygon: the

largest zone determines the

fault detection characteristic – simple setting of load

encroachment area with

Rmin and ϕLoad

f o r w a r d s

f o r w

a r d s

r e v e r s e

ϕ LoadLoad

Distance protection: Zone characteristics

2007-08

PTD SE PTI Author

Comparison of zone characteristics: MHO versus polygonal

Grading of the zones radial network

2007-08

PTD SE PTI Author

Grading of the zones - radial network

= 0.85 Z A-B

Z2= 0.85 (Z A-B + 0.85 ZB-C)

= 0.85 [ Z A-B

+ ZB-C + 0.85 ZC-D ]

G di f h i f d b h d

2007-08

PTD SE PTI Author

grading time

Ring with grading towards opposite line end

Grading of the zones - infeed at both ends

1 t Z S tti

2007-08

PTD SE PTI Author

1st Zone Settings

BA A B

Normal Situation

Z1.zone= 0.85 x ZA,B

No relay in the next station

Z2.zone = 0.85 x (ZA,B + ZB,C)

Spur line

Z1.zone = 1.20 x ZA,B Z1.zone=Z2.zone=Z3zone

Transformer

Z1.Zone = 0.85 x Ztransf. Z1.zone=Z2.zone=Z3.zone

2nd Zone Settings

2007-08

PTD SE PTI Author

2nd Zone Settings

Z2.zone = 0.90 x ( ZA,B + 0.85 x min ZB… )

2nd zone impedance grading acc. to the

shortest 1st zone setting and the next

busbar ( ZB,D < ZB,C < ZB,F ), hereby spur

lines are neglected (ZB,E).

Z2.zone = 0.90 x ( ZA,B + 0,85 x ZB,D )

2 d Z S tti i C f Sh t d L Li i S i

2007-08

PTD SE PTI Author

2nd Zone Settings in Case of Short and Long Lines in Series

Example

long line short cable line

2007-08

PTD SE PTI Author

2nd Zone Settings in Case of Short and Long Lines in Series

Protection strategy 1

R1 R2B CA

Z2.zone = 0.85 x ( ZAB + 0.85 x ZAC ) < 1.00 ZAB

Comment: absolutely selective grading schedule, but short-circuit

faults on the last part of long line will be tripped in the 3rd zone.

Protection strategy 2

Z2.zone = 1.2 x ZAB

Comment: fast 1st zone and 2nd zone will trip all short-circuit faults on

the long line, but no selective tripping in the 2nd and higher zones.

Alternative:

Protection relay R2 at

the terminal B can be

graded with 2nd zonein reverse direction.

3rd Zone Settings

2007-08

PTD SE PTI Author

3rd Zone Settings

Z3.zone = 0.85 x ( ZA,B + 0.85 ( ZB,C + 0.85 x ZC,E ) )ZB,C + 0.85 x ZC,E < ZB,D + 0.85 x ZD,G

Grading according to the shortest 2nd zone of the outgoing lines at

the next station . Fault at station C will not be cleared with 3rd zone!

3rd Zone Settings

2007-08

PTD SE PTI Author

3rd Zone Settings

Infeed Cable with Distance Protection

2007-08

PTD SE PTI Author

Infeed Cable with Distance Protection

Impedance Plan with Relay Zone Reach

2007-08

PTD SE PTI Author

2007-08

PTD SE PTI Author

Coordination of Relays, Fuses and

LV-Circuit breakers

Case Study

Inverse time Relay Setting Parameters

2007-08

PTD SE PTI Author

Phase Fault :

Earth Fault :

I > T >

I >> T >>

I >>> T >>>

I Ep TEp

I E> T E>

I E>> T E>>

*) characteristic

Definite Time Relay SettingCharacteristics

2007-08

PTD SE PTI Author

time [s]

current [A]

Relay inverse Time Characteristics acc. to IEC and BS142

2007-08

PTD SE PTI Author

Relay inverse Time Characteristics acc. to IEC and BS142

time [s]

current [A]

normal inverse

very inverse

extremly inverse

LV Circuit Breaker Setting Parameters

2007-08

PTD SE PTI Author

Phase Fault :

Earth Fault :

I d t d

I i t i

I g tg

tiI2t=const.

Protection Area - „Transformer“

2007-08

PTD SE PTI Author

SC limit

primary

thermal

SC limitsecondary

time limit of

Protection below

Example: Network 20/6/0.4 kV

2007-08

PTD SE PTI Author

Data base for short circuit calculation

2007-08

PTD SE PTI Author

Short circuit calculation results

2007-08

PTD SE PTI Author

Summary of results - maximum 3-phase short circuit

2007-08

PTD SE PTI Author

Summary of results - minimum 2-phase short circuit

2007-08

PTD SE PTI Author

CT data and protection devices

2007-08

PTD SE PTI Author

Protection Coordination – Motor feeder

2007-08

PTD SE PTI Author

Requirements:

Ip ~ 110 % * In,motor

tmot[Istart,motor] < tcurve

Istart,motor < I>> < Isc,min

Protection Coordination (1)– Transformer feeder 20/0,4kV

2007-08

PTD SE PTI Author

Check settings !!!

2007-08

PTD SE PTI Author

Requirements HV side:

Requirements LV side:

Ip ~ 1.1 * In,tr

I>> ~ 3 – 4 * In,tr

I>> < Isc,min

I> ~ I>>sec.sideT> = T>>sec side + 1 time step

I>> > Isc,max of sec. side

I>> < Isc,min of prim side

2007-08

PTD SE PTI Author

2007-08

PTD SE PTI Author

Protection Coordination –Transformer 20/6kV

2007-08

PTD SE PTI Author

Check Protection Coordination – Motor & Transformer

2007-08

PTD SE PTI Author

111-187_prot of mv and lv systems_quazvin

Documents

abb mv-lv transformer

abb lv mv sc cal

mv/lv cast resin transformers

mv lv catalogue-tnhh kimxuan

protection of mv converters in the grid: the case of mv/lv...

2015 lv mv electrical installation guide by...

mv-lv cable catalogue

mv, pp. 111 - 137

mv & lv protection coordination

protection of mv-lv substation transformers

future growth fgp - mv & lv switchgear

hyundai mv y lv breakers

mv-lv catalogue.pdf

mv & lv architecture selection guide

mv/lv transformers for distribution network solutions...

d mv-lv-architecture-selection-guide

the new lub...

global leading company - · pdf filedangjin cable accessory...

lv & mv hydrocarbon resistant_cable_joints-

mv & lv architecture selection guide - electrical · pdf...