Siemens Protection Schemes.pdf

Typical Protection Schemes

Page 87

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Typical protection for a radial system ¾ Most distant relay gets the shortest delay time ¾ Definite-Time (51, 51N) System impedance (Infeed) high, no current selectivity ¾ Inverse-Time (51, 51N) System impedance (Infeed) medium, current selectivity ¾ Very Extremely Inverse-Time (51, 51N) System impedance (Infeed) small, high current selectivity 1) Auto reclosing cycle only for overhead lines (79) 2) Negative-phase sequence system as back up protection (46, unbalance protection)

Page 88

2007-08

Author: G. Ziegler

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Typical protection of ring feeders ¾ Switch off time of the relays has to be coordinated with downstream fuses ¾ Inverse-time characteristic curves (51, 51N) ¾ Thermical overload (49) for cables ¾ Negative-phase system protection (46) as sensitive back up protection

(52: Circuit-breaker)

Page 89

2007-08

Author: G. Ziegler

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Typical protection for a distribution feeder with reclosing ¾ The relay settings and the auto reclosing cycle (79) must be coordinated with the down-streamed protection devices.

Page 90

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Feeder protection – Distribution System

Page 91

2007-08

Author: G. Ziegler

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Feeder protection – Transmission System

Page 92

2007-08

Author: G. Ziegler

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Feeder protection – Transmission System

Page 93

2007-08

Author: G. Ziegler

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Small transformers < 5 MVA Main protection OS ¾ Undelayed I>>, IE>> (50, 50N)

>

¾ Buchholz (63) Back-up protection OS ¾ Time-delayed overcurrent-time (51) ¾ Overload (49) ¾ Negative-phase sequence system (46) Main protection US ¾ Limited earth-fault (87N) Back-up protection US (OS: Overvoltage side)

¾ Time-delayed overcurrent I > (51G) (Earth path)

(US: Undervoltage side) Page 94

2007-08

Author: G. Ziegler

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Dual infeed with single transformer

Page 95

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Important transformer infeeds

Main protection ¾ Differential (87T) ¾ Limited earth-fault (87N) ¾ Buchholz (63) Back-up protection ¾ Overcurrent-time (50, 51, 51N) ¾ Neg.-phase sequence system (46) ¾ Earth-fault current protection(51G) Overload protection ¾ Thermal (49)

Page 96

2007-08

Author: G. Ziegler

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Three-winding transformer

Page 97

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Autotransformer

Page 98

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Large autotransformer bank

Page 99

2007-08

Author: G. Ziegler

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Small and medium motors with nominal outputs < 1MW a)

In systems with solid grounding or low-resistance neutral earthing (IE> IN Motor)

(37) Undercurrent relay

b) In systems with high-resistance neutral earthing (IEŠ IN Motor)

1) Cable-type current transformer is necessary for sensitive earth-fault protection 2) Directional protection, Earth-fault monitoring

Page 100

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Big high voltage motors > approx. 1 MW

Optional

1) Cable-type current transformers for the sensitive earth-fault detection 2) Sensitive directional earth-fault detection in operation with a Petersencoil 3) Startup supervision 4) Temperature sensor

(27) Undervoltage-relay

Page 101

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Micro generators < 500 kW a) Solid grounding

b) Earthed via resistance

Page 102

2007-08

Author: G. Ziegler

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Busbar protection Reverse interlocking principle Applicable to distribution buses without considerable (< 0.25 In) back feeding from the outgoing feeders

Page 103

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Low impedance - Busbar protection ¾ Especially used in multiple busbars for which an isolator replica is necessary ¾ Feeder protection can be connected to the same current transformer core ¾ Current transformers can be different (87): Differential protection (86): Tripping relay (BF): Breaker failure protection

Page 104

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

High impedance busbar protection

Page 105

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

1-1/2-breaker arrangement

Page 106

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Typical protection for parallel service without back-feed ¾ Directional overcurrent - time protection relays (67, 67N) switch off fault on the protected line without delay

¾ Non-directional relays (51, 51N) must be delayed about 1 grading zone

Page 107

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Dual transformer infeed Main protection ¾ Overcurrent-time Phase/Earth directional (67, 67N) non-directional (50, 51, 51N) ¾ Buchholz (63) Back-up protection ¾ Overcurrent-time Phase/Earth (51, 51N) ¾ Negative-phase sequence system (46) Overload protection ¾ Limited earth-fault (51G) ¾ Thermal (49)

Page 108

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Cable / short overhead line < 20km with infeed of both sides Main protection ¾ Differential (87) Back-up protection ¾ Overcurrent-time (51, 51N) Overload protection ¾ Thermal 1) Automatic reclosing only in overhead lines (79) 2) Overload protection (49) mainly in cables

Page 109

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI

Overhead lines or long cables with infeed of from sides

Main protection ¾ Distance (21, 21N) 1) Signal comparison (85)

Back-up protection 2) Directional Overcurrent-time (67N)

3) Auto reclosing (79) (single or multiple) only in overhead lines

Page 110

2007-08

Author: G. Ziegler

Copyright © Siemens AG 2007. All rights reserved. PTD SE PTI