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Understanding electrical networks to enhance their protection

?. Situate the protection relay. TOLED. Understanding electrical networks to enhance their protection. Points to remember. G. Network protection. F. The various discrimination types. E. D. The various earthing system types. C. Network disturbances. B. Network architecture. A.

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Understanding electrical networks to enhance their protection

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  1. ? Situate the protection relay TOLED Understanding electrical networks to enhance their protection Points to remember G Network protection F The various discrimination types E D The various earthing system types C Network disturbances B Network architecture A What exactly is protection Expert: André TRUONG Training: François BECHERET Layout: Bernadette ETIENNE Duration: 43:35 min Understanding networks – June 04

  2. SITUATE THE PROTECTION RELAY Production units Generator Transformers Overhead lines Underground cables MV/MV distribution substations HV/MV substations Motors MV/LV distribution substations Industries

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

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

  5. CHOICE OF RELAY - The protection plan Network architectures PROTECTION PLAN Types of disturbance Type of protection function Earthing systems Discrimination Settings Components to protect

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

  7. Safety Open $ Maint Conti Op - Choosing a network Safety of equipment and people Technical and economic aspects Open-endedness Continuity of operation Maintainability Ease of operation

  8. Supplied Not supplied Safety Safety Open Open $ $ Maint Maint Conti Strong point Conti Op Op Weak point - Loop distribution Large distances Open loop Closed loop Rural secondary networks = geographical area and simplicity Urban secondary networks = geographical area and continuity of supply

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

  10. Supplied Not supplied Safety Open $ Maint Conti Strong point Op Weak point - Double tap-off distribution Heavy process industries and large tertiary: continuity

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

  12. Supplied Not supplied - Local production Partial permanent production Main / standby production Sites with priority for continuity of supply High consumption industry Expensive electricity

  13. Low costs Rural secondary Open loop Public distribution Urban secondary Closed loop Continuity of supply Simple tertiary Single antenna Low costs Tertiary Large tertiary Simple processes Double antenna Double tap-off Industry Continuous processes Continuity of supply / Ease of maintenance Complexity of operation « Heavy » continuous processes Double busbars - Points to remember

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

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

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

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

  18. no no yes Input-output crossing withstand Earthing switch: making capacity on a fault no yes no 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 no yes if draw-out yes no Nominal breaking and making capacity Maximum load capacity in breaking and making Service and durability characteristics no yes if draw-out yes yes Breaking capacity on short-circuit Making capacity on short-circuit no no yes Minimum breaking capacity on short-circuit Maximum breaking capacity on short-circuit - Equipment short-circuit withstand Devices Isolation function Current switching function In service On fault Main constraints Disconnector Switch Contactor Circuit-breaker Fuse

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

  20. - Earthing systems and earthing 1 earthing type limits the effects of network disturbances Continuity of supply SERVICE Simple protection OPERATING COSTS Personnel skills Fault energy SAFETY OF PEOPLE Transient phenomena Surges

  21. R L Z • Earthed: connection R • Earthed via a resistor • Earthed via a reactance L • Earthed via a compensated reactance Z - 5 types of earthing system • Unearthed: no connection

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

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

  24. Continuity of supply SERVICE Simple protection OPERATING COSTS Personnel skills Fault energy SAFETY OF PEOPLE Transient phenomena Surges - Earthing via a resistor • Advantages R • Isc / surge compromise • Simple & selective protection • Drawbacks • Breaking on 1st fault • Expensive resistor • Type of protection • Overcurrent • Applications • Public & industrial distribution

  25. Continuity of supply SERVICE Simple protection OPERATING COSTS Personnel skills Fault energy SAFETY OF PEOPLE Transient phenomena Surges - Earthing via a small reactance • Advantages L • Limited lsc • Inexpensive reactance • Drawbacks • Breaking on 1st fault • Surges • Type of protection • Directional earth protection • Applications • Public distribution > 40 kV

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

  27. Personnel skills Continuity of supply Transient phenomena • Earthed: connection Fault energy • Earthed via a resistor Simple protection Continuity of supply • Earthed via a reactance Fault energy Surges • Earthed via a compensated reactance Simple protection Continuity of supply - Summary of the 5 earthing systems • Unearthed: no connection

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

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

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

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

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

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

  34. - Discrimination by differential protection • Principle: "differential" Source • IA = IB ? • Tripping on a difference! • Advantages • Sensitive Section • Instantaneous Protected area • Drawbacks • Cost • Implementation • Standby to provide

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

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

  37. X X X incomer line feeder - Connection protection: overhead lines Overhead lines: 80 % of problems 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 • Against transient contacts: automation

  38. X X X incomer cable feeder - Connection protection: underground cables Underground distribution in urban environments 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. busbar X X X X X X X - Connection protection: busbars Electrical switchboards • « energy concentration » ! • need to eliminate the fault quickly Fault Schéma F2 • 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. Directional protection set if fault - Protection example of substation busbars with 2 incomers • protections • Overcurrent protection (50/51) • Residual overcurrent protection (50N/51N) • Directional phase protection (67) • discrimination • current

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

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

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

  44. - Switchgear protection: the capacitor Faults Impacts Protections Internal short-circuit • Reduction in capacity • Thermal overload 49RMS • Max. reverse component 46 • Specific Short-circuit in the connection • Destruction of connections with capacitors • Overcurrent 50/51 • Thermal overload 49RMS • Max. reverse component46 Earth fault • Max. Io 50N/51N • Residual overvoltage 59N • Max. reverse component46 • Destruction of insulators • Unbalance Surge • Destruction of insulators • Overvoltage 59

  45. Electrical network protection Protection Guide network - The protection guidewill provide you with more details • Networks • Earthing systems • Isc • Sensors • Protection functions • Discrimination • Network protection

  46. Network architectures CHOICE OF RELAY PROTECTION PLAN Types of disturbance Type of protection function Earthing systems Discrimination Settings Components to protect POINTS TO REMEMBER

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