Upload
gmbugus
View
227
Download
0
Embed Size (px)
Citation preview
8/18/2019 1_FUNDAMENTLE Protection Principles
1/36
8/18/2019 1_FUNDAMENTLE Protection Principles
2/36
Energy Sector Energy Automation
© Siemens AG 2009
Power System Structure
Generation Transmission / Sub transmission Distribution
Extra High Voltage 765 kV400 kV220 kV
High Voltage 132 kV110 kV66 kV
Medium Voltage 33 kV22 kV11 kV
Medium 24 kVVoltage 21 kV
15 kV13.8 kV
The purpose of an electrical power system is to generate and supply electrical energy toconsumers. The system should be designed and managed to deliver this energy to the
utilisation points with both reliability and economy.
The purpose of an electrical power system is to generate and supply electrical energy toconsumers. The system should be designed and managed to deliver this energy to the
utilisation points with both reliability and economy.
Many items of equipment are very expensive, and so the complete power systemrepresents a very large capital investment.
.
Many items of equipment are very expensive, and so the complete power systemrepresents a very large capital investment.
.
8/18/2019 1_FUNDAMENTLE Protection Principles
3/36
Energy Sector Energy Automation
© Siemens AG 2009
Owner of high voltage networks
Public utility companies
Interconnected system, National network, Regional system, Urban network
Industrial companies
Steel, Cement, Chemistry, Automobile . . .
Power plantsRailways
Special systems
Airports, Hospitals, Testing stations, Ships . . .
8/18/2019 1_FUNDAMENTLE Protection Principles
4/36
Energy Sector Energy Automation
© Siemens AG 2009
Protective Relaying is the most important
feature of power system design aimed at
minimising the damage to equipment and
interruption to service in the event of faults. It
is therefore a co-factor among other factors
resorted to improve reliability of power system.
Protective Relaying
Role of Protection
8/18/2019 1_FUNDAMENTLE Protection Principles
5/36
Energy Sector Energy Automation
© Siemens AG 2009
The Purpose of Protection
But it can:Limit the damage caused by shortcircuits
While:Protecting people and plant fromdamage
Selectively clearing faults inmiliseconds
Protecting plant from overload
conditions
The protection can not prevent system faults,
Power system must operate in a safe manner at all times.
8/18/2019 1_FUNDAMENTLE Protection Principles
6/36
Energy Sector Energy Automation
© Siemens AG 2009
Causes and Probability of System Disturbances
Causes§ Operator Mistakes
§ Pollution/Condensation
§ Equipment failures, e.g. P.T.'s, Isolators
§ Transient Overvoltages
Probability
§ System faults (220/400 kV): 3p.a. and 100 km
§ 10-20 kV metal clad switchgear: 10-3 p.a. and feeder
§ GIS switchgear: 5-10-2 p.a. and bus
§ outdoor switchgear: 110/132 kV 7*10-2 p.a. and bus
220/275 kV 10-1
p.a. and bus400 kV 2*10-1 p.a. and bus
8/18/2019 1_FUNDAMENTLE Protection Principles
7/36
Energy Sector Energy Automation
© Siemens AG 2009
Since protective relaying comes into action at the time of
equipment distress, a certain safeguard is necessary in the
unlikely event of its failure to act at the hour of need.
Hence, two groups of protective schemes are generally
employed -
a) Primary Protection
b) Back-up Protection
Primary Protection is the first line of defense, whereas back-up
relaying takes over the protection of equipment, should the primary
protection fail.
Principles of Relaying
8/18/2019 1_FUNDAMENTLE Protection Principles
8/36
Energy Sector Energy Automation
© Siemens AG 2009
The Primary Protection has following characteristic features -
1. It has always a defined zone of operation.
2. It should operate before any back-up protection
could operate, therefore, it should be faster in
operation.
3. It should be able to completely isolate the fault
from all the current feeding sources.
4. It should be stable for all operating conditions.
Primary Protection
8/18/2019 1_FUNDAMENTLE Protection Principles
9/36
8/18/2019 1_FUNDAMENTLE Protection Principles
10/36
Energy Sector Energy Automation
© Siemens AG 2009
Primary protections failure could be due to any of
the following reasons -
1. Current or Potential Transformer failure
2. Loss of Auxiliary Control Voltage
3. Defective Primary Relays
4. Open Circuits in Control & Trip Coil
5. Failure of Breaker
It is therefore logical that back-up relays should not
utilise any of the above items as common with
primary relays.
Reasons of Primary Protection Failure
8/18/2019 1_FUNDAMENTLE Protection Principles
11/36
Energy Sector Energy Automation
© Siemens AG 2009
Protection Concept
§ The system is only as strong as the weakest link!
DISTANCE RELAY
Circuit Breaker CT / VT
Protection Battery
Cabling
8/18/2019 1_FUNDAMENTLE Protection Principles
12/36
Energy Sector Energy Automation
© Siemens AG 2009
System structure: meshed network
8/18/2019 1_FUNDAMENTLE Protection Principles
13/36
Energy Sector Energy Automation
© Siemens AG 2009
System structure: radial network for public supply
8/18/2019 1_FUNDAMENTLE Protection Principles
14/36
Energy Sector Energy Automation
© Siemens AG 2009
System structure: radial network in the industry
G G
M
M
M
8/18/2019 1_FUNDAMENTLE Protection Principles
15/36
Energy Sector Energy Automation
© Siemens AG 2009
Neutral earthing
Solid earthing Low-impedanceNeutral earthing
Isolated neutralEarth fault-compensation
8/18/2019 1_FUNDAMENTLE Protection Principles
16/36
Energy Sector Energy Automation
© Siemens AG 2009
Main components of electrical networks
Bus coupler
Generator Three-windingtransformer
Cable
Shunt reactorOverhead
line
Consumer
MotorM
Filter circuit
Short-circuit currentlimiting reactor
Switch
Substation
Doublebusbar
Earth faultcompensation coil
8/18/2019 1_FUNDAMENTLE Protection Principles
17/36
Energy Sector Energy Automation
© Siemens AG 2009
Protection target
Selective Fast
8/18/2019 1_FUNDAMENTLE Protection Principles
18/36
Energy Sector Energy Automation
© Siemens AG 2009
Basic Protection Requirements
§ Reliability dependability (availability)
high dependability = low risk of failure to trip
§ Security stable for all operating conditions ,
high security = low risk of over-trip
§ Speed high speed minimizes damage
high speed reduces stability problems
§ Selectivity trip the minimum number of circuit breakers
§ Sensitivity notice smallest fault value
8/18/2019 1_FUNDAMENTLE Protection Principles
19/36
Energy Sector Energy Automation
© Siemens AG 2009
Protected zone
Circuit-breaker
Current transformer
8/18/2019 1_FUNDAMENTLE Protection Principles
20/36
Energy Sector Energy Automation
© Siemens AG 2009
Zones of Protection
n To limit the extent of the power system that is disconnected when a faultoccurs, protection is arranged in zones
n Zones of protection should overlap, so that no part of the power system isleft unprotected
n Location of the CT connection to the protection usually defines the zone
n Unit type protections have clear zones reach e.g Diff. Relay, REF relay
n Zone reach depends on measurement of the system quantities e.g OC ,EF, distance relays . The start will be defined but the extent (or ‘reach’) issubject to variation, owing to changes in system conditions andmeasurement errors.
8/18/2019 1_FUNDAMENTLE Protection Principles
21/36
Energy Sector Energy Automation
© Siemens AG 2009
Criteria indicating fault condition
Current I I > > I >> I I
Voltage U U< U>
Impedance Z Z<
Phase angle
Power S S (t)
Frequency f f
r r
P Q
U
I
ddt
I r
I
I I (t) = sin t + e-
t
T×
8/18/2019 1_FUNDAMENTLE Protection Principles
22/36
Energy Sector Energy Automation
© Siemens AG 2009
Overcurrent-time protection
Definite-time
overcurrent-protection
Inverse-time
overcurrent-protection
t
I I N I > I >>
t2
t1
t
I I N
t
I I N
8/18/2019 1_FUNDAMENTLE Protection Principles
23/36
Energy Sector Energy Automation
© Siemens AG 2009
Differential protection
Load condition
Fault condition
Load condition
Fault condition
I A I B
I C
I A I B
I C
Line
Busbar
Istart - Iend = 0 è DI = 0
Istart - Iend¹ 0 è DI ¹ 0
IA + IB + IC ¹ 0 è SI ¹ 0
IA + IB + IC = 0 è SI = 0
8/18/2019 1_FUNDAMENTLE Protection Principles
24/36
Energy Sector Energy Automation
© Siemens AG 2009
Overvoltage - Undervoltage
U >
UN
U <
Overvoltage
Undervoltage
8/18/2019 1_FUNDAMENTLE Protection Principles
25/36
Energy Sector Energy Automation
© Siemens AG 2009
Impedance protection
Load
Load
I
I
U
U
LoadZ
U=
I
FaultZ
U=
I
LoadFaultZZ
8/18/2019 1_FUNDAMENTLE Protection Principles
26/36
Energy Sector Energy Automation
© Siemens AG 2009
Distance protection
Load
LineX
R
LineFaultZ'l=Z ×
Load
2
NLoad =
S
U Z
8/18/2019 1_FUNDAMENTLE Protection Principles
27/36
Energy Sector Energy Automation
© Siemens AG 2009
Back-up protection I
t = 700 ms
t = 400 ms
t = 100 ms
I > I > I >
I > I > I >
8/18/2019 1_FUNDAMENTLE Protection Principles
28/36
Energy Sector Energy Automation
© Siemens AG 2009
Back-up protection II
Z<
I > I > I >
t = 400 ms
t = 100 ms
t = 1000 ms
Z< Z<
t = 700 ms
t = 300 ms
t = 0 ms
I
I
I
8/18/2019 1_FUNDAMENTLE Protection Principles
29/36
Energy Sector Energy Automation
© Siemens AG 2009
Survey Equipment - Type of protection
Line
TransformerHigh voltage - Medium voltage
Busbar
TransformerMedium voltage - Low voltage
Motor
Time-graded protectionDifferential protection
Differential protection
Time-graded protection
Reverse interlockDifferential protection
FuseTime-graded protection
Time-graded protectionOverload protection
8/18/2019 1_FUNDAMENTLE Protection Principles
30/36
Energy Sector Energy Automation
© Siemens AG 2009
History
1900Electromechanical relays
1980Analog electronical relays
1990Numerical relays
8/18/2019 1_FUNDAMENTLE Protection Principles
31/36
Energy Sector Energy Automation
© Siemens AG 2009
EquipmentSignal
conversion
Signal
tailoring
Processing(calculation)
Signalanalysis
Trippingsignal
Trippingcoil
Circuitbreaker
Protection device
Auxiliary supply Settings Annunciation
Equipment : Lines, cables, transformers, machines Processing : Digital Filters,Numerical Methods,
Measuring AlgorithmsSignal Conversion : CTs and VTs Signal Analysis : Comparisonwith
Settings, gradingSignal Tailoring : Signal matching, Anti-Aliasing Filters, A/ D Conversion
Binary Inputs
General Structure of a Numerical Protection Device
8/18/2019 1_FUNDAMENTLE Protection Principles
32/36
Energy Sector Energy Automation
© Siemens AG 2009
PCPC--InterfaceInterfaceSystemSystem--InterfaceInterface
Hardware for Digital RelaysHardware for Digital Relays
100V/ 1A, 5A100V/ 1A, 5Aanalogueanalogue
IInput/nput/OutputOutputPortsPorts
32/16 Bit32/16 Bitprocessorprocessor--SystemSystem
Memory :Memory :RAMRAMEEPROMEEPROM
EPROMEPROM
RS232/RS232/485/FO485/FOSerialSerial
InterfacesInterfaces
0001000101010101
00110011
AmplifierAmplifier
A/DA/D--ConverterConverter
FilterFilter
Measur.inputMeasur.inputss(max. 11)(max. 11)
max. 7max. 7VoltageVoltage--inputsinputs
(140 V cont.)(140 V cont.)
max. 11max. 11CurrentCurrent--InputsInputs(100/N. 1s)(100/N. 1s)
10V10Vanalogueanalogue
digitaldigital InputInput--/Output/Outputcontactscontacts
Input/OutputInput/Output--
unitunit
2....112....11binarybinaryInputsInputs
5....115....11AlarmAlarmRelaysRelays
2....52....5TripTripRelaysRelays
8....168....16LEDLED
IndicatorsIndicators
8/18/2019 1_FUNDAMENTLE Protection Principles
33/36
Energy Sector Energy Automation
© Siemens AG 2009
Analog to Digital ( A / D ) Conversion of Measuring Signals
IL1
Filter
•
•
•
•
•
•
1 kHz
S & H
MUX
ME
IL2 ; IL3 ; IE
UL1 ; UL2 ; UL3
UE•
•
•
•
•
•
1 kHz
ME Measuring Input S & H Sample u. Hold
MUX Multiplexer
PGA
1 1 10 00A
D
PGA Programmable Gain Ampliflier
8/18/2019 1_FUNDAMENTLE Protection Principles
34/36
Energy Sector Energy Automation
© Siemens AG 2009
Analog to Digital ( A / D ) Conversion of Measuring Signals
Example of an A/D Conversion of a Sinusoidal Signal.
A voltage signal 10 sinω
t is sampled at a rate of 1 kHz (Sampling time Δ
T = 1 ms) .ω = 2πf, with f being the power frequency = 50 Hz..
How does the output of a 12 bit (11 bits + sign) ADC look like ?
Note : 1 ms for a 50 Hz system corresponds to 18 electrical degrees
t t
Input of ADC Output of ADC
10 sin ω t
8/18/2019 1_FUNDAMENTLE Protection Principles
35/36
Energy Sector Energy Automation
© Siemens AG 2009
Sampling Rates used in Siemens Numerical Protection
S.No Relay Designation Sampling Rate
1. 7UT612 12 Samples / Cycle
600 Hz for 50 Hz system
2. 7UT613 16 Samples / Cycle
800 Hz for 50 Hz system
3. 7UT63 16 Samples / Cycle
800 Hz for 50 Hz system
4. 7SJ61-64 16 Samples / Cycle
800 Hz for 50 Hz system
5. 7SA... 20 Samples / Cycle
1000 Hz for 50 Hz system
6. 7SD... 20 Samples / Cycle
1000 Hz for 50 Hz system
7. 7SS... 20 Samples / Cycle
1000 Hz for 50 Hz system
8. 7UM Depends on network frequency
8/18/2019 1_FUNDAMENTLE Protection Principles
36/36
Energy Sector Energy Automation
© Siemens AG 2009
Further Readings
The Art & Science of Protective RelayingBy : C Russel Mason