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Carelabs

IEEE 1584 · Engineering

Leading Relay Coordination Study For Indian Industries

Evaluate the relay settings and protection coordination with Care Labs’ proven solutions. Leverage our expertise in optimizing your power systems. Carelabs builds the study from your facility's one-line diagram, modeling every protective device in ETAP to confirm each one trips only for the fault closest to it.

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Grading that holds on grid and on generation

A plant with captive generation runs in at least three states: on grid, on generation, and in parallel. Protection graded for one of them is not necessarily selective in the others.

What We Deliver

Every source state graded

Coordination is verified on grid supply, on captive generation and in parallel operation, because fault current differs substantially between them and a scheme selective in one can fail in another.

WHY IT MATTERS

Selective on grid, blind on generation

The most common failure is a downstream fault that clears correctly on grid supply and is left uncleared on generation, because decaying generator current never reaches the pick-up the setting assumes.

  • Settings read from each device rather than transcribed from the schedule, because the two frequently disagree after years of adjustment.
  • Generator parameters taken from the machine's own data, since subtransient reactance and excitation response govern fault contribution.
  • Earthing arrangement examined per source, as available earth fault current can differ substantially between grid and generator supply.
  • Transfer and islanding behaviour assessed, because changeover having worked previously is not evidence that protection discriminates during it.
  • Every recommended change reported with its arc flash consequence, so selectivity is not bought at an unexamined safety cost.
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DELIVERABLES

What you receive

Issued against CEA Regulations 2010 and IS 3043 where earthing is relevant, signed by the engineer who performed the grading.

  1. 1As-found settings register covering every relay and adjustable trip unit
  2. 2Time-current curves per grading path for each source state, with margins annotated
  3. 3Discrimination register naming each failing pair and the source condition under which it fails
  4. 4Separate earth fault grading with the earthing arrangement stated per source
  5. 5Recommended settings with a verification checklist for application
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How the study runs

01

Establish the operating states

We identify how the plant actually runs: grid only, generation only, parallel, and any islanded configuration used during interruptions.

02

Audit the protection

Settings are read from every device on site and CT ratios, polarity and burden verified against the schematics rather than assumed.

03

Model sources and network

Grid supply and captive generation are modelled with real parameters, including the decay characteristic that governs late-fault behaviour.

04

Grade each state

Discrimination is calculated for every source condition across the full fault range, not only at the maximum value.

05

Resolve the conflicts

Where no single setting is selective in all states, options are presented including setting groups, with the trade-offs stated.

06

Issue and verify

Settings are issued with a verification checklist so applied values can be proven against the approved schedule afterwards.

Frequently asked questions

A generator's fault contribution is much lower than the grid's and decays within seconds as the machine's flux collapses. Current available to operate a downstream device late in a fault can fall below its pick-up, so a fault that would clear promptly on grid supply may not clear at all on generation.
Sometimes, but not always. Where the fault current difference between grid and generation is large, a single setting selective in one state is frequently unselective or insensitive in the other. Relays with multiple setting groups can switch automatically on changeover, which resolves the conflict where the hardware supports it.
It often does, and it matters. Available earth fault current depends on how the source neutral is earthed, so a scheme graded for grid supply may have very different earth fault current available on generation. This is assessed per source rather than assumed constant.
Yes, because they share inputs and pull in opposite directions. Clearing time governs incident energy while grading margins tend to lengthen it. Running both against one model means the trade-off is resolved once and deliberately, rather than one study quietly undoing the other's recommendation.

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