87-110_typical protection schemes_qazvin.pdf
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Page 87 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Typical Protection Schemes
Page 88 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Typical protection for a radial system
Most distant relay gets the shortest delay time
Definite-Time (51, 51N)
System impedance (Infeed) high, no current selectivity
Inverse-Time (51, 51N)
System impedance (Infeed) medium, current selectivity
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 89 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Typical protection of ring feeders
Switch off time of the relays has to be coordinated with down-stream fuses
Inverse-time characteristic curves (51, 51N)
Thermical overload (49) for cables
Negative-phase system protection (46) as sensitive back up protection
(52: Circuit-breaker)
Page 90 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Typical protection for a distribution feeder with reclosing
The relay settings and the auto reclosing cycle (79) must be coordinated with the down-streamed protection devices.
Page 91 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Feeder protection – Distribution System
Page 92 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Feeder protection – Transmission System
Page 93 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Feeder protection – Transmission System
Page 94 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Undelayed I>>, IE>> (50, 50N)
Main protection OS
Time-delayed overcurrent-time (51)
Back-up protection OS
Buchholz (63)
Overload (49)Negative-phase sequence system (46)
Limited earth-fault (87N)Main protection US
Time-delayed overcurrent I > (51G) (Earth path)
Back-up protection US
(OS: Overvoltage side)
(US: Undervoltage side)
>
Small transformers < 5 MVA
Page 95 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Dual infeed with single transformer
Page 96 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Important transformer infeeds
Differential (87T)
Main protection
Overcurrent-time (50, 51, 51N)
Back-up protection
Limited earth-fault (87N)
Neg.-phase sequence system (46)
Thermal (49)
Overload protection
Buchholz (63)
Earth-fault current protection(51G)
Page 97 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Three-winding transformer
Page 98 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Autotransformer
Page 99 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Large autotransformer bank
Page 100 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Small and medium motors with nominal outputs < 1MW
1) Cable-type current transformer is necessary for sensitive earth-fault protection
b) In systems with high-resistance neutral earthing (IE IN Motor)
a) In systems with solid grounding or low-resistance neutral earthing (IE IN Motor)
2) Directional protection, Earth-fault monitoring
(37) Undercurrent relay
Page 101 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Big high voltage motors > approx. 1 MW
1) Cable-type current transformers for the sensitive earth-fault detection
2) Sensitive directional earth-fault detection in operation with a Petersen-coil
3) Startup supervision
4) Temperature sensor
(27) Undervoltage-relay
Optional
Page 102 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Micro generators < 500 kW
b) Earthed via resistance
a) Solid grounding
Page 103 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Busbar protection Reverse interlocking principle
Applicable to distribution buses without considerable (< 0.25 In) back feeding from the outgoing feeders
Page 104 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Low impedance - Busbar protection
Especially used in multiple busbars for which an isolator replica is necessary
Current transformers can be different
Feeder protection can be connected to the same current transformer core
(87): Differential protection
(86): Tripping relay
(BF): Breaker failure protection
Page 105 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
High impedance busbar protection
Page 106 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
1-1/2-breaker arrangement
Page 107 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Typical protection for parallel service without back-feed
Directional overcurrent - time protection relays (67, 67N) switch off fault on the protected line without delay
Non-directional relays (51, 51N) must be delayed about 1 grading zone
Page 108 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Overcurrent-time Phase/Earth directional (67, 67N) non-directional (50, 51, 51N)
Main protection
Overcurrent-time Phase/Earth (51, 51N)
Back-up protection
Thermal (49)
Overload protection
Buchholz (63)
Limited earth-fault (51G)
Negative-phase sequence system (46)
Dual transformer infeed
Page 109 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Cable / short overhead line < 20km with infeed of both sides
Differential (87)
Main protection
Overcurrent-time (51, 51N)
Back-up protection
Thermal
Overload protection
1) Automatic reclosing only in overhead lines (79)
2) Overload protection (49)mainly in cables
Page 110 2007-08Copyright © Siemens AG 2007. All rights reserved.
PTD SE PTIAuthor: G. Ziegler
Overhead lines or long cables with infeed of from sides
Distance (21, 21N)
Main protection
2) Directional Overcurrent-time (67N)
Back-up protection
3) Auto reclosing (79)(single or multiple) only in overhead lines
1) Signal comparison (85)
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