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Understanding electrical networks to enhance their protection ? Situate the protection relay Ask the customer the right questions Duration: 43:35 min Expert:

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Presentation on theme: "Understanding electrical networks to enhance their protection ? Situate the protection relay Ask the customer the right questions Duration: 43:35 min Expert:"— Presentation transcript:

1 Understanding electrical networks to enhance their protection ? Situate the protection relay Ask the customer the right questions Duration: 43:35 min Expert: André TRUONG Training: François BECHERET Layout: Bernadette ETIENNE A B C D E F Network disturbances What exactly is protection Network architecture Points to remember The various earthing system types The various discrimination types Network protection G Help him formulate his needs Gather the information required for the offer Understanding networks – June 04 TOLED

2 Understanding networks – June 04 TOLED 2 SITUATE THE PROTECTION RELAY Industries Production units HV/MV substations MV/MV distribution substations MV/LV distribution substations Generator Overhead lines Motors Underground cables Transformers

3 Understanding networks – June 04 TOLED 3 - Network disturbances Natural phenomena –branches –lightning Short-circuit Overloads Short-circuit Transient surges Transient losses Works Use –capacity problem –reconfiguration –dust –insulators –machine start-up –pump/turbine blocking... –harmonics...

4 Understanding networks – June 04 TOLED 4 WHAT EXACTLY IS PROTECTION Sensor current voltage A protection device does not prevent the fault from occurring, but limits the consequences... Tripping coil Tripping coil Tripping coil Detect and isolate the fault Preserve continuity of supply Measure Compare Decide

5 Understanding networks – June 04 TOLED 5 - The protection plan Types of disturbance Earthing systems Network architectures PROTECTION PLAN Settings Components to protect Type of protection function Discrimination CHOICE OF RELAY

6 Understanding networks – June 04 TOLED 6 Network architecture NETWORK ARCHITECTURE ? Situate the protection relay A B C D E F Network disturbances What exactly is protection Points to remember The various earthing system types The various discrimination types Network protection G Network architecture

7 Understanding networks – June 04 TOLED 7 Maintainability Safety of equipment and people Technical and economic aspects Open-endedness Ease of operation Maint Conti Op Safety $ Open - Choosing a network Continuity of operation

8 Understanding networks – June 04 TOLED 8 Large distances Maint Conti Op Safety $ Open Maint Conti Op Safety $ Open Strong point Weak point Supplied Not supplied Open loopClosed loop Urban secondary networks = geographical area and continuity of supply Rural secondary networks = geographical area and simplicity - Loop distribution

9 Understanding networks – June 04 TOLED 9 Large to average distances Single antenna Maint Conti Op Safety $ Open Supplied Not supplied Maint Conti Op Safety $ Open Strong point Weak point Continuous process industries: continuity Simple industries and tertiary: reduced costs - Antenna distribution Double antenna

10 Understanding networks – June 04 TOLED 10 Strong point Weak point Supplied Not supplied Maint Conti Op Safety $ Open Heavy process industries and large tertiary: continuity - Double tap-off distribution

11 Understanding networks – June 04 TOLED 11 Maint Conti Op Safety $ Open Solution for cubicles Strong point Weak point Supplied Not supplied Continuous process industries Oil & Gas: continuity - Double busbar distribution

12 Understanding networks – June 04 TOLED 12 Main / standby productionPartial permanent production Supplied Not supplied High consumption industry Expensive electricity Sites with priority for continuity of supply - Local production

13 Understanding networks – June 04 TOLED 13 Public distribution Tertiary Industry Simple tertiaryLarge tertiarySimple processes Continuous processes « Heavy » continuous processes Rural secondaryOpen loopUrban secondarySingle antennaDouble antenna Double tap-off Double busbars Continuity of supply / Ease of maintenance Complexity of operation Low costs Closed loop Continuity of supply Low costs - Points to remember

14 Understanding networks – June 04 TOLED 14 Network disturbances DISTURBANCES ? Situate the protection relay A B C D E F What exactly is protection Network architecture Points to remember The various earthing system types The various discrimination types Network protection G Network disturbances

15 Understanding networks – June 04 TOLED 15 - Network disturbances Natural phenomena Works Use Simple fault Complex fault short-circuit Surges short-circuit overloads Transient Losses short-circuit Transient Effects –Customer power supply suspended –Incorrect network operation –Material damage –Bodily damage –branches –capacity problem –lightning –reconfiguration –dust –insulators –machine start-up –pump/turbine blocking... –harmonics

16 Understanding networks – June 04 TOLED 16 - The short-circuit Origin Rare but destructive Duration Location –mechanical –electrical –human –self-extinguishing –transient –permanent –equipment –link phase-to-earth lsc Isc: short-circuit –non-resistive –impedant The most common Energy loss phase-to-phase Isc Isolated two-phase short-circuit Three-phase short-circuit (5% of cases) Earth single-phase short-circuit Two-phase short-circuit (80% of cases)

17 Understanding networks – June 04 TOLED 17 - Other disturbances Overload In time Surges Undervoltage and voltage sags Frequency fluctuations, harmonics and transient phenomena Ur time Temperature rise thus ageing Voltage sag Arcing Saturation Overspeed Destruction Current increase Overload Temperature rise

18 Understanding networks – June 04 TOLED 18 - Equipment short-circuit withstand Disconnector Switch Contactor Circuit-breaker Fuse Devices no yes if draw-out no yes no yes if draw-out Isolation function Main constraints Input-output crossing withstand Earthing switch: making capacity on a fault Breaking and making of normal load current Making capacity on short-circuit In association with the fuse: breaking capacity in the fuse non-blowing zone Nominal breaking and making capacity Maximum load capacity in breaking and making Service and durability characteristics Breaking capacity on short-circuit Making capacity on short-circuit Minimum breaking capacity on short-circuit Maximum breaking capacity on short-circuit Current switching function In service On fault no yes no yes no yes

19 Understanding networks – June 04 TOLED 19 The various earthing system types EARTHING SYSTEMS AND THEIR IMPACTS ? Situate the protection relay A B C D E F Network disturbances What exactly is protection Network architecture Points to remember The various discrimination types Network protection G The various earthing system types

20 Understanding networks – June 04 TOLED 20 - Earthing systems and earthing Surges 1 earthing type limits the effects of network disturbances Transient phenomena Simple protection Personnel skills Continuity of supplySERVICE Fault energy OPERATING COSTS SAFETY OF PEOPLE

21 Understanding networks – June 04 TOLED types of earthing system Unearthed: no connection Earthed: connection R R Earthed via a resistor L Earthed via a reactance L Z Earthed via a compensated reactance Z

22 Understanding networks – June 04 TOLED 22 - Unearthed neutral Advantages –Continuity of supply Drawbacks Type of protection Applications –2nd fault = Isc phase-to-phase –Max. directional lo and Max. residual Vo –Industry Surges Transient phenomena Simple protection Personnel skills Continuity of supplySERVICE Fault energy OPERATING COSTS SAFETY OF PEOPLE surges & transients –Difficult discrimination –Insulation monitor

23 Understanding networks – June 04 TOLED 23 - Directly earthed neutral Advantages –No surges Drawbacks Type of protection Applications –High lsc –Max. Io –US public distribution Surges Transient phenomena Simple protection Personnel skills Continuity of supplySERVICE Fault energy OPERATING COSTS SAFETY OF PEOPLE –No specific protection –No continuity of supply on the 1st fault –For small lsc

24 Understanding networks – June 04 TOLED 24 - Earthing via a resistor R Advantages Drawbacks Type of protection Applications –Breaking on 1st fault –Overcurrent –Public & industrial distribution –Isc / surge compromise –Simple & selective protection –Expensive resistor Surges Transient phenomena Simple protection Personnel skills Continuity of supplySERVICE Fault energy OPERATING COSTS SAFETY OF PEOPLE

25 Understanding networks – June 04 TOLED 25 - Earthing via a small reactance Advantages Drawbacks Type of protection Applications –Directional earth protection –Public distribution > 40 kV –Limited lsc –Breaking on 1st fault L Surges Transient phenomena Simple protection Personnel skills Continuity of supplySERVICE Fault energy OPERATING COSTS SAFETY OF PEOPLE –Inexpensive reactance –Surges

26 Understanding networks – June 04 TOLED 26 - Earthing via a compensation reactance Advantages Drawbacks Type of protection Applications –Expensive reactance –Max. directional Io –Public distribution with high capacitive l –Limited lsc Z Surges Transient phenomena Simple protection Personnel skills Continuity of supplySERVICE Fault energy OPERATING COSTS SAFETY OF PEOPLE –Continuity of supply –Discrimination implementation –Surges

27 Understanding networks – June 04 TOLED 27 - Summary of the 5 earthing systems Unearthed: no connection Continuity of supply Personnel skills Surges Earthed via a reactance Fault energy Earthed: connection Transient phenomena Fault energy Earthed via a resistor Continuity of supply Simple protection Earthed via a compensated reactance Continuity of supply Simple protection

28 Understanding networks – June 04 TOLED 28 The various discrimination types DISCRIMINATION ? Situate the protection relay A B C D E F Network disturbances What exactly is protection Network architecture Points to remember The various earthing system types Network protection G The various discrimination types

29 Understanding networks – June 04 TOLED types of discrimination to optimise continuity of supply Isolate only the faulty part Choice of protection relay as per: Supply the healthy sector Network Disturbances incurred Earthing system Discrimination: 6 discrimination principles: time current logic by directional protection by differential protection combined

30 Understanding networks – June 04 TOLED 30 - Time discrimination Principle: “time” Advantages –simple Drawbacks –tripping too long in A, in event of fault at this level –time delays increasingly short as we move away from the source TA =1.1 s. TB =0.8 s. TC =0.5 s. TD =0.2 s. –tripping as close as possible to the fault –automatic standby Source Phase-to-phase fault

31 Understanding networks – June 04 TOLED 31 - Current discrimination Principle: “current” Advantages –Each relay monitors its section Drawbacks –No « standby » protection –The further the fault from the source, the weaker the fault current –Simple, inexpensive and fast Section A Section B Source Condition IsA > IscBmax IsA > IscAmin IscBmax

32 Understanding networks – June 04 TOLED 32 - Logic discrimination Principle: “ … ” Advantages –Avoids over long tripping times Drawbacks –Standby system –A (blue) additional network connects all the protection relays to allow exchanges and decisions as to « which relay is concerned ». –Tripping time not dependent on number of protection devices –An additional wiring network is required Additional wiring Source Logic wait Phase-to-phase fault

33 Understanding networks – June 04 TOLED 33 - Discrimination by directional protection Principle: “directional” Advantages –Preserves 1 out of the 2 power supplies in event of fault in 1 Drawback –Simple solution –Measures flow direction –The cost of the voltage transformers –Network in loop on 2 sources Busbar Cable Vref.

34 Understanding networks – June 04 TOLED 34 - Discrimination by differential protection Source Principle: "differential" Advantages –Sensitive Drawbacks –IA = IB ? –Instantaneous –Standby to provide –Tripping on a difference! –Implementation –Cost Section Protected area

35 Understanding networks – June 04 TOLED 35 - In short, discrimination is... 1 … time 2 … current 3 … logic 5 … difference 4 … direction 6 ? Discrimination applies to – I phase – Io earth Global discrimination and redundancy – Mix discrimination types 6 Discrimination combination

36 Understanding networks – June 04 TOLED 36 Network protection NETWORK PROTECTION ? Situate the protection relay A B C D E F Network disturbances What exactly is protection Network architecture Points to remember The various earthing system types The various discrimination types G Network protection

37 Understanding networks – June 04 TOLED 37 - Connection protection: overhead lines XXX line feeder incomer Overhead lines: 80 % of problems –Against transient contacts: automation Downstream faults: Short-circuits Breakage of a phase Recommended protections: –overcurrent protection (50/51) –max. Io protection (50N/51N) –phase unbalance protection (46) –distance protection (21) –line differential protection (87L) Protection provided by other devices –Against lightning: overvoltage protection devices

38 Understanding networks – June 04 TOLED 38 - Connection protection: underground cables Underground distribution in urban environments cable feeder XXX incomer Downstream faults: short-circuits breakage of a phase No reclosing Recommended protections: –Directional earth protection (67N) –Overcurrent protection (50/51) –Residual overcurrent protection (50N/51N) –Phase unbalance protection (46) –Line differential protection (87L)

39 Understanding networks – June 04 TOLED 39 - Connection protection: busbars Electrical switchboards Schéma F2 – « energy concentration » ! – need to eliminate the fault quickly XXXXXXX busbar Fault – short-circuits (between bars and with the earth) – temperature rise – insulation loss Recommended protections –Logic discrimination: overcurrent (50/51) and residual overcurrent protection (50N/51N) –Time discrimination: busbar differential protection (87B)

40 Understanding networks – June 04 TOLED 40 - Protection example of substation busbars with 2 incomers discrimination Directional protection set if fault protections –Overcurrent protection (50/51) –Residual overcurrent protection (50N/51N) –Directional phase protection (67) –current

41 Understanding networks – June 04 TOLED 41 - Switchgear protection: the transformer Protections Faults Short-circuit Earth fault Overload Max. Io 50N/51N Restricted differential 64REF Tank earth 50N/51N, 50G/51G Overcurrent 50/51 transformer differential 87T Buchholz DGPT 63 Overcurrent 50/51 Thermal overload 49RMS Temperature 49T Coiling Tank Magnetic circuit Coiling Magnetic circuit Insulators Impacts

42 Understanding networks – June 04 TOLED 42 - Switchgear protection: the motor Voltage sag Unbalance Short-circuit Earth fault Loss of synchronism Overload Starting too long Locked rotor Frequent starting Overcurrent 50/51 Machine differential 87M Max. Io 50N/51N, 78PS Undervoltage 27 Max. reverse component 46 Overpower 32P Thermal overload 49RMS 48 51LR Min. I 37, P, 37P Limited number of start-ups 66 Active power return: voltage sag Destruction of coiling and magnetic circuit Motor deceleration Overcurrent Stator temperature rise Pump unpriming Mechanical breakage Temperature rise Protections FaultsImpacts Upstream Internal Downstream Use

43 Understanding networks – June 04 TOLED 43 - Switchgear protection: the generator Short-circuit Overcurrent 50/51 Machine differential 87M Overcurrent with voltage retention 50V/51V Active power return Unbalance Surge 32P, 46, 59 Loss of synchronism 78PS Min. impedance 21B Earth fault Max. Io 50N/51N Restricted earth differential 64REF Residual overvoltage 59N Faults relating to incorrect regulation Over and under frequency 81H/81L Undervoltage 27 Destruction of coiling & magnetic circuit Mechanical danger for turbine + rotor temperature rise Overspeed Absorption Reactive power (operates as motor) then temperature rise Temperature rise and poor efficiency Destruction of coiling & destruction of magnetic circuit Protections FaultsImpacts Internal Upstream

44 Understanding networks – June 04 TOLED 44 - Switchgear protection: the capacitor Internal short-circuit Overcurrent 50/51 Thermal overload 49RMS Max. reverse component 46 Overvoltage 59 Earth fault Max. Io 50N/51N Residual overvoltage 59N Max. reverse component 46 Destruction of insulators Unbalance Surge Destruction of insulators Thermal overload 49RMS Max. reverse component 46 Specific Reduction in capacity Short-circuit in the connection Protections FaultsImpacts Destruction of connections with capacitors

45 Understanding networks – June 04 TOLED 45 - The 2003 protection guide will provide you with more details Networks Earthing systems Isc Sensors Protection functions Discrimination Network protection Electrical network protection Protection Guide network

46 Understanding networks – June 04 TOLED 46 POINTS TO REMEMBER Types of disturbance Earthing systems Network architectures Components to protect PROTECTION PLAN Settings Type of protection function Discrimination CHOICE OF RELAY


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