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Power System Protection and Relay Coordination

Overcurrent Phase/Earth Relays

Distance Relays

Other Power System Protection Related Links
Power System Protection and Relay Coordination

Overcurrent Phase/Earth Relays

Distance Relays

Other Power System Protection Related Links
Power System Protection and Relay Coordination

Overcurrent Phase/Earth Relays

Distance Relays

Other Power System Protection Related Links
Power System Protection and Relay Coordination

Overcurrent Phase/Earth Relays

Distance Relays

Other Power System Protection Related Links

Power System Protection Studies and Relay Coordination

CASE STUDY : Protection Co-ordination Study

In any power system netowrk,  protection should be designed such that protective relays isolate the faulted portion of the network at the earliest, to prevent equipment damage, injury to operators and to ensure minimum system disruption enabling continuity of service to healthy portion of the network.

When relays meant to protect specific equipments, transmission/distribution lines/feeders or primary zone protective relays, do not operate and clear the fault in their primary protection zone, backup relays located in the backup zone, must operate to isolate the fault, after providing sufficient time discrimination for the operation of the primary zone relays.

The protective relays must also be able to discriminate between faulted conditions, normal operating conditions and abnormal operating conditions and function only for the specific protection for which they are designed, without operating for any normal and short term acceptable abnormal events for which they are not intended to act and provide protection.

The term or phrase relay coordination therefore covers the concept of discrimination, Selectivity and backup protection as explained in the foregoing discussion. Further the coordination is not confined only to relays and equipment operating characteristics, but also includes other protective device characteristics such as Fuse, MCB's, Circuit Breakers as applicable.

Relay coordination calculation module must consider the operating characteristics of the relays, normal operating and thermal or mechanical withstand characteristics of the equipments and must determine the optimum relay settings to achieve the objectives stated to protect the equipments and to ensure continuity of power supply to healthy part of network.

Apart from the fault or short circuit conditions, protection system must also be designed to provide protection against thermal-withstand limits, motor stalling, negative sequence current with-stand limits, protection against abnormal frequencies, and protection against unbalance operating conditions as applicable to various equipments and operating situations.

Frequency relay settings can be determined by using a dynamic simulation tool, such as transient stability analysis.Frequency Control Engineering ; Transient Stability Analysis


Overcurrent Phase/Earth Fault Relays


  • Overcurrent phase fault relays.
  • Overcurrent earth fault relays.
  • High set relay settings to ensure protection against primary zone faults.
  • Coordination with maximum load current.
  • Coordination with fuse characteristics.
  • Coordination with maximum motor starting current and time.
  • Coordination with transformer inrush current.
  • Coordination with primary-back up pairs.
  • Coordination with thermal withstand capabilities ([I-square]t = K characteristics).
  • Coordination with safe stall limits for Motors.
  • Automatic generation of TCC’s showing all relevant coordination.
  • Automatic identification of primary and back up relay pairs.
  • Provision for user defined back up relays for specific primary relays.
  • Solution for multiple island networks.
  • Multiple study cases for different network and source configurations in a single execution of the program.
  • Built in libraries of commercial relays, IEEE and IEC characteristics.

time current Characteristics of Over current protection


Distance Relay Settings


  • Zone setting calculations for zone 1 and 2.
  • Zone 3 setting calculations based on inbuilt short circuit calculations.
  • Settings for different commercially available relays.
  • Different relay characteristics MHO , Polygonal , Lens , Circle , R/X Blinder, Offset characteristic.
  • R/X diagrams.
  • Solution for multiple islanded network in a single execution of the program.
  • Solution for multiple study cases with different network configurations in a single execution of program.

distance relay protection zone characteristics

Related Links


http://www.powerapps.org/PAES_TransformerProtection.aspx
http://www.powerapps.org/PAES_EquiProApps.aspx
http://www.powerapps.org/PAES_GeneratorProtection.aspx
http://www.powerapps.org/PAES_ShortCircuit.aspx

http://www.google.com
http://www.activesearchresults.com
Mail your questions, enquiries to raghunatha@powerapps.org